Photodissociation Dynamics

Schinke, Reinhard

doi:10.1002/0470845015.cpa011

Cited by 32 publications

(62 citation statements)

References 64 publications

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“…Direct dissociation is characterized by a diffuse, almost structureless absorption spectrum. A comparison among the absorption cross sections of bands corresponding to direct, nearly direct and indirect dissociations can be found in Figure 1.6 of Schinke [1993]. In the case of N 2 O, the broad envelope, with a superimposed weak structure, indicates that the dissociation proceeds primarily in a direct way.…”

Section: Theorymentioning

confidence: 98%

“…This procedure automatically includes the contribution due to the partial absorption cross sections corresponding to various quantum states of dissociating molecule. The formal theory for this behavior for multidimensional systems is due to Heller [1978] and an early version is described by Schinke [1993]. It is summarized here, together with a more accurate version given by Lee et al [1983].…”

Section: Theorymentioning

confidence: 99%

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Isotopomer fractionation in the UV photolysis of N₂O: Comparison of theory and experiment

2005

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[1] In the photodissociation of N 2 O, absorption cross sections differ with isotopic substitution, leading to a wavelength-dependent fractionation of the various isotopomers. Several models ranging from shifts by zero-point energy differences to propagation of wave packets on the excited electronic state potential energy surface have been proposed to explain the observed fractionations. We present time-independent fractionation calculations for the isotopomers 447, 448, 456, 546, and 556. Besides largely agreeing with the experimental data, these calculations have the advantage of not being computationally intensive, as well as satisfying the physical facts that the asymmetric stretch and the doubly degenerate bending vibration are the principal Franck-Condon active modes in the photodissociation. The latter is reflected in the actual dissociation and in the high rotational excitation and lack of vibrational excitation of the N 2 product. The calculations are based on a multidimensional reflection principle using an ab initio potential energy surface. The theory for the absorption cross section and isotopomer fractionation accompanying photodissociation is described. The absolute value of the theoretically calculated absorption cross section is very close (90%) to the experimentally observed value. The present computations also provide data for the slope of a threeisotope plot of the fractionation of 447/446 relative to 448/446, using the fractionations at different wavelengths. The resulting slope is compared with a perturbation theoretical expression for direct photodissociation given elsewhere.

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Section: Theorymentioning

confidence: 98%

Section: Theorymentioning

confidence: 99%

Isotopomer fractionation in the UV photolysis of N₂O: Comparison of theory and experiment

2005

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“…UV photolysis of N 2 O is essentially a direct dissociation, since the shape of the absorption spectrum is a broad envelope with a only weak structure superimposed. Thereby, the time-dependent expression for the absorption cross section can be rewritten in a time-independent form using the reflection principle in conjunction with the Franck-Condon principle [Heller, 1978;Schinke, 1993]. The absorption cross section s is given as…”

Section: Absorption Cross Sectionmentioning

confidence: 99%

“…[3] Frequently, the process is treated as a two-electronicstate process in which the lower electronic state is excited to the upper state by absorption of radiation [e.g., Schinke, 1993]. However, for polyatomic molecules, N 2 O being an example, there are usually a number of excited electronic states which are accessible even though the excitation to only one of them may be dominant in the wavelength region of interest.…”

Section: Introductionmentioning

confidence: 99%

Isotopomer fractionation in the UV photolysis of N₂O: 2. Further comparison of theory and experiment

2008

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[1] Wavelength-dependent fractionation of various isotopomers in the photodissociation of N 2 O is studied. The absorption cross sections are calculated by a time-independent reflection principle, related to the treatment but now with an inclusion of the NN stretching coordinate and both the 2A 0 and 1A 00 electronic excited states. The added 1A 00 state is found to have little effect on both the absorption cross section and the fractionation. The improvements include more physical details in the photodissociation of N 2 O, while maintaining an advantage of a treatment in the work by Prakash et al. (2005) that was not computationally intensive. The present calculated fractionation, without a significant adjustable parameter, gives good agreement with experiments in the absorption cross section in the low-energy region, the important region for the experimentally observed isotopic fractionation.

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“…[16] Using these rules, one may predict some features of the absorption spectra obtained from combined MD/QC approach, and in fact some information on this subject has been published long time ago, for example, in Refs. [17][18][19]. Nowadays, owing to the available software, such theoretically described effects may be observed in simulated spectra.…”

Section: Introductionmentioning

confidence: 99%

Effect of molecular vibrations on the MD/QC-simulated absorption spectra

Eilmes

2013

Int. J. Quantum Chem.

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Effect of molecular vibrations on the absorption spectra simulated via a sequential approach combining molecular dynamics (MD) with quantum‐chemical calculations has been investigated. Simulated spectra have been obtained from the time‐dependent density functional theory results averaged over series of molecular geometries retrieved from Born–Oppenheimer MD trajectories. Distributions of bond lengths have been analyzed and related to the features of calculated spectra. For NVE simulations of small systems, absorption spectra exhibit bimodal bandshape as a result of classical treatment of vibrations. For NVE trajectories of larger systems or simulations in the NVT ensemble calculated absorption bands are symmetric, however, they may not agree with the results of Franck–Condon analysis. These results are practical manifestations of effects predicted theoretically from general principles. Consequences for the modeling of absorption spectra have been discussed. © 2013 Wiley Periodicals, Inc.

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Photodissociation Dynamics

Cited by 32 publications

References 64 publications

Isotopomer fractionation in the UV photolysis of N₂O: Comparison of theory and experiment

Isotopomer fractionation in the UV photolysis of N₂O: Comparison of theory and experiment

Isotopomer fractionation in the UV photolysis of N₂O: 2. Further comparison of theory and experiment

Effect of molecular vibrations on the MD/QC-simulated absorption spectra

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Photodissociation Dynamics

Cited by 32 publications

References 64 publications

Isotopomer fractionation in the UV photolysis of N2O: Comparison of theory and experiment

Isotopomer fractionation in the UV photolysis of N2O: Comparison of theory and experiment

Isotopomer fractionation in the UV photolysis of N2O: 2. Further comparison of theory and experiment

Effect of molecular vibrations on the MD/QC-simulated absorption spectra

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Isotopomer fractionation in the UV photolysis of N₂O: Comparison of theory and experiment

Isotopomer fractionation in the UV photolysis of N₂O: Comparison of theory and experiment

Isotopomer fractionation in the UV photolysis of N₂O: 2. Further comparison of theory and experiment