We present the results of an accurate quantum scattering study of collisional energy transfer in the collinear He + CS2 system, considering energies up to 92 kcal/mol. These results are generated using a coupled channel calculation with a basis of 1000 vibrational states from a discrete variable representation calculation. Detailed comparisons with the results of classical trajectory calculations are performed so as to assess classical/quantum correspondence for energy transfer moments, and for the energy transfer probability distribution function. We find very good agreement of the energy averaged first moments over a wide range of molecular vibrational energies, provided that the translational energy is not too low (translational temperatures below 300K). The second moments, as well as 〈ΔE〉up and 〈ΔE〉down show poorer agreement, especially at low temperatures. The quantum energy transfer distribution functions show considerable mode-specific behavior, but the overall envelope is approximately exponential for |ΔE| > 2 kcal/mol, with a faster than exponential drop for ΔE < - 20 kcal/mol and ΔE > + 5 kcal/mol, and with a broad spike for |AE| < 2 kcal/mol. All of these results accurately match the corresponding classical trajectory distributions. The connection of the shape of these distributions with the individual state-to-state probabilities is studied in detail, and it is found that much of this behavior may be connected with the probability of symmetric stretch excitation and deexcitation.
ASJC Scopus subject areas
- Chemical Engineering(all)