Threehyphen;photon resonance ionization of H2

摘要

Calculations are performed for the ionization of parahyphen;H2by absorption of three 6.6 eV photons. Two photons are absorbed to excite H2to theE,Fthinsp;1Sgr;+gstate, and a third photon is absorbed to ionize this state. The twohyphen;photon Rabi rate and onehyphen;photon ionization rate are linear in the laser intensity (I) and are thus competitive. This competition produces a strong dependence of the threehyphen;photon ionization rate on the vibrationalhyphen;rotational levels of the boundndash;bound electronic transition and on the electron ejection angle. For example, forI= 1 GW cmminus;2the strong (maximum ionization rate 6times;108sminus;1/molecule)vJ= 00rarr;vprime;Jprime; = 30 transition is 70percnt; saturated at 0deg; and 100percnt; saturated at 90deg; ejection angle relative to the linear polarization direction of the photon. The weak (maximum ionization rate 2times;1 07sminus;1/molecule)vJ= 00rarr;vprime;Jprime; = 32 transition is 0.3percnt; saturated at 0deg; and 80percnt; saturated at 90deg; ejection angle. These calculations suggest use of multiphoton ionization data to study onehyphen;photon excitedhyphen;state angular distributions. The latter occur for an excited state which has a nonstatistical distribution of rotationalMprime; sublevels belonging to theJprime; level of the excited state (in contrast to the photoionization of a ground state having a statistical distribution ofMsublevels belonging toJ).