Dynamic stabilization of ground-state hydrogen in superintense circularly-polarized laser pulses
We present a comprehensive calculation of 3D dynamic stabilization (DS) of ground-state hydrogen in superintense circularly polarized laser pulses. Three laser-pulse envelopes have been considered: Gaussian, sech, and Lorentzian. The ionization probability at the end of the pulse Pion was calculated for a range of high frequencies w ranging from 0.65 to 8 au, for peak fields up to about 60 au (depending on ohgr), and for full width at half maximum pulse lengths tgrp extending from 0.25 to 100 cycles (depending on w). This is a very accurate calculation, very much more time consuming than its linear polarization counterpart. For Gaussian and sech pulses we find prominent DS and substantial atomic survival under conditions where our nonrelativistic, dipole approximation calculation is expected to be valid. For Lorentzian pulses there is no DS in the range studied, and we explain the reasons. We find that the evolution of the atom is adiabatic and amenable to single-state Floquet theory, up to very large peak fields (several au), and down to very short pulses (few cycle, subfemtosecond). The general case of nonadiabatic pulses is interpreted in terms of the multistate Floquet theory. We compare the results for Pion in the cases of circular and linear polarization and find a surprising resemblance, when represented as a function of the peak intensity. Our results indicate the possibility of observing DS experimentally with the VUV--FEL light sources that are now in test operation, or with the attosecond pulses obtained from high harmonic generation, in a state-of-the-art experiment, however.