Chaoyuan ZHU and Hiroki NAKAMURA
[Chem. Phys. Lett. 274, 205 (1997)]
A resonant multi-channel curve crossing problem is investigated by using the two-state semiclassical theory recently completed by the authors. The complex phase integral in the nonadiabatic tunneling type curve crossing is accurately replaced by the phase integral on the real axis. Thanks to this, the transition matrix propagation method based on the two-state theory can be easily applied to multi-state curve crossing problems without any restriction on the number of crossings and states. The present theory can nicely handle even the case that the collision energy is lower than the highest avoided crossing. Numerical comparisons with the exact quantum results for a three-state problem clearly demonstrate excellence of the theory. Even detailed feature of dense resonances is very accurately reproduced. It should be emphasized that the theory does not require any complex calculus, any diabatization procedure, and any information on the couplings.