MCHF oscillator strength and lifetime calculations in neutral calcium

Abstract

We report extensive multiconfiguration Hartree-Fock (MCHF) calculations, taking into account valence correlation and core-relaxation effects, of energy levels, eigenvector compositions, electric dipole and quadrupole oscillator strengthsstates in Ca 1. On the whole, the agreement between theory and obselvation has been improved by our set of MCHF results. The theoretical transition probabilities allow the evaluation of the lifetimes for the levels 454p, 4s5p 'Po; 4s4d,4p2 'D and 3d4p, 4s4f 'Fo which are compared with the most recent measurements. The differences between MCHF calculations for series perturbed by doubly-exdted states in Ca and Sr are discussed. It is concluded that corepolarization effects are of about the same importance in the two atom but that the effects on the 3d (Ca) and 4d (Sr) orbitals are such that the total core-polarization effects for series and perturbers are of the same magnitude in Sr while large differences exist in Ca.

Electronic isotope shift factors for the Ir 5d76s24F9/2Schiffmann1, Godefroid2 2021Journal of Quantitative Spectroscopy and Radiative Transfer6100View full textAdd to dashboardCite

“…Therefore, we must pay a careful attention that the computed level corresponds to the level involved in the measured transition, i.e., that its absolute position in the theoretical Hamiltonian spectrum of the ordered roots for the considered ( π , J ) block symmetry is the same as the experimental energy ordering. The inversion of two energy levels compared to experiments is referred to as root-flipping [32] . A case of root-flipping appeared in the 1 F series of Ca II studied by Vaeck et al [32] , and was attributed to the omission of the core polarization that is usually captured by including core-valence correlation effects.…”

“…The inversion of two energy levels compared to experiments is referred to as root-flipping [32] . A case of root-flipping appeared in the 1 F series of Ca II studied by Vaeck et al [32] , and was attributed to the omission of the core polarization that is usually captured by including core-valence correlation effects. This issue was later resolved by improving the correlation model, including core-valence and core-core correlation [33] .…”

Combined configuration-interaction and many-body-perturbation-theory calculations of energy levels and transition amplitudes in Be, Mg, Ca, and Sr

“…We found, for example, that frozen-core CI calculations in Ca gave energies so inaccurate that it was difficult, if at all possible, to identify many closely spaced levels of experimental interest. Multi-configuration Dirac-Fock (MCDF) and Hartree-Fock (MCHF) methods have also been used to obtain energies and oscillator strengths in divalent atoms: MCHF for Be-like ions [7] and neutral calcium [8], and MCDF for Mg-like ions [9]. The accuracy of MCHF and MCDF calculations in neutral atoms is poor, basically because of computational limits on the number of con-figurations.…”

Entrance Channel Effects in the Reaction of Aligned Ca(1P) with HCl

“…For the computation of the electronic wave functions and the quadrupole moment of the Ca atom in its 1 P excited state, we used the same multiconfiguration self-consistent-field (MCSCF) approach as in ref 26 40 Therefore, we believe that we can use the same basis here to describe the 4s4p 1 P state. Moreover, this basis will also be suitable for the 3d4p 1 P perturber state, which contributes 15.5% to the 4s4p 1 P state.…”