Multiphoton ionization of H-2(+)

We present results of calculations of rates for ionization of H-2(+) by up to six photons in lowest nonvanishing order of perturbation theory, for a fixed internuclear separation of 2 a.u. There are numerous intermediate state resonances, which we identify by united-atom-limit quantum numbers. We also report on ionization rates at nonperturbative intensities at the wavelength 228 nm, calculated by resumming the Rayleigh-Schrodinger perturbation series for the ac quasienergy; we compare our results with those of previous calculations.