Memory effects during collisional energy transfer from highly excited CS2

Time dependent thermal lensing has been used to monitor energy transfer from CS2 (optically excited at 31250 cm(-1)) to Kr gas at 50-600 Torr. The results show that the energy transferred per collision is significantly more efficient at lower collision frequencies: a memory effect. This can be explained with a model which includes collision-free radiationless transitions between excited electronic states and collisional vibrational relaxation within each electronic state. The model also explains why the bulk average energy transfer exhibits a dramatic transition in energy transfer efficiency at bulk average energies corresponding to the triplet state origin.