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

K beta-to-K alpha x-ray intensity ratios of Cr, Mn and Co have been measure d in pure metals and in CrSe, MnSe, MnS and CoS compounds following excitat ion by 59.54 keV gamma-rays from a 200 mCi Am-241 point-source. Comparison of the measured K beta-to-K alpha intensity ratios with the results of mult iconfiguration Dirac-Fock (MCDF) calculations indicates a significant incre ase of the 3d electron population (in relation to the pure metals) for Cr i n CrSe (by 1.0 +/- 0.3) and for Mn in MnS (by 0.9 +/- 0.3). Our K beta-to-K alpha intensity ratio for Co in CoS does not show any significant change o f 3d electron population. The only observed increase of the K beta-to-K alp ha intensity ratio for Mn in MnSe indicates the decrease of the number of 3 d 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 f rom the 3d state of the metal to the ligand atom or vice versa. Although th e sulphide compounds (MnS, CoS) show similar behaviour, the selenide compou nds (CrSe, MnSe) show opposite behaviour which may be attributed to anomalo us 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 par tly responsible for the increased K beta-to-K alpha ratio of Mn in MnSe and a comparison of the results for MnS and MnSe suggests that the nature of c ovalent bonding in MnSe is stronger than that of MnS. (C) 2000 Elsevier Sci ence B.V. All rights reserved.