Effect of tunneling on ionization of Rydberg states in intense fields: Hydrogenic atoms

Abstract

The ionization probabilities of hydrogenic Rydberg states in intense fields are calculated using a trajectory method, which was previously shown to be accurate for ionization of the ground-state hydrogen atom [J. S. Cohen, Phys. Rev. A 64, 043412 (2001)]. It is found that the ionization probability approaches the classical over-the-barrier probability for sufficiently large n quantum numbers, but that tunneling still significantly decreases the onset field strengths at surprisingly high n. Calculations are done for ns, ${\mathrm{np}}_{0},$ and ${\mathrm{np}}_{\ifmmode\pm\else\textpm\fi{}}$ targets, subjected to sudden and adiabatically ramped pulses in the long-wavelength limit. The dependence on the angular-momentum projection m along the field axis is also examined for circular orbits.