Vibrational relaxation of OH(v= 1) and OD(v= 1) by HNO3, DNO3, H2O, NO and NO2

Abstract

A pulsed photolysis, laser-induced fluorescence method has been used to study the kinetics of OH(v= 1) and OD(v= 1). The following rate constants (cm³ molecule^–1 s^–1) for relaxation of these vibrationally excited radicals have been measured at 298 ± 4 K: (a) for OH(v= 1) with HNO₃, H₂O, NO and NO₂: (2.54 ± 0.11)× 10^–11, (1.36 ± 0.1)× 10^–11, (3.8 ± 0.6)× 10^–11 and (4.8 ± 0.8)× 10^–11; (b) for OD(v= 1) with DNO₃, NO and NO₂: (1.5₃± 0.2)× 10^–11, (2.7 ± 0.3)× 10^–11 and (4.3 ± 0.3)× 10^–11. Rate constants are also reported for recombination of OH(v= 0) and, for the first time, OD(v= 0) with NO and NO₂ in the presence of 18 Torr Ar. The ratios of rate constants (k_OH/k_OD) under these conditions are (1.0 ± 0.16) for association with NO and (0.99 ± 0.17) for combination with NO₂. The rate data for all processes involving radical–radical collisions are discussed in terms of models developed by Quack and Troe for treating processes proceeding via strongly bound collision complexes.