Intramolecular electronic coupling enhanced collisional deactivation of highly vibrationally excited molecules

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Abstract
The collisional deactivation of highly vibrationally excited NO2 and CS2 by a variety of buffer gases has been examined by time-resolved Fourier transform IR emission spectroscopy. The results show that there is a dramatic increase in the average energy removed per collision for NO2 excited above ∼10 000 cm−1 and for CS2 above ∼26 000 cm−1. These energies correspond to the origins of the lowest excited à 2B2/B̃ 2B1 states of NO2 and the lowest excited R 3A2 state of CS2. Mixing between these excited electronic states with the ground electronic state enhances collisional relaxation by allowing the electronic transition dipole to contribute to collisional energy transfer.