C 1s and O 1s photoelectron spectra of formaldehyde with satellites: theory and experiment

Shake-up satellite spectra accompanying the C 1s and O 1s photoelectron main lines of formaldehyde were studied by the combination of high-resolution X-ray photoelectron spectroscopy and accurate ab initio calculations. The symmetry adapted cluster-configuration interaction (SAC-CI) general-R method finely reproduced the details of the experimental spectra and enabled quantitative assignments for the seven satellite bands: some were newly interpreted. The shake-up transitions were mainly attributed to the valence excitations accompanying the inner-shell ionization. The Rydberg excitations were found to be minor. Three-electron processes such as 1s−1n−2π*2 and 1s−1π−2π*2 were predicted in the low-energy region where the valence shake-up states such as 1s−1n-σ*, π-π* exist.