Collisional deactivation of N2O(00°1) studied by time-resolved infrared fluorescence

Abstract

<jats:p>The time-resolved infrared fluorescence (IRF) technique has been used to study the vibrational deactivation of excited N2O by large polyatomic colliders at ambient temperature (295±2 K). N2O(0001) molecules were prepared by direct pumping with the P(18) line of a pulsed CO2 laser at 9.536 μm. The bimolecular rate constant for self-deactivation was determined to be (0.763±0.006)×103 Torr−1 s−1, in very good agreement with previous work. The rate constants for deactivation by Ar and H2 were found to be (0.103±0.003) and (4.89±0.52)×103 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)×103 Torr−1 s−1, respectively. Experimental deactivation probabilities and average energies removed per collision are calculated and compared. There is little difference in deactivation probabilities between the acyclic ring compounds and their aromatic analogues and the partially-fluorinated benzenes but the perfluorinated 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 result of near-resonant intermolecular V–V energy transfer. The results are compared with our recent work on the deactivation of CO2(0001) by the same group of large polyatomic colliders [K. L. Poel, Z. T. Alwahabi, and K. D. King, Chem. Phys. 201, 263 (1995)].</jats:p>