Open AccessTheory of Ca L 2,3 ‐edge XAS using a novel multichannel multiple‐scattering method
Author(s) -
Krüger Peter,
Natoli Calogero R.
Publication year - 2005
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049504027888
Subject(s) - multiplet , x ray absorption spectroscopy , wave function , scattering , atomic physics , coulomb , physics , configuration interaction , electronic structure , chemistry , absorption spectroscopy , electron , quantum mechanics , spectral line , excited state
A new method for calculating X‐ray absorption spectroscopy (XAS) at the L 2,3 edges of Ca and transition metals is presented. It is based on the multichannel multiple‐scattering theory by Natoli et al. [ Phys. Rev. B , (1990), 42 , 1944–1968] combined with the eigen‐channel R‐matrix formalism. Atomic multiplet‐like effects, owing to the Coulomb interaction of photoelectrons and the 2 p hole, are taken into account through a configuration interaction ansatz for the final‐state wavefunction. The various multiplet states lead to a set of channels for the photoelectron wavefunction, which is calculated in multiple‐scattering theory. The method is applied to Ca, an important element for biological applications of XAS. An L : L branching ratio of 3:4 is found, in good agreement with experiment but in contrast to the statistical value 2:1 obtained in all one‐electron approaches. By using a linear mixture between statically screened (∼90%) and unscreened (∼10%) core‐hole potential, the line shape, too, agrees well with the experimental one.