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  • 1
    Electronic Resource
    Electronic Resource
    Rotational analysis of the ν1 band of trichlorofluoromethane from high resolution Fourier transform and diode laser spectra of supersonic jets and isotopically enriched samples (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 8846-8853 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The spectrum of CCl3F (trichlorofluoromethane, CFC 11) has been measured in the region of the ν1 fundamental (1050–1120 cm−1) by high resolution interferometric Fourier-transform spectroscopy [0.004 cm−1 bandwidth full width at half maximum, apodized] and by diode laser spectroscopy (bandwidth 0.0008–0.0020 cm−1 FWHM) at room temperature, in cold cells and in supersonic jet expansions. Fourier-transform infrared and diode laser spectra of isotopically pure C35Cl3F have been recorded at room temperature in static cells. The C35Cl3F spectra allowed an analysis of the rotational structure to be started successfully for the first time. The rotational analysis of the isotopic species C35Cl237ClF and C35Cl37Cl2F, which are asymmetric rotors, was initiated from diode laser spectra of natural CCl3F with a rotational temperature of about 20 K (5% seeded in He) resulting from expansion in a supersonic pulsed slit jet. The rotational analysis yielded effective Hamiltonian constants including accurate band centers for the three most abundant isotopomers C35Cl3F (ν1=1081.2801 cm−1), C35Cl237ClF (ν1=1080.7330 cm−1), and C35Cl37Cl2F (ν1=1080.0663 cm−1), excited state rotational constants, and for C35Cl3F, quartic centrifugal distortion constants. The results are important for and discussed in relation to simulations of atmospheric absorption, line coincidences with CO2 lasers for sub-Doppler spectroscopy, as well as IR multiphoton excitation and infrared laser chemistry. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470073
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  • 2
    Electronic Resource
    Electronic Resource
    High resolution FTIR spectra of CDF3 in the CD stretching fundamental and overtone regions (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 34-39 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: FTIR spectra of 12CDF3 are reported at resolutions up to 0.006 cm−1 for the CD stretching fundamental and overtone transitions. For the band associated most closely with the CD stretching fundamental, the rotational J and K structure is largely resolved and analysis gives ν˜eff1=2261.2637 cm−1, A'=B'=0.329 5858 cm−1, C'=0.189 0758 cm−1, D'J=3.006×10−7 cm−1, DJK=−3.62×10−7 cm−1, and D'K=1.94×10−7 cm−1. (For further constants see Tables I and 2). The large value of B‘−B'=0.001 347 cm−1 is interpreted in terms of a strong Fermi resonance between ν1 and 2ν2 (symmetrical CF3 stretching vibration) with an effective two-state coupling constant ||k122||(approximately-equal-to)80 cm−1. Alternatives to this assignment are discussed and it is shown that the two-state coupling model is only part of a larger coupling scheme involving several states in addition to 2ν2. The rotational structure of the second Fermi resonance component shows severe perturbations for values of K〉33. Analysis of 157 assigned lines gives a band center at 2152.2796 cm−1, with unusual ΔB and ΔC values providing further evidence for multistate interactions. This interpretation is also supported by the structure of the CD overtone transition (2νeff1=4383.858 cm−1) and further evidence. The results are discussed in relation to Fermi resonances observed in CHF3 and substantial differences in vibrational redistribution involving the CH and the CD chromophores are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451609
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  • 3
    Electronic Resource
    Electronic Resource
    Structure and dynamics of the excited CH–chromophore in (CF3)3CH (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 1186-1194 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The absorption spectra of gaseous (CF3) 3CH (1,1,1,3,3,3-hexafluoro, 2-trifluoromethyl propane) were recorded in the IR between 800 and 12 000 cm−1 by high resolution interferometric Fourier transform techniques and in the visible from 12 000 to 17 000 cm−1 by laser photoacoustic spectroscopy. Instead of single bands in the CH overtone region, complex multiplet structures were observed. Thirty-nine bands were assigned as arising from the interacting CH-stretching and CH-bending manifolds, which account for most of the absorption in the overtone region. The results can be understood quantitatively with an effective, tridiagonal many-level Fermi resonance Hamiltonian. Close agreement is obtained for the positions and intensities of the observed spectral features using only seven spectroscopic parameters. The experimental and theoretical results are summarized in Tables II, III, and IV. The Hamiltonian can be used to calculate and understand the time-dependent redistribution of vibrational energy between the coupled CH-stretching and CH-bending vibrations. The role of broad vibrational band shapes and the possible exponential decay of CH excitation into a background of states from low-frequency vibrations is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448492
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  • 4
    Electronic Resource
    Electronic Resource
    Tridiagonal Fermi resonance structure in the vibrational spectrum of the CH chromophore in CHF3. II. Visible spectra (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 634-646 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The near IR and visible vibrational absorption spectra of CHF3 were recorded up to wave numbers of 17 500 cm−1 providing complete frequency coverage, together with paper I, from the low frequency fundamentals to the N=6 CH stretching–bending overtone multiplet. All strong bands in the high overtone spectra could be predicted and assigned by means of the tridiagonal Fermi resonance Hamiltonian, including a few combinations with intense CF3 stretching vibrations already observed for the low overtones. Improved vibrational Fermi resonance constants are presented on the basis of a fit to 35 assigned bands. An analysis of the rotational fine structure of the 2ν4 (E) overtone component and several Fermi resonance component bands result in values for αb and αs, which allow us to determine Be. In the high overtone bands no rotational fine structure is observed. The bands can be understood by introducing additional homogeneous rovibrational structures of phenomenological widths Γ≈1 to 10 cm−1. The results are discussed in relation to the separation of time scales for mode selective vibrational redistribution and further evolution. The overtone band strengths are reported and analyzed approximately with the empirical local Mecke dipole function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452318
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  • 5
    Electronic Resource
    Electronic Resource
    On the validity of the quasiresonant approximation for molecular infrared-multiphoton excitation (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3805-3812 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum dynamical calculations of the IR-multiphoton excitation of two molecular model systems are presented. One is an anharmonic oscillator and the other the rovibrational structure of the lowest three excitation steps in the stretching manifolds of the ozone molecule. Systematic comparisons are made between solutions using either the Floquet approximation or the weak field quasiresonant approximation (WF-QRA). The WF-QRA is shown to be adequate for typical transition moments in molecular many level systems and intensities up to the TW cm−2 range in agreement with previous analytical considerations. The implications of these findings for an efficient approach to the computational treatment of IR-multiphoton excitation and for the mechanism of molecular IR-multiphoton excitation as a series of stepwise one photon transitions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449143
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  • 6
    Electronic Resource
    Electronic Resource
    Fermi resonance structure in the CH vibrational overtones of CD3CHO (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3944-3951 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Gas-phase fundamental and CH and CO overtone spectra (700–17 500 cm−1) of 2,2,2-trideuteroacetaldehyde were recorded using FTIR and laser photoacoustic techniques. The Fermi resonance structure in the overtone spectra of the coupled CH stretching and in-plane CH bending vibrations is analyzed with a tridiagonal Hamiltonian, yielding a large effective coupling constant, ||k'sbb|| =93 cm−1, corresponding to subpicosecond redistribution times. No coupling between the out-of-plane CH bending mode and the Fermi resonance system is apparent. This study presents the first detailed analysis of the anharmonic couplings in the CH chromophore at an sp2 carbon atom. The in-plane CH bending vibration couples in a manner similar to the CH(sp3) bending vibrations, whereas the out-of-plane bending vibration is decoupled, similar to the CH(sp) bending vibrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455805
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  • 7
    Electronic Resource
    Electronic Resource
    Spectra and Dynamics of Coupled Vibrations in Polyatomic Molecules (1990)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 41 (1990), S. 839-874 
    Details
    ISSN: 0066-426X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pc.41.100190.004203
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  • 8
    Electronic Resource
    Electronic Resource
    Vibrational spectra of (HF)"2, (HF)"n and their D-isotopomers: Mode selective rearrangements and nonstatistical unimolecular decay
    Amsterdam : Elsevier
    Chemical Physics 139 (1989), S. 31-53 
    Details
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-0104(89)90003-7
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  • 9
    Electronic Resource
    Electronic Resource
    Statistical models for product energy distributions in bimolecular reactions with metastable intermediates
    Amsterdam : Elsevier
    Chemical Physics 51 (1980), S. 353-367 
    Details
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-0104(80)80110-8
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  • 10
    Electronic Resource
    Electronic Resource
    Primary photophysical processes in IR multiphoton excitation: Wavepacket motion and state selectivity
    Amsterdam : Elsevier
    Infrared Physics 25 (1985), S. 163-173 
    Details
    ISSN: 0020-0891
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0020-0891(85)90073-9
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