A laser-induced fluorescence determination of the complete internal state distribution of OH produced in the reaction: H+NO2→OH+NO

Abstract

Laser-induced fluorescence (LIF) spectra have been recorded of OH radicals produced when H atoms and NO2 react in thermal energy collisions in the region where two uncollimated beams containing the reagents intersect. Spectra of the (0,0) and (1,1), (0,1) and (1,2), and (0,2) and (1,3) bands of the A 2Σ+−X 2Π system have been observed. Distributions of OH over the whole energetically accessible range of rovibrational levels have been determined using surprisal analysis to deduce complete rotational distributions from the observed distributions over high rotational levels (N≥10). Both the vibration and rotation of OH are more excited than expected on a purely statistical basis, the average fractional yields of energy being 〈fvib〉OH=0.23 and 〈frot〉 OH=0.29. Mild preferences are also found for the lower 2Π3/2 spin–orbit component and for the Π(A′) Λ-doublet levels. The last finding is consistent with reaction via a short-lived HONO complex with some consequent constraint to planarity. The paper immediately following this one describes experiments on the energy disposal into the NO product of the H+NO2 reaction and the collision dynamics of this radical-radical reaction are discussed in that paper.