EFFECTS OF ADDITION GASES ON THE IR MULTIPHOTON DISSOCIATION OF HALOETHANES

The effects of addition gases on the rate of the IR multiphoton dissoc iation (IRMPD) of CClF2CH2Cl have been studied. He, CF4, CF3CdBrCl and CCl2CF2 were employed as the addition gases and IRMPD yield was measu red as a function of addition gas mole fraction. The results revealed that molecular collisions play an important role in the excitation pro cess and that the reaction rate is determined by the competition of tw o collision induced processes, one of which suppresses, and the other enhances, the reaction. In the case of 961.9 cm(-1) irradiation, both effects have been clearly observed, whereas in the case of 1023.2 cm(- 1) irradiation, the latter effect seems weak. The results also show th at the addition of CF4 or He always lowers the reaction rate. We concl ude that the relaxation of the anharmonicity bottleneck by a resonant vibrational-energy transfer is important for IRMPD of this molecule.