PUB - Publikationen an der Universität Bielefeld

In this paper a generalized Fourier transform method for solving the initial-value problem associated with the interaction of an atom with a semiclassical laser field is presented. The method is combined with a variational technique of expanding the atomic potential. The energy-transform of the total wavefunction is obtained algebraically, while the wavefunction itself, at a time t, is given as a quadrature over the explicit algebraic expressions. Furthermore, the method permits one to determine the long-time limit t --> + infinity without the quadrature. Analytic expressions of the ATI transition amplitudes are given. As an illustration of the use of the method, we apply it to the problem of determining the above-threshold-detachment (ATD) spectra of a 3D model of H-. Results of computations for (a) the stationary ATD spectra, (b) the perturbed energies of the initial bound state, (c) the total rate of detachment and (d) the ATD spectra for individual photon absorption channels are presented for a range of intensities.