New reduced dimensionality rate constants for D + H2(v = 0,1) and H + D2(v = 0,1) and a test of CEQB/G theory

A new expression for the reduced dimensionality (CEQB) cumulative reaction probability is given after taking careful account of total angular momentum constraints. New CEQB rate constants are calculated from 200 to 2,000 K for the reactions D + H2 and H + D2 by using the ab initio LSTH potential, and for the reactions with H2(v = 1) and D2(v = 1) from 200 to 600 K. A comparison with rate constants calculated by using the more approximate CEQB/G theory is made. Very good agreement is found between the CEQB and CEQB/G thermal rate constants. However, for the vibrationally excited reactions, some differences are found, especially at and below room temperature due to subtle vibrationally nonadiabatic effects in the tunneling region. These are analyzed by using a simple vibrationally adiabatic model