Photoabsorption and Photoionization of Acetaldehyde in the 10.8-21.4 eV Range.

An experimental and theoretical investigation of acetaldehyde's photoabsorption and photoionization in the vacuum-ultraviolet energy range is presented. The absorption cross sections and the ionization efficiency were measured using a double-ion-chamber spectrometer in the 10.8-21.4 eV and 13.5-21.4 eV ranges, respectively. No previous reports of these quantities were found in the literature in this energy range. Photoionization and neutral-decay cross sections were derived from these results. Theoretical calculations were performed using the Padé approximant technique and the single-center partial-wave expansion method, which were applied to solve the Lippmann-Schwinger equation to obtain the asymmetry parameters and the photoionization cross sections for the seven outermost valence orbitals. The calculations were performed in the energy range from near-threshold to 35 eV at static-exchange and static-exchange-polarization levels of approximation. Our results are contextualized with recent studies on dissociative photoionization channels and high-resolution photoelectron spectra, enabling correlations with ionic fragmentation pathways. Our experimental and theoretical results were compared between each other and with previous results from the literature, exhibiting good agreement with the available data and providing a comprehensive data set essential for modeling photochemical processes in atmospheric and astrophysical environments.