Electronic-to-rotational energy transfer in molecular collisions

✍ Scribed by Paul L. Devries; Thomas F. George

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 311 KB
• Volume: 43
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(76)85327-4

✦ Synopsis

4 quantum mechanical study of collision induced electronic-to-rotational energy transfer !n the fluorine-para-hydrogen system (F + Ha) is reported. The three potential energy surfaces of the system, constrained to lie in a fmed plane, are obtained by the diatomics-in-molecules approach, and close-coupling calculations are performed in a diabatic representation. An enhancement of rotationally inelastic (cornoared to rotationally elastic) transitions is observed when fluorine makes a transition from its upper to itsiower spin-orbit state. Collision induced transfer of rotational energy [ 1,2] has been the subject of theoretical [3-201 and experimental [21-281 studies, and recent experimental advances [26-281 have made it possible to observe specific rotational transitions in non-polzr as well as polar molecules. The transitions which are normally observed are between rotational states of the same electronic state. However, the ability to select and analyze spin-orbit states [29] makes it experimentally feasible to observe rotational transitions between different electronic states and lends motivation for the present work.

In this paper the F-H2 collision system has been investigated computationally for para-hydrogen with respect to such (non-reactive) transitions at low energies. As we are interested in effects, 2s opposed to quantitative predictions, our computations were performed with the hydrogen diatom having only two internal degrees of freedom, corresponding to vibration and rotation in 2 (fured) plane. The potential surfaces used in this work are the diatomics-in-molecules surfaces of Tully [30], suitably modified to our purposes*, resulting in three model surfaces corresponding asymptotically to the hydrogen ground electronic state and