Chemical Dynamics of H Abstraction by OH Radicals: Vibrational Excitation of H2O, HOD, and D2O Produced in Reactions of OH and OD with HBr and DBr

Abstract

Infrared chemiluminescence from vibrationally excited H2O, HOD, and D2O molecules in the ranges 3200−3900 cm-1 (O−H stretch) and 2400−2900 cm-1 (O−D stretch) was observed from the reactions of OH and OD radicals with hydrogen and deuterium bromide in a fast flow reactor with 0.5−2 Torr of Ar carrier gas at 300 K. Hydroxyl radicals were produced via the H + NO2 reaction; the H atoms were generated by microwave discharge in a H2/Ar mixture. Vibrational distributions for H2O, HOD, and D2O were determined by computer simulation of the experimental emission spectra. The H2O emission from OH + HBr reaction shows inverted populations for both the collisionally coupled stretching modes and the bending mode. Inversion in the bending distribution with a maximum for v2 = 1 is more apparent in the v1,3 = 1 level, which is populated up to the thermochemical limit of v2 = 5. The HOD emission from OD + HBr shows an inverted population in the O−H stretching mode with a maximum for v3 = 2 and shows a decreasing population...