Intrinsic channel closing in strong-field single ionization of H2

The ionization of H-2 in intense laser pulses is studied by numerical integration of the time-dependent Schrodinger equation for a single-active-electron model including the vibrational motion. The electron kinetic-energy spectra in high-order above-threshold ionization are strongly dependent on the vibrational quantum number of the created H-2(+) ion. For certain vibrational states, the electron yield in the midplateau region is strongly enhanced. The effect is attributed to channel closings, which were previously observed in atoms by varying the laser intensity.