The effect of vibrational excitation on the reaction of O(3P) with H2 and the distribution of vibrational energy in the product OH

Abstract

The overall rate constant and the product branching rate constants have been measured for the first time for the reaction where k2=k2a+k2b. The measurements were made in a flow tube apparatus at T=302±2 °K at a total pressure of 3 Torr. O(3P) was produced by the titration of active nitrogen with NO. H2(v=1) was produced by a heated tungsten filament and its concentration was determined from vuv absorption measurements in the Lyman band system of H2. Absolute concentrations of OH(v=0) and OH(v=1) were deduced from laser induced fluorescence in OH in a calibrated fluorescence system. The rates and uncertainties are k2= (1.0+0.9−0.6) ×10−14 cc/molecule-sec, k2a= (1.0+0.4−0.6) ×10−14 cc/molecule-sec, k2b?4.7×10−15 cc/molecule-sec. The reported value for k2 represents an increase owing to vibrational excitation in hydrogen by a factor of ?2.6×103 over the fully ground state reaction rate constant. Measurements of the fully ground state reaction rate constant and recent theoretical treatments of the O+H2 reaction are discussed in relation to these results.