Laser-induced bound and metastable states in bound-continuum systems.

Abstract

A monochromatic laser is shown to be capable of inducing a bound state and multiple metastable states not originally present in the field-free spectrum of a bound-continuum system. For the bound state to exist, the field intensity must be larger than a certain frequency-dependent critical value. The widths of the metastable states are found to be in general proportional to renormalized field intensities rather than the physical field intensity. The energies can be classified as being in the metastable or unstable regimes, depending on whether the observed widths are smaller or larger than the corresponding ``bare'' widths predicted by perturbation theory. The relation of the Fano or laser-induced ``autoionization'' states to the scattering states is also demonstrated.