Collisional relaxation of highly vibrationally excited CF2O prepared with different initial energies and distribution functions

The collisional relaxation of highly vibrationally excited CF2O* molecules prepared by infrared laser multiphoton absorption is compared with the resu lts obtained when CF2O* is generated as a product of the reactions of CF3 a nd CF2Cl radicals with NO2. The three methods produce molecules with probab ly different energy distributions and also different average excitation ene rgies [E]. Thus, IR laser excitation results in a bimodal distribution, wit h average excitation energies in the range 3 000- 20 000 cm(-1), while the chemical reactions of CF3 and CF2Cl radicals produce CF2O* with a undetermi ned level of vibrational excitation that depends on the specific energy cha nge of the process. Irrespective of the method of preparation, the same exp onential decays are obtained for the each of various colliders studied (Ar, N-2, NO2, and CF2O). It is shown that under these conditions, the observed bulk average energy transferred per collision, [[Delta E]], is equal to th e microscopic value [Delta E]. However, a single exponential energy decay i s not sufficient condition to assure that equality. (C) 1999 American Insti tute of Physics. [S0021-9606(99)00404-3].