Quasi-discrete resonances observed in photoionization to the A2Πu state of the CS2+ molecule

We report total and dispersed fluorescence studies of the A2Πu–X2Πg emission system in the CS2+ molecule. The single-electron Rydberg series converging to the B2Σu+ and C2Σg+ states have been observed in the undispersed fluorescence spectrum as pronounced window-type resonances. Autoionization from these states gives rise to a non-Franck–Condon distribution of the vibrational population of the final CS2+(A2Πu) state. It is shown that the vibrational branching ratios primarily depend on the l-quantum number of the Rydberg state and they may give information about perturbations of the Rydberg states. At 20–21.5 eV excitation energy the undispersed fluorescence spectrum reveals a previously unobserved structure which has been tentatively attributed to a 2πu−1 shape resonance. No deviations of the branching ratio have been found in agreement with the predictions of multichannel theory.