Three-photon resonant four-photon ionization of ${\mathrm{H}}_2$ via the $C {}_{}{}^1{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$ state

Ab initio calculations are presented for the vibrational branching ratios in three-photon resonant four-photon ionization of ${\mathrm{H}}_2$ via the $C {}_{}{}^1{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$ state. Energy and internuclear distance dependences of the boundfree electronic transition matrix element are explicitly included to estimate deviations from the Franck-Condon approximation. While our calculated branching ratios confirm certain important trends seen experimentally, some differences remain.