Electron Energy and Angular Spectra at the TunnelingIonization of Hydrogen Molecular Ion by a Strong LaserField

Abstract

Simple analytical expressions for the electron energy and angulardistributions at the tunneling ionization of the hydrogen molecularion by low-frequency linearly polarized laser radiation are obtainedin the frames of the Keldysh–Faisal–Reiss approach.Moderate and large internuclear separations are considered. Coulombcorrection is taken into account in the calculations. It is found thatthe distributions differ essentially from the known expressions forthe tunneling ionization of atoms. In the case of atoms the electronyield decreases monotonically with the electron kinetic energy. Incontrast, the electron yield from the hydrogen molecular ionoscillates as a function of the electron kinetic energy. The amplitudeof oscillations diminishes with increasing field strength of theradiation and of the internuclear separation. The total ionizationrate of the hydrogen molecular ion coincides with the correspondingexpression for the hydrogen atom at the large internuclearseparations.