Energy transfer in collisions between two vibrating molecules

✍ Scribed by J. Recamier; D.A. Micha; B. Gazdy

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 401 KB
• Volume: 119
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(85)80439-5

✦ Synopsis

We study vrbrarional energy transfer in rnelastic collmear collisions betBeen IWO diaromrc molecules The system is represemed by IWO linearly driven parametric oscillators with a bilinear_ time-dependent residua1 coupling between them. We amu& for Ihe time evolution of the Irncarly dnvcn par;lmetric osciilarow with an operator algebra. and use perturbation theory and basis expansions LO include the residual couphng Rcsulls are prcserued Ior H,-FH and N2-CO. Direct twequantum transitions are found to be important even Zor low relst~rr collrs~on enrrgics. 1. In~oduction The problem of vibrational energy transfer between diatomic molecules has been studied by several authors [l-7], but most of them neglect operators in the vibration-translation couplings that change the number of vibrational quanta by two or more, implying that a two-quan~m transition occurs mostly through two successive one-quantum Jumps rather than by a direct two-quantum jump. It has been said that the latter process is much less probable than the former one [8], but we have found otherwise, at least for the systems we have considered here. In what foflows we represent the system by two linearly driven parametric oscihators with a bilinear coupling; we first eliminate the motion of the parametric oscillators by means of an exact transformation which we construct using an algebra of operators [9] and then make use of: (1) a basis expansion method to solve for the t~ne~volution operator due to the residual coupling; and (2) further ehmination of the driving potential followed by fust-order perturbation theory. The advantage of using procedure (1) over au expansion from the very beginning is that the number * The presrnr work has ban parliy supported by NSF gram CHE 83-15696.