Accurate ab initio thermal rate constants for reaction of O((3)P) with H2 and isotopic analogues.

Semiclassical transition state theory, in combination with high accuracy quantum chemistry, is used to compute thermal rate constants from first principles for the O((3)P) + H2 reaction and its isotopic counterparts. In the temperature regime of 298-3500 K (which spans 8 orders of magnitude for rate constants), our theoretical results are in excellent agreement (within 5-15%) with all available experimental data from 298 to 2500 K but are somewhat too low (from 15 to 35%) at higher temperatures. Several possible reasons that might cause the degradation at high temperatures are discussed. Vibrational state-selected rate constants and their correlations with normal thermal rate constant are derived and are given in the Supporting Information.