INFLUENCE OF ABOVE-THRESHOLD IONIZATION ON THE EXCITATION AND DECAY OF AUTOIONIZING ATOMIC STATES

We use the model of essential states to consider the influence of abov e-threshold ionization on the resonance excitation and decay of autoio nizing states of atoms. We demonstrate that the autoionizing width and the widths corresponding to the photodecay of an autoionizing state a nd a discrete level, as well as the widths of quasienergy states of th e system, are renormalized. Renormalizing factors are expressed in ter ms of the matrix elements of transitions between essential states thro ugh continued fractions. These factors decrease with the growth of the intensity of the resonance electromagnetic field. As a consequence, i n strong fields, when the relevant matrix elements are large, the auto ionizing width tends to zero and the photodecay rates of the autoioniz ing state, the discrete level, and the system as a whole increase with the growth of the field intensity more slowly than they would increas e in the absence of above-threshold ionization. Thus, above-threshold ionization plays the role of a stabilizing factor.