Photoabsorbtion and Photoionization of Diatomic Molecules

The photodissociation spectra of HeH$^+$ will be presented together with photoionization cross sections of the alkali dimer cations Li$^+_2$, Na$^+_2$, and LiNa$^+$. The latter have been calculated using two methods: a time-independent perturbative method and a time-dependent non-perturbative one. The photodissociation of HeH$^+$ which is of interest for astrophysics and the tritium neutrino-mass experiments currently draws special attention because of the newly developed FEL experimental set-up FLASH in Hamburg at which dissociation of HeH$^+$ by VUV radiation has been investigated [{\it Phys. Rev. Lett.}\ {\bf 98}, 223202 (2007)]. The alkali dimer cations are presented as a first methodological step to the photoionization of the alkali dimers, but they are also interesting by themselves since no ab initio data were available for the continuum spectra.