Ionisation of excited one-dimensional hydrogen atoms by low-frequency fields

Abstract

The author develops an approximate quantal treatment of the ionisation of an excited one-dimensional hydrogen atom by a strong periodic electric field. By representing the wavefunction in terms of an adiabatic basis, ionisation can be viewed as the escape of the electron over a moving barrier; the dominant ionisation mechanism is then excitation to states near the barrier minimum. For large quantum numbers and for low-frequency fields the equations of motion solved are essentially exact during most of the field period; but for a short time, whilst the moving barrier is near its minimum, the author introduces complex energies in order to represent loss to the continuum. The net result is to obtain the relative, but not the absolute, variation of the ionisation probabilities with system parameters reasonably accurately by numerically solving a small number of coupled equations.