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  • LUNAR AND PLANETARY EXPLORATION  (3,867)
  • Inorganic Chemistry  (3,613)
  • GEOPHYSICS  (3,293)
  • 1990-1994  (10,773)
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  • 1
    Publication Date: 2019-04-02
    Description: Exploration of the Moon and planets began with telescopic studies of their surfaces, continued with orbiting spacecraft and robotic landers, and will culminate with manned exploration and sample return. For the Moon and Mars we also have accidental samples provided by impacts on their surfaces, the lunar and martian meteorites. How much would we know about the lunar surface if we only had lunar meteorites, orbital spacecraft, and robotic exploration, and not the Apollo and Luna returned samples? What does this imply for Mars? With martian meteorites and data from Mariner, Viking, and the future Pathfinder missions, how much could we learn about Mars? The basis of most of our detailed knowledge about the Moon is the Apollo samples. They provide ground truth for the remote mapping, timescales for lunar processes, and samples from the lunar interior. The Moon is the foundation of planetary science and the basis for our interpretation of the other planets. Mars is similar to the Moon in that impact and volcanism are the dominant processes, but Mars' surface has also been affected by wind and water, and hence has much more complex surface geology. Future geochemical or mineralogical mapping of Mars' surface should be able to tell us whether the dominant rock types of the ancient southern highlands are basaltic, anorthositic, granitic, or something else, but will not be able to tell us the detailed mineralogy, geochemistry, or age. Without many more martian meteorites or returned samples we will not know the diversity of martian rocks, and therefore will be limited in our ability to model martian geological evolution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 491
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  • 2
    Publication Date: 2019-04-02
    Description: Chondrule J2689, a large (8-mm) RP chondrule from Bachmut (L6) was previously found to be in disequilibrium with its host in a variety of features: (1) It has a fine-grained hornfelsic texture; (2) it contains low amounts of metal with a low-Ni taenite composition not found in the matrix; (3) the Ni/Co ratio of that metal is close to the solar ratio, which is equal to the bulk Ni/Co ratio (23) of the chondrule; (4) the bulk alkali content of the chondrule is high and the Na/K ratio is fractionated with respect to the average L chondrite ratio of 8; (5) Cr is depleted in spite of the high pyroxene content; (6) the siderophile elements are strongly depleted but are fractionated with their abundances increasing with volatility; and (7) the O isotopes of the chondrule and the host are out of equilibrium. However, the (Fe,Mg) silicates, feldspar, and chromite have chemical compositions indistinguishable from that of the host chondrite. We have studied a chip of the chondrite and of adjacent matrix by stepwise heating and by combustion in O for N and Xe isotopic abundances. (1) The chondrule preserved distinct bulk, metal, and O isotopic compositional features. It is therefore unlikely that the 'equilibration' of the major silicates Fe/Mg ratios could have taken place after accretion; (2) the chondrule was well equilibrated before break-up and exposure to cosmic rays; (3) two N signatures in the matrix also indicate that the matrix is not equilibrated; and (4) all data collected so far point toward the presence of unequilibrated Bachmut components. Very few reactions took place after accretion.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 483
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  • 3
    Publication Date: 2019-04-02
    Description: We wish to draw attention to a major controversy that has arisen in the area of CM-chondrite petrology. The problem is important because its resolution will have profound implications for ideas concerning nebular dynamics, gas-solid interactions in the nebula, and accretionary processes in the nebula, among other issues. On the one hand, cogent arguments have been presented that 'accretionary dust mantles,' were formed in the solar nebula prior to accretion of the CM parent asteroid(s). On the other hand, no-less-powerful arguments have been advanced that a significant fraction of the CM lithology is secondary, produced by aqueous alteration in the near-surface regions of an asteroid-sized object. Because most, if not all, CM chondrites are breccias, these two views could coexist harmoniously, were it not for the fact that some of the coarse-grained lithologies surrounded by 'accretion dust mantles' are themselves of apparently secondary origin. Such an observation must clearly force a reassessment of one or both of the present schools of thought. Our objective here is to stimulate such a reassessment. Four possible resolutions of this conflict may be postulated. First, perhaps nature found a way of permitting such secondary alteration to take place in the nebula. Second, maybe dust mantles could form in a regolith, rather than a nebular, environment. Third, it is possible that dust mantles around secondary lithologies are different from those around primary lithologies. Finally, perhaps formation of CM chondrites involved a more complex sequence of events than visualized so far, so that some apparently 'primary' processes postdated certain 'secondary' processes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 481
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  • 4
    Publication Date: 2019-04-02
    Description: A fragment of a carbonaceous chondrite (#53.12, maximal dimension about 2 mm) containing a phyllosilicate-sulfide vein was found during an inspection of small pieces of the Kaidun meteorite. Phyllosilicate veins are apparently rare in carbonaceous chondrites and have so far only been reported from the Y82162 CI chondrite. In hand sample the vein was visible on two perpendicular faces. The polished section prepared from one side displays a complex structure. A single vein, 150 microns in width, bifurcates, and each branch narrows toward a large rounded object (RO). The section contains abundant ROs, most of them less than or equal to 100 microns in diameter. The vein has sharp contacts to the surrounding matrix, whereas the RO contacts are diffuse. The phyllosilicate in the main vein has a massive texture along the contact, which becomes platy toward the vein center where the crystals protrude into an open space. The texture of the largest RO resembles that of a barred olivine (BO) chondrule. Some of the smaller ROs also texturally resemble chondrules. The BO chondrule contains rounded sulfide-silicate objects and small metal grains covered by oxides. Phyllosilicates of the main vein consist mainly of serpentine. The phyllosilicate near the contact with the matrix has low contents of minor elements and a high Mg/Fe ratio. The composition changes in a regular manner toward the center: Al, Na, Ca, Ni, and S increase, indicating increasing amounts of sulfates admixed. The phyllosilicate vein could only have formed after a substantial rock was formed. Mechanical stress probably opened a crack that was subsequently filled by phyllosilicate, pyrrhotite, and finally by a (Fe,Mg)-sulfate. The source of the matter mobilized to form the vein could have been within the rock itself or outside. No compositional or mineralogical zoning is apparent at the vein-rock contacts. The nature of the transporting agent (liquid H2O or vapor) must also remain an enigma. M. Zolensky has recently observed similar phyllosilicate-filled veins in dark, wet clasts in the Al Rais CR chondrite.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 477
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  • 5
    Publication Date: 2019-04-02
    Description: Compound chondrules are considered to be the product of collisions between molten chondrules during chondrule formation Wasson, J. T. et al. (1994) have argued that some compound chondrules are formed when a chondrule with an accretional rim experienced a flash-melting event similar to a chondrule-forming event. We have designed experiments to investigate the formation of compound chondrules by both methods. Experiments were performed on a Deltech vertical muffle tube furnace to form synthetic chondrules to use as accretion rim material. For our experimental conditions, it is clear that compound chondrules can only be made by a collisional event. Our changes maintain their spherical shape and produce distinct boundaries between charges that are similar to natural compound chondrules. Furthermore, collision event(s) between chondrules will cause nucleation if they are molten and undercooled, thus producing chondrule textures. Flash melting chondrules with accretionary rims will not produce compound chondrules but will produce new chondrules with new textures.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 458
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  • 6
    Publication Date: 2019-03-29
    Description: Ranging in size from mere grains and palm-size stones to boulders and many-mile- wide hunks of rock, meteorites hold many secrets of our solar system, and indeed of our universe. The 57th Annual Meeting of the Meteoritical Society discussed many aspects of this fascinating 'chunk' of the evolution of the Solar System. Topics covered included: chemical composition, meteorite types, meteorite age determination, meteorite origins, and find locations, as well as a multitude of other important subjects.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4
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  • 7
    Publication Date: 2019-04-02
    Description: Kaidun is a remarkable chondrite breccia fall containing lithic clasts that span a wide range of chondrite groups including C and E chondrites, as well as having clasts with characteristics not yet found in existing chondrite samples. The dominant lithology in Kaidun appears to be CR chondritic, consonant with recent O isotope data. The carbonates in Kaidun are presented as one mineralogical basis for comparing it to the other hydrated chondrites and to better understand its relative alteration history. The four polished thin sections of Kaidun studied contained a variety of lithologies that we classified into four groups -- CR, E, CM-like, and dark inclusions (DIs). DIs contain sulfide and magnetite morphologies that superficially resemble CI chondrites, and some of the previously reported CI lithologies in Kaidun may be what we term DIs. Carbonates were found in all lithologies studied. Carbonates in Kaidun are similar in composition to those in CR chondrites. Some of the DIs in Kaidun, previously characterized as CI, have carbonates similar to those in CR chondrites and are unlike those in CI or CM chondrites. Most carbonates in Kaidun and CR chondrites are calcites, some of which formed at temperatures above 250 C. Dolomite is less common and some may be metastable. Alteration temperatures in the Renazzo CR chondrite were estimated to be approximately 300 C, based on O isotope fractionation between phyllosilicates and magnetite. Temperatures of up to 450 C were proposed for the alteration of a CR-like dark inclusion in Kaidun, based on the presence of hydrothermal pentlandite veins. The alteration temperatures for Kaidun and the other CR chondrites are considerably higher than those suggested for CI or CM parent bodies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 549-550
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  • 8
    Publication Date: 2019-04-02
    Description: ALH 84001, a ferroan martian orthopyroxenite, originally consisted of three petrographically defined components: a cumulus assemblage of orthopyroxene + chromite, a trapped melt assemblage of orthopyroxene(?) + chromite + maskelynite + apatite + augite +/- pyrite, and a metasomatic assemblage of carbonate +/- pyrite. We present the results of Instrumental Neutron Activation Analysis (INAA) study of five bulk samples of ALH 84001, combined with Scanning Ion Mass Spectrometer (SIMS) data on the orthopyroxene, in order to attempt to set limits on the geochemical characteristics of the latter two components, and therefore on the petrogenesis of ALH 84001. The INAA data support the petrographic observations, suggesting that there are at least three components in ALH 84001. We will assume that each of the three geochemically required components can be equated with one of the petrographically observed components. Both trapped melt and metasomatic components in ALH 84001 have higher Na than orthopyroxene based on compositions of maskelynite, apatite, and carbonate. For the metasomatic component, we will assume its Na content is that of carbonate, while for a trapped melt component, we will use a typical Na content inferred for martian meteorite parent melts, approximately 1 wt% Na2O. Under these assumptions, we can set limits on the Light Rare Earth Elements/Heavy Rare Earth Elements (LREE/HREE) ratios of the components, and use this information to compare the petrogenesis of ALH 84001 with other martian meteorites. The above calculations assume that the bulk samples are representative of different portions of ALH 84001. We will also evaluate the possible heterogeneous distribution of mineral phases in the bulk samples as the cause of compositional heterogeneity in our samples.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 504
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  • 9
    Publication Date: 2019-04-02
    Description: Recognition and characterization of the different CM lithologies as components in all meteorites could reveal details of the nature and chronology of alteration and brecciation events on hydrous asteroids. The CM chondrites are of particular interest, as they are the most common carbonaceous chondrites and are found as clasts within other types of meteorites, which suggests that the CM parent asteroids are (or were) widespread in the sections of the asteroid belt providing samples to Earth. Some CM2s, including EET 90047, ALH 83100, and Y 82042, are more 'extensively' altered, and are distinguished by a high proportion of Mg-rich phyllosilicates and Ca-Mg carbonates, frequently in rounded aggregates, and near absence of olivine or pyroxene. 'Completely' altered CMs, called CM1s, essentially lack olivine or pyroxene; these include EET 83334, ALH 88045, and the CM1 clasts in Kaidun. Cold Bokkeveld and EET 84034, both highly brecciated CMs, consist of both extensively and completely altered lithologies. We describe how these lithologies further cosntrain physicochemical conditions on hydrous asteroids. We conclude that CM chondrites exhibit the petrologic range 2 through 1, and that progressive alteration on the parent hydrous asteroid(s) was accompanied by significant increases in temperature (to a peak of approximately 450 C), fO2, water-rock ratio, and (locally) degree of chemical leaching, all well beyond the conditions recorded by CM2s.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 556
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  • 10
    Publication Date: 2019-04-02
    Description: The purpose of this study is to develop a standard method for measuring modal abundances of glass in single agglutinates in the lunar regolith. Not only does agglutinitic glass increase in single agglutinates as clasts of older agglutinates get incorporated into newer agglutinates with increasing maturity, but it is in this glassy phase that nanophase superparamagnetic Fe metal originates as a result of reduction reactions during the agglutination process. We report the results of two sets of independent measurements using two different methods to determine the proportion of glass in single agglutinates. We have used polished grain mounts (PGM) of five hand-picked single agglutinates from Apollo 16 soil 61181. The ISI Scanning Electron Microscope (SEM) fitted with a high-resolution Backscattered Electron (BSE) detector was used to collect high-contrast BSE images of the agglutinates. Several images were collected to represent each single agglutinate. The contrast, brightness, and focus were adjusted to optimize each image collected. Histograms of the grayscale range for all images produced four 'peaks' corresponding to epoxy, glass, crystalline phases, and metal grains. We analyzed every grid point for 12 elements with a less than 1 micron electron beam using a CAMECA SX-50 electron probe microanalyzer (EPM). If any analysis was not within about 10% of the stoichiometry of a known lunar mineral, we considered that point to be nonmineralic. Our results show that there is a remarkable correspondence in the glass percentages obtained by the two methods. The EPM method may overestimate glass because secondary fluorescence from dusty clasts in agglutinitic glass can give the appearance of nonmineralic targets. The BSE method may underestimate glass because the diversity of compositions of agglutinitic glass may not be contained under one grayscale 'peak' during image analysis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 537-538
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  • 11
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    In:  Other Sources
    Publication Date: 2019-04-02
    Description: The origin of mesosiderites, which consist of approximately equal-weight proportions of Fe-Ni metal and silicates (gabbros, basalts, orthopyroxenites, dunites), remains an interesting and complex problem in meteoritics. There is general agreement that multiple impact events were probably involved in the formation of these brecciated stony-iron meteorites, but given the heterogeneity of mesosiderites, additional processes have been invoked to explain the unique and intricate textural and compositional makeup of mesosiderites. We conducted a series of shock recovery experiments to test the impact event(s) scenario. The results indicated significant similarities between the shocked analogs and many mesosiderites. We have compared our analogs with a suite of thin sections of Barea mesosiderite. I have conducted a series of flash heating experiments in which equal-weight proportions of gabbro and stainless steel (SS304) powders were compressed into small charges and heated under reducing conditions for short times. These experiments were used to bracket localized, peak postshock temperatures in our analog shots and to compare the mixing relations between the silicate and metal. The shock recovery experiments used porous metal-silicate powder starting mixtures, therefore our experiments are most analogous to an impact scenario where the target is an asteroidal regolith surface composed of a loose mixture of Fe-Ni metal and heterogeneous silicates. Analog experiments may really describe a secondary impact process similar to the late-stage, localized impact melting event. This leaves one of the crucial questions about mesosiderite genesis unanswered, namely what is the source of the Fe-Ni metal that is so intimately distributed in these meteorites?
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 524
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  • 12
    Publication Date: 2019-04-02
    Description: Martian orthopyroxenite ALH 84001 is unusual compared to other martian meteorites in its abundance of Mg-Fe-Ca carbonites. Becasue textural evidence indicates that these carbonates are undoubtedly of martian origin, we have undertaken stable isotopic studies to elucidate their origin by evaluating whether they represent primordial martian C that was outgassing from the mantle of Mars, or volatile additions to the ALH 84001 protolith that equilibrated with the martian atmosphere. If precipitation occurred in a closed system then the isotopic results are compatible with the observed chemical zonation. A unique temperature of formation can be calculated using the difference in C-13 and O-18 between the Fe and Mg carbonates, assuming that precipitation occurred at a constant temperature. Precipitation of approximately one-half of the CO2 reservoir at 320 C can account for the observed values, with the original CO2 reservoir having a delta C-13 of approximately 45% and delta O-18 of approximately 22%. If carbonate precipitated in equilibrium with a large isotopically homogeneous CO2 reservoir (open system), isotopic differences must be attributed to a change in temperature of at least several hundreds of degrees. This temperature change is compatible with a calculated range of temperatures based on carbonate geothermometry. Clearly, carbonate in ALH 84001 is in delta O-18 disequilibrium with orthopyroxene groundmass. Most likely, the carbonate precipitated from a fluid that equilibrated with the martian atmosphere. The deposits or fluids in equilibrium with these deposits were remobilized in the crust producing the carbonate in ALH 84001. This observation establishes a link for the first time between the atmospheric and lithospheric C and O pools that reside on Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 523
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  • 13
    Publication Date: 2019-04-02
    Description: The production rates of cosmogenic nuclides depend on the primary cosmic-ray particles, the irradiated-body's bulk composition, size, and shape, and the sample's composition and shielding depth. Although much work has been done on some of these dependencies, more detailed studies still need to be done on others. This work describes the influence of irradiation geometry on nuclide production in lunar rocks. In most cases, computer simulations of cosmogenic nuclide production were restricted to spherical objects irradiated with a 4 pi isotropic flux (meteoroids) or in lunar core samples irradiated by a 2 pi flux incident on semi-infinite layers or cylinders of huge sizes. Many lunar samples are rocks found on top of the lunar surface. For these rocks, neither of the above-mentioned models correspond to the real conditions. We present results of our simulations of cosmogenic nuclide production in models simulating the irradiation of rocks sitting on top of the lunar surface. The Galactic Cosmic Rays (GCR) production profiles in lunar rocks were calculated using the Los Alamos 3-D Monte Carlo LAHET Code System (LCS). The irradiated object was modeled as the union of a sphere with the radius of the Moon and a small hemisphere with radii varying from 10 to 100 g/sq cm simulating the lunar rock. These calculations for the production of cosmogenic nuclides in lunar rocks by GCR particle show that there are important differences between the results obtained by commonly used geometric irradiation models and the lunar-rock models presented. The steeper GCR production profiles for a rock could help to explain the poor agreement for Be-10 in rock 68815, where slab models give GCR profiles flatter than the observed profiles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 521
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  • 14
    Publication Date: 2019-04-02
    Description: Twenty-eight chondrules separated from Chainpur (LL3.4) were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by Instrumental Neutron Activation Analysis (INAA). Six, weighting 0.6-1.5 mg each, were chosen for Scanning Electron Microscopy (SEM)/Energy Dispersive X-ray (EDX) and high-precision Ce-isotopic studies. LL-chondrite-normalized (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) were found to be useful in categorizing them. Five chondrules (CH-16, -17, -18, -23, and -28) were in the range 0.5 less than (Mn/Fe)(sub LL) less than 1. 4 and 0.5 less than (Sc/Fe)(sub LL) less than 1.4. The sixth (CH-25) had (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) ratios of 0.40 and 8.1, respectively, and was enriched in the refractory lithophile elements Sc and Hf and the refractory siderophile element Ir by 2.7 and 4.4x LL abundances respectively. SEM/EDX of exterior surfaces of the chondrules showed they consisted of varying proportions of low- and high-Ca pyroxenes, olivine, glass, kamacite/taenite, and Fe-sulfides. Chromium-53/chromium-52 for the six chondrules and bulk Chainpur (WR) are presented. Chromium-54/chromium-52 is close to terrestrial and does not correlate with Mn/Cr. We provisionally ignore the possibility of initial Cr isotopic heterogeneities among the chondrules. Omitting both the CH-25 and WR data, a linear regression gives initial (Mn-53/Mn-55)(sub I) = 8 +/- 4 x 10(exp -6), corresponding to chondrule formation at Delta(t)(sub LEW) = -9 +/- 4 Ma prior to igneous crystallization of the LEW 86010 angrite. If initial (Mn-53/Mn-55)(sub 0) in the solar system were as high as approximately 4.4 x 10(exp -5) when Allende CAI formed, our data suggest Chainpur chondrules formed approximately 9 Ma later, in qualitative agreement with 'late' I-Xe formation ages for most Chainpur chondrules.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 512-513
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  • 15
    Publication Date: 2019-04-02
    Description: Angrite LEW 87051 consists of large olivine crystals set in a fine-grained groundmass that clearly represents a crystallized melt. A few olivines contain Ca-poor, Cr-rich cores that crystallized from a very different melt than the outer part of the crystals constituting the majority of olivine in LEW 87051. We evaluate a model in which the cores formed through fractional crystallization of one melt, then were incorporated into a different melt as xenocrysts, whereupon the original zoning patterns were modified by diffusion. Using a similar approach, we calculate zoning patterns for the cores that would result from perfect fractional crystallization, compare them with the observed zoning, and determine whether the differences could result from diffusive modification consistent with known diffusion rates for Ca, Mn, and Cr. Using distribution coefficients from the 1400 C, IW + 1 experiments, we computed CaO, Cr2O3, and MnO abundances in the hypothetical parent melt by inverting the olivine at the centers of the cores. We further assumed that the primary zoning profile for CaO is essentially unmodified, because the diffusion rate of Ca in olivine is slow. We carried out the fractional crystallization calculation until the calculated Ca content was that observed at break in zoning profiles at the outer edge of the core. We then normalized the distance of this calculated profile to the length of the observed profile in the olivine core and calculated profiles for MnO and Cr2O3. The CaO zoning profile agrees well with the observed profile. The observed MnO profile is slightly higher than the calculated profile near the edge. Diffusion calculations indicate that reversal of the general trend of primary zoning through diffusion would require that diffusion of Cr is 5-10x faster than that of Mn.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 503-504
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  • 16
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    Publication Date: 2019-04-02
    Description: Significant advances in the understanding of space weathering processes were recently reported. Submicroscopic iron blebs were produced in lunar simulant glass and natural terrestrial minerals by high-temperature reduction in controlled atmosphere furnaces. These experiments altered the samples' optical properties and microtextures so that they resembled those of extremely mature lunar soil. The results contributed to a revised model for natural reduction in the regolith. Subsequently, supporting results were obtained by reduction of lunar samples. Research to date has focused on reduction of three lunar surface components: basalt, pyroclastic glass, and mare soil. An extensive set of H reduction experiments with simulants has led to a detailed understanding of reaction mechanisms and kinetics. Reduction experiments using lunar basalt were recently conducted by Carbotek. Reduced samples from these test were analyzed. Reduction experiments on lunar glass 74220 were run at temperatures of 900-1100 C. Reduction efficiency of volcanic glass proved to be a function of the sample's FeO abundance and reaction temperature. We also reduced mare soil 75061 at temperatures of 900-1050 C. Partial reduction of FeO in olivine and pyroxene occurred, but was slower and less complete than reduction of ilmenite. Our experiments on simulants and lunar samples have indicated that the most readily reduced phases in the regolith are ilmenite and glass. Based on initial tests with simulants we proposed refinements to the accepted model for space weathering of the regolith. The impact of a micrometeoroid flash heats and melts and ejects from the impact point a small volume of soil that contains trapped solar wind H and C. Reduction occurs rapidly, while the melt volume is still in motion. When a droplet encounters unmelted soil, it envelopes cold mineral grains. The melt is chilled rapidly. Our analyses of experimentally reduced lunar basalt, glass, and mare soil support the proposed model for space weathering.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 500
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  • 17
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    Publication Date: 2019-04-02
    Description: The asteroid 4 Vesta, with its unique basaltic crust, remains a key mystery of planetary evolution. A localized olivine feature suggests excavation of subcrustal material in a crater or impact basin comparable in size to the planetary radius (R(sub vesta) is approximately = 280 km). Furthermore, a 'clan' of small asteroids associated with Vesta (by spectral and orbital similarities) may be ejecta from this impact 151 and direct parents of the basaltic achondrites. To escape, these smaller (about 4-7 km) asteroids had to be ejected at speeds greater than the escape velocity, v(sub esc) is approximately = 350 m/s. This evidence that large fragments were ejected at high speed from Vesta has not been reconciled with the present understanding of impact physics. Analytical spallation models predict that an impactor capable of ejecting these 'chips off Vesta' would be almost the size of Vesta! Such an impact would lead to the catastrophic disruption of both bodies. A simpler analysis is outlined, based on comparison with cratering on Mars, and it is shown that Vesta could survive an impact capable of ejecting kilometer-scale fragments at sufficient speed. To what extent does Vesta survive the formation of such a large crater? This is best addressed using a hydrocode such as SALE 2D with centroidal gravity to predict velocities subsequent to impact. The fragmentation outcome and velocity subsequent to the impact described to demonstrate that Vesta survives without large-scale disassembly or overturning of the crust. Vesta and its clan represent a valuable dataset for testing fragmentation hydrocodes such as SALE 2D and SPH 3D at planetary scales. Resolution required to directly model spallation 'chips' on a body 100 times as large is now marginally possible on modern workstations. These boundaries are important in near-surface ejection processes and in large-scale disruption leading to asteroid families and stripped cores.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 440-441
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  • 18
    Publication Date: 2011-08-24
    Description: We report on the observations of a number of quasi-dc electric field events associated with large-scale atmospheric weather formations. The observations were made by the electric field experiment onboard the San Marco D satellite, operational in an equatorial orbit from May to December 1988. Several theoretical studies suggest that electric fields generated by thunderstorms are present at high altitudes in the ionosphere. In spite of such favorable predictions, weather-related events are not often observed since they are relatively weak. We shall report here on a set of likely E field candidates for atmospheric-ionospheric causality, these being observed over the Indonesian Basin, northern South America, and the west coast of Africa; all known sites of atmospheric activity. As we shall demonstrate, individual events often be traced to specific active weather features. For example, a number of events were associated with spacecraft passages near Hurricane Joan in mid-October 1988. As a statistical set, the events appear to coincide with the most active regions of atmospheric weather.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A10; p. 19,475-19,483
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  • 19
    Publication Date: 2011-08-24
    Description: A radiation model, together with National Meteorological Center temperature observations, was used to compute daily net heating rates in the northern hemisphere (NH) for the Arctic late fall and winter periods of both 1988-1989 and 1991-1992 and in the southern hemisphere (SH) for the Antarctic fall and winters of 1987 and 1992. The heating rates were interpolated to potential temperature (theta) surfaces between 400 K and 2000 K and averaged within the polar vortex, the boundary of which was determined by the maximum gradient in potential vorticity. The averaged heating rates were used in a one-dimensional vortex interior descent model to compute the change in potential temperature with time of air parcels initialized at various theta values, as well as to compute the descent in log pressure coodinates. In the NH vortex, air parcels which were initialized at 18 km on November 1, descended about 6 km by March 21, while air initially at 25 km descended 9 km in the same time period. this represents an average descent rate in the lower stratosphere of 1.3 to 2 km per month. Air initialized at 50 km descended 27 km between November 1 and March 21. In the SH vortex, parcels initialized at 18 km on March 1, descended 3 km, while air at 25 km descended 5-7 km by the end of October. This is equivalent to an average descent in the lower stratosphere of 0.4 to 0.9 km per month during this 8-month period. Air initialized at 52 km descended 26-29 km between March 1 and October 31. In both the NH and the SH, computed descent rates increased markedly with height. The descent for the NH winter of 1992-1993 and the SH winter of 1992 computed with a three-dimensional trajectory model using the same radiation code was within 1 to 2 km of that calculated by the one-dimensional model, thus validating the vortex averaging procedure. The computed descent rates generally agree well with observations of long-lived tracers, thus validating the radiative transfer model.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D8; p. 16,677-16,689
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  • 20
    Publication Date: 2011-08-24
    Description: Statistically significant reductions of ozone compared to a climatological profile have been measured above the Observatoire de Haute Provence (OHP) in Southern France (43.9 deg N, 5.7 deg E) during the months of July and August, 1992. Lidar profiles of ozone, temperature and aerosols were recorded on 25 separate nights during that time. The change in the ozone profile is correlated with the presence of volcanic aerosols from the eruption of Mt. Pinatubo. The total ozone loss amounts to approximately a 10% reduction in the total ozone column over OHP.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 25; p. 2801-2804
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  • 21
    Publication Date: 2011-08-24
    Description: Spatial correlation among densely packed particles can substantially change their single-scattering properties, thus making questionable the applicability of the independent scattering approximation in calculations of light scattering by planetary regoliths. The same problem arises in geophysics in light scattering computations for snow, frosts, and bare soil. In this paper, we use a dense-medium light-scattering theory based on the introduction of the static structure factor to calculate asymmetry parameters of the phase function for densely packed particles with real refractive indices 1.31 and 1.66, approximating water ice and soil particles, respectively, and imaginary refractive indices 0, 0.01, and 0.3. For sparsely distributed, independently scattering grains, the calculated asymmetry parameters are always positive and always larger than those for densely packed particles. For densely packed grains, the asymmetry parameters may be negative but only for radius-to-wavelength ratios from about 0.1 to about 0.4. With decreasing particle size, the calculated asymmetry parameters tend to zero independently of the compaction state. In the geometrical optics regime, the asymmetry parameters for densely packed scatterers are positive and very close to those for independently scattering grains. These results may have important implications for remote sensing of the Earth and solid planetary surfaces. In particular, it is demonstrated that negative asymmetry parameters derived with some approximate multiple-scattering theories may be physically irrelevant and can be the result of using an inaccurate bidirectional reflection function combined with the ill-conditionally of the inverse scattering problem.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Quantitative Spectroscopy & Radiative Transfer (ISSN 0022-4073); 52; 1; p. 95-110
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  • 22
    Publication Date: 2011-08-24
    Description: A combined 3-dimensional circulation model and aerosol microphysical/transport model is used to simulate the dispersion of the Mt. Pinatubo volcanic cloud in the stratosphere for the first few months following the eruption. Radiative heating of the cloud due to upwelling infrared radiation from the troposphere is shown to be an important factor affecting the transport. Without cloud heating, cloud material stays mostly north of the equator, whereas with cloud heating, the cloud is transported southward across the equator within the first two weeks following the eruption. Generally the simulations agree with Total Ozone Mapping Spectrometer (TOMS), Advanced Very High Resolution Radiometer (AVHRR), and Stratospheric Aerosol and Gas Experiment (SAGE) satellite observations showing the latitude distribution of cloud material to be between about 20 deg S and 30 deg N within the first few months. Temperature perturbations in the stratosphere induced by the aerosol heating are generally 1-4 K, in the range of those observed.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 5; p. 369-372
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  • 23
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    Publication Date: 2011-08-24
    Description: Vertical ocean loading amplitudes are determined by analysis of IRIS geodetic Very Long Baseline Interferometry (VLBI) data. The 4 nearly diurnal (K(sub 1), P(sub 1), O(sub 1), Q(sub 1)) and 4 nearly semidiurnal (K(sub 2), S(sub 2), M(sub 2), and N(sub 2)) component amplitudes can be inferred from the data with accuracies of 1-2 mm. Uncertainties of total displacements can approach 1 cm. Empirically determined total displacements are considerably larger than the values calculated from two geophysical models. The Scherneck model is found to give a better representation of VLBI delay data than the model of Pagiatakis by about 3 mm in residuals at 6 sites. Empirical estimation of the ocean loading amplitudes reduces Chi squared by 3067 for the 96 additional degrees of freedom in a fit to 273,000 IRIS VLBI observations, and reduces the RMS residuals by 3 mm relative to a fit using the fixed Scherneck model. Vertical ocean loading amplitudes can thus be inferred from VLBI data at a level which improves the overall model, but detailed assessment of individual tidal components is presently obscured by incomplete modeling at the tidal frequencies.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 5; p. 357-360
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  • 24
    Publication Date: 2011-08-24
    Description: We use geodetic data from Very Long Baseline Interferometry (VLBI) to determine the pre- and postseismic velocities of two sites. We then place limits on variations in interseismic strain buildup. The 1987 and 1988 Gulf of Alaska earthquakes (each Ms = 7.6) broke the Pacific plate interior. During the earthquakes the Cape Yakataga site moved 78 mm toward southwest. During the 1989 Loma Prieta earthquake (Ms = 7.1) the Fort Ord site moved 48 mm toward north. Baselines (a) from Fairbanks to Cape Yakataga and (b) from Mojave to Fort Ord change at nearly the same rate before and after the earthquakes. Postseismic transients, which we determine from differences between post- and preseismic rates, are minor: at Cape Yakataga the transient is 3 +/- 4 mm in a postseismic interval of 23 months, and at Fort Ord the transient is 6 +/- 5 mm in 21 months. The slip beneath the Loma Prieta rupture needed to generate the Fort Ord transient is 0.22 +/- 0.19 m, one-tenth the coseismic slip (2 m). We analyze elastic lithosphere-viscous asthenosphere models to determine that the characteristic time describing exponential decay in deep fault slip is longer than 6 years. The VLBI measurements are consistent with uniform interseismic strain buildup. They disagree with fast postseismic rates caused by an asthenosphere with very low viscosity.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 5; p. 333-336
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  • 25
    Publication Date: 2011-08-24
    Description: Simultaneous profiles of aerosol backscatter ratio were measured over Lauder, New Zealand (45 deg S, 170 deg E) on the night of November 24, 1992. Instrumentation comprised two complementary lidar systems and a backscattersonde, to give measurements at wavelengths 351, 490, 532, and 940 nm. The data from the lidars and the backscattersonde were self-consistent, enabling the wavelength dependence of aerosol backscatter to be determined as a function of altitude. This wavelength-dependence is a useful parameter in radiative transfer calculations. In the stratosphere, the average wavelength exponent between 351 and 940 nm was -1.23 +/- 0.1, which was in good agreement with values derived from measured physical properties of aerosols.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 9; p. 789-792
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  • 26
    Publication Date: 2011-08-24
    Description: We present predictions of the signatures of magnetosheath particle precipitation (in the regions classified as open low-latitude boundary layer, cusp, mantle and polar cap) for periods when the interplanetary magnetic field has a southward component. These are made using the 'pulsating cusp' model of the effects of time-varying magnetic reconnection at the dayside magnetopause. Predictions are made for both low-altitude satellites in the topside ionosphere and for midaltitude spacecraft in the magnetosphere. Low-altitude cusp signatures, which show a continuous ion dispersion signature, reveal 'quasi-steady reconnection' (one limit of the pulsating cusp model), which persists for a period of at least 10 min. We estimate that 'quasi-steady' in this context corresponds to fluctuations in the reconnection rate of a factor of 2 or less. The other limit of the pulsating cusp model explains the instantaneous jumps in the precipitating ion spectrum that have been observed at low altitudes. Such jumps are produced by isolated pulses of reconnection: that is, they are separated by intervals when the reconnection rate is zero. These also generate convecting patches on the magnetopause in which the field lines thread the boundary via a rotational discontinuity separated by more extensive regions of tangential discontinuity. Predictions of the corresponding ion precipitation signatures seen by midaltitude spacecraft are presented. We resolve the apparent contradiction between estimates of the width of the injection region from midaltitude data and the concept of continuous entry of solar wind plasma along open field lines. In addition, we reevaluate the use of pitch angle-energy dispersion to estimate the injection distance.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); p. 8531-8553
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  • 27
    Publication Date: 2011-08-24
    Description: The electron cyclotron maser instability (CMI) driven by momentum space anisotropy (df/dp (sub perpendicular) greater than 0) has been invoked to explain many aspects, such as the modes of propagation, harmonic emissions, and the source characteristics of the auroral kilometric radiation (AKR). Recent satellite observations of AKR sources indicate that the source regions are often imbedded within the auroral acceleration region characterized by the presence of a field-aligned potential drop. In this paper we investigate the excitation of the fundamental extraordinary mode radiation due to the accelerated electrons. The momentum space distribution of these energetic electrons is modeled by a realistic upward loss cone as modified by the presence of a parallel potential drop below the observation point. On the basis of linear growth rate calculations we present the emission characteristics, such as the frequency spectrum and the emission angular distribution as functions of the plasma parameters. We will discuss the implication of our results on the generation of the AKR from the edges of the auroral density cavities.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); p. 8671-8686
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  • 28
    Publication Date: 2011-08-24
    Description: An analytical model of the bidirectional reflectance for optically semi-infinite plant canopies has been extended to describe the reflectance of finite depth canopies contributions from the underlying soil. The model depends on 10 independent parameters describing vegetation and soil optical and structural properties. The model is inverted with a nonlinear minimization routine using directional reflectance data for lawn (leaf area index (LAI) is equal to 9.9), soybeans (LAI, 2.9) and simulated reflectance data (LAI, 1.0) from a numerical bidirectional reflectance distribution function (BRDF) model (Myneni et al., 1988). While the ten-parameter model results in relatively low rms differences for the BRDF, most of the retrieved parameters exhibit poor stability. The most stable parameter was the single-scattering albedo of the vegetation. Canopy albedo could be derived with an accuracy of less than 5% relative error in the visible and less than 1% in the near-infrared. Sensitivity were performed to determine which of the 10 parameters were most important and to assess the effects of Gaussian noise on the parameter retrievals. Out of the 10 parameters, three were identified which described most of the BRDF variability. At low LAI values the most influential parameters were the single-scattering albedos (both soil and vegetation) and LAI, while at higher LAI values (greater than 2.5) these shifted to the two scattering phase function parameters for vegetation and the single-scattering albedo of the vegetation. The three-parameter model, formed by fixing the seven least significant parameters, gave higher rms values but was less sensitive to noise in the BRDF than the full ten-parameter model. A full hemispherical reflectance data set for lawn was then interpolated to yield BRDF values corresponding to advanced very high resolution radiometer (AVHRR) scan geometries collected over a period of nine days. The resulting parameters and BRDFs are similar to those for the full sampling geometry, suggesting that the limited geometry of AVHRR measurements might be used to reliably retrieve BRDF and canopy albedo with this model.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D5; p. 10,577-10,600
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  • 29
    Publication Date: 2011-08-24
    Description: We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and Ar-39-Ar-40 age dating. The ropy glasses have potassium rare earth elements phosphorous (KREEP)-like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith-derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component. Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine-grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a Ar-39-Ar-40 degassing age of 800 +/- 15 Ma. Measurements of 39-Ar-40-Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the Copernicus impact. Our new data reinforce this model. If these ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus site, a part of the Moon that has not been sampled directly.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 3; p. 323-333
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  • 30
    Publication Date: 2011-08-24
    Description: Geochemical profiles of surface units, impact, and volcanic features are studied in detail to determine the underlying structure in an area of extensive mare/highland interface, Sinus Amoris. This study region includes and surrounds the northeastern embayment of Mare Tranquillitatis. The concentrations of two major rock-forming elements (Mg and Al), which were derived from the Apollo 15 orbital geochemical measurements, were used in this study. Mapped units and deposits associated with craters in the northwestern part of the region tend to have correlated low Mg and Al concentrations, indicating the presence of Potassium (K)-Rare Earth Elements (REE)-Phosphorus (P) (KREEP)-enriched basalt. Found along the northeastern rim of Tranquillitatis were areas with correlated high Mg and Al concentration, indicating the presence of troctolite. Distinctive west/east and north/south trends were observed in the concentrations of Mg and Al, and, by implication, in the distribution of major rock components on the surface. Evidence for a systematic geochemical transition in highland or basin-forming units may be observed here in the form of distinctive differences in chemistry in otherwise similar units in the western and eastern portions of the study region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth, Moon, and Planets (ISSN 0167-9295); 64; 2; p. 165-185
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  • 31
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    Publication Date: 2011-08-24
    Description: The Global Positioning System (GPS) has become, in recent years, the main space-based system for surveying and navigation in many military, commercial, cadastral, mapping, and scientific applications. Better receivers, interferometric techniques (DGPS), and advances in post-processing methods have made possible to position fixed or moving receivers with sub-decimeter accuracies in a global reference frame. Improved methods for obtaining the orbits of the GPS satellites have played a major role in these achievements; this paper gives a personal view of the main developments in GPS orbit determination.
    Keywords: GEOPHYSICS
    Type: Satellite Orbits; Technical Panel on Satellite Dynamics (Meeting P1) of the COSPAR Plenary Meeting, 29th, Washington, DC, August 28-September 5, 1992 . A95-61505 (ISSN 0273-1177); 14; 5; p. (5)5-(5)15
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  • 32
    Publication Date: 2011-08-24
    Description: By the middle of the decade, several new Laser Geodynamic Satellites will be launched to join the current constellation comprised of the laser geodynamic satellite (LAGEOS) (US), Starlette (France), Ajisai (Japan), and Etalon I and II (USSR). The satellites to be launched, LAGEOS II and III (US & Italy), and Stella (France), will be injected into orbits that differ from the existing constellation so that geodetic and gravimetric quantities are sampled to enhance their resolution and accuracy. An examination of various possible tracking strategies adopted by the network of laser tracking stations has revealed that the recovery of precise geodetic parameters can be obtained over shorter intervals than is currently obtainable with the present constellation of satellites. This is particularly important in the planning of mobile laser tracking operations, given a network of permanently operating tracking sites. Through simulations, it is shown that laser tracking of certain satellite passes, pre-selected to provide optimal sky-coverage, provides the means to acquire a sufficient amount of data to allow the recovery of 1 cm station positions.
    Keywords: GEOPHYSICS
    Type: Satellite Orbits; Technical Panel on Satellite Dynamics (Meeting P1) of the COSPAR Plenary Meeting, 29th, Washington, DC, August 28-September 5, 1992 . A95-61505 (ISSN 0273-1177); 14; 5; p. (5)27-(5)33
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  • 33
    Publication Date: 2011-08-24
    Description: We use potential field calculations and solar magnetic observations during 1976 to 1993 to infer the evolution of interplanetary sector structure, coronal holes, and solar wind streams at heliographic latitudes ranging from 80 deg S to 80 deg N. The results are presented in the form of stackplots, which show long-lived patterns that rotate quasi-rigidly at rates determined by the photospheric distribution of nonaxisymmetric magnetic flux. The fastest wind streams and their coronal hole sources form slowly rotating patterns near the poles just after sunspot maximum but migrate to lower latitudes and tend to rotate at near-equatorial rates as sunspot activity declines.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A4; p. 6597-6608
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  • 34
    Publication Date: 2011-08-24
    Description: We present a generalization of earlier analysis of the motion of the heliospheric termination shock in response to heliospheric disturbances (Barnes, 1993) (paper 1), to allow jump conditions that include an energy sink at the shock front. The motivation for this study is that acceleration of the anomalous cosmic ray component may in fact represent such a sink. We have idealized the situation by assuming an infinitely thin shock parameterized by a quantity lambda(0 less than or equals lambda less than or equals 1), defined as the fraction of solar wind energy that is lost due to acceleration of the energetic particle component. If the sink is strong (consuming, say, 50% or more of the incident solar wind energy), the model leads to the following principal conclusions: (1) the shocked plasma would be much denser and cooler than in the standard gasdynamic case, thereby leading to more favorable conditions for direct observation of the shocked plasma; (2) the equilibrium shock position would be slightly farther (less than 10%) from the Sun than in the standard model; (3) as in the gasdynamic case, the shock would normally be in motion, so that the instantaneous position of the termination shock is not determined by interstellar conditions but by the recent history of the wind that has passed through the termination shock; and (4) the response of the shock to upstream disturbances would be similar to the response in the gasdynamic case, but the speed of the new termination shock would be somewhat smaller (probably by a f actor of 4 or less). We estimate that this speed is typically, approximately a few tens of kilometers per second corresponding to an inward or outward excursion of order of less than 1 to several AU, rather less than conventional estimates of several tens of AU.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A4; p. 6553-6560
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  • 35
    Publication Date: 2011-08-24
    Description: The speeds of 936 features in 673 coronal mass ejections have been determined from trajectories observed with the Solar Maximum Mission (SMM) coronagraph in 1980 and 1984 to 1989. The distribution of observed speeds has a range (from 5th to 95th percentile) of 35 to 911 km/s; the average and median speeds are 349 and 285 km/s. The speed distributions of some selected classes of mass ejections are significantly different. For example, the speeds of 331 'outer loops' range from 80 to 1042 km/s; the average and median speeds for this class of ejections are 445 and 372 km/s. The speed distributions from each year of SMM observations show significant changes, with the annual average speeds varying from 157 (1984) to 458 km/s (1985). These variations are not simply related to the solar activity cycle; the annual averages from years near the sunspot maxima and minimum are not significantly different. The widths, latitudes, and speeds of mass ejections determined from the SMM observations are only weakly correlated. In particular, mass ejection speeds vary only slightly with the heliographic latitudes of the ejection. High-latitude ejections, which occur well poleward of the active latitudes, have speeds similar to active latitude ejections.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A4; p. 6543-6552
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  • 36
    Publication Date: 2011-08-24
    Description: Evidence is presented for a new Jovian radio emission component in the frequency range from approximately 40 to approximately 200 kHz observed during the Ulysses-Jupiter outbound pass at high Jovian southern latitudes along the dusk terminator. The new radio component (referred to as sKOM) occurs in the same frequency range as the observed broadband kilometric (bKOM) radio emission, but its characteristics are distinctly different. It has the opposite polarization, is about 100 times weaker, and has a characteristically smooth intensity profile. It is consistently observed in the longitudinal range from approximately 120 degs to approximately 230 degs central meridian longitude, where the intermittent bKOM is often absent, and is found to originate in the Jovian magnetosphere about 5R(sub j) from Jupiter and at a latitude of about 35 deg S. Its observed right-hand circular polarization suggests that it is generated in the O mode in the source region.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A4; p. 6137-6144
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  • 37
    Publication Date: 2011-08-24
    Description: We propose a new type of telescope designed specifically for the lunar environment of high vacuum and low temperature. Large area UV-Visible-IR telescope arrays can be built with ultra-light-weight replica optics. High T(sub c) superconductors provide support, steering, and positioning. Advantages of this approach are light-weight payload compatible with existing launch vehicles, configurable large area optical arrays, no excavation or heavy construction, and frictionless electronically controlled mechanisms. We have built a prototype and will be demonstarting some of its working characteristics.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 14; 6; p. (6)137
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  • 38
    Publication Date: 2011-08-24
    Description: An observational approach to Planetary Sciences and exploration from Earth applies to a quite limited number of targets, but most of these are spatially complex, and exhibit variability and evolution on a number of temporal scales which lie within the scope of possible observations. Advancing our understanding of the underlying physics requires the study of interactions between the various elements of such systems, and also requires study of the comparative response of both a given object to various conditions and of comparable objects to similar conditions. These studies are best conducted in 'campaigns', i.e. comprehensive programs combining simultaneous coherent observations of every interacting piece of the puzzle. The requirements include both imaging and spectroscopy over a wide spectral range, from UV to IR. While temporal simultaneity of operation in various modes is a key feature, these observations are also conducted over extended periods of time. The moon is a prime site offering long unbroken observation times and high positional stability, observations at small angular separation from the sun, comparative studies of planet Earth, and valuable technical advantages. A lunar observatory should become a central piece of any coherent set of planetary missions, supplying in-situ explorations with the synoptic and comparative data necessary for proper advance planning, correlative observations during the active exploratory phase, and follow-up studies of the target body or of related objects.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 14; 6; p. (6)143-(6)158
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  • 39
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    Publication Date: 2011-08-24
    Description: The Space Exploration Initiative presents an opportunity to construct astronomical telescopes on the Moon using the infrastructure provided by the lunar outpost. Small automatically deployed telescopes can be carried on the survey missions, be deployed on the lunar surface and be operated remotely from the Earth. Possibilities for early, small optical telescopes are a zenith pointed transit telescope, a student telescope, and a 0.5 to 1 meter automatic, fully steerable telescope. After the lunar outpost is established the lunar interferometers will be constructed in an evolutionary fashion. There are three lunar interferometers which have been studied. The most ambitious is the optical interferometer with a 1 to 2 -km baseline and seven 1.5 aperture elements arranged in a 'Y' configuration with a central beam combiner. The Submillimeter interferometer would use seven, 5-m reflectors in a 'Y' or circular configuration with a 1-km baseline. The Very Low Frequency (VLF) array would operate below 30 mHz with as many as 100 elements and a 200-km baseline.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 14; 6; p. (6)123-(6)127
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  • 40
    Publication Date: 2011-08-24
    Description: The ultimate imaging resolution in the UV and photometric precision achievable with a small (less than 1-meter) telescope located on the Moon is considered. The imaging resolution and photometric precision that might be practically achieved when the effects of the Lunar environment and equipment limitations are accounted for is then suggested. Finally, the practicality of soft landing such a telescope on the moon is considered, along with suggestions of how it might be directly controlled by using astronomers without any significant permanent staff.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 14; 6; p. (6)115
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  • 41
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    Publication Date: 2011-08-24
    Description: The 21st century is likely to see the start of the manned exploration and settlement of the inner solar system. NASA's plans for this endeavor are focused upon the Space Exploration Initiative which calls for a return to the Moon, to stay, followed by manned missions to Mars. To execute these missions safely provides solar physics with both a challenge and an opportunity. As the past solar maximum has clearly demonstrated, the Sun, through the solar flare process, is capable of generating and accelerating to high energies large fluxes of protons whose cumulative dose to unprotected astronauts can be fatal. It will be the responsibility of solar physicists to develop an accurate physical description of the mechanisms of flare energy storage and release, and of particle acceleration and propagation through interplanetary space upon which to base a sound method of flare and energetic particle prediction.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 14; 6; p. (6)33-(6)42
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  • 42
    Publication Date: 2011-08-24
    Description: Oxygen production from a lunar rock has been experimentally demonstrated for the first time. A 10 g sample of high-Ti basalt 70035 was reduced with hydrogen in seven experiments at temperatures of 900-1050 C and pressures of 14.7-150 psia. In all experiments, water evolution began almost immediately and was essentially complete in tens of minutes. Oxygen yields ranged from 2.93 to 4.61% of the starting sample weight, and showed weak dependence on temperature and pressure. Analysis of the solid samples demonstrated total reduction of Fe(2+) in ilmenite and small degrees of reduction in olivine and pyroxene. Ti O2 was also partially reduced to one or more suboxides. Data from these experiments provide a basis for predicting the yield of oxygen from lunar basalt as well as new constraints on natural reduction in the lunar regolith.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; E5; p. 10,887-10,897
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  • 43
    Publication Date: 2011-08-24
    Description: Highly relativistic electron precipitation events (HRE's) can provide a major source of energy affecting mesospheric constituents and ionization. Based on satellite data, these events are most pronounced near the minimum of the solar sunspot cycle, increasing in intensity, spectral hardness, and frequency of occurrence as the solar cycle declines. Since such events can be sustained up to several days, their integrated effect in the mesosphere can dominate over those of other energy sources such as relativistic electron precipitation events (REP's) and auroral precipitation. The energy deposition data to be discussed and analyzed were obtained by rocket at Poker Flat, Alaska, in May 1990 during a modest HRE observed at midday near the peak of the sunspot cycle. Using a NASA two dimensional model, significant enhancement of OH and depletion of O3 at 75 +/- 10 km altitude from the measured radiation are found. Estimates of enhanced effects were made for more intense HRE events, as might be expected during solar minimum. By causing O3 depletion, the electron precipitation can also regulate the penetration of solar UV radiation, which could affect the thermal properties of the mesosphere.
    Keywords: GEOPHYSICS
    Type: ESA, Proceedings of the 11th ESA Symposium on European Rocket and Balloon Programmes and Related Research; p 209-212
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  • 44
    Publication Date: 2011-08-24
    Description: The ORBSIM program was developed for the accurate extraction of geophysical model parameters from Doppler radio tracking data acquired from orbiting planetary spacecraft. The model of the proposed planetary structure is used in a numerical integration of the spacecraft along simulated trajectories around the primary body. Using line of sight (LOS) Doppler residuals, ORBSIM applies fast and efficient modelling and optimization procedures which avoid the traditional complex dynamic reduction of data. ORBSIM produces quantitative geophysical results such as size, depth, and mass. ORBSIM has been used extensively to investigate topographic features on the Moon, Mars, and Venus. The program has proven particulary suitable for modelling gravitational anomalies and mascons. The basic observable for spacecraft-based gravity data is the Doppler frequency shift of a transponded radio signal. The time derivative of this signal carries information regarding the gravity field acting on the spacecraft in the LOS direction (the LOS direction being the path between the spacecraft and the receiving station, either Earth or another satellite). There are many dynamic factors taken into account: earth rotation, solar radiation, acceleration from planetary bodies, tracking station time and location adjustments, etc. The actual trajectories of the spacecraft are simulated using least squares fitted to conic motion. The theoretical Doppler readings from the simulated orbits are compared to actual Doppler observations and another least squares adjustment is made. ORBSIM has three modes of operation: trajectory simulation, optimization, and gravity modelling. In all cases, an initial gravity model of curved and/or flat disks, harmonics, and/or a force table are required input. ORBSIM is written in FORTRAN 77 for batch execution and has been implemented on a DEC VAX 11/780 computer operating under VMS. This program was released in 1985.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NPO-16671
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  • 45
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    Unknown
    In:  Other Sources
    Publication Date: 2011-08-24
    Description: The Four-D Global Reference Atmosphere program was developed from an empirical atmospheric model which generates values for pressure, density, temperature, and winds from surface level to orbital altitudes. This program can generate altitude profiles of atmospheric parameters along any simulated trajectory through the atmosphere. The program was developed for design applications in the Space Shuttle program, such as the simulation of external tank re-entry trajectories. Other potential applications are global circulation and diffusion studies; also the generation of profiles for comparison with other atmospheric measurement techniques such as satellite measured temperature profiles and infrasonic measurement of wind profiles. GRAM-88 is the latest version of the software GRAM. The software GRAM-88 contains a number of changes that have improved the model statistics, in particular, the small scale density perturbation statistics. It also corrected a low latitude grid problem as well as the SCIDAT data base. Furthermore, GRAM-88 now uses the U.S. Standard Atmosphere 1976 as a comparison standard rather than the US62 used in other versions. The program is an amalgamation of two empirical atmospheric models for the low (25km) and the high (90km) atmosphere, with a newly developed latitude-longitude dependent model for the middle atmosphere. The Jacchia (1970) model simulates the high atmospheric region above 115km. The Jacchia program sections are in separate subroutines so that other thermosphericexospheric models could easily be adapted if required for special applications. The improved code eliminated the calculation of geostrophic winds above 125 km altitude from the model. The atmospheric region between 30km and 90km is simulated by a latitude-longitude dependent empirical model modification of the latitude dependent empirical model of Groves (1971). A fairing technique between 90km and 115km accomplished a smooth transition between the modified Groves values and the Jacchia values. Below 25km the atmospheric parameters are computed by the 4-D worldwide atmospheric model of Spiegler and Fowler (1972). This data set is not included. GRAM-88 incorporates a hydrostatic/gas law check in the 0-30 km altitude range to flag and change any bad data points. Between 5km and 30km, an interpolation scheme is used between the 4-D results and the modified Groves values. The output parameters consist of components for: (1) latitude, longitude, and altitude dependent monthly and annual means, (2) quasi-biennial oscillations (QBO), and (3) random perturbations to partially simulate the variability due to synoptic, diurnal, planetary wave, and gravity wave variations. Quasi-biennial and random variation perturbations are computed from parameters determined by various empirical studies and are added to the monthly mean values. The GRAM-88 program is for batch execution on the IBM 3084. It is written in STANDARD FORTRAN 77 under the MVS/XA operating system. The IBM DISPLA graphics routines are necessary for graphical output. The program was developed in 1988.
    Keywords: GEOPHYSICS
    Type: MFS-28397
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  • 46
    Publication Date: 2011-08-24
    Description: MSIS is an empirical model of the thermosphere based on Mass Spectrometer and Incoherent Scatter data. It provides a description of atmospheric temperature, density, and composition for altitudes higher than 85 kilometers. There are coefficients in MSIS to account for yearly and daily variations, geodetic latitude and longitude, altitude, and solar activity. Variations due to magnetic storms are represented by three-hour magnetic ap indices. The MSIS model enables a more timely prediction of aeronomic densities for specific events, such as rocket flights. The database for this model is a comprehensive summary of rocket flight, satellite, incoherent scatter radar, grenade, and falling sphere measurements. Subsets of data were formed by random selection after sorting on altitude, latitude, time of day, etc. Curve fitting was done with four to five thousand data points at a time. The resulting coefficients are presented in subroutines which calculate thermospheric composition and temperature for a user-supplied position and time. MSIS is written in FORTRAN 77 for use with batch or interactive programs and has been implemented on a DEC VAX series computer operating under VMS 4.3 with a central memory requirement of approximately 25K of 8 bit bytes. MSIS is based on a 1977 thermosphere model and was last updated in 1987 to reflect the CIRA 1986 Neutral Thermosphere Model.
    Keywords: GEOPHYSICS
    Type: GSC-12989
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  • 47
    Publication Date: 2019-01-25
    Description: As described by Grun et al. the dust impact detector on the Ulysses spacecraft detected a totally unexpected series of dust streams in the outer solar system near the orbit of Jupiter. Five considerations lead us to believe that the dust streams emanate from the jovian system itself: (1) the dust streams only occur within about 1 AU of the jovian system, with the strongest stream being the one closest to Jupiter (about 550 R(sub J) away); (2) the direction from which they arrive is never far from the line-of-sight direction to Jupiter; (3) the time period between streams is about 28 (plus or minus 3) days; (4) the impact velocities are very high - mostly around 40 km s(exp -1); and (5) we can think of no cometary, asteroidal, or interstellar source that could give rise to the above four phenomena; such streams have never before been detected.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Workshop on the Analysis of Interplanetary Dust Particles; p 57-58
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  • 48
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 160-166 
    ISSN: 0044-2313
    Keywords: Tetraphosphorus tetraselenide, P4Se4 ; Tetraphosphorus triselenide, P4Se3 ; thermochemistry ; preparation ; structure, 31P-n.m.r. ; glass ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Results on P4Se4Preparation of P4Se4 from the elements yields always the β-modification of P4Se4. α-P4Se4 is obtained only with selenium deficient samples. However, it is also observed, when P4Se3 is annealed and then extracted with CS2. The insoluble part has the X-ray pattern of α-P4Se4. A reversible α-β transition is not observed. MAS-31P-NMR investigations on solid P4Se4 by Eckert et al. [2] reveal P2Se4/2 building units, which are, in view of our results, not dimer but linked to a polymeric network. Well-crystallized samples of β-P4Se4 are obtained only at measuring temperatures above 573 K. The structure is of monoclinic symmetry with the space group P21/n (a = 114.9, b = 729.0, c = 1211.0 pm, β = 120.80°).The reaction of α-P4Se3I2 with bis-(trimethyltin)selenide in CS2 at low temperature yields molecular α-P4Se4, which can be detected in solution by 31P-NMR spectroscopy. α-P4Se4 has D2d-symmetry like α-P4S4. It polymerizes at higher temperature. α-P4Se3I(SeSnMe3) and α-P4Se3(SeSnMe3)2 were observed in the course of this reaction, too. The analogous reaction of α-P4Se3I2 with bis-(trimethyltin)sulfide leads to comparable results.
    Notes: Bei der Synthese von P4Se4 aus den Elementen erhält man stets die aus der Literatur als β-P4Se4 bekannte Modifikation, nur mit einem Selenunterschuß wird α-P4Se4 erhalten, dessen Röntgenbeugungsmuster auch in getemperten P4Se3-Proben gefunden wird, nachdem man die löslichen Anteile extrahiert hat. Eine reversible-α-β-Umwandlung wird nicht beobachtet. MAS-31P-NMR-Messungen von Eckert et al. [2] zeigen, daß β-P4Se4 aus P2Se4/2-Einheiten aufgebaut ist, die nach unseren Untersuchungen allerdings nicht zu Dimeren verknüpft, sondern polymer vernetzt sind. β-P4Se4 kristallisiert störungsfrei nur oberhalb von 573 K mit monokliner symmetrie in der Raumgruppe P21/n (a = 1141,9 pm, b = 729,0 pm, c = 1211,0 pm, β = 120,80°).Die Reaktion von α-P4Se3I2 mit Bis-trimethylzinnselenid in CS2 bei tiefer Temperatur führt erstmals zum NMR-spektroskopischen Nachweis des molekularen α-P4Se4, das eine mit dem α-P4S4 vergleichbare D2d-Symmetrie besitzt und bei Temperaturerhöhung polymerisiert. Die bei der Reaktion eben-falls entstehenden Verbindungen α-P4Se3I(SeSnMe3) und α-P4Se3(SeSnMe3)2 können anhand der 31P-NMR-Daten nachgewiesen werden. Die analoge Reaktion von α-P4Se3I2 mit Bistrimethylzinnsulfid führt zu vergleichbaren Resultaten.
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  • 49
    ISSN: 0044-2313
    Keywords: Trigold manganese cluster ; (Ph3PAu)3Mn(CO)4 ; synthesis ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of (Ph3PAu)3Mn(CO)4Photolysis of (Ph3PAu)Mn(CO)5, Ph3PAuN3 and Ph3PAuNCO yields (Ph3PAu)3Mn(CO)4 (1). 1 crystallizes in the monoclinic space group P21/n with a = 1 031.3(1); b = 3 095.2(3), c = 3 386.3(3) pm; β = 97.58(3)°; Z = 8. The crystal structure contains two symmetry independent clusters 1 of the same geometry. Their inner core MnAu3 forms a rhombus with distances Mn—Au of about the same lengths between 258.4(4) and 262.0(4) pm. The distances Au—Au range from 276.6(2) to 281.3(2) pm. The bonding in 1 is discussed and compared with those of (Ph3PAu)3Co(CO)3 having the same total number of electrons but a tetrahedral framework.
    Notes: Photolyse einer Mischung von (Ph3PAu)Mn(CO)5, Ph3PAuN3 und Ph3PAuNCO in THF führt zur Bildung von (Ph3PAu)3Mn(CO)4 (1). 1 kristallisiert in der monoklinen Raumgruppe P21/n mit a = 1 031,3(1); b = 3 095,2(3), c = 3 386,3(3) pm; β = 97,58(3)°; Z = 8. Die Kristallstruktur enthält zwei symmetrieunabhängige Cluster 1 gleicher Gestalt, deren MnAu3-Gerüst die Struktur einer Raute mit nahezu gleich langen Mn—Au-Abständen zwischen 258,4(4) und 262,0(4) pm aufweist. Die Au—Au-Abstände liegen zwischen 276,6(2) und 281,3(2) pm. Die Bindungsverhältnisse in 1 werden diskutiert und mit denjenigen des Clusters (Ph3PAu)3Co(CO)3 mit gleicher Gesamtelektronenanzahl aber tetraedrischer Gerüststruktur verglichen.
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  • 50
    ISSN: 0044-2313
    Keywords: Silicate hydrate ; 1,1,4,4-tetramethylpiperazinium ; 1,4-dimethyl-1,4-diazoniabicyclo[2.2.2]octane ; 1,1-dimethylpiperidinium ; clathrate ; crystal structure ; double four-ring silicate anion ; hydrogen bonding ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: [TMPA]4[Si8O20] · 34 H2O und [DDBO]4[Si8O20] · 32 H2O sind Heteronetzwerk-Clathrate mit 1,1,4,4-Tetramethylpiperazinium (TMPA) und 1,4-Dimethyl-1,4-Diazoniabicyclo[2.2.2]octan (DDBO) Gastkationen[TMPA]4[Si8O20] · 34 H2O (1) und [DDBO]4[Si8O20] · 32 H2O (2) wurden durch Kristallisation aus wäßrigen Lösungen der entsprechenden quartären Alkylammoniumhydroxide und SiO2 erhalten. Die Kristallstrukturen wurden mittels Einkristallröntgenbeugung bestimmt. 1: Monoklin, a = 16,056(2), b = 22,086(6), c = 22,701(2) Å, β = 90,57(1)° (T = 210 K), Raumgruppe C2/c, Z = 4. 2: Monoklin, a = 14,828(9), b = 20,201(7), c = 15,519(5) Å, β = 124,13(4)° (T = 255 K), Raumgruppe P21/c, Z = 2. Die Polyhydrate sind strukturverwandte Wirt-Gast-Verbindungen mit dreidimensionalen Wirtstrukturen aus über Wasserstoffbrücken verknüpften oligomeren Anionen [Si8O20]8- und H2O-Molekülen. Die Silicat-Anionen haben eine würfelförmige Doppelvierring-Struktur und eine lokale Umgebung, die von 24 H2O-Molekülen und sechs Kationen (TMPA, [C8H20N2]2+, oder DDBO, [C8H18N2]2+) gebildet wird. Die Kationen befinden sich als Gastspezies in großen, unregelmäßigen, käfigartigen Hohlräumen. Untersuchungen mittels der 29Si-NMR-Spektroskopie und der Trimethylsilylierungsmethode haben gezeigt, daß die gesättigten Lösungen von 1 und 2 hohe Anteile an Doppelvierring-Anionen enthalten. Derartige Anionen sind auch in der gesättigten Lösung des Heteronetzwerk-Clathrats [DMPI]6[Si8O18(OH)2] · 48,5 H2O (3) mit 1,1-Dimethylpiperidinium-Kationen (DMPI, [C7H16N]+) als Gastspezies enthalten.
    Notes: [TMPA]4[Si8O20] · 34 H2O (1) and [DDBO]4[Si8O20] · 32 H2O (2) have been prepared by crystallization from aqueous solutions of the respective quaternary alkylammonium hydroxide and SiO2. The crystal structures have been determined by single-crystal X-ray diffraction. 1: Monoclinic, a = 16.056(2), b = 22.086(6), c = 22.701(2) Å, β = 90.57(1)° (T = 210 K), space group C2/c, Z = 4. 2: Monoclinic, a = 14.828(9), b = 20.201(7), c = 15.519(5) Å, β = 124.13(4)° (T = 255 K), space group P21/c, Z = 2. The polyhydrates are structurally related host-guest compounds with three-dimensional host frameworks composed of oligomeric [Si8O20]8- anions and H2O molecules which are linked via hydrogen bonds. The silicate anions possess a cube-shaped double four-ring structure and a characteristic local environment formed by 24 H2O molecules and six cations (TMPA, [C8H20N2]2+, or DDBO, [C8H18N2]2+). The cations themselves reside as guest species in large, irregular, cage-like voids. Studies employing 29Si NMR spectroscopy and the trimethylsilylation method have revealed that the saturated aqueous solutions of 1 and 2 contain high proportions of double four-ring silicate anions. Such anions are also abundant species in the saturated solution of the heteronetwork clathrate [DMPI]6[Si8O18(OH)2] · 48.5 H2O (3) with 1,1-dimethylpiperidinium (DMPI, [C7H16N]+) guest cations.
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  • 51
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 781-785 
    ISSN: 0044-2313
    Keywords: Oxothallate(III) ; Preparation ; Structure ; MAPLE ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Oxidation of Intermetallic Phases: K4{Na2[Tl2O6]} from NaTl and K2O2The hitherto unknown K4{Na2[Tl2O6]} was prepared in form of transparent, yellow single crystals from NaTl and KO1,08 (molar ratio 1:1.3; sealed Ag-cylinder; 450°C, 30 d). The structure determination (four-circle diffractometer, MoKα, 1 280 out of 1 523 Io(hkl), R = 5.75%, Rw = 4.58%) confirms the space group P21/c with a = 641.3 pm, b = 691.1 pm, c = 1188.5 pm, β = 95.69° and Z = 2. As characteristic building units of the structure there are doubles of tetrahedra of [Tl2O6] and [Na2O6]. The compound is isotypic with Cs6[In2O6] and Rb6[Tl2O6]. The Madelung Part of Lattice Energy, MAPLE, the Mean Fictive Ionic Radii, MEFIR, Effective Coordination Numbers, ECoN, and Charge Distribution, CHARDI, are calculated.
    Notes: Bisher unbekanntes K4{Na2[Tl2O6]} wurde durch Oxydation von NaTl mit KO1,08 (1:1,3; geschlossener Ag-Zylinder; 450°C; 30 Tage) in Form transparenter, gelber Einkristalle dargestellt. Die Strukturaufklärung (Vierkreisdiffraktometerdaten, MoKα, 1 280 von 1 523 Io(hkl), R = 5,75%, Rw = 4,58%) erfolgte in der Raumgruppe P21/c mit a = 641,3 pm, b = 691,1 pm, c = 1 188,5 pm, β = 95,69° und Z = 2. Charakteristisches Motiv sind über Kanten verknüpfte, von ihresgleichen „isolierte“ Tetraederdoppel [Tl2O6] und [Na2O6]. Die Verbindung ist isotyp zu Cs6[In2O6] und Rb6[Tl2O6]. Der Madelunganteil der Gitterenergie, MAPLE, die Mittleren fiktiven Ionenradien, MEFIR, Effektive Koordinationszahlen, ECoN, sowie die Ladungsverteilung, CHARDI, werden berechnet.
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  • 52
    ISSN: 0044-2313
    Keywords: Dilithium magnesium tetrachloride ; dilithium vanadium tetrachloride ; dilithium cadmium tetrachloride ; crystal structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal Structures of MgCrO4-type Li2VCl4 and Spinel-type Li2MgCl4 and Li2CdCl4The crystal structures of the ternary lithium chlorides Li2MCl4 (M = Mg, V, Cd) have been determined firstly by X-ray single-crystal experiments. Li2MgCl4 and Li2CdCl4 crystallize in an inverse spinel structure (space group Fd3m, Z = 8, a = 1 040.1(2) and 1 062.06(9) pm, structural parameters u = 0.25699(2) and 0.2550(1), R = 1.7 and 3.7% for 218 and 211 unique reflections). The Li—Cl distances of the tetrahedrally coordinated Li+ ions are significantly greater than calculated with Shannon's crystal radii ( 〉 238 ± 1 instead of 233 pm). Contrary to the results of X-ray powder data reported in the literature, Li2VCl4 crystallizes in the distorted spinel structure of MgCr2O4 type (space group F43m, Z = 8, a = 1 037.49(2) pm, R = 5.9% for 217 unique reflections). The decrease of the site symmetry of the octahedrally coordinated ions (V2+, Li+) from 3m to 3m resulting in contracted and widened tetrahedral M4 entities of the spinel structure is obviously caused by V—V metal - metal bonds (shortest V—V distance 366.2(7) pm).
    Notes: Die Kristallstrukturen der ternären Lithiumchloride Li2MCl4 (M = Mg, V, Cd) wurden mittels Röntgen-Einkristallmessungen bestimmt. Li2MgCl4 und Li2CdCl4 kristallisieren in einer inversen Spinell-Struktur (Raumgruppe Fd3m, Z = 8, a = 1 040,1(2) und 1 062,06(9) pm, Lageparameter u = 0,25699(2) bzw. 0,2550(1), R = 1,7 bzw. 3,7% bei 218 bzw. 211 symmetrieunabhängigen Reflexen). Die Li—Cl-Abstände der tetraedrisch koordinierten Li+-Ionen sind signifikant größer als erwartet ( 〉 238 ± 1 anstatt 233 pm). Li2VCl4 kristallisiert entgegen Literaturangaben in der verzerrten Spinell-Struktur des MgCrO4-Typs (Raumgruppe F43m, Z = 8, a = 1 037,49(2) pm, R = 5,9% bei 217 symmetrieunabhängigen Reflexen). Die Erniedrigung der Lage-Symmetrie der oktaedrisch koordinierten Ionen (V2+, Li+) von 3m nach 3m, die alternierend zu einer Kontraktion und einer Aufweitung der tetraedrischen M4-Baueinheiten der Spinell-Struktur führt, wird von V—V—Metall - Metall-Bindungen verursacht (kürzester V—V-Abstand 366,2(7) pm).
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  • 53
    ISSN: 0044-2313
    Keywords: Cobalt(III) complexes functionalized N2S2-macrocyclic ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of Cobalt(III) Complexes of 14-Membered cis- and trans-N2S2 Dibenzo Macrocycles with two Pendant Acetato GroupsThe isomeric fourteen membered macrocyclic ligands 6,7,9,15,16,18-hexahydrodibenzo[f,m][1,8]dithia[4,11]diazacyclotetradecine-8,17-diacetic acid-0.5-hydrate (H2L3), C22H26N2O4S2 · 0.5 H2O and 6,7,13,15,16,18-hexahydrodibenzo-[e,m][1,4]dithia[8,11]diazacyclotetradecine-14,17-diacetic acid-1.5-hydrate (H2L6), C22H26N2O4S2 · 1.5 H2O with cis- and trans-N2S2 donorsets and two pendant acetato groups form the stable complexes [Co(L3)]ClO4 · 2 H2O (1) and [Co(L6)]ClO4 · H2O (2). Co(III) is octahedrally coordinated herein to all six donor centers of the respective ligand. The macrocyclic rings are folded. The metal ions are located outside the macrocyclic cavity. The mean Co—N, Co—O and Co—S distances are 196, 190 and 224 pm, respectively.Crystal data: 1, monoclinic, space group C2/c, a = 3 797.7(9), b = 763.8(3), c = 2 207.0(7) pm, β = 123.17(2), Z = 8, 3 445 reflections, R(Rw) = 0.072(0.070); 2, monoclinic, space group C2/c, a = 3 197.1(6), b = 880.4(2), c = 1 890.6(4) pm, β = 112,19(3)°, Z = 8, 4 415 reflections, R(Rw) = 0.062(0.064).
    Notes: Die beiden isomeren Liganden 6,7,9,15,16,18-Hexahydrodibenzo[f,m][1,8]dithia[4,11]diazacyclotetradecin-8,17-diessigsäure-0,5-hydrat (H2L3), C22H26N2O4S2 · 0,5 H2O bzw. 6,7,13,15,16,18-Hexahydrodibenzo[e,m][1,4]dithia-[8,11]diazacyclotetradecin-14,17-diessigsäure-1,5-hydrat (H2L6), C22H26N2O4S2 · 1,5 H2O mit cis- bzw. trans-N2S2-Donorzentren im vierzehngliedrigen makrocyclischen Ring und zwei Acetat-Seitenketten bilden die stabilen Komplexe [Co(L3)]ClO4 · 2H2O (1) und [Co(L6)]ClO4 · H2O (2). CoIII ist jeweils von allen 6 Donorzentren der Liganden oktaedrisch umgeben. Die Liganden sind gefaltet. Die Metallatome liegen außerhalb der makrocyclischen Kavität.Kristalldaten: 1, monoklin, Raumgruppe C2/c, a = 3 797,7(9), b = 763,8(3), c = 2 207,0(7) pm, β = 123,17(2)°, Z = 8, 3 445 Reflexe, R(Rw) = 0,072(0,070); 2, monoklin, Raumgruppe C2/c, a = 3 197,1(6), b = 880,4(2), c = 1 890,6(4) pm, β = 112,19(3)°, Z = 8, 4415 Reflexe, R(Rw) = 0,062(0,064).
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  • 54
    ISSN: 0044-2313
    Keywords: Cesium disodium trihydroxide hexahydrate ; deuterated material ; neutron diffraction ; hydrogen bonding ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hydrates of Weak and Strong Bases. IX. Hydrogen Bonding in CsNa2(OD)3 · 6D2O: A Single-Crystal Neutron-Diffraction Study at 120 KThe title compound is the first hydrate of a ternary alkali hydroxide reported. Its structure is related to the hexagonal perovskites and at the same time shaped by a complex system of hydrogen bonds. In a previous X-ray structure analysis at room temperature of the isotypic undeuterated material, these had been characterized only insufficiently. Therefore a complete structure determination has now been performed on a perdeuterated single crystal using low-temperature neutron-diffraction data (Pca21, Z = 4; a = 13.86, b = 6.070, c = 12.41 Å at 120 K; 1 655 observed independent reflections, R = 0.027).
    Notes: Die Titelverbindung ist das erste beschriebene Hydrat eines ternären Alkalihydroxids. Ihre Struktur ist verwandt mit der der hexagonalen Perowskite und zugleich durch ein komplexes System von Wasserstoffbrücken geprägt. Dieses war in einer vorangegangenen Röntgenstrukturanalyse bei Raumtemperatur an der isotypen nicht deuterierten Substanz nur unzureichend charakterisiert worden. Daher wurde nun eine vollständige Strukturbestimmung an einem perdeuterierten Einkristall mit Tieftemperatur-Neutronenbeugungsdaten durchgeführt (Pca21, Z = 4; a = 13,86, b = 6,070, c = 12,41 Å bei 120 K; 1 655 beobachtete unabhängige Reflexe, R = 0,027).
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  • 55
    ISSN: 0044-2313
    Keywords: Lithiumtetrahydrogenorthoperiodate monohydrate ; crystal structure ; tetrahydrogenorthoperiodate Ion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Existence of the Tetrahydrogenorthoperiodate Ion. The Crystal Structure of LiH4IO6 · H2OThe crystal structure of LiH4IO6 · H2O has been determined (P1; a = 564.74(12), b = 574.41(13), c = 970.4(6) pm, α = 101.37(2), β = 96.37(2), γ = 114.72(2)°; Z = 2; 5 731 independent reflections; R = 0.038). All hydrogen-atoms were localized from difference fourier map and refined without applying constraints. Thus the existence of the tetrahydrogenorthoperiodate-ion in the solid state is proved, unambigously. The crystal structure is discussed and compared to other alkaliorthoperiodates.
    Notes: Die Kristallstruktur von LiH4IO6 · H2O wurde bestimmt (P1; a = 564,74(12), b = 574,41(13), c = 970,4(6) pm, α = 101,37(2), β = 96,37(2), γ = 114,72(2)°; Z = 2; 5 731 unabhängige Reflexe, R = 0,038). Alle Wasserstofflagen konnten aufgefunden und frei verfeinert werden und beweisen erstmals die Existenz des Tetrahydrogenorthoperiodations im Festkörper. Die Kristallstruktur wird diskutiert und mit denjenigen anderer Alkaliorthoperiodate verglichen.
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  • 56
    ISSN: 0044-2313
    Keywords: Sodium Tetrachlorotitanate(II) ; Synthesis ; Crystal Structure ; Magnetism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Crystal Structure and Magnetism of Sodium Tetrachlorotitanate(II), Na2TiCl4Na2TiCl4 is obtained as single crystals by metallothermic reduction of TiCl3 with sodium (525°C, 90 d, Ta container). Pure powder samples may be prepared by synproportionation of TiCl3 with Ti in the presence of NaCl (950-520°C, 21 d). The structure refinement from four-circle diffractometer data confirms that Na2TiCl4 is isotypic with Sr2PbO4 (orthorhombic, space group Pbam (No. 55), Z = 2 a = 694.2(1), b = 1 198.9(2), c = 385.6(1) pm, R = 0.055, Rw = 0,038). Ti2+ is surrounded by a distorted octahedron of Cl-. The octahedra are connected via common edges to chains, ∞1[TiCl2/1Cl4/2]2-, that run in the [001] direction. Magnetic susceptibility data were recorded in the 2 to 300 K temperature range at various field strengths. The interpretation of the data was carried out with the aid of crystal-field calculations taking magnetic interactions into account. The non-Curie behaviour of the reciprocal magnetic susceptibility of Ti2+ in Na2TiCl4 is due to the influence of spin-obit coupling.
    Notes: Na2TiCl4 entsteht in Form von Einkristallen bei der metallothermischen Reduktion von TiCl3 mit Na (525°C, 90 d, Ta-Ampulle). Reine Pulverproben von türkis-grünem Na2TiCl4 sind durch Synproportionierung von TiCl3 mit Titan in Gegenwart von NaCl zugänglich (950-520°C, 21 d). Die Strukturverfeinerung aus Vierkreis-Diffraktometer-Daten bestätigt, daß Na2TiCl4 im Sr2PbO4-Typ kristallisiert (orthorhombisch, Raumgruppe Pbam (Nr. 55), Z = 2, a = 694,2(1), b = 1 198,9(2), c = 385,6(1) pm, R = 0,055, Rw = 0,038). Ti2+ ist in Form eines verzerrten Oktaeders von Cl- umgeben. Die Oktaeder sind über gemeinsame Kanten zu Ketten ∞1[TiCl2/1Cl4/2]2- verknüpft, die längs [001] angeordnet sind. Die magnetische Suszeptibilität wurde im Bereich von 2-300 K bei verschiedenen Feldstärken bestimmt. Die Interpretation der Meßdaten erfolgte über Kristallfeld-Rechnungen unter Berücksichtigung magnetischer Wechselwirkungen. Das Nicht-Curie-Verhalten der reziproken magnetischen Suszeptibilität von Ti2+ in Na2TiCl4 ist auf den Einfluß der Spin-Bahn-Kopplung zurückzuführen.
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  • 57
    ISSN: 0044-2313
    Keywords: GdIII and SmIII octahedra complexes ; synthesis ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Complexes of the Lanthanoides with Bidentate Ligands. The Crystal Structures of [(C17H17N2)GdBr2(thf)2] and [(C17H17N2)3Ln] (L = Sm, Gd)Reaction of [(AIP)Li] with GdBr3 leads to a new mononuclear complex [(AIP)GdBr2(thf)2] 1. In contrast to this with SmI2 the compound [(AIP)3Sm] 2 is build up. Such complexes are also formed with Gd(OR*)3 (R* = OtBu2C6H3) and [(AIP)Li] in a 1:3 ratio, [(AIP)3Gd] 3. The structures of 1-3 were characterized by X-ray single crystal structure analysis (1: space group Pna21 (No. 33), Z = 4, a = 1 972.7(9) pm, b = 984.7(5) pm, c = 1 425.0(8) pm, α = β = γ = 90°; 2 · 2 THF: space group C2/c (No. 15), Z = 8, a = 3 644.4(9) pm, b = 1 437.5(5) pm, c = 2 334.4(7) pm, β = 1 21.07(6)°; 3: space group P2(1)/c (No. 14), Z = 4, a = 1 872.9(1) pm, b = 1 064.6(1) pm, c = 2 282.4(2) pm, β = 103.75(8)°).
    Notes: GdBr3 reagiert mit [(AIP)Li] zu dem einkernigen Komplex [(AIP)GdBr2(thf)2] 1. Mit SmI2 bildet sich dagegen überraschenderweise die Komplexverbindung [(AIP)3Sm] 2. Komplexe dieser Art bilden sich auch bei der Umsetzung von Gd(OR*)3 (R* = OtBu2C6H3) mit [(AIP)Li] im Verhältnis 1:3, [(AIP)3Gd] 3. Der Aufbau von 1-3 konnte durch Kristallstrukturanalyse geklärt werden (1: Raumgruppe Pna21 (Nr. 33), Z = 4, a = 1 972,7(9) pm, b = 984,7(5) pm, c = 1 425,0(8) pm, α = β = γ = 90°; 2 · 2 THF: Raumgruppe C2/c (Nr. 15), Z = 8, a = 3 644,4(9) pm, b = 1 437,5(5) pm, c = 2 334,4(7) pm, β = 1 21,07(6)°; 3: Raumgruppe P2(1)/c (Nr. 14), Z = 4, a = 1 872,9(1) pm, b = 1 064,6(1) pm, c = 2 282,4(2) pm, β = 103,75(8)°).
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  • 58
    ISSN: 0044-2313
    Keywords: MoIV ; GdIII ; Mo—Gd heterobimetallic complex ; X-ray structure analysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and structure of a Molybdenum-Gadolinium Heterometallic Complex. The Structure of [Li(thf)4]2[Cp2MoSGdBr4(thf)]2[Cp2MoHLi] reacts in THF with S and GdBr3 to yield the tetranuclear heterobimetallic complex [Li(thf)4]2[Cp2MoSGdBr4(thf)]2. The bonding situation and the structure of this compound were characterized by X-ray structure analysis (space group P1 (No. 2), Z = 1, a = 10.845(2) Å, b = 12.166(2) Å, c = 15.881(2) Å, α = 101.74(2)°, β = 97.62(2)°, γ = 103.97(2)°). Each S atom of the central Mo2S2-ring is coordinated by a GdBr4(thf) fragment. Additionally each Mo atom is connected to two Cp ligands. This leads to a tetrahedral coordination of the Mo atoms and a octahedral coordination of the Gd ions.
    Notes: [Cp2MoHLi] reagiert in THF mit S und GdBr3 zu dem vierkernigen Heterometallkomplex [Li(thf)4]2[Cp2MoSGdBr4(thf)]2. Die Bindungsverhältnisse und der Aufbau dieser Verbindung konnten durch eine Kristallstrukturanalyse geklärt werden (Raumgruppe P1 (Nr. 2), Z = 1, a = 10,845(2) Å, b = 12,166(2) Å, c = 15,881(2) Å, α = 101,74(2), β = 97,62(2)°, γ = 103,97(2)°). An den zentralen Mo2S2-Vierring koordiniert ein GdBr4(thf)-Fragment, so daß jedes Gd-Ion an sechs Liganden gebunden ist. Zusätzlich ist jedes Mo-Atom von zwei Cp-Liganden umgeben und erhält dadurch die Koordinationszahl 4.
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  • 59
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 833-838 
    ISSN: 0044-2313
    Keywords: Fluoromanganate(III) hydrates, Mn3F8 · 12H2O, AgMnF4 · 4 H2O ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Neue Fluoromanganat(III)-Hydrate: Mn3F8 · 12H2O and AgMnF4 · 4H2ODie Fluoridhydrate Mn3F8 · 12H2O und AgMnF4 · 4 H2O wurden in Form von Einkristallen hergestellt und durch Röntgenbeugungsmethoden charakterisiert. Mn3F8 · 12H2O kristallisiert in Raumgruppe P1 (a = 623.0(3), b = 896.7(4), c = 931.8(4) pm, α = 110.07(2)°, β = 103.18(2)°, γ = 107.54(2)°, Z = 1); AgMnF4 · 4 H2O kristallisiert in Raumgruppe P21/m (a = 700.9(2), b = 726.1(1), c = 749.4(3) pm, β = 107.17(3)°, Z = 2). Beide Strukturen enthalten Jahn-Teller-verzerrte [Mn(H2O)2F4]-Anionen und zeigen ein komplexes Wasserstoffbrücken-Netzwerk zwischen Anionen und Kationen, nämlich [Mn(H2O)6]2+ in der ersteren und einem polymeren [Ag(H2O)2]--Kation in der zweiten Verbindung.
    Notes: Single crystals of fluoride hydrates Mn3F8 · 12 H2O and AgMnF4 · 4 H2O have been prepared and characterized by X-ray methods. Mn3F8 · 12 H2O crystallizes in the space group P1 (a = 623.0(3), b = 896.7(4), c = 931.8(4) pm, α = 110.07(2)°, β = 103.18(2)°, γ = 107.54(2)°, Z = 1); AgMnF4 · 4 H2O crystallizes in the space group P21/m (a = 700.9(2), b = 726.1(1), c = 749.4(3) pm, β = 107.17(3)°, Z = 2). Both structures contain Jahn-Teller-distorted [Mn(H2O)2F4]- anions as well as crystal water molecules and exhibit a complex hydrogen bond network between anions and cations, i. e. [Mn(H2O)6]2+ for the first and a polymeric [Ag(H2O)2]- cation for the second compound.
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  • 60
    ISSN: 0044-2313
    Keywords: Single crystal structure ; Fluorzirkonates ; Fluorstannates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Crystal Structure of SmZrF7 with an Appendix on EuSnF7 and YSnF7SmZrF7 again was obtained as colourless single crystals and investigated by X-ray methods: It crystallizes in space group P 21/c-C2h5 (Nr. 14; P 21/n) with a = 1 140.9(2) pm, b = 574.6(1) pm, c = 914,4(2) pm, β = 107.32(2)°, Z = 4 but not in space group P 21-C22 (Nr. 4) [1]. In addition EuSnF7 and YSnF7 are isotypic with the following lattice constants: EuSnF7: a = 1 121.8(2) pm, b = 563.7(1) pm, c = 901.7(1) pm, β = 107.35(2)° with Z = 4; YSnF7: a = 1 106.7(2) pm, b = 556.4(1) pm, c = 884.7(1) pm, β = 107.51(1)° and Z = 4 (Powder data).
    Notes: SmZrF7 wurde erneut in Form farbloser Einkristalle dargestellt und röntgenographisch untersucht: Danach kristallisiert es in der Raumgruppe P 21/c-C2h5 (Nr. 14; Aufstellung P 21/n) mit a = 1 140,9(2) pm, b = 574,6(1) pm, c = 914,4(2) pm, β = 107,32(2)°, Z = 4, also nicht in der Raumgruppe P 21-C22 (Nr. 4) [1]. Aufgrund neuer Strukturrechnungen kristallisieren EuSnF7 und YSnF7 ebenfalls in der zentrosymmetrischen Raumgruppe P 21/c-C2h5 (Nr. 14) mit folgenden Gitterkonstanten für EuSnF7: a = 1 121,8(2) pm, b = 563,7(1) pm, c = 901,7(1) pm, β = 107,35(2)° mit Z = 4 sowie für YSnF7 a = 1 106,7(2) pm, b = 556,4(1) pm, c = 884,7(1) pm, β = 107,51(1)° und Z = 4 (Pulverdaten).
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  • 61
    ISSN: 0044-2313
    Keywords: Bis(fluorosulfonyl)difluoromethane ; gas-phase structure ; conformation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Die Gasphasen-Struktur von Bis(fluorosulfonyl)difluormethan, (SO2F)2CF2Es wird über neue Syntheseverfahren und das Infrarotspektrum von Bis(fluorsulfonyl) Difluormethan, (SO2F)2CF2 berichtet. Die geometrische Struktur und die Konformationseigenschaften dieser Verbindung wurden mittels der Elektronenbeugung an Gasen untersucht. Je nach Stellung der zwei SO2F Gruppen können vier Konformere mit unterschiedlichen Symmetrien auftreten: C2v Symmetrie, falls beide S—F Bindungen auf Lücke zu CF2 stehen, C2 oder Cs Symmetrie, falls eine S=O Bindung jeder SO2F Gruppe auf Lücke zu CF2 steht und C1 Symmetrie, falls eine S—F und eine S=O Bindung auf Lücke zu CF2 stehen. Die experimentellen Elektronenbeugungsintensitäten können mit einem C1 Konformeren oder mit einem Gemisch aus C2v, C2 und Cs Konformeren im Verhältnis 3:2:5 nahezu gleich gut angepaßt werden. Die folgenden geometrischen Parameter (ra Abstände und ∠α Winkel mit 3σ Fehlergrenzen) wurden erhalten: C—F = 1,340(6) Å, S=O = 1,412(2) Å, S—F = 1,550(3) Å, C—S = 1,848(4) Å, S—C—S = 113,6(7)°, F—C—F = 110,0(10)°, O=S=O = 124,6(18)°, C—S—F = 96,5(16)° und C—S=O = 108,4(14)°.
    Notes: New synthetic pathways and the infrared spectrum of bis(fluorosulfonyl)difluoromethane, (SO2F)2CF2, are reported. The geometric structure and conformational properties of the title compound have been studied by gas electron diffraction. Depending on the rotational position of the two SO2F groups, four conformers with different symmetries can occur in this compound: C2v symmetry, if both S—F bonds stagger the CF2 group. C2 or Cs symmetry, if one S=O bond of each group staggers the CF2 group. The experimental electron diffraction intensities can be fitted equally well with a C1 conformer or with a mixture of C2v, C2 and Cs conformers, in a ratio of 3:2:5. The following geometric parameters (ra distances, ∠α angles with 3σ uncertainties) were derived: C—F = 1.340(6) Å, S=O = 1.412(2) Å, S—F = 1.550(3) Å, C—S = 1.848(4) Å, S—C—S = 113.6(7)°, F—C—F = 110.0(10)°, O=S=O = 124.6(18)°, C—S—F = 96.5(16)° and C—S=O = 108.4(14)°.
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  • 62
    ISSN: 0044-2313
    Keywords: Chromium niobate ; chemical transport reactions ; block structure ; high resolution electron microscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Investigation of Inorganic Non-Stoichiometric Compounds. XLIII. Preparation and Electron Microscopic Investigation of (Cr, Nb)12O29Transport experiments in the system Cr/Nb/O yielded the compound (Cr, Nb)12O29 as crystalline green needles. The lattice parameters of the monoclinic cell are a = 31.162(8) Å, b = 3.8324(6) Å, c = 20.579(6) Å, β = 113.22(3)°. (Cr, Nb)12O29 is isotypic with monoclinic Nb12O29 as shown by Guinier diagrams and high resolution transmission electron microscopy. Characteristic structural building elements are [3 × 4]-blocks which are columnar sections from the ReO3 structure. In the real structure one finds numerous defects. Under the influence of the electron beam we observed reversible changes of contrast which indicates that the positions of the M-particles (M = Cr, Nb) have shifted.
    Notes: Grüne, nadelförmige Kristalle von monoklinem (Cr, Nb)12O29 entstanden bei Transportexperimenten im System Cr/Nb/O. Die Gitterparameter a = 31,162(8) Å, b = 3,8324(6) Å, c = 20,579(6) Å, β = 113,22(3)° aus Guinieraufnahmen zeigen ebenso wie Strukturabbildungen mit der hochauflösenden Durchstrahlungselektronenmikroskopie Isotypie zu monoklinem Nb12O29. Auf den Aufnahmen erkennt man als charakteristisches Bauelement [3 × 4]-Blöcke, säulenförmige Ausschnitte aus der ReO3-Struktur, sowie zahlreiche Baufehler. Reversible Veränderungen des Kontrastes unter der Einwirkung des Elektronenstrahls lassen auf Änderungen der M-Positionen (M = Cr, Nb) schließen.
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  • 63
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 847-850 
    ISSN: 0044-2313
    Keywords: Diorganoindium cations ; syntheses ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diorganoindium Cations. The Crystal Structure of [Mes2In][BF4](PhCH3)2In and Mes3In react with BF3 · OEt2 in a ratio of 3:4 at 80°C in toluene to the corresponding salts [R2In][BF4] [R = PhCH2 (1), Mes (2)]. The same results could be obtained, when the diorganoindium fluorides (PhCH2)2InF and Mes2InF were treated with BF3 · OEt2 at 80°C in toluene. 1 und 2 were characterized by NMR-, IR- und MS-techniques. The arrangement of the ions in 2 could be established by an X-ray structure determination. The cations and anions of 2 are forming infinite chains. The metal centers are coordinated by two BF4--ions, so that every In atom possesses a distorted octahedral coordination sphere.
    Notes: (PhCH2)3In und Mes3In reagieren mit BF3 · OEt2 im Verhältnis 3:4 bei 80°C in Toluol zu den entsprechenden Salzen [R2In][BF4] [R = PhCH2 (1), Mes (2)]. Zum selben Ergebnis gelangt man, wenn die Diorganoindiumfluoride (PhCH2)2InF und Mes2InF mit BF3 · OEt2 bei 80°C in Toluol behandelt werden. 1 und 2 wurden mittels NMR- und IR-Spektroskopie sowie Massenspektrometrie charakterisiert. Die Anordnung der Ionen in 2 konnte durch eine Röntgenstrukturanalyse aufgeklärt werden. 2 bildet danach unendliche Ketten aus Kationen und Anionen, wobei durch eine chelatartige Anordnung zweier BF4--Ionen an jedes Metallzentrum eine verzerrt oktaedrische Koordinationssphäre der Indiumatome resultiert.
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  • 64
    ISSN: 0044-2313
    Keywords: System lithium hydroxide/lithium iodide ; crystal structure of Li2I(OH) and Li5I(OH)4 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Li2I(OH): A Compound with Onedimensional Infinite Edge Sharing [Li4/2(OH)+] PyramidsThe pseudobinary system LiOH/LiI was investigated by X-ray methods. Two compounds, Li2I(OH) and Li5I(OH)4 exist. The structure of Li2I(OH) was solved by single-crystal data. For Li5I(OH)4 lattice constants and space group symmetry are given:Li2I(OH): Pnma, Z = 4, a = 10.339(4) Å, b = 5.567(1) Å, c = 6.643(2) Å, Z(Fo) mit (Fo)2 ≧ 3σ(Fo)2 = 439, Z (parameter) = 23, R/Rw = 0.030/0.040Li5I(OH)4: Pmmn or P21mn(= Pmn21), Z = 2, a = 10.42 Å, b = 5.30 Å, c = 5.81 ÅLi2I(OH) crystallizes in a new type of structure. The motif of a distorted hexagonal close-packed arrangement of iodide ions is penetrated by chains of ∞1[Li4/2(OH)+].
    Notes: Das pseudobinäre System LiOH/LiI wurde röntgenographisch untersucht. Es gibt zwei Verbindungen, Li2I(OH) und Li5I(OH)4. Die Struktur von Li2I(OH) wurde mittels Einkristallröntgenstrukturanalyse aufgeklärt, von Li5I(OH)4 konnte die Elementarzellmetrik und Symmetrie ermittelt werden:Li2I(OH): Pnma, Z = 4, a = 10,339(4) Å, b = 5,567(1) Å, c = 6,643(2) Å, Z(Fo) mit (Fo)2 ≧ 3σ(Fo)2 = 439, Z (Parameter) = 23, R/Rw = 0,030/0,040Li5I(OH)4: Pmmn oder P21mn(= Pmn21), Z = 2, a = 10,42 Å, b = 5,30 Å, c = 5,81 ÅLi2I(OH) kristallisiert in einem eigenen Strukturtyp, dem das Motiv einer verzerrten hexagonal dichtesten Anordnung von Iodidionen zugrunde liegt, die von Strängen aus ∞1[Li4/2(OH)+] durchdrungen wird.
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  • 65
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 479-482 
    ISSN: 0044-2313
    Keywords: System lithium amide/lithium bromide ; crystal structure of Li2Br(NH2) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Li2Br(NH2): The First Ternary Alkali Metal Amide HalideThe pseudobinary system LiNH2/LiBr was investigated by X-ray methods. The crystal structure of the compound Li2Br(NH2) was solved by single crystal data:Li2Br(NH2): Pnma, Z = 8, a = 12.484(2) Å, b = 7.959(1) Å, c = 6.385(1) Å, Z(Fo) with (Fo)2 ≧ 3σ(Fo)2 = 348, Z (parameter) = 51, R/Rw = 0.019/0.021Li2Br(NH2) crystallizes in a new type of structure. To one another isolated chains of ∞1[Li2Li4/2(NH2)22+] show the motif of closest rod packing. They are connected via bromide ions in a distorted cubic primitive arrangement.
    Notes: Das pseudobinäre System LiNH2/LiBr wurde röntgenographisch untersucht. Die Struktur einer Verbindung, Li2Br(NH2), wurde mittels Einkristallröntgenstrukturanalyse aufgeklärt:Li2Br(NH2): Pnma, Z = 8, a = 12,484(2) Å, b = 7,959(1) Å, c = 6,385(1) Å, Z(Fo) mit (Fo)2 ≧ 3σ(Fo)2 = 348, Z (Parameter) = 51, R/Rw = 0,019/0,021Die Verbindung kristallisiert in einem eigenen Strukturtyp. Von ihresgleichen isolierte Stränge aus ∞1[Li2Li4/2(NH2)22+] bilden eine dem Motiv nach dichteste Stabpackung. Bromidionen verknüpfen die Stäbe in verzerrt kubisch primitiver Anordnung.
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  • 66
    ISSN: 0044-2313
    Keywords: Dithiatetrazine ; synthesis ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Darstellung und Röntgenstrukturanalyse von 1,4,2,3,5,6-DithiatetrazinDie Umsetzung von Schwefeldichlorid mit sym-EtO2CNHNHCO2Et 1 ergibt S2[N(CO2Et)]4 2, das analytisch, durch NMR und röntgenographisch charakterisiert wird. Die Strukturanalyse von 2 zeigt, daß der S2N4-Ring Sessel-Konformation hat mit allen vier Estergruppen in pseudoaxialen Positionen. Die Bindungslängen und -winkel werden mit denen in 1 und S4(NR)2 verglichen.
    Notes: Reaction of sulfur dichloride with sym-EtO2CNHNHCO2Et 1 gives the title ring system which has been characterised by microanalyses, nmr, and X-Ray crystallography. The X-ray structure of S2[N(CO2Et)]4 2 reveals that the S2N4 ring adopts a chair conformation with all four ester groups in pseudo-axial positions. Bond lengths and angles are compared with 1 and S4(NR)2.
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  • 67
    ISSN: 0044-2313
    Keywords: o-1λ5,3λ5-Diphosphaphenylene-bis(diphenylphosphane) ; nickel(II) chloride chelate complex ; crystal structure ; NMR, Ir spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: o-1λ5,3λ5-Diphosphaphenylene-bis(diphenylphosphane) and its Chelating PropertiesBis(diphenylphosphanyl)acetylene and 1,1′,3,3′-tetrakis(dimethylamino)-1λ5,3λ5-diphosphete react at higher temperatures to yield the title compound 5, which forms easily the chelate complex 6 with nickel(II) chloride.
    Notes: Bis(diphenylphosphanyl)acetylen und 1,1′,3,3′-Tetrakis(dimethylamino)-1λ5,3λ5-diphosphet reagieren bei höheren Temperaturen zur Titelverbindung 5, die mit Nickel(II)-chlorid leicht den Chelatkomplex 6 bildet.
    Additional Material: 3 Ill.
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  • 68
    ISSN: 0044-2313
    Keywords: Thiooxalates ; 1,1-Dithiooxalate ; 1,1-Dithiooxalic ester ; transition metal complex ; Crystal structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,1-Dithiooxalic Acid Derivatives as Ligands in Transition Metal Complexes: Structure of O-Methyl-1,1-dithiooxalato-bis(triphenylphosphine)copper(I) and silver(I)Despite O-Alkyl-1,1-dithiooxalates are also tetradentate thioligands their tendency towards the formation of multi-nuclear bridged chelates as found for the basic 1,1-dithiooxalate does practically not exist because of derivatisation. The reaction with triphenylposphinemetal(I)-halogenides yields defined mono-nuclear mixed ligand complexes: O-Methyl-1,1-dithiooxalato-bis(triphenylphosphine)copper(I) (2) and silver(I) (1). X-ray analysis shows that both complexes (1 and 2) are isostructural and crystallize in the monoclinic space group P21/n: (Ph3P)2Ag(S2C2O2Me) (1) with a = 12.794(1), b = 21.314(4), c = 13.560(1) Å, β = 97.983(6)°, and (Ph3P)2Cu(S2C2O2Me) (2) with a = 12.622(1), b = 21.196(2), c = 13.426(1) Å, β = 96.533(7)°. These complexes are the first authentic examples of exclusively end-on coordinated thiooxalate.
    Notes: Obwohl potentiell auch vierzähnig, ist die Tendenz von O-Alkyl(bzw. Aryl)-1,1-dithio-oxalaten zur Ausbildung von Brücken in Mehrkern-Chelaten durch die Derivatisierung gegenüber dem Stammliganden 1,1-Dithiooxalat praktisch nicht mehr vorhanden. Durch Umsetzung mit Triphenylphosphinmetall(I)-halogeniden sind definierte einkernige Gemischtligandenkomplexe zugänglich. O-Methyl-1,1-dithiooxalato-bis(triphenylphosphin)kupfer(I) und -silber(I) konnten mittels Röntgenkristallstrukturanalyse strukturell gesichert werden. Beide Komplexe sind isostrukturell und kristallisieren in der monoklinen Raumgruppe P21/n: (Ph3P)2Ag(S2C2O2Me) (1), mit a = 12,794(1), b = 21,314(4), c = 13,560(1) Å, β = 97,983(6)° und (Ph3P)2Cu(S2C2O2Me) (2), mit a = 12,622(1), b = 21,196(2), c = 13,426(1) Å, β = 96,533(7)°. Diese beiden Komplexe sind die ersten strukturell gesicherten Vertreter mit ausschließlich end-on koordiniertem Thiooxalat.
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  • 69
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 505-508 
    ISSN: 0044-2313
    Keywords: O-methyl-1,1-dithiooxalate ; nucleophilic attack on dithiocarbon ; perthio ligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Surprising Reactions on O-Methyl-1,1-dithiooxalatesThe O-methyl-1,1-dithiooxalate ligand (i-dtoMe) reacts with metalII-acetylacetonates of d8 metal centers (NiII, PdII) forming mononuclear mixed ligand complexes with two remarkable aspects: The formation of a perthioligand, first time described for thiooxalates, and the first example of a nucleophilic attack of a CH-acidic compound (acetylacetonate) on dithiocarbon of coordinated dithiocompounds (here i-dtoMe). X-ray structure is shown for Ph4P[(ptoMe)Ni(i-dtoMeacac)].
    Notes: O-Methyl-1,1-dithiooxalat (i-dtoMe) reagiert mit Acetylacetonatkomplexen von d8-Metallen (NiII, PdII) unter Bildung von einkernigen Gemischtligandenkomplexen Ph4P[(ptoMe)M(i-dtoMeacac)] unerwarteter Konstitution. Durch Röntgenkristallstrukturanalyse des NiII-Komplexes konnte erstmals ein nukleophiler Angriff einer CH-aciden Verbindung (Acetylacetonat) am Dithiokohlenstoff einer koordinativ gebundenen Dithioverbindung (i-dtoMe) nachgewiesen werden.Gefunden wurde weiterhin die Entstehung einer Perthiogruppierung, die bisher für Thiooxalate bzw. deren Derivate unbekannt war.
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  • 70
    ISSN: 0044-2313
    Keywords: K2Fe[P2S6] ; Hexathiodiphosphate(IV) ; Hexathiohypodiphosphate ; Crystal Structure ; Magnetism ; Vibrational Spectrum ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese, Kristallstruktur, Magnetismus und Schwingungsspektrum von Dikaliumeisen(II)hexathiodiphosphat(IV), K2Fe[P2S6]K2Fe[P2S6] wurde aus den Elementen bei 1173 K in evakuierten, abgeschmolzenen Quarzampullen dargestellt. Die Verbindung bildet transparente, orangefarbene, luft- und feuchtigkeitsbeständige Kristalle. K2Fe[P2S6] kristallisiert monoklin, Raumgruppe P21/n (Nr. 14), mit den Gitterkonstanten (T = 298,5 K): a = 6,0622(4), b = 12,172(1) und c = 7,3787(8) Å, β = 101,113(7)°, Z = 2. Der neuartige Strukturtyp (mP22) wird durch Säulen von alternierend flächenverknüpften S6-Oktaedern und trigonalen Antiprismen (beide verzerrt) charakterisiert, die parallel zur a-Achse verlaufen und durch K+-Kationen (KZ 10; {2,6,2}-Polyeder; d(K—S) = 3,231 - 3,845 Å) miteinander verbunden sind. Die S6-Polyeder der Säulen werden alternierend durch Fe (d̄(Fe—S) = 2,577 Å) bzw. P2-Paare zentriert, die zur a-Achse um 73,4° geneigt sind. Die Bindungslängen in den Hexathiodiphosphat(IV)-Anionen [P2S6]4- mit angenäherter 32/m - D3d-Symmetrie betragen d(P—P) = 2,20 und d̄(P—S) = 2,02 Å. Die Titelverbindung ist oberhalb TN = 28 K paramagnetisch mit μ = 4,69 B.M. und ordnet unterhalb TN antiferromagnetisch. Die beobachteten inneren Moden der Raman- und Infrarotspektren von K2Fe[P2S6] stehen im Einklang mit der Faktorgruppenanalyse. Die Schwingungsbanden werden auf der Basis von [P2S6]4--Einheiten unter Berücksichtigung der Abweichungen von der D3d-Symmetrie zugeordnet.
    Notes: K2Fe[P2S6] was synthesized from the elements at 1173 K in sealed quartz tubes. The compound forms transparent orange crystals, stable against air and moisture. K2Fe[P2S6] crystallizes in the monoclinic system, space group P21/n (No. 14), with cell dimensions (T = 298.5 K) a = 6.0622(4), b = 12.172(1) and c = 7.3787(8) Å, β = 101.113(7)°, Z = 2. The novel structure type (mP22) is characterized by columns of alternating face-sharing S6 octahedra and trigonal antiprisms (both distorted) parallel to the a axis, which are interconnected by inserted K+ (CN 10; {2,6,2}-polyhedra; d(K—S) = 3.231 - 3.845 Å). The S6 polyhedra of the columns are centered alternately by Fe (d̄(Fe—S) = 2.577 Å) and P2 pairs which are inclined to the a axis by 73.4°. The bond lengths in the hexathiodiphosphate(IV) anions, [P2S6]4-, with approximate 3 2/m - D3d symmetry, are d̄(P—P) = 2.20 and d̄(P—S) = 2.02 Å. The compound is paramagnetic above TN = 28 K with μ = 4.69 B.M. and orders antiferromagnetically below TN. The internal modes of the observed Raman and FIR spectra of K2Fe[P2S6] are in accord with the factor group analysis, and the spectra are assigned on the basis of [P2S6]4- units, taking into account the deviation from D3d symmetry.
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