COLLISIONAL RELAXATION OF VIBRATIONAL-EXCITATION - EFFECTS OF BATH GAS STRUCTURE

Infrared multiple photon dissociation has been used to study the relaxation of vibrationally excited trifluoroacetate anion. The internal energy of the ensemble of ions was monitored by measuring the extent of photodissociation in a Fourier-transform, ion cyclotron resonance spectrometer. Bimolecular quenching rate constants are measured in the presence of excess bath gases. Comparison of the experimental collision efficiencies with calculations of purely statistical energy redistribution has been done and indicates that species which can interact chemically with a trifluoroacetate anion exhibit a marked increase in the efficiency of collisional deactivation. Systematic use of the ratio R, defined as the average energy transferred per collision derived from experiment divided by the average energy transferred calculated from a statistical model is proposed. A correlation of R with the hypothetical, limiting statistical lifetimes of the collision complexes is observed. This suggests that both the number and nature of oscillators of the bath gases as well as the intermolecular well depths with trifluoroacetate are important in determining the extent of energy transfer. It further suggests that energy transfer is limited by the collision