Method of evaluating chemical shifts of X-ray emission lines in molecules and solids

摘要

Method of evaluating chemical shifts of X-ray emission lines for sufficientlyheavy atoms (beginning from period 4 elements) in chemical compounds isdeveloped. This method is based on the pseudopotential model and one-centerrestoration method (to reconstruct the proper electronic structure inheavy-atom cores). The approximations of instantaneous transition and frozeninner core spinors of the atom are used for derivation of an expression forchemical shift as a difference between mean values of some effective operator.The method allows one to avoid evaluating small values (chemical shifts ~$0.01{-}1$ eV) as differences of very large values (transition energies ~$1{-}100$ keV in various compounds). The results of our calculations ofchemical shifts for the $K\alpha_1$, $K\alpha_2$, and L transitions of thegroup 14 metal cations with respect to neutral atoms are presented. Thecalculations of chemical shift of $K\alpha_1$-line in the Pb-core transitionwithin PbO and PbF$_2$ with respect to the neutral Pb are also performed anddiscussed. The accuracy of the used approximations is discussed and quality ofthe performed calculations is analyzed.