The solution of the time-dependent Schrödinger equation by the (t,t′) method: Multiphoton ionization/dissociation probabilities in different gauges of the electromagnetic potentials

A new approach is introduced for the calculation of multiphoton partial decay rates in ionizing and dissociative processes. The partial decay rates (partial resonance widths) are calculated by carrying out asymptotic analysis of a complex scaled resonance quasienergy solution of the time-dependent Schrödinger equation obtained when the acceleration, momentum, reduced momentum, or length gauges are used. The partial width analysis is made only after applying the proper complex-scaled transformations on the resonance solution. The recently developed (t,t′) algorithm [J. Chem. Phys. 99, 4590 (1990)] significantly reduces the computational effort when the Hamiltonian is represented in the momentum gauge or in the length gauge. The new approach is applied to a model Hamiltonian which describes the multiphoton detachment of Cl^- in the A_rF laser field.