REVERSIBILITY OF BOUND-TO-CONTINUUM TRANSITIONS INDUCED BY A STRONG SHORT LASER-PULSE AND THE SEMICLASSICAL UNIFORM APPROXIMATION

We show that the problem of the net absorption of one photon from a st rong laser pulse in a bound-to-continuum transition can he recast as a single integral equation. For a certain class of absorption spectra. this integral equation can be converted to a second-order Schrodinger- like differential equation, which can be accurately solved in an essen tially closed form using the semiclassical uniform approximation. With the aid of the integral equation and the uniform solutions we find th at for strong short pulses, irreversible transitions to a perfectly ab sorbing continuum in the weak-field regime become reversible. in parti cular, continuum levels may execute Rabi oscillations with the precurs or bound stale. These oscillations occur at different frequencies, dep ending on tile continuum energy. As a result, spectral migrations and formations of transparent lines may occur. Field-induced interferences between neighboring lines is also investigated.