Rotationally and vibrationally inelastic scattering of glyoxal at E=80 meV

Abstract

Results of quantum calculations on rotationally and vibrationally inelastic scattering of 1Au(S1) trans-glyoxal by H2,He, and Ar(E=80 meV) are presented. For scattering of 00 glyoxal and 72 glyoxal by H2, a quantitative comparison with a recent crossed beam experiment is made. The calculated cross sections for rotationally inelastic scattering are in good agreement with the experimental values, and the trend that σ(72, k=0→72, k′) falls off faster with k′ than σ(00, k=0→00, k′) is reproduced. Our calculations do not reproduce the experimental finding that, for the initial 72 level, the cross sections for the Δv7=−1 and Δv7=+1 transitions are nearly identical. The calculations on 72 glyoxal + He and Ar show important differences with 72 glyoxal + H2 in the competition of rotational excitation with vibrational excitation. Model calculations also presented here yield some interesting trends in the k′ dependence of the cross sections σ(00, k=0→x1, k′) on the vibrational mode x excited.

State-to-State Inelastic Scattering from S1 Glyoxal with the Rare Gas Series: Uniform Rotational vs Changing Vibrational Channel Competition

“…Three-dimensional fully quantal inelastic close-coupled infinite-order-sudden-scattering calculations designed for our beam conditions have been reported for the collision partners H 2 6-8 and He. , Comparisons between the predicted and experimental cross sections are included in Figure . Since the calculations used an identical interaction PES for both gases derived from ab initio treatment of S 0 formaldehyde + He, − , the impressive match for H 2 and He further emphasizes the secondary role of the PES in controlling the competition.

6 Plot of predicted (open symbols) and experimental cross sections (solid symbols or dashed lines) for inelastic scattering of glyoxal (0 0 K 0 ) by H 2 , He, and Ar against the energy transferred, Δ E .

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“…The H 2 and He cross sections are from ref (experimental) and refs and (predicted). The predicted Ar cross sections are from ref . …”

“…Most of the glyoxal crossed beam experiments have involved the collision partners H 2 or He. − In the present paper, we report new results that allow the channel competition to be seen for the entire rare gas series, He to Xe. Since earlier work has shown that the internal degrees of freedom of the collision partner H 2 do not participate in the inelastic scattering, − we have also included H 2 in this rare gas series for the purpose of comparison.…”

Factors controlling the competition among rotational and vibrational energy transfer channels in glyoxal

“…Fully quantal, three-dimensional inelastic scattering predictions (15)(16)(17)(18)(19) are available for some of the results of the present study, specifically the scattering by H 2 and He. A comparison of our H 2 and He cross sections with the theoretical predictions has been shown elsewhere (9).…”

“…The good fit between theory and experiment was obtained with identical intermolecular potentials for both He and H 2 . Furthermore, the potential used to fit these S 1 electronic state experiments is calculated from atom-atom pair potentials derived from the interaction of He with ground electronic state (S 0 ) formaldehyde (16). Even deliberate changes to make the potential more repulsive or more attractive had only limited effect on the predicted cross sections (16).…”