A time-dependent semiclassical wavepacket method using a fast Fourier transform (FFT) algorithm

A new semiclassical propagator based on a local expansion of the potential up to second order around the moving center of the wavepackt is proposed. Formulas for the propagator are derived and the implementation using grid and fast Fourier transform (FFT) methods is discussed. The semiclassical propagator can be improved up to the exact quantum mechanical limit by including anharmonic corrections using a split operator approach. Preliminary applications to the CH3I photodissociation problem show the applicability and accuracy of the proposed method. (orig.)D