Efficient polynomial expansion of the scattering Green’s function: Application to the D+H2(v=1) rate constant

We apply the absorbing boundary condition (ABC) discrete variable representation (DVR) theory of quantum reactive scattering to the initial state selected D+H2(v=1, j)→DH+H reaction. The ABC-DVR Green’s function is efficiently computed by a Newton polynomial expansion. We compute accurate reaction probabilities for the total energies and angular momenta required to obtain the thermal rate constants kv=1, j(T). At T=310 K, a thermal average over j=(0,1,2,3) is performed to yield the final result kv=1(310 K)=1.87×10−13 cm3 molecule−1 s−1, in quantitative agreement with the most recent experimental value (1.9±0.2)×10−13 cm3 molecule−1 s−1. The J-shifting approximation using accurate J=0 reaction probabilities is tested against the exact results. It reliably predicts kv=1(T) for temperatures up to 700 K, but individual (v=1, j) selected rate constants are in error by as much as 41%.