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  • 1
    Electronic Resource
    Electronic Resource
    A time-dependent interpretation of the absorption spectrum of CH3ONO (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1-13 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We use time-dependent quantum theory to interpret the absorption spectrum of CH3ONO in terms of the nuclear motion on the upper potential surface. The model uses one excited potential energy surface and two nuclear coordinates: the NO stretch and the CH3O–NO bond. The latter bond breaks upon excitation leading to dissociation. The spectrum consists of a broad band and two progressions corresponding to predissociation resonances. The band width is inverse proportional to the time scale on which the NO bond length increases to adjust to the longer equilibrium bond length of the upper potential energy surface. The progression of intense narrow resonances corresponds to the NO stretching motion. The other progression is due to oscillations along the reaction coordinate of the wave function temporarily trapped in the predissociation well. Our calculations show that important dynamic information can be obtained by "smearing off'' the high resolution spectrum to generate a series of low resolution versions which reveal the time scales on which various spectral features develop in the spectrum. We also show that time-dependent theory can be used efficiently to calculate the lifetime of relatively long lived resonances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458463
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  • 2
    Electronic Resource
    Electronic Resource
    Photodissociation of vibrationally excited water in the first absorption band (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7630-7637 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the photodissociation of highly excited vibrational states of water in the first absorption band. The calculation includes an ab initio potential energy surface for the A˜-state and an ab initio X˜→A˜ transition dipole function. The bending angle is fixed at the equilibrium value within the ground electronic state. Most interesting is the high sensitivity of the final vibrational distribution of OH on the initially prepared vibrational state of H2 O. At wavelengths near the onset of the absorption spectrum the vibrational state distribution can be qualitatively understood as a Franck–Condon mapping of the initial H2 O wave function. At smaller wavelengths final state interaction in the excited state becomes stronger and the distributions become successively broader. Our calculations are in satisfactory accord with recent measurements of Vander Wal and Crim.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457233
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  • 3
    Electronic Resource
    Electronic Resource
    Diffuse vibrational structures in photoabsorption spectra: A comparison of CH3ONO and CH3SNO using two-dimensional ab initio potential energy surfaces (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2016-2029 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigated the photodissociation of methyl nitrite (CH3 ONO) and methyl thionitrite (CH3 SNO) within the first absorption band (S1 ←S0 ). The calculations were based on a two-dimensional model including the O–NO/S–NO and N=O bond distances as active coordinates. The S1 -potential energy surfaces were calculated with quantum chemical methods and the dynamical calculations were performed exactly within the time-independent approach. The main emphasis is on the origin of diffuse vibrational structure in the photoabsorption spectrum of both molecules. A low potential barrier of 0.086 eV along the O–NO dissociation coordinate in CH3 ONO prevents immediate dissociation and leads to an initial state dependent lifetime for the excited complex of 100–250 fs corresponding to 3–8 NO vibrational periods. CH3 ONO decays nonadiabatically via vibrational predissociation. The absorption spectrum of CH3 ONO is dominated by narrow Feshbach-like scattering resonances which can be characterized by two quantum numbers, m and n*: m=0 and 1 specifies the quanta of excitation in the O–NO bond and n*=0,1,2,... specifies the excited vibrational level of the N=O bond. The potential barrier is absent in CH3 SNO and the dissociation is direct on the time scale of about 10 fs corresponding to only one third of a NO vibrational period. Nevertheless, the absorption spectrum exhibits diffuse vibrational structures. The shape of the individual absorption peaks is determined by the classical Franck–Condon reflection principle. The dissociation of CH3 SNO is primarily adiabatic which leads to a pronounced energy dependence of the final NO vibrational state distribution. The diffuse structures originate in both cases from excitation of the NO stretching vibration. In order to make contact with time-dependent theory we calculated the autocorrelation function of the time-dependent wave function by inverse Fourier transformation of the energy-dependent spectra. The agreement with available experimental data for both molecules is quite satisfactory. This includes the energy spacing of the vibrational structure, the overall shape of the absorption spectrum, and thelifetime of the excited complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457061
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  • 4
    Electronic Resource
    Electronic Resource
    Photodissociation dynamics of methylnitrite (CH3O–NO) in the 300–400 nm range: An ab initio quantum mechanical study (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 3522-3529 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the results of a two-dimensional, quantal study of the photodissociation of CH3O–NO within the first continuum (S0→S1, 300–400 nm) taking into account only the O–N and the N=O separations. The S1 potential energy surface is taken from recent ab initio calculations. The calculated absorption spectrum consists of two band progressions of narrow resonance lines with widths of ∼0.3 and ∼5 meV, respectively. These resonances can be associated with excitation of the O–N bond (m=0,1) and excitation of the N=O chromophore (n*=0,1,2,...). The intensities of the m=1 band are negligibly small compared to those of the m=0 band. The decay mechanism in the two cases is different: The m=0 resonances decay primarily via vibrational predissociation, i.e., a nonadiabatic transition from n* to n*−1, and yield NO products with a preferential population of the (n*−1) level. The m=1 resonances decay mainly via tunneling through a potential barrier yielding preferentially NO products in state n*. Several of the theoretical results agree qualitatively (ratio of peak intensities) or even quantitatively (energy spacing between peaks) with the measurements. Most important, however, is the good agreement found for the vibrational NO distributions at several excitation wavelengths of the parent, which reveals that vibrational predissociation within the S1 state is the main decay mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452997
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  • 5
    Electronic Resource
    Electronic Resource
    Vibrational state distributions following the photodissociation of (collinear) triatomic molecules: The vibrational reflection principle in model calculations for CF3I (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 5444-5454 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational state distributions following the direct photodissociation of a collinear, triatomic molecule is investigated with particular emphasis on the so-called final state interaction, i.e., the translational–vibrational coupling due to the excited state interaction potential. In order to separate the various effects which determine the state distribution we performed calculations on three levels of accuracy: The energy sudden (ES) approximation, the modified sudden (MS) approximation, and the exact close-coupling (CC) formulation. The pure ES distributions peak at high states and are very broad. They are explained within the semiclassical limit as a mapping of an amplitude onto the quantum number axis. We call this effect vibrational reflection principle in analogy to the equivalent effect in rotational excitation processes. It is a direct and sensitive probe of the parameters of the system, most importantly the potential energy surface. Energy conservation strongly modifies the ES distributions. The MS and CC distributions are much narrower and peak at considerably lower states. A detailed analysis is given within the MS approximation. Based on these general conclusions we suggest a particular excited state potential for the dissociation of CF3I which qualitatively reproduces the recently reported experimental CF3 distribution. The essential feature of this potential is a distance dependent local frequency which we find necessary to obtain distributions as broad as in the experiment. Because of the inherent difficulties with the time-of-flight technique if several energy transfer channels are involved we certainly do not know how realistic our final potential energy surface is. However, the general trends found in this study should be valid for a larger class of systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449953
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  • 6
    Electronic Resource
    Electronic Resource
    Mutations in DNAH5 cause primary ciliary dyskinesia and randomization of left–right asymmetry (2002)
    [s.l.] : Nature Publishing Group
    Nature genetics 30 (2002), S. 143-144 
    Details
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Primary ciliary dyskinesia (PCD, MIM 242650) is characterized by recurrent infections of the respiratory tract due to reduced mucociliary clearance and by sperm immobility. Half of the affected offspring have situs inversus (reversed organs), which results from randomization of left-right (LR) ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/ng817
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