Photoelectron soft x-ray fluorescence coincidence spectroscopy on free molecules

Coincidence and total photoelectron spectra and their differences induced by internal degrees of freedom

Recent progress in experimental techniques have made it possible to measure photoelectron spectra in coincidence with particles emitted during the decay of the photoionized species. In this work it will be shown that, contrary to intuition, these coincident photoelectron spectra can be qualitatively different from the photoelectron spectra resulting when all photoelectrons are detected. In particular they carry information on the decay mechanism following photoionization as soon as the decay is influenced by internal degrees of freedom of the photoionized system. This is shown explicitly for the case of vibrational degrees of freedom of molecules and demonstrated with a model study.