State-to-state reactive scattering amplitudes from single-arrangement propagation with absorbing potentials

A new paradigm is presented for calculation of reactive state-to-state transition amplitudes. The wave function is propagated in one arrangement (either reagents or the sought products, the choice being at one’s convenience); other arrangements are blocked with an absorbing potential. Reactive information is then obtained from the integral expression for the T matrix (〈ψ‖H−H0‖Ψ〉). The approach is exemplified on a collinear system, yielding accurate transition probabilities that are insensitive to the parameters of the absorbing potential. Expressions for the complete T matrix in the new reactive IOS are then derived, based solely on an IOS assumption in one of the arrangements, without a need to invoke matching procedures between different arrangements.