Theoretical energies and transition probabilities of argon

Polarizabilities and Verdet constants are calculated using a relativistic particle-hole configuration-interaction (CI) method. Particle-hole CI is saturated by including quasicontinuum states built by enclosing an atom in a cavity. Agreement with experiment is achieved, and the method is more accurate than, for example, the Hartree-Fock method. The accuracy of the particle-hole CI method is limited by the omission of configurations with double excitations. Perturbation theory can be applied to account for these excitations, and we expect in the future to further improve the accuracy. The method can be also applied to the calculations of polarizabilities of excited states and can be generalized to other open-shell atoms.

Section: B Evaluation Of Error In Calculations Due To Second-order Ementioning

confidence: 80%

Section: Introductionmentioning

confidence: 78%

Particle-hole configuration-interaction polarizabilities and Verdet constants of noble-gas atoms

Savukov

2012

“…The CI+MBPT method was successfully used for a number of atoms with two or three valence electrons [16,17,22] (or an electron and a hole [20,21]). Its extension to atoms with more electrons in open shells meets some difficulties.…”

Section: Introductionmentioning

confidence: 99%

Core-valence correlations for atoms with open shells

Dzuba

Flambaum

2007

We present an efficient method of inclusion of the core-valence correlations into the configuration interaction (CI) calculations. These correlations take place in the core area where the potential of external electrons is approximately constant. A constant potential does not change the core electron wave functions and Green's functions. Therefore, all operators describing interaction of M valence electrons and N − M core electrons (the core part of the Hartree-Fock Hamiltonian V N−M , the correlation potentialΣ1(r, r ′ , E) and the screening of interaction between valence electrons by the core electronsΣ2) may be calculated with all M valence electrons removed. This allows one to avoid subtraction diagrams which make accurate inclusion of the core-valence correlations for M > 2 prohibitively complicated. Then the CI Hamiltonian for M valence electrons is calculated using orbitals in complete V N potential (the mean field produced by all electrons);Σ1 +Σ2 are added to the CI Hamiltonian to account for the core-valence correlations. We calculateΣ1 andΣ2 using many-body perturbation theory in which dominating classes of diagrams are included in all orders. We use neutral Xe I and all positive ions up to Xe VIII as a testing ground. We found that the core electron density for all these systems is practically the same. Therefore, we use the sameΣ1 andΣ2 to build the CI Hamiltonian in all these systems (M = 1, 2, 3, 4, 5, 6, 7, 8). Good agreement with experiment for energy levels and Landé factors is demonstrated for all cases from Xe I to Xe VIII.

“…A more general R-matrix approach has been used, but owing to the complexity of implementation, it is not easy to incorporate into existing precision atomic-structure methods to systematically improve accuracy. Configuration-interaction relativistic-manybody-theory (CI-RMBPT) formalism has been successful in predicting energies, matrix elements, and other properties of bound states of atoms [3][4][5][6], which is quite promising, but it has not applied to photoionization problems owing to extra complications arising from continuum states. In this paper a method is introduced to convert discrete CI-(R)MPBT oscillator strengths (OS) to photoionization cross sections with minimal modifications of the codes and CI-RMBPT cross sections are computed.…”

mentioning

confidence: 99%

“…These atoms are chosen for the following reasons: (1) noble-gas atom photoionization cross sections have been measured with high precision; (2) the number of particle-hole configurations is relatively small, facilitating the investigation of the effects of various parameters on the accuracy; (3) an accurate particle-hole CI+MBPT method has been previously developed for these atoms with agreement demonstrated for energies, oscillator strengths, and g-factors [6]; and (4) these atoms are of considerable interest for applications.…”

mentioning

confidence: 99%

Configuration-interaction relativistic-many-body-perturbation-theory calculations of photoionization cross sections from quasicontinuum oscillator strengths

Savukov

Filin

2014

Many applications are in need of accurate photoionization cross sections, especially in the case of complex atoms. Configuration-interaction relativistic-many-body-perturbation theory (CI-RMBPT) has been successful in predicting atomic energies, matrix elements between discrete states, and other properties, which is quite promising, but it has not been applied to photoionization problems owing to extra complications arising from continuum states. In this paper a method that will allow the conversion of discrete CI-(R)MPBT oscillator strengths (OS) to photoionization cross sections with minimal modifications of the codes is introduced and CI-RMBPT cross sections of Ne, Ar, Kr, and Xe are calculated. A consistent agreement with experiment is found. RMBPT corrections are particularly significant for Ar, Kr, and Xe and improve agreement with experimental results compared to the particle-hole CI method. The demonstrated conversion method can be applied to CI-RMBPT photoionization calculations for a large number of multivalence atoms and ions.