Characteristic features of the 3p absorption spectra of free iron-group elements due to the duplicity of the 'inner-valence' 3d electrons. Application to Mn2+

The 3p absorption spectrum of Mn2+(3d(5 6)S) over the 3p --> 4s and 3p --> 3d resonance regions is theoretically studied for the first time. The calculations were performed within the 'spin-polarized' random-phase approximation with exchange. The ordering of these resonances is found to be opposite to that in Cr, Cr+ and Mn+. As a result, the 3p absorption of Mn2+ differs markedly from that of Mn+. The 'permutation' of the 3p --> 4s and 3p --> 3d resonances is proved to be inevitable for a 3d element with the increase in its ionic charge. This arises from the fact that the 3d electrons of iron-group elements are valence by energy but inner by spatial distribution. The duplicity of the 3d electrons is also found to result in additional characteristic features of the 3p absorption spectra, such as, at first glance, the 'inconsistent' energy ordering of the 3p --> 4s and 3p --> 3d resonance structures in neutral and low charged elements and the insensitivity of the 3p --> 3d transition energy to the degree of ionization of a given element from the iron-group.