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

Abstract

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, k_1a=(1.5 ± 0.4)× 10^–11 cm³ molecule^–1 s^–1; NO₂, k_2a=(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.