Time-dependent wave-packet method for the complete determination ofS-matrix elements for reactive molecular collisions in three dimensions

An alternative time-dependent wave-packet method for treating three-dimensional gas phase reactive atom-diatom collisions is presented. The method employs a nonreactive body-frame wave-packet propagation procedure, made possible by judicious use of absorbing optical potentials, a novel scheme for interpolating the wave function from coordinates in one arrangement to those in another and the fact that the time-dependent Schrödinger equation is an initial-value problem. The last feature makes possible a computationally viable and accurate procedure for changing from one arrangement’s coordinates to another. In addition, the method allows the determination of S-matrix elements over a wide range of energies from a single wave-packet propagation. The determination of scattering into any particular arrangement is effectively decoupled from that into other arrangements by means of complex absorbing potentials. The method is illustrated by carrying out detailed calculations of inelastic and reactive scattering in the H+${\mathrm{H}}_2$ system using the Liu-Siegbahn-Truhlar-Horowitz potential surface.