COMPLEX-SCALING FOURIER-GRID HAMILTONIAN METHOD .3. OSCILLATORY BEHAVIOR OF COMPLEX QUASI-ENERGIES AND THE STABILITY OF NEGATIVE-IONS IN VERY INTENSE LASER FIELDS

A complex-scaling Fourier-grid Hamiltonian (CSFGH) method in momentum representation along with Floquet formalism is presented and applied to the nonperturbative treatment of the complex quasienergies of a one-dimensional-model negative chlorine ion in an ArF excimer-laser field. The CSFGH method leads to a simple and highly efficient variational procedure for accurate determination of resonance states, without the need of using an L2-basis-function expansion. A variety of laser intensities are considered covering those from perturbative to very intense laser fields, and the stability of the ion is investigated under realistic experimental conditions. Oscillatory structures of the photodetachment rate as a function of field strength are found in our study, revealing that the decreasing of the detachment rate (or the so-called "stabilization" or "suppression-of-ionization" phenomenon) may not necessarily be a monotonic behavior. Physical insight into this interesting feature is explored in the Kramers-Henneberger frame, and the feasibility for the experimental observation of the oscillatory behavior of the negative ions is also discussed.