Influence of the core hole on K beta emission following photoionization or orbital electron capture: A comparison using MnO and (Fe2O3)-Fe-55

The Mn K beta fluorescence emission in MnO after photoionization and in (Fe2O3)-Fe-55 after radioactive electron capture decay from the K shell have been measured using a crystal array spectrometer with an instrumental energy bandwidth of 0.7 eV (full width at half maximum). Both compounds have a 3d(5) valence electron configuration in the ionic approximation. It is found that the spectral features after K capture in (Fe2O3)-Fe-55 are shifted in emission energy and are sharper, compared to the spectra following photoionization in MnO, i.e., the spectra exhibit a dependence on the mode of excitation. Crystal-field multiplet calculations including ligand-to-metal charge transfer have been carried out for the 1 s intermediate states as well as for the 3p to 1 s (K beta) radiative transition. The populated I s intermediate states after photoionization are found to be spread over several eV. In comparison, only the lowest-lying Is intermediate states split by the weak (1s, 3d) exchange interaction are populated after K capture. It is proposed that the differences in population of the Is intermediate states together with a term-dependent final-state lifetime broadening can account for the changes in the spectral shapes due to the different modes of excitation.