Single-photon double and triple ionization of acetaldehyde (ethanal) studied by multi-electron coincidence spectroscopy

Highlights: • The first ever valence double ionization spectrum of acetaldehyde is reported. • The first ever site-selectively extracted Auger spectra of acetaldehyde are reported. • The first ever Auger spectra of acetaldehyde involving shake-up states are reported. • The first ever triple ionization spectra of acetaldehyde are reported. • The first ever energy sharing of electron pairs emitted by acetaldehyde is presented. - Abstract: Single-photon multiple ionization processes of acetaldehyde (ethanal) have been experimentally investigated by utilizing a multi-particle coincidence technique based on the time-of-flight magnetic bottle principle, in combination with either a synchrotron radiation source or a pulsed helium discharge lamp. The processes investigated include double and triple ionization in the valence region as well as single and double Auger decay of core-ionized acetaldehyde. The latter are studied site-selectively for chemically different carbon core vacancies, scrutinizing early theoretical predictions specifically made for the case of acetaldehyde. Moreover, Auger processes in shake-up and core-valence ionized states are investigated. In the cases where the processes involve simultaneous emission of two electrons, the distributions of the energy sharing are presented, emphasizing either the knock-out or shake-off mechanism.