Dissociative recombination for vibrationally excited H-2(+) ions: The effect of laser photodissociation on the initial vibrational distribution

We report on measurements of dissociative recombination of H-2(+) ions populated in a range of initial vibrational levels with free electrons in the energy range of 0-20 eV. A photodissociation technique was applied to modify the vibrational distribution, and the influence on the dissociative-recombination (DR) spectrum was studied. To estimate the vibrational distribution in the experiment, the results of a simple model calculation describing a part of the measured spectrum are presented. From the comparison between the experimental data and the model calculation, we conclude that when laser photodissociation is not applied, our result is consistent with a Franck-Condon vibrational distribution from the ion source. When laser photodissociation is applied, a dramatic change of the DR spectrum is observed, which is consistent with the expected effect, based on theoretical photodissociation cross sections.