Relativistic four-component static-exchange approximation for core-excitation processes in molecules
2006 (English)In: Physical review A, ISSN 1050-2947 (print), 1094-1622 (online), Vol. 73, no 2, 022501- p.Article in journal (Refereed) Published
A generalization of the static-exchange approximation for core-electron spectroscopies to the relativistic four-component realm is presented. The initial state is a Kramers restricted Hartree-Fock state and the final state is formed as the configuration-interaction single excited state, based on the average of configurations for (n–1) electrons in n near-degenerate core orbitals for the reference ionic state. It is demonstrated that the static-exchange Hamiltonian can be made real by considering a set of time-reversal symmetric electron excitation operators. The static-exchange Hamiltonian is constructed at a cost that parallels a single Fock matrix construction in a quaternion framework that fully exploits time-reversal and spatial symmetries for the D2h point group and subgroups. The K- and L-edge absorption spectra of H2S are used to illustrate the methodology. The calculations adopt the Dirac-Coulomb Hamiltonian, but the theory is open ended toward improvements in the electron-electron interaction operator. It is demonstrated that relativistic effects are substantial for the L-edge spectrum of sulfur, and substantial deviations from the statistical 2:1 spin-orbit splitting of the intensity distribution are found. The average ratio in the mixed region is 1.54 at the present level of theory.
Place, publisher, year, edition, pages
2006. Vol. 73, no 2, 022501- p.
hydrogen compounds, relativistic corrections, configuration interactions, HF calculations, excited states, spin-orbit interactions
IdentifiersURN: urn:nbn:se:liu:diva-12688DOI: 10.1103/PhysRevA.73.022501OAI: oai:DiVA.org:liu-12688DiVA: diva2:16862