Ac Stark splitting and ionization broadening of atomic Rydberg levels in a strong electromagnetic field are escribed. The quasi-energy atomic spectrum is shown to consist of a quasi-continuum plus two sets of narrow quasi-energy levels: weakly split and broadened almost field-free levels and strongly perturbed levels, whose width is a decreasing function of the field strength amplitude. The strong-field asymptotics of the photoelectron spectrum and of the time-dependent total photoionization probability are described. The photoelectron spectrum is shown to have a multipeak structure, and the shape of each peak is shown to be different from the Lorenz shape found earlier. This effect is explained by the contribution of the quasi-continuous quasi-energy spectrum. The same reason explains a partially nonexponential time dependence of the total photoionization probability.
© 1989 Optical Society of America
M. V. Fedorov and A. M. Movsesian, "Ac Stark effect and trapping of population on Rydberg levels in a strong ionizing field," J. Opt. Soc. Am. B 6, 1504-1512 (1989)