Collisional relaxation of highly vibrationally excited cis-ClFC=CFCl prepared by multiphoton excitation

Highly vibrationally excited gas-phase cis-ClFC=CFCl was prepared with a pulsed, high-powered pulsed TEA CO2 laser operating at 948 cm(-1), and the subsequent collisional relaxation was followed by infrared fluorescence from the nu(2) mode (1168 cm(-1)). Energy transfer data were obtained for Ar and ClFC=CFCl molecules as collisional partners. The exponential decay of the average energy together with the linear microcanonical dependence of I(E) on [E] in a wide energy range allowed for the determination of the dependence of bulk average energy transfer per collision, [[Delta E]], on the average energy, [[E]]. In both cases, [[Delta E]] is found to be a linear function of [[E]]. As the energy decay profiles ate exponential, they are independent of the shape of the initial distribution and of the fraction of molecules excited, allowing one to obtain the dependence of the microscopic first moment of P(E',E), [Delta E], on [E]. The following dependences of [Delta E] on [E] were found:[Delta E](P) = 4.5 +/- 1.0 - (7.3 +/- 1.5) x 10(-3)[E] cm(-1) for self-relaxation and [Delta E](M) = 0.63 +/- 0.06 - (1.0 +/- 0.1) x 10(-3) [E] cm(-1) for the relaxation with Ar.