OH vibrational distribution in the reaction O( 1D)+CH 4

Abstract

Vibrationally excited OH radicals were generated by 266 nm laser photolysis of ozone in the presence of methane. Temporal profiles of OH (ν=0, 1, 2) concentrations were directly monitored by standard LIF techniques at various CH 4 pressures. The total vibrational distribution of OH product in the reaction O ( 1D) + CH 4 was found to be much hotter than the statistical distribution P(ν=0): P(ν=1): P(ν=2): P(ν=3): P(ν=4) = 0.18: 0.29: 0.37: 0.15: 0.01. The rate constants for vibrational relaxation of OH(ν=1, 2, 3) in collisions with CH 4 were measured to be (5.1±1.0) × 10 −13, (1.5±0.4) × 10 −12 and (6.8±2.0) × 10 −12 cm 3/s, respectively.