Do all nuclei recoil on photoemission in compounds?

Hard and soft x-ray photoelectron spectroscopy was performed for core and valence electrons in solid compounds containing V and O atoms. The single-nucleus recoil effects on photoelectron emission were observed in the form of recoil shifts for all core levels and the valence band in a heavy Fermion material LiV 2 O 4 , whereas such shifts were negligible in VO 2 even in the high-temperature metal phase. The valence band recoil shifts of V 5 O 9 and V 2 O 3 metal are found to be in between. These differences in the valence band are ascribable to the difference in the relative spectral weight of the O 2p component near the Fermi level.