Multiphoton ionisation from a short-range potential by short-pulse lasers

Abstract

The time-dependent Schrodinger equation is solved numerically for an electron which is bound in a one-dimensional short-range potential and exposed to a strong laser pulse. Total ionisation, and photoelectron spectra as a function of laser intensity, frequency and pulse length are calculated. There are features due to multiphoton resonances, which appear and disappear as the laser intensity changes during the pulse, similar to those observed recently in experiments. Results from a quasisteady state (complex-coordinate Floquet) calculation compare well with those from the time-dependent solution. The quasi-energies are shown to be complicated functions of laser intensity and frequency. For the short-range potential considered, new bound states appear as the ponderomotive barrier deepens the potential.