Time-resolved measurements on the relaxation of OH(v= 1) by NO, NO2 and O2

Time-resolved measurements have been made on the kinetics of OH X2Π(v= 1). This state was selectively populated using indirect optical pumping. Pulses from a frequency-doubled dye laser promoted OH to A2Σ+(v= 1), whence radicals return almost exclusively to X2Π(v= 1, 0). Measurements on the infrared fluorescence from X2Π(v= 1) gave the following rate constants for relaxation by: NO, k1a=(1.5 ± 0.4)× 10–11 cm3 molecule–1 s–1; NO2, k2a=(1.3 ± 0.3)× 10–11 cm3 molecule–1 s–1; and O2, k8 < 4 × 10–13 cm3 molecule–1 s–1. The efficient deactivation by NO and NO2 is discussed in terms of a mechanism involving strongly bound (HNO2) and (HNO3) collision complexes.