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  • International Union of Crystallography (IUC)  (21)
  • American Institute of Physics (AIP)  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    Quenching rate constants of excited halogen atoms in quartet states (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4876-4883 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Excited halogen atoms in quartet spin states F*(2p43s, 4P5/2), Cl*(3p44s, 4P5/2), and Br*(4p45s, 4P5/2) were produced from helium sensitized radiation chemical decomposition of SF6, CF3Cl, CF3Br, and CF2Br2. Quenching rate constants of these excited halogen atoms by simple gas molecules such as O2, N2, H2, CO, CO2, NO, NO2, N2O, CH4, C2H6, and Xe including parent molecules were determined from absorption decay curves at 685.8 nm for F*, 837.5 nm for Cl*, and 827.4 nm for Br*. The optical densities were assumed to be proportional to (number of excited atoms per one cubic centimeter)0.9. The quenching rate constants obtained here were compared to those reported of metastable rare-gas atoms and an excited oxygen atom O*(2p33s, 5S2), and further discussed in terms of several theoretical kinetic models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467207
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  • 2
    Electronic Resource
    Electronic Resource
    Branching ratios and bond dissociation energies from the excimer laser photolysis of group 6 metal carbonyls (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5471-5480 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photolysis of the group 6 (Cr, Mo, W) metal carbonyls in the gas phase, at excimer laser wavelengths, may lead to more than one primary product. Branching ratios between these products have been measured as a function of photolysis wavelength, buffer gas pressure, and temperature using time-resolved infrared spectroscopy. The results are modeled using a sequential dissociation mechanism in which branching ratios are determined by competition between unimolecular dissociation and collisional relaxation. The sensitivity of the results to thermochemical input parameters and assumptions concerning energy disposal mechanisms is discussed. Under qualified assumptions the branching ratio measurements provide estimates for CO bond dissociation energies for coordinatively unsaturated metal carbonyls. For Mo and W the individual bond dissociation energies are close to the average values but for Cr the first three ligands coordinated are significantly less strongly bound than the last three. This finding is discussed in terms of recent ab initio calculations on bonding in metal carbonyls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460482
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  • 3
    Electronic Resource
    Electronic Resource
    Quartet excited halogen atoms produced in the electron pulse irradiation of rare gases containing halogenated compounds (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 999-1005 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quartet excited halogen atoms F*(2p4 3s,4PJ), Cl*(3p4 4s,4PJ), Br*(4p4 5s,4PJ), and I*(5p4 6s,4PJ), where the J's are 5/2, 3/2, and 1/2, were found to be produced in the electron pulse irradiation of Ne or Ar containing one of SF6, CCl4, CClF3, CBrF3, CBr2F2, and CF3I. The population distribution ratios at the stage of production were 1.0(J=5/2):0.41(J=3/2):0.06(J=1/2) for F* in Ne containing SF6, 1.0(J=5/2):0.27(J=3/2):0.14(J=1/2) for Cl* in Ne containing CCl4, 1.0(J=5/2):0.29(J=3/2):0.2–0.3(J=1/2) for Br* in Ne containing CBr2F2, and 1.0(J=5/2):0.13(J=3/2):0.54(J=1/2) for I* in Ar containing CF3I. The observed ratios considerably differ from those calculated from the Boltzmann distribution law. F*(4P5/2), F*(4P3/2), and Cl*(4P5/2) are mainly produced by the reactions of lowest triplet excited diatomic molecules of neon with SF6 and CCl4. Cl*(4P3/2) and Cl*(4P1/2) are produced in a rapid process and deactivated into lower Cl*(4P5/2). Several reaction channels probably contribute to the formation of Br*(4PJ) and I*(4PJ). Rate constants for reactions of triplet excited diatomic molecules of neon or argon with these parent molecules were determined from observed absorption decay curves for Ne2* or Ar2* in the presence of parent molecules. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470700
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  • 4
    Electronic Resource
    Electronic Resource
    Reactions of highly excited oxygen atoms O(2p33s,5S) with simple gas molecules (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9094-9098 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electron pulse irradiation of 10 atm He containing one of CO, CO2, NO, NO2, or N2O at small amounts produced highly excited oxygen atoms O(2p33s,5S), which subsequently disappeared by their reactions with parent molecules. The rate constants have been determined from the absorption decay curves at 777.3 nm O(2p33p,5P)←O(2p33s,5S). The rate constants for the reactions of O(2p33s,5S) with Xe, H2, N2, CH4, and C2H6 could be determined in the irradiation of mixtures of He, O2, and these gases with electron pulses. The upper limit of a quenching rate constant was estimated for Kr. The observed rate constants showed good correlation with the quenching rate constants of Kr(4p55s,3P2) or Xe(5p56s,3P2) by the same gas molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463336
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  • 5
    Electronic Resource
    Electronic Resource
    Anisotropic spin fluctuations in the itinerant-electron ferromagnet MnP (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3400-3402 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The paramagnetic scattering cross section of the anisotropic metallic ferromagnet MnP has been measured up to the zone boundaries along the [100] and [010] directions perpendicular to the easy magnetization axis. The spectral shape functions in both directions are well fitted to a Lorentzian form at T=TC (290.5 K), 1.03TC, and 1.20TC except those close to the zone boundaries. Near TC the linewidth along [010] follows the dynamical scaling prediction for the isotropic ferromagnet Γ(q)∝q2.5. On the contrary, a unique q dependence, Γ(q)∝q3.2, along [100] was observed. However, these q dependencies deviate at small q(q〈0.1 A−1 along [100] and q〈0.02 A−1 along [010]), suggesting the existence of a residual linewidth of Γ0∼0.02 meV at q=0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338787
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  • 6
    Electronic Resource
    Electronic Resource
    Metalorganic chemical vapor deposition selective growth and characterization of InGaN quantum dots (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 950-952 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InGaN quantum dots (QDs) have been formed by metalorganic chemical vapor deposition selective growth on Si-patterned GaN/sapphire substrates. The QDs were fabricated on GaN plinths grown within nanoscale circular windows opened in the Si mask by both focused ion-beam irradiation and photoassisted wet chemical etching. Using this process, the epitaxial growth of GaN plinths could be achieved on an underlying GaN layer spared from process-induced damage. The optical properties of the InGaN QDs have been investigated by low-temperature cathodoluminescence measurements. Compared to the band-gap emission from a reference sample of InGaN/GaN multiple quantum wells, the evident blueshift of the emission peak from the InGaN QDs was demonstrated. This result suggests that the carriers in the InGaN QDs were three-dimensionally confined. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124564
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  • 7
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    Crystal structure of 6,7-dichloro-4-oxo-4H-chromene-3-carbaldehyde (2015)
    International Union of Crystallography (IUC)
    Details
    Publication Date: 2015-08-13
    Description: In the title compound, C10H4Cl2O3, a dichlorinated 3-formylchromone, the non-H atoms of the 4H-chromene ring are essentially coplanar (r.m.s. = 0.0188 Å), with the largest deviation from the least-squares plane [0.043 (2) Å] being for the pyran C=O C atom. The α,β-unsaturated carbonyl O atom deviates from the least-square plane by 0.124 (2) Å. The dihedral angle between the chromone and formyl least-square planes is 6.76 (3)°. In the crystal, molecules are linked through C—H...O hydrogen bonds between the translation-symmetry and inversion-symmetry equivalents to form tetrads, which are further assembled by stacking interactions [centroid–centroid distance between the benzene rings = 3.769 (2) Å]. van der Waals contacts are found between the Cl atoms at the 6-position and the Cl atoms at 7-position of the glide-reflection-symmetry equivalents [Cl...Cl = 3.4785 (16) Å, C—Cl...Cl = 160.23 (7)° and Cl...Cl—C = 122.59 (7)°].
    Keywords: crystal structurechromonehydrogen bondinghalogen–halogen contactstacking interaction
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography (IUC)
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  • 8
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    Crystal structure of 6-bromo-7-fluoro-4-oxo-4H-chromene-3-carbaldehyde (2015)
    International Union of Crystallography (IUC)
    Details
    Publication Date: 2015-06-28
    Description: In the title compound, C10H4BrFO3, a brominated and fluorinated 3-formylchromone derivative, all atoms are essentially coplanar (r.m.s. deviation of 0.025 Å for the non-H atoms), with the largest deviation from the least-squares plane [0.050 (6) Å] being for a benzene-ring C atom. In the crystal, molecules are linked through stacking interactions [centroid–centroid distance between the benzene and pyran rings = 3.912 (4) Å], C—H...O hydrogen bonds and short C...O contacts [2.865 (7) Å]. Unsymmetrical halogen...halogen interactions between the bromine and fluorine atoms [Br...F = 3.116 (4) Å, C—Br...F = 151.8 (2), C—F...Br = 154.1 (4)°] are also formed, giving a meandering two-dimensional network propagating in the (041) plane. A comparison with related structures is made and the various types of weak interactions are ranked in importance.
    Keywords: crystal structurechromonehydrogen bondinghalogen interaction
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography (IUC)
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  • 9
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    Crystal structure of 3-(hydroxymethyl)chromone (2015)
    International Union of Crystallography (IUC)
    Details
    Publication Date: 2015-06-20
    Description: In the title compound, C10H8O3 (systematic name 3-hydroxymethyl-4H-chromen-4-one), the fused-ring system is slightly puckered [dihedral angle between the rings = 3.84 (11)°]. The hydroxy O atom deviates from the heterocyclic ring by 1.422 (1) Å. In the crystal, inversion dimers linked by pairs of O—H...O hydrogen bonds generate R22(12) loops. The dimers are linked by aromatic π–π stacking [shortest centroid–centroid distance = 3.580 (3) Å], and C—H...O hydrogen bonds, generating a three-dimensional network.
    Keywords: crystal structurechromonehydrogen bondingπ–π stacking
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography (IUC)
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  • 10
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    Crystal structure of 4-oxo-4H-chromene-3-carboxylic acid (2015)
    International Union of Crystallography (IUC)
    Details
    Publication Date: 2015-07-18
    Description: In the title compound, C10H6O4, also known as 3-carboxychromone, the non-H atoms of the chromone ring are essentially coplanar (r.m.s. deviation = 0.0057 Å), with the maximum deviation from their least-squares plane [0.011 (2) Å] being for a pyran C atom. The dihedral angle between the fused ring and plane of the carboxy group is 3.06 (2)°. An intramolecular hydrogen bond is formed between the ring carbonyl O atom and the carboxy O—H atom, closing an S(6) loop. In the crystal, molecules are assembled by stacking interactions [centroid–centroid distance between the benzene and pyran rings = 3.844 (3) Å] and C—H...O hydrogen bonds, generating a three-dimensional network. Short contacts are also observed between the carboxy O and C atoms [C=O...C=O = 3.002 (3) Å].
    Keywords: crystal structurechromonehydrogen bondingstacking interaction
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography (IUC)
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