ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 2517-2521 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report measurements of dissociative electron attachment (DEA) to gaseous 5-bromouracil (BrU) for incident electron energies between 0 and 16 eV. Low energy electron impact on BrU leads not only to the formation of a long lived parent anion BrU−, but also various anion fragments resulting from endo- and exo-cyclic bond ruptures, such as Br−, uracil-yl anions, i.e., (U-yl)−, OCN−, and a 68 amu anion tentatively attributed to H2C3NO−. The incident electron energy dependent signatures of either the Br− and (U-yl)− yields (at 0, 1.4, and 6 eV), or the OCN− and H2C3NO− yields (at 1.6 and 5.0 eV) suggests competing DEA channels for anion fragment formation. The production cross sections, at 0 eV incident electron energy, for BrU−, Br−, and (U-yl)− are estimated to be about 6×10−15, 6×10−14, and 1.0×10−15 cm2, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes the design and tests of an ultrahigh vacuum apparatus built for the study of particle surface interactions, with emphasis on ion scattering experiments. The system was designed to provide facilities for angle resolved electron spectroscopy, ion scattering spectroscopy (ISS), Auger electron spectroscopy (AES), and ultraviolet photoelectron spectroscopy (UPS). It has provisions for photon spectroscopy and fixed angle time-of-flight (TOF) scattering and recoiling spectrometry. Mass selected ion beams in the energy range from a few eV to a few keV can be produced in a continuous or pulsed mode. Two independent, parallel plate tandem electrostatic analyzers, which can rotate around the sample are employed. The angular range spanned is analysis-type dependent and varies from 0° to 135°. One of the analyzers was designed for low energy secondary electron spectroscopy (0–100 eV) and the other one for ISS and AES measurements in the energy range from a few eV to 5 keV. The system disposes of a Czerny–Turner monochromator for optical spectroscopy in the visible. TOF analysis can be performed for 7° and 38° scattering angles and a flight length of 2.2 m. Alternatively, a large area detector set at 20 cm from the collision center allows TOF and charge fraction measurements over an angular range from 0° to 110°. We describe various tests of the different components of the apparatus and some results of experiments on ion scattering. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3940-3956 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present measurements of O− electron stimulated desorption yields obtained under identical experimental conditions from 0.15 monolayers (ML) of O2 deposited onto disordered substrates consisting of 4 ML of either Kr, Xe, C2H6, C2H4, N2O, CH3Cl, or H2O, all condensed on Pt (polycrystalline). The resulting O− yield functions, for incident electron energies below 20 eV, are compared to that obtained from the O2/Kr solid; this allows us to assess the order of magnitude effects of the local substrate environment on dissociative electron attachment (DEA) via the 2Πu and gas phase forbidden 2Σ+g,u resonances of O−2. We note that, in addition to electron energy losses in the substrate prior to DEA to O2 and post-dissociation interactions of the O− with the substrate molecules, charge or energy transfer from the O−2 transient anion to a substrate molecule, and capture of the incident electron into a dissociative anion resonance of the substrate molecule may contribute to a reduced O− yield from the physisorbed O2. In the case of O2 deposited on amorphous ice, we find that the O− signal from DEA to O2 is completely absent for electron energies below 14 eV; we attribute this to a complete quenching of the dissociative O−2(2Πu, 2Σ+) resonances by the adjacent water molecules.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2017-09-12
    Description: The so-called 8.2 ka event represents one of the most prominent cold climate anomalies during the Holocene warm period. Accordingly, several studies have addressed its trigger mechanisms, absolute dating and regional characteristics so far. However, knowledge about subsequent climate recovery is still limited although this might be essential for the understanding of rapid climatic changes. Here we present a new sub-decadally resolved and precisely dated oxygen isotope (δ¹⁸O) record for the interval between 7.7 and 8.7 ka BP (10³ calendar years before AD 1950), derived from the calcareous valves of benthic ostracods preserved in the varved lake sediments of pre-Alpine Mondsee (Austria). Besides a clear reflection of the 8.2 ka event, showing a good agreement in timing, duration and magnitude with other regional stable isotope records, the high-resolution Mondsee lake sediment record provides evidence for a 75-year-long interval of higher-than-average δ¹⁸O values directly after the 8.2 ka event, possibly reflecting increased air temperatures in Central Europe. This observation is consistent with evidence from other proxy records in the North Atlantic realm, thus most probably reflecting a hemispheric-scale climate signal rather than a local phenomenon. As a possible trigger we suggest an enhanced resumption of the Atlantic meridional overturning circulation (AMOC), supporting assumptions from climate model simulations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2016-11-25
    Description: Abstract
    Description: We investigated the sedimentary record of Lake Hancza (northeastern Poland) using a multi-proxy approach, focusing on early to mid-Holocene climatic and environmental changes. AMS 14C dating of terrestrial macrofossils and sedimentation rate estimates from occasional varve thickness measurements were used to establish a chronology. The onset of the Holocene at c. 11 600 cal. a BP is marked by the decline of Lateglacial shrub vegetation and a shift from clastic-detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation. Between 10 000 and 9000 cal. a BP, a further environmental and climatic improvement is indicated by the spread of deciduous forests, an increase in lake organic matter and a 1.7% rise in the oxygen isotope ratios of both endogenic calcite and ostracod valves. Rising d18O values were probably caused by a combination of hydrological and climatic factors. The persistence of relatively cold and dry climate conditions in northeastern Poland during the first one and a half millennia of the Holocene could be related to a regional eastern European atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the retreating Scandinavian Ice Sheet might have blocked the influence of warm and moist Westerlies and attenuated the early Holocene climatic amelioration in the Lake Hancza region until the final decay of the ice sheet.
    Language: English
    Type: Dataset , Dataset
    Format: 8 Datasets
    Format: application/xls
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0039-6028
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 6775-6782 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report electron stimulated desorption (ESD) measurements of O− yields produced by dissociative electron attachment (DEA) to physisorbed CO2. The molecules are condensed at about 17–20 K on polycrystalline Pt, either as pure multilayer films, or in submonolayer (ML) quantities onto thick rare gas substrates. For the pure disordered multilayer solids, we observe four peaks in the O− yield function at incident electron energies, E(e), of about 4.1, 8.5, 11.2, and 15 eV. The lowest two are assigned, respectively, to the 2Πu and 2Πg resonance states of CO−2, which dissociate into O−(2P)+CO(X 1Σ+), and are known to dominate the gas phase DEA O− production cross section for E(e)≤20 eV. Measurements of ESD CO* metastable yields from similar CO2 multilayer solids on Pt(111), also presented here, suggest that the 11.2 and 15 eV O− peaks are associated with the manifold of close-lying CO2*− states which dissociate into O−(2P)+CO* (a 3Π, a′ 3Σ+, or d 3Δ). For 0.15 ML of CO2 physisorbed on 20 ML thick rare gas substrate films significant sharp enhancements (fwhm ≤0.5 eV) are observed in the ESD O− yields at about 0.3–0.4 eV below the lowest substrate exciton energy. These enhancements are attributed to a coupling of the (electron plus exciton) core-excited anion resonances of the rare gas atoms to the dissociative Rydberg anion states of the coadsorbed CO2 at the solid's surface. This is followed by a transfer of the charge and excitation energy to the coadsorbate. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 0168-583X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 8635-8640 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Anion desorption stimulated by the impact of 0–20 eV electrons on O2/hydrocarbon mixed films is reported. It is shown that part of the H−, OH−, CH−, and CH2〈sup ARRANGE="STAGGER"〉− desorption yields from O2/hydrocarbon films is the result of reactive scattering of O− fragments produced via dissociative electron attachment (DEA) in the alkane and alkene thin films. These results support the interpretation that the DEA O− react with the hydrocarbon molecules to form a transient molecular anion complex which, in addition to autodetachment, may decay by dissociation into various anion and neutral fragments, and thus cause chemical modification of the solid. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...