TIME-RESOLVED INFRARED FLUORESCENCE STUDIES OF THE COLLISIONAL DEACTIVATION OF CO2(00(0)1) BY LARGE POLYATOMIC-MOLECULES

The time-resolved infrared fluorescence (IRF) technique has been used to study the vibrational deactivation of CO2(00 degrees 1) by large po lyatomic molecules at ambient temperature (295 +/- 2 K). The excited C O2 molecules were prepared by direct pumping with the P(21) line of a pulsed CO2 laser at 10.6 mu m The bimolecular rate constant for deacti vation by CO2 was determined to be (0.353 +/- 0.026) X 10(3) Torr(-1) s(-1), in excellent agreement with previous work. The rate constants f or deactivation by the large polyatomic molecules, c-C6H10, cC(6)H(12) , C6H6, C6D6, C7H8, C7D8, C6H5F, p-C6H5F2, C6HF5 and C6F6, were found to be (143 +/- 18), (150 +/- 12), (120 +/- 4), (238 +/- 9), (140 +/- 5 ), (234 +/- 15), (121 +/- 7), (132 +/- 23), (132 +/- 12), and (94 +/- 5) X 10(3) Torr(-1) s(-1), respectively. Experimental deactivation pro babilities and average energies removed per collision are calculated a nd compared. There is little difference in deactivation probabilities between the acyclic ring compounds and their aromatic analogues but th e perfluorinated compound, C6F6 is clearly less efficient than its hyd rocarbon analogue, C6H6. The perdeuterated species, C6D6 and C7D8 show considerably enhanced deactivation relative to the other species, pro bably as a result of near-resonant intermolecular V-V energy transfer.