Collision-induced state-to-state flow of vibrational energy in S1 toluene

State-to-state flow of vibrational energy in the S1 state of toluene vapor under ‘‘single collision’’ conditions has been measured. The 6b1 level (ν′6b=530 cm−1 ) was pumped by pulsed laser excitation, and resolved fluorescence spectra revealed which vibrational levels in the S1 state were produced by collisions with three added gases. Energy flow was found to be selective and occurred into four channels. Endergonic flow of energy to identified, accessible vibrational levels is not observed. Collision cross sections increased with increasing molecular complexity of the collision partners, but similar energy flow patterns were observed with all collision partners. Energy flow between 6a1 and 6b1 levels, which have a spacing of about 90 cm−1, was found to be very inefficient.