Gas phase hydrogen atom recombination

Abstract

Recombination rate measurements are presented for the reaction H+H+M→H 2 +M for M=N 2 , CH 4 , CO 2 , and SF 6 at temperatures from 77 to 295°K for N 2 and CH 4 , and about 160 to 295°K for CO 2 and SF 6 . Data from our earlier work on M=H 2 , He and Ar are included, all rate constants are tabulated and their ratios and temperature dependences are discussed. Compared to k H 2 =8.1×10 −33 cm 6 sec −1 (specific rate constant, T =295°K) k m / k H 2 ratios are 0.87, 1.14, 1.13, 1.89, 2.02, and 2.41 in the order M=He, Ar, N 2 , CH 4 , CO 2 SF 6 . Temperature dependences of k m , in T −n form are n =0.60 for H 2 and 0.40, 0.81, 1.33, 1.2, 2.27, and 1.8 for the other M in the above order. Comparison with theoretical calculations suggests that the recombinantion proceeds almost entirely by the energy transer mechanism and that quantum-mechanical resonances are important intermediates at low temperatures. The results are compared with other published data and attempts are made to correlate them with high temperature results from flame and shock tube studies.