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

•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.

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.

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