Fragmentation and electronic decay of vacuum-ultraviolet-excited resonant states of molecular CsCl

Electronic and nuclear relaxation of molecular CsCl following photoexcitation in the vacuum ultraviolet region is investigated. From the total ion yield and the Cs + and Cl + partial ion yield spectra covering the 8–22 eV photon energy range, a number of resonating excited states are identified. The fragmentation patterns of the excited and ionized CsCl molecules and also the Cs 2 Cl 2 dimers are studied in detail from ion time-of-flight mass spectra recorded at and around the resonances. Molecular dissociation following the resonant excitation is discussed and an ionic model is applied to explain the observations, emphasizing some principal differences from other alkali chloride molecules (KCl). The valence photoelectron spectra are found to show strong enhancement and pronounced new structures at resonant photon energies. These effects are assigned to a 'cross-ionic' autoionization decay process and are found to be due to a lifetime-dependent interplay between the electronic and nuclear relaxation.