Effect of vibration and internuclear axis orientation on multiphoton ionization of H-2(+)

Multiphoton processes in H-2(+) induced by a linearly polarized monochromat ic laser have been studied within the framework of lowest-order perturbatio n theory. To illustrate the convergence of the une-centre B-spline expansio n used, we present results for fixed internuclear distance. In a further st ep the vibrational motion has been taken into account using the reflection approximation. The frequency dependence of the ionization cross section has been calculated for the parallel as well as perpendicular orientation of t he molecule with respect to the polarization vector of the laser field. It is found that in the multiphoton, in contrast to the tunnelling regime, ion ization occurs dominantly in the perpendicular orientation, ii vertical tra nsitions From low-lying vibronic states are considered.