Doublet-quartet energy separation in boron: A partitioned-correlation-function-interaction method

Abstract

No lines have been observed for transitions between the doublet and quartet levels of B I. Consequently, energy levels based on observation for the latter are obtained through extrapolation of wavelengths along the isoelectronic sequence for the 2s 2 2pP 5/2 transition. In this paper, accurate theoretical excitation energies from a partitioned-correlation-function-interaction (PCFI) method are reported for B I that include both relativistic effects in the Breit-Pauli approximation and a finite mass correction. Results are compared with extrapolated values from observed data. For B I our estimate of the excitation energy 28 959 ± 5 cm −1 is in better agreement with the values obtained by Edlén et al. (1969) than those reported by Kramida and Ryabtsev (2007). Our method is validated by applying the same procedure to the separation of these levels in C II.

Multiconfiguration Dirac-Hartree-Fock calculations of excitation energies, oscillator strengths, and hyperfine structure constants for low-lying levels of Sm I

“…Recently, partitioned correlation function interaction (PCFI) approach was developed for complicated atoms [30,31], which relax the orthonormality restriction on the orbital basis and break down the originally very large calculations into a series of smaller calculations. The subspace of CFSs makes it easier to capture the effects weakly connected to total energy, which could be significant for some atomic properties.…”

Advanced multiconfiguration methods for complex atoms: I. Energies and wave functions

“…Similar detailed and systematic convergence studies of energies have been done for other Li-like systems[50] as well as for Be-and B-like systems[48,49,51,177], adding to our understanding of correlation effects and how they can be accounted for in multiconfiguration methods.…”

“…There are basically two ways to approach this, either one derives theoretical expressions that give upper limits of the error in a computed result [43,44], or one designs an approach that, in a systematic fashion, extends the complexity or simply the size of the calculations [45][46][47]. If the complexity could be described quantitatively, it is then possible to estimate the convergence of the calculations, or even extrapolate to give the deviation from the 'exact' value [48][49][50][51]. The methods we describe here offer a clear way to define a systematic approach since, as we will see in later sections, an atomic state is represented by an atomic state function (ASF), ( ) Y GJ , which is expanded in a set of configuration state functions (CSFs), ( )…”

“…The PCFI method uses a biorthonormal transformation method [179] to relax the orthogonality constraint of the orbitals and correlation effects can be described by several non-orthogonal sets of correlation orbitals, each set being optimally localized for the considered correlation effect. The PCFI method captures correlation effects more efficiently than do the ordinary MCHF and MCDHF methods [51].…”