Semiclassical study of the ionization spectra of Rydberg atoms driven by intense half-cycle pulses

We present a new semiclassical method, based on an extension of the van Vleck-Gutzwiller propagator, for the study of bound-free transition amplitudes of Rydberg H atoms, initially prepared in quasi-one-dimensional Stark states (n = 100), which are ionized by intense half-cycle pulses. Oscillations in the ionization spectra are described by interference between pairs of classical path amplitudes. The rate of the oscillations depends linearly on the initial principle quantum number n, and the amplitude of the oscillations depends sensitively upon the pulse length and whether the initial state is orientated with or against the direction of electromagnetic polarization.