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  • 1
    Monograph available for loan
    Monograph available for loan
    Singapore : World Scientific Publ.
    Call number: AWI A12-97-0207
    Type of Medium: Monograph available for loan
    Pages: X, 941 S.
    ISBN: 9810218680
    Series Statement: Advanced series in physical chemistry 3
    Branch Library: AWI Library
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 333 (1988), S. 310-310 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THERE has long been a popular belief that gallium arsenide (GaAs) will eventually replace silicon as the basic material for advanced integrated-circuit technology. The argument is usually based on the assumption that industry needs ever-faster electronic devices and the fact that gallium arsenide ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 1383-1391 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The collisional deactivation of vibrationally excited pyrazine (C4N2H4) in the electronic ground state by 19 collider gases was studied using the time-resolved infrared fluorescence (IRF) technique. The pyrazine was photoexcited with a 308 nm laser and its vibrational deactivation was monitored following rapid radiationless transitions to produce vibrationally excited molecules in the electronic ground state. The IRF data were analyzed by a simple approximate inversion method, as well as with full collisional master equation simulations. The average energies transferred in deactivating collisions (〈ΔE〉d) exhibit a near-linear dependence on vibrational energy at lower energies and less dependence at higher energies. The deactivation of ground state pyrazine was found to be similar to that of ground state benzene [J. R. Barker and B. M. Toselli, Int. Rev. Phys. Chem. 12, 305 (1990)], but it is strikingly different from the deactivation of triplet state pyrazine [T. J. Bevilacqua and R. B. Weisman, J. Chem. Phys. 98, 6316 (1993)]. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4953-4966 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recently, Kiefer et al. [J. H. Kiefer, S. S. Kumaran, and S. Sundaram, J. Chem. Phys. 99, 3531 (1993)] studied shock-heated norbornene (NB) in krypton bath gas using the laser-schlieren technique and observed vibrational relaxation, unimolecular dissociation (to 1,3-cyclopentadiene and ethylene), and dissociation incubation times. Other workers have obtained an extensive body of high-pressure limit unimolecular reaction rate data at lower temperatures using conventional static and flow reactors. In the present work, we have developed a vibrational energy transfer-unimolecular reaction model based on steady-state RRKM calculations and time-dependent master equation calculations to satisfactorily describe all of the NB data (incubation times, vibrational relaxation times, and unimolecular rate coefficients). The results cover the temperature range from ∼300 to 1500 K and the excitation energy range from ∼1 000 to 18 000 cm−1. Three different models (based on the exponential step-size distribution) for the average downward energy transferred per collision, 〈ΔE〉down were investigated. The experimental data are too limited to enable the identification of a preferred model and it was not possible to determine whether the average 〈ΔE〉down is temperature dependent. However, all three 〈ΔE〉down models depend linearly on vibrational energy and it is concluded that standard unimolecular reaction rate codes must be revised to include energy-dependent microcanonical energy transfer parameters. The choice of energy transfer model affects the deduced reaction critical energy by more than 2 kcal mol−1, however, which shows the importance of energy transfer in determining thermochemistry from unimolecular reaction fall-off data. It is shown that a single set of Arrhenius parameters gives a good fit of all the low temperature data and the shock-tube data extrapolated to the high pressure limit, obviating the need to invoke a change in reaction mechanism from concerted to diradical for high temperature conditions. Some possible future experiments are suggested. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2013-08-31
    Description: Several celestial objects, including UV rich regions of planetary and reflection nebulae, stars, H II regions, and extragalactic sources, are characterized by the unidentified infrared emission bands (UIR bands). A few years ago, it was proposed that polycyclic aromatic hydrocarbon species (PAHs) are responsible for most of the UIR bands. This hypothesis is based on a spectrum analysis of the observed features. Comparisons of observed IR spectra with lab absorption spectra of PAHs support the PAH hypothesis. An example spectrum is represented, where the Orion Bar 3.3 micron spectrum is compared with the absorption frequencies of the PAHs Chrysene, Pyrene, and Coronene. The laser excited 3.3 micron emission spectrum is presented from a gas phase PAH (azulen). The infrared fluorescence theory (IRF) is briefly explained, followed by a description of the experimental apparatus, a report of the results, and discussion.
    Keywords: SPACE RADIATION
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 151-156
    Format: application/pdf
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 1809-1817 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Collisional deactivation of highly vibrationally excited gas phase toluene-d8 and benzene-d6 pumped at 248 nm, has been investigated by monitoring the time resolved infrared fluorescence from the C–D stretch modes near 4.3 μm. For toluene-d8, energy transfer data were obtained for about 20 collider gases, including unexcited toluene-d8; for benzene-d6, only a few colliders were investigated. For both systems the data were analyzed by an inversion technique that converts the fluorescence decay to the bulk average energy, from which is calculated the average energy transferred per collision, 〈〈ΔE〉〉inv. Data obtained earlier for benzene-d0 were reanalyzed and the revised results are reported. Results for both normal and deuterated excited species show 〈〈ΔE〉〉inv to be nearly directly proportional to the vibrational energy 〈〈E〉〉inv of the excited molecule from 5 000 to 25 000 cm−1. However, for pure toluene-d8, benzene-d6, and a few other collider gases at high energies, the slope of the 〈〈ΔE〉〉inv vs 〈〈E〉〉inv curve is reduced and even becomes negative at sufficiently high energies. The results obtained for normal and deuterium-containing species are discussed in terms of possible quantum effects and mechanisms for energy transfer. In particular, it is considered likely that V–T/R energy transfer dominates over V–V, and the lowest frequency vibrational modes are the conduits for the energy transfer, in agreement with results for small molecules. Attention is called to a fundamental difference between classical and quantum statistics and how this difference may adversely affect classical trajectory simulations of large molecules.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The collisional loss of vibrational energy from gas-phase toluene, pumped by a pulsed KrF laser operating at 248 nm, has been observed by monitoring the time-resolved infrared fluorescence from the C–H stretch modes near 3.3 μm. The fragmentation quantum yield of toluene pumped at 248 nm was determined experimentally to be ∼6%. Energy-transfer data were obtained for 20 collider gases, including unexcited toluene, and analyzed by an improved inversion technique that converts the fluorescence intensity to the bulk average energy, from which is extracted 〈〈ΔE〉〉, the bulk average amount of energy transferred per collision. Comparisons are presented of these results with similar studies of benzene and azulene, and with the time-resolved ultraviolet absorption study of toluene carried out by Hippler et al. [J. Chem. Phys. 78, 6709 (1983)]. The present results show 〈〈ΔE〉〉 to be nearly directly proportional to the vibrational energy of the excited toluene from 5000 to 25 000 cm−1. For many of the colliders at higher energies, the energy dependence of 〈〈ΔE〉〉 is somewhat reduced. A simple method is described for obtaining good estimates of 〈ΔE〉d (the energy transferred per collision in deactivating collisions) by carrying out an appropriate least-squares analysis of the 〈〈ΔE〉〉 data. The values of 〈ΔE〉d are then used in master-equation calculations to investigate possible contributions from "supercollisions'' (in which surprisingly large amounts of energy are transferred) in the deactivation of toluene.
    Type of Medium: Electronic Resource
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