Collision induced intramolecular vibrational energy transfer in 1 B 2 aniline

The technique of SVL fluorescence spectroscopy was used to observe collision‐induced intramolecular energy transfer in a large polyatomic molecule in the gas phase. Vibrational energy transfer was traced from eight vibronic levels in 1 B 2 aniline with argon as a collision partner. Overall rates for depletion of the initial level range from 0.1 to 0.5 of the equivalent hard sphere collision rate. The vibrational levels below 800 cm−1 are found to fall into groups: energy transfer is much more efficient between levels in the same group than between levels in different groups. This pattern of energy disposal indicates that specific dynamic characteristics of the vibrational modes are as important as the energy gap and vibrational overlap integrals. Another interesting feature of the results is the importance of endoergic processes, even when exoergic pathways for vibrational energy exchange are available. Rotational relaxation was also examined, but only with low resolution, and not in a systematic study. The rate of rotational equilibration found approximates the collision rate.