Excitation energy dependence of 3d-metal L2,3 x-ray emission spectra of M[N(CN)2]2 (M = Mn, Fe, Co, Ni, Cu) near 2p threshold

Measurements of resonant inelastic x-ray spectra (RIXS) of M[N(CN)2]2 (M = Mn, Fe, Co, Ni, Cu) molecular magnets are performed near 2p-threshold excitation. The L2,3 x-ray emission spectra reveal features in fine structure in dependence on excitation energy, some of which are common for all 3d elements and others are typical only for the elements located in the middle (Mn, Fe, Co) or at the end of the series (Ni, Cu). The relative role of two channels for radiative decay from the excited (RXES, resonant x-ray emission spectra) and the ionized (NXES, non-resonant x-ray emission spectra) states under variation of atomic number of 3d element is discussed. The full atomic calculation of RIXS spectra for a whole energy range of excitation energies is presented for Mn[N(CN)2]2. A reasonable agreement is found for the shape, the relative intensities and dynamics of energy position for the experimental and calculated RXES. This evidences of many-electron nature of resonance x-ray emission spectra, at least for Mn. In contrast, we could not describe the non-resonant x-ray emission spectra in the atomic approach because the Coster-Kronig transitions 2p-11/23dN → 2p-11/23dN-1 were forbidden energetically in free ions though allowed in solids