DISTORTION OF ATOMIC STATES BY TIME-DEPENDENT ELECTRIC-FIELDS .2. COUPLING TO THE CONTINUUM

The previously derived approximation for an atom in time-dependent electric fields [P. Krstić and Y. Hahn, Phys. Rev. A 48, 4515 (1993)] is improved for electric pulses of both short and long duration. The transitions that involve a distorted continuum are studied in detail, and the phenomenon of momentum coherence is shown to greatly enhance the transition amplitudes. A detailed comparison with the recent experiment of Jones, You, and Bucksbaum [Phys. Rev. Lett. 70, 1236 (1993)] is presented, where a half-cycle high-power laser pulse was used to ionize Rydberg atoms. © 1994 The American Physical Society.