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Relativistic four-c...
Relativistic four-component static-exchange approximation for core-excitation processes in molecules
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- Ekström, Ulf (author)
- Linköpings universitet,Beräkningsfysik,Tekniska högskolan
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- Norman, Patrick (author)
- Linköpings universitet,Beräkningsfysik,Tekniska högskolan
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- Carravetta, V. (author)
- Istituto per i Processi Chimico-Fisici, Area della Ricerca del C.N.R., Pisa, Italy
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(creator_code:org_t)
- American Physical Society, 2006
- 2006
- English.
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 73:2
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http://urn.kb.se/res...
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Abstract
Subject headings
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- 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 H2 S 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.
Subject headings
- NATURVETENSKAP -- Kemi -- Teoretisk kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences -- Theoretical Chemistry (hsv//eng)
Keyword
- Approximation theory
- Electrons
- Ionization
- Dirac-Coulomb Hamiltonian
- Relativistic effects
- Substantial deviations
- Molecules
- NATURAL SCIENCES
Publication and Content Type
- ref (subject category)
- art (subject category)
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