Reexamination of over-the-barrier and tunneling ionization of the hydrogenatom in an intense field - art. no. 043412

Ionization of the hydrogen atom in an intense laser field is calculated usi ng the classical-trajectory Monte Carlo method with allowance of tunneling at the classical turning points. With an initial condition of zero angular momentum. excellent agreement with an accurate quantum-mechanical calculati on is obtained. The usually mentioned classical threshold for ionization at field strength 0.0625e/a(0)(2) is shown to be irrelevant to realistic puls es, the effective classical thresholds for an adiabatically ramped dc pulse are found to be 0.080e/a(0)(2) in one dimension and 0.130e/a(0)(2) in thre e dimensions.