Photoelectron–photoion–photoion momentum spectroscopy as a direct probe of the core-hole localization in C 1s photoionization of C₂H₂

Abstract

Angular distributions of C 1s photoelectrons, relative to a dissociation axis for C2H2, have been measured with a photoelectron–photoion–photoion coincidence technique. The photoelectron angular distribution (PAD) for three two-body fragmentations (symmetric, non-symmetric and proton-migration fragmentations) is completely different. The PADs for non-symmetric fragmentation provide direct evidence of a localized core-hole and preferential bond breaking following Auger decays. Moreover, the PAD for symmetric fragmentation has been interpreted as the interference between photoemissions from the two carbon atoms.