COLLISIONAL DEACTIVATION OF N2O(00(0)1) STUDIED BY TIME-RESOLVED INFRARED FLUORESCENCE

The time-resolved infrared fluorescence (IRF) technique has been used to study the vibrational deactivation of excited N2O by large polyatom ic colliders at ambient temperature (295+/-2 K). N2O(00(0)1) molecules were prepared by direct pumping with the P(18) line of a pulsed CO2 l aser at 9.536 mu m. The bimolecular rate constant for self-deactivatio n was determined to be (0.763+/-0.006)X10(3) Torr(-1) s(-1), in very g ood agreement with previous work. The rate constants for deactivation by Ar and H-2 were found to be (0.103+/-0.003) and (4.89+/-0.52)X10(3) Torr(-1) s(-1), respectively. The deactivation rate constants for the large polyatomic molecules, c-C6H10, c-C6H12, C6H6, C6D6, C7H8, C7D8, C6H5F, p-C6H4F2, C6HF5 and C6F6, were found to be (176+/-10), (153+/- 22), (115+/-4), (201+/-2), (127+/-11), (407+/-52), (144+/-14), (173+/- 13), (129+/-8), and (48+/-9)X10(3) Torr(-1) s(-1), respectively. Exper imental deactivation probabilities and average energies removed per co llision are calculated and compared. There is little difference in dea ctivation probabilities between the acyclic ring compounds and their a romatic analogues and the partially-fluorinate benzenes but the perflu orinated compound, C6F6 is much less efficient than the other species. The perdeuterated species, C6D6 and C7D8, especially the latter, show enhanced deactivation relative to the other species, probably as a re sult of near-resonant intermolecular V-V energy transfer. The results are compared with our recent work on the deactivation of CO2(00(0)1) b y the same group of large polyatomic colliders [K. L. Poel, Z. T. Alwa habi, and K. D. King, Chem. Phys. 201, 263 (1995)]. (C) 1996 American Institute of Physics.