Coherence and Interference in Strong-Field Photo-Induced Bound-Free Transitions

A. K. Popov, V.V. Kinberg

Mikhail Vladimirovich Fedorov, Misha Ivanov

Excitation and photoionization of Rydberg wave packets are described. Interference of bound-free transitions from many coherently populated Rydberg levels is shown to affect the dependence of the photoionization probability on the duration of interaction. Strong-field interference effects in such a system are described also. The most important of these is the field-induced interference stabilization of Rydberg atoms in a strong ionizing field. The intensity range in which this effect can exist is determined. The results derived are used for a qualitative model describing supercontinuum emission in the process of multiphoton ionization.

B Ya Dubetskiĭ, A. P. Kazantsev, V. P. Chebotaev +1 more

A. K. Popov, Victor Kimberg

Summary form only given. Atomic coherence and interference of quantum pathways provides the means to manipulate the spectral features of absorption-gain and refractive indexes as well as the nonlinear-optical response of a medium. These open opportunities for lasing without inversion, forming laser-induced transparency, for manipulating by phase matching, and for increase in output of frequency-mixing generation. Theory and first experimental evidence of laser-induced continuum structures (LICS) have been reported. In this paper we develop the theory of LICS on the case of two strong fields coupled to bound-free transitions.

Mikhail Vladimirovich Fedorov, A. M. Movsesian

Continuum–continuum, bound–bound, bound–free, and free–bound atomic field-induced transitions are investigated. The initial atomic state is supposed to be given by a wave packet of coherently populated levels of continuous or discrete spectra. Interference effects were found to increase the probabilities of these types of transition and to change their dependence on the pulse duration τ. Interference is shown to occur also in the two-photon ionization probability with highly excited Rydberg levels as intermediate states. Criteria of applicability of the energy diffusion model are formulated. The different diffusion criteria are shown to be incompatible with each other, owing particularly to described interference effects. An alternative picture of multiphoton excitation is suggested. This picture is similar to the above-threshold ionization and predicts the appearance of some maxima in the spectrum of excited electrons below the ionization threshold.

M.I. Podgoretskii, O.A. Khrustalev