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 (kOH/kOD) 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.