An investigation of vibration to rotation transfer in vibrational relaxation of S1 aromatics

A study of vibrational energy transfer for four aromatics with the collision partners Hz and He has been undertaken to assess the role of V → R transfer when a low moment of inertia collision partner is involved. Significant transfer occurs to 0° (the only channel for which V → R transfer can occur) in relaxation of benzene and benzene-d6 by H2, but not by He. For both p-difluorobenzene and toluene there is significant transfer to 0° by both He and H2, preventing the observation of V → R transfer in these polyatomics. It is found that He adopts different pathways when heavy groups are attached to the ring. H2 is more consistent in its preferences.