Photodissociation of the {HeH+^+} molecular ion

The photodissociation cross section of the molecular ion HeH$^+$ was calculated within the Born-Oppenheimer approximation for a parallel, a perpendicular, and an isotropic orientation of the molecular axis with respect to the field, considering also different initial vibrational and rotational states. The results were compared to recent data from a free-electron laser experiment performed at the FLASH facility [H.B. Pedersen {\it et al.}, Phys. Rev. Lett. 98, 223202, (2007)]. Within the experimental uncertainties theoretical and experimental results are compatible with each other.Comment: 16 pages, 8 figure

Alignment-Dependent Ionization of Molecular Hydrogen in Intense Laser Fields

The alignment dependence of the ionization behavior of H$_2$ exposed to intense ultrashort laser pulses is investigated on the basis of solutions of the full time-dependent Schr\"odinger equation within the fixed-nuclei and dipole approximation. The total ionization yields as well as the energy-resolved electron spectra have been calculated for a parallel and a perpendicular orientation of the molecular axis with respect to the polarization axis of linear polarized laser pulses. For most, but not all considered laser peak intensities the parallel aligned molecules are easier to ionize. Furthermore, it is shown that the velocity formulation of the strong-field approximation predicts a simple interference pattern for the ratio of the energy-resolved electron spectra obtained for the two orientations, but this is not confirmed by the full ab initio results.Comment: 4 figure