Competition between resonant Raman scattering and fluorescence at the L-3-edges with final 3s hole in CoO and in NiO

We present results on inelastic photon scattering in NiO and CoO in the L-3 threshold region ending with a final 3s hole i.e. 2p(6)3d(n)-->2p(5)3d(n+1)-->2p(6)3d(n+1)3s(1). The spectra show the presence of Raman features dispersing with the incident photon energy and of a strong feature at constant outgoing photon energy. in CoO the results show that this constant energy feature is present only when the core excitation is 2-3 eV above the core absorption thresholds. This supports a simple model based on the energy loss due to the creation of electron hole pairs across the gap. This mechanism can convert the intermediate excited state into a state of lower energy decaying with the emission at constant photon energy. The implications of these results are briefly discussed.