Polyelectronic theory of atoms in strong laser fields. CO₂-laser seven-photon ionisation of H^-

The authors present a non-perturbative many-electron many-photon approach to the calculation of ionisation rates by monochromatic intense radiation. This approach aims at the efficient solution of appropriate complex eigenvalue matrix equations, with realistic correlated bound wavefunctions and with complexified, square-integrable 'continuum' orbitals having angular momenta up to very high values. For the seven-photon CO₂ laser ionisation of H^-, the authors find that the 1s² correlation may decrease or increase (above 2.5*10¹⁰ W cm^-2) the ionisation rates while for intensities above 10¹⁰ W cm^-2 there is a structure as a function of small variations of the laser frequency.