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  • 1
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1990)
    Springer
    Journal of molecular medicine 68 (1990), S. 396-396 
    Details
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01648578
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  • 2
    Electronic Resource
    Electronic Resource
    The spontaneous resonance Raman scattering of CH3I in a supersonic jet (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2806-2817 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The resonance Raman scattering of methyl iodide cooled in neat and seeded supersonic jets has been observed. The incident radiation is resonant with the X→B Rydberg transition (∼200 nm). To our knowledge this is the first reported observation of the resonance Raman scattering of jet-cooled species. Depolarization ratio measurements determine the rotational temperature of the molecular beam to be 10 K (4% CH3I/2 atm He). The only observed spectral evidence of (CH3I)n species (n≥2) in the cooled molecular beam is the appearance of the resonance Raman spectra of I2 produced by the photodecomposition of methyl iodide clusters. The nascent I2 is born with an extremely hot (∼1000 K) vibrational distribution. The excitation profile of the I2 vibrational resonance Raman scattering reveals that the absorption band of the clusters are much broader than that of the monomer. Semiempirical calculations (AM1) predict a CH3I dimer with a bent "heat-to-head'' ground-state equilibrium structure which is a favorable orientation for the production of I2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457927
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  • 3
    Electronic Resource
    Electronic Resource
    Subpicosecond predissociation dynamics of the methyl radical Rydberg 3 s state (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 270-276 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The subpicosecond dissociation dynamics of the methyl radical 3 s Rydberg state have been examined using rotational resonance Raman spectroscopy. The rovibronic dependence of the excited state predissociation rates and lifetimes are obtained for the B˜ state origin vibrational level of CH3 and CD3. Analysis of the tunneling rates using a cubic potential barrier yields estimates for the height (2200 cm−1) and position of the barrier along the dissociation coordinate (1.38 A(ring)). A comparison of the potential energy surface parameters for the Rydberg 3 s states of methyl radical and ammonia is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460394
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  • 4
    Electronic Resource
    Electronic Resource
    An experimental study of radiation-induced pure dephasing: ArF excited emission of O2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8605-8615 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effects of incoherent incident light on both nonresonant and resonant secondary radiation (RSR) are demonstrated for the spontaneous emission of O2. ArF excimer radiation (FWHH∼120 cm−1) is resonant with several rovibronic features of the v'=4 band of the Schumann–Runge absorption system. Off-resonant contributions to the RSR spectrum are Raman-like (v‘=1) but carry the linewidth of the incident incoherent radiation. Purely resonant emission features are found to be entirely fluorescence-like (v‘≥6). Other RSR vibrational bands of O2 exhibit contributions of both types of emission including interferences between Raman (off-resonant) and fluorescence (resonant) amplitudes. The observed depolarization ratios also reflect these various emission characters. The RSR spectra of O2 excited by incoherent (ArF) driving fields are contrasted with that due to monochromatic excitation. Convolution of the incident spectral density with a rovibronic Kramers–Heisenberg irreducible tensor treatment of resonance Raman scattering cross sections is shown to capture all the observed RSR emission characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459247
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  • 5
    Electronic Resource
    Electronic Resource
    Depolarization ratios of resonance Raman scattering in the gas phase (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4125-4143 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: All three scattering invariants, isotropic, antisymmetric, and anisotropic, contribute to the resonance Raman (RR) activity of randomly oriented gas phase scatterers as shown in a sum-over-all-rovibronic-states approach regardless of the symmetry of the vibrational transition. Thus, in the gas phase, totally symmetric modes may have Raman depolarization ratios (ρ)〉3/4 and nontotally symmetric modes may have ρ≠3/4 for resonance excitation frequencies. Large ρ dispersion effects are predicted when the RR scattering cross section is dominated by the contribution of a single vibronic band. The extent of this purely rotational effect sensitively depends on the excitation frequency and the resonant dephasing rate. These depolarization ratio effects are demonstrated by the resonance Raman scattering of CH3I (B state) and NH3, ND3 (A state) for both a and e vibrational bands as well as for J (NH3) and K (CH3I) resolved rovibrational features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455771
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  • 6
    Electronic Resource
    Electronic Resource
    The vibronic theory of resonance hyper-Raman scattering (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 7287-7294 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The intensities of vibrational resonance hyper-Raman transitions are developed in the usual framework of vibronic theory. In analogy to linear Raman scattering, the leading terms of RHR scattering, A, B, and C, are found when the electronic transitions moments, appearing in the transition hyperpolarizability, are expanded to first order in nuclear coordinate dependence. Noncentrosymmetric molecules are predicted to be the strongest nonlinear scatterers and derive activity from the RHR A term. In contrast to the vibronic analysis of linear Raman scattering, both one and two-photon allowed transitions contribute to RHR scattering cross section at the same order of vibronic theory (B term) for centrosymmetric molecules. RHR scattering spectra of gas phase CH3I, NH3, and CS2 illustrate A- and B-term RHR activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454339
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  • 7
    Electronic Resource
    Electronic Resource
    Rotational hyper-Raman excitation profiles: Further evidence of J-dependent subpicosecond dynamics of NH3 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4692-4699 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonance hyper-Raman (RHR) excitation profiles of rovibrational transitions of NH3 are observed as the incident blue radiation is tuned through two-photon resonance with the v‘2 =2 and v‘2 =3 bands of the UV X→A Rydberg transition. The excitation frequency dependence of the rotationally resolved HREPs are fit by our previously derived intensity expressions [L. D. Ziegler et al., J. Chem. Phys. 87, 4498 (1987)]. These fits to theory reveal J-dependent photodissociation rates for both vibronic bands on the A state surface that correspond to subpicosecond lifetimes. The rotationally assisted dynamical effects are consistent with the previous results of linear rotational Raman excitation profile studies and with an adiabatic centrifugal mechanism which couples rotational motion with the photodissociative reaction coordinate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455663
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  • 8
    Electronic Resource
    Electronic Resource
    Resonance rotational hyper-Raman scattering intensities of symmetric top molecules (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4498-4509 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonance rotational hyper-Raman scattering cross sections excited by identical linearly polarized incident photons are derived for symmetric tops. In the absence of pure dephasing, the rotational structure of a RHR vibrational transition is described, in general, by five scattering invariants which are derived in an irreducible tensor framework. The pattern of relative rotational RHR intensities is a sensitive function of the two-photon resonant vibronic state dephasing constant. High quality rotational RHR spectra of NH3 are obtained using blue incident radiation at half the X˜→A˜ transition energy. Fits to the observed patterns of relative rotational RHR intensities determine lifetimes of 38, 60, and 100 fs for the v′2 =1,2,3 A˜ state vibronic bands respectively. Although seven rotational branches (N,O,P,Q,R,S,T) are possible in HR, only three (P,Q,R) are observed in these RHR spectra of ammonia due to the magnitude and relative signs of vibronic matrix elements in the scattering cross section expressions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452863
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  • 9
    Electronic Resource
    Electronic Resource
    Rovibrational Raman scattering of CH3I vapor: Resonance with a perpendicularly polarized electronic transition (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4115-4124 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Raman scattering due to resonance with a perpendicularly polarized electronic transition of a symmetric top molecule in the gas phase is described in a sum-over-all-states approach. The derived intensity and depolarization ratio expressions in an irreducible two-photon tensor basis are applied to the analysis of the ν2 (a1 ) and ν6 (e) bands of CH3 I derived from resonance with the predissociated X→B absorption system. A lifetime of 0.5±0.1 ps is determined for the electronic origin and several K-specific rovibronic levels of the v'6 =1 band of the resonant excited state. These results are contrasted with recent dynamical interpretations of the corresponding jet-cooled CH3 I absorption spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455770
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  • 10
    Electronic Resource
    Electronic Resource
    Rotational Raman excitation profiles of symmetric tops: Subpicosecond rotation dependent lifetimes in the A˜ state of ammonia (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1703-1714 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The analysis of Raman excitation profiles of rotational scattering transitions is shown to be a sensitive measure of rotationally specific intramolecular dynamics in the subpicosecond time regime. O, P, Q, R, and S Raman REPs of ammonia are reported and theoretically treated using previously derived resonance rotational scattering intensity expressions. Resonance rovibrational Raman spectra are obtained with UV Raman excitation continuously resonant with the v'2 =2 vibronic band (207–210 nm) of the NH3 X˜ → A˜ absorption spectrum. The resulting REP analysis reveals that the rates of photodissociation on the A˜ state surface have a significant rotational quantum dependence in the 22 band. Rovibronic lifetimes decrease from 140 to 70 fs as J increases from 2 to 8 in this resonant A˜ state vibrational level. These lifetime effects are largely ascribed to centrifugal effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452169
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