Influence of chemical effect on the Kβ-to-Kα x-ray intensity ratios of Cr, Mn and Co in CrSe, MnSe, MnS and CoS

Abstract

Kβ-to-Kα x-ray intensity ratios of Cr, Mn and Co have been measured in pure metals and in CrSe, MnSe, MnS and CoS compounds following excitation by 59.54 keV γ-rays from a 200 mCi 241Am point-source. Comparison of the measured Kβ-to-Kα intensity ratios with the results of multiconfiguration Dirac–Fock (MCDF) calculations indicates a significant increase of the 3d electron population (in relation to the pure metals) for Cr in CrSe (by 1.0 ± 0.3) and for Mn in MnS (by 0.9 ± 0.3). Our Kβ-to-Kα intensity ratio for Co in CoS does not show any significant change of 3d electron population. The only observed increase of the Kβ-to-Kα intensity ratio for Mn in MnSe indicates the decrease of the number of 3d electrons by 0.6 ± 0.3. To explain evaluated changes of the 3d electron population for all the compounds, one can consider either rearrangement of electrons between 3d and 4s states of the metal or transfer of electrons from the 3d state of the metal to the ligand atom or vice versa. Although the sulphide compounds (MnS, CoS) show similar behaviour, the selenide compounds (CrSe, MnSe) show opposite behaviour which may be attributed to anomalous behaviour of rearrangement of electrons between the valence states of Cr as it happens in the case of free atom. The d–p hybridization effect which was not taken into account in our model theoretical calculation may be partly responsible for the increased Kβ-to-Kα ratio of Mn in MnSe and a comparison of the results for MnS and MnSe suggests that the nature of covalent bonding in MnSe is stronger than that of MnS.