Outer-core emission spectroscopy of the heavy alkaline-earth metals

Optical emission spectra from the np$\sp5$ initial core-excited configurations of the alkaline-earth metals calcium, strontium, and barium are presented. The spectra are found to be anomalously broad and red-shifted with regard to XPS core positions. With the help of data from complementary core-level spectroscopies, a model for both the creation and the annihilation of these core configurations is inferred.By considering the structure of the core-hole screening in a pseudo-atomic format, the set of symmetry allowed recombination events is determined. The initial core-excited configuration is found to involve a strongly local, d-like charge which is spin polarized parallel to the core. Because the optical transition between this configuration and the ground configuration is dipole forbidden, the emission spectra mainly reflect those allowed transitions which leave the local environment in a valence-excited configuration. The dynamics of the creation of the core-hole configuration are found to strongly influence both the photoelectron spectra and the optical absorption spectra for these cores.The optical emission spectra from alkaline-earths as impurities in alkali-metal host lattices, show little modification from the pure metal spectra. The minor differences which do occur upon dilution take the form of small chemical-shifts and some very slight line-shape alterations. The alloys thus serve to illustrate the strongly local character of these outer-core transitions. Beginning at very low alkaline impurity concentrations, in contrast to the behavior of the alkaline bands, the emission bands associated with the alkali host metals show both a strong quenching of the pure-metal x-ray edge peaks and a substantial suppression of threshold emission intensity.U of I OnlyETDs are only available to UIUC Users without author permissio