Combining configuration interaction with perturbation theory for atoms with a large number of valence electrons

Dzuba, V. A.; Berengut, J. C.; Harabati, C.; Flambaum, V. V.

doi:10.1103/physreva.95.012503

Cited by 69 publications

(73 citation statements)

References 65 publications

(79 reference statements)

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“…The small side contains a subset of CSFs that make the largest contribution to the CI expansion. Perturbation theory estimates performed in [31] show that the remaining off-diagonal terms, shown in white, produce a negligible contribution for the small number of states of interest, and can be set to zero without serious loss of accuracy.…”

Section: Emu CImentioning

confidence: 99%

ambit: A programme for high-precision relativistic atomic structure calculations

Kahl¹,

Berengut²

2019

Computer Physics Communications

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We present the ambit software package for general atomic structure calculations. This software implements particle-hole configuration interaction with many-body perturbation theory (CI+MBPT) for fully relativistic calculations of atomic energy levels, electric-and magneticmultipole transition matrix elements, g-factors and isotope shifts. New numerical methods and modern high-performance computing techniques employed by this software allow for the calculation of open-shell systems with many valence-electrons (N ≥ 5) to a high degree of accuracy and in a highly computationally efficient manner. PROGRAM SUMMARYProgram Title: ambit Licensing provisions: GPLv3 Programming language: C++11 Program available from: https: // github. com/ drjuls/ AMBiT Nature of problem: Calculation of atomic/ionic spectra, including energy levels, electric and magnetic multipole transition matrix elements, and isotope shifts. Solution method: The program calculates energy levels and wavefunctions using either configuration interaction (CI) only, or CI with many-body perturbation theory (CI+MBPT) in the Brillouin-Wigner MBPT formalism. Restrictions: The program is not designed to treat highly-excited (Rydberg) states or continuum processes to a high degree of accuracy.

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Section: Emu CImentioning

confidence: 99%

ambit: A programme for high-precision relativistic atomic structure calculations

Kahl¹,

Berengut²

2019

Computer Physics Communications

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“…To determine the sensitivity coefficients k α for each absorption line used in this study, we perform ab initio calculation of the spectrum for each element by solving the Dirac Hamiltonian in flat spacetime (curvature corrections are subdominant) and then compute k α by a finite difference. The spectra are computed using a combination of the configuration interaction (CI) method with many-body perturbation theory (MBPT) [41][42][43][44] the AMBiT software [45]. The full details of the calculations are presented in Appendix A; here we just outline briefly the main aspects of the method.…”

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confidence: 99%

Search for a Variation of the Fine Structure Constant around the Supermassive Black Hole in Our Galactic Center

Hees

Roberts

et al. 2020

Phys. Rev. Lett.

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Searching for space-time variations of the constants of Nature is a promising way to search for new physics beyond General Relativity and the standard model motivated by unification theories and models of dark matter and dark energy. We propose a new way to search for a variation of the fine-structure constant using measurements of late-type evolved giant stars from the S-star cluster orbiting the supermassive black hole in our Galactic Center. A measurement of the difference between distinct absorption lines (with different sensitivity to the fine structure constant) from a star leads to a direct estimate of a variation of the fine structure constant between the star's location and Earth. Using spectroscopic measurements of 5 stars, we obtain a constraint on the relative variation of the fine structure constant below 10 −5 . This is the first time a varying constant of Nature is searched for around a black hole and in a high gravitational potential. This analysis shows new ways the monitoring of stars in the Galactic Center can be used to probe fundamental physics.

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“…[14,15] This approach has been tested in calculations of energy levels of neutral scandium, titanium, and iodine with three, four, and seven valence electrons, respectively. [14,15] This approach has been tested in calculations of energy levels of neutral scandium, titanium, and iodine with three, four, and seven valence electrons, respectively.…”

Section: Discussionmentioning

confidence: 99%

Configuration Interaction and Many‐Body Perturbation Theory: Application to Scandium, Titanium, and Iodine

Imanbaeva

Kozlov

2018

Annalen der Physik

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A number of atoms and ions with complex valence configurations are considered as candidates for atomic clocks with high sensitivity to the possible variation of the fine-structure constant. Present level of the theory is not sufficient to predict frequencies of the clock transitions with accuracy, required for the experiment. Here an approach is tested, where the second-order perturbation theory is used to iteratively saturate configuration space for valence electrons. On the examples of scandium, titanium, and iodine, it is demonstrated that this improves the efficiency of the CI+MBPT method for systems with strong configuration interaction and/or more than three valence electrons.

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Combining configuration interaction with perturbation theory for atoms with a large number of valence electrons

Cited by 69 publications

References 65 publications

ambit: A programme for high-precision relativistic atomic structure calculations

ambit: A programme for high-precision relativistic atomic structure calculations

Search for a Variation of the Fine Structure Constant around the Supermassive Black Hole in Our Galactic Center

Configuration Interaction and Many‐Body Perturbation Theory: Application to Scandium, Titanium, and Iodine

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