Quasisemiclassical trajectory approach its tunneling chemical reactions

A quasisemiclassical trajectory method (QSCT) is proposed, which provides a practical procedure to study tunneling chemical reaction dynamics in multi dimensional systems. QSCT incorporates the semiclassical tunneling paths th at are generated by our previously proposed method [K. Takatsuka and H. Ush iyama, Phys. Rev. A 51, 4353 (1995)] into the so-called quasiclassical traj ectory method, whereby the chemical reactions in a wide energy range are ca lculated in a systematic way. The accuracy of this approach is tested with the system of collinear H+H-H reaction on the so-called LSTH (Liu-Siegbahn- Truhlar-Horowitz) potential surface. The thermal rate constants at 1-3000 I t are calculated. The resultant reaction rates are compared with the quantu m mechanical values [Bondi et al., J. Chem. Phys. 76, 4986 (1982)], showing that they are in a systematically good agreement in this wide temperature range. We have also examined the dependence of the reaction probability on the initial sampling of the quasiclassical method. The contribution of the paths of dynamical tunneling to chemical reaction above the reaction thresh old is estimated for the first time. (C) 1998 American Institute of Physics . [S0021-9606(98)00646-1].