LASER-INDUCED CONTINUUM STRUCTURES AND ABOVE-THRESHOLD IONIZATION

The time-dependent photoelectron spectrum is studied in the context of laser-induced continuum structures (LICSs), where a bound atomic stat e is embedded into an atomic continuum by a strong laser field and the structure probed from a second bound state with another (weak or stro ng) laser. The situation where a second atomic continuum is also coupl ed to the first via the lasers allows for the possibility of above-thr eshold ionization (ATI) and the effect of LICS on ATI is examined here . Weak- and strong-ATI regimes are identified and theoretical expressi ons for the photoelectron spectra for both regimes obtained. The stron g-ATI regime is characterized by non-Markoffian equations, unlike the weak-ATI regime. Numerical results are presented for the weak-ATI regi me and the criterion for weak and strong regimes obtained. The weak-re gime photoelectron spectrum is determined from the eigenvalues and eig envectors of the damped Hamiltonian matrix associated with the Schrodi nger equation for the bound-state amplitudes. An interesting non-Loren tzian sinc2 feature is found at the confluence point.