A new application of the interaction picture to calculate reactive scattering matrix elements

The interaction picture is used together with the channel-packet method in a new time-dependent approach to compute reactive scattering matrix element s. The channel-packet method employs the correlation function between two M oller states to compute scattering matrix elements. The interaction picture reduces wavepacket spreading when computing the Moller states. The details of this new approach are illustrated using a simple one-dimensional exampl e where the size of the grid required for computing the Mailer state in the interaction picture is reduced by a factor of 2 when compared with require d grid size in the Schrodinger picture.