Exponentially correlated Hylleraas-Configuration Interaction studies of atomic systems. IV. The Five Lowest singlet S and Five Lowest singlet P States of He and Oscillator Strengths, including Upper and Lower Bounds, for their Allowed Transitions

Published

October 6, 2026

Author(s)

James Sims, Maria Ruiz, Bholanath Padhy

Abstract

The Exponentially Correlated Hylleraas-Configuration Interaction method (E-Hy-CI) is a generalization of the Hylleraas-Configuration Interaction method (Hy-CI) in which the single r_ij} of an Hy-CI wave function is generalized to include both linear and exponential r_ij} terms. This work continues the exploration, begun in the first three papers of this series, of whether wave functions containing both linear and exponential r_ij} factors converge more rapidly than either one alone. In the present study we calculate the five lowest singlet S states of He I in one wave function and the five lowest singlet P states of He I in another wave function. These wave functions are used to calculate oscillator strengths, including upper and lower bounds, for the 25 lines arising from allowed transitions among these five singlet S and five singlet P states. The results of this study are oscillator strengths for the n singlet S -> m singlet P transitions for which n = 1-5, m= 2-6 with rigorous upper and lower bounds which in the best case (1 singlet S -> 1 singlet P) are 0.0000 0001 % and probable precision <= 0.0000 0000 01 Comparisons are made with previous experimental and theoretical results.

Citation

Atoms

Volume

14

Pub Type

Journals

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Keywords

Atoms, excited states, Exponentially Correlated Hylleraas-Configuration-Interaction, E-Hy-CI, f-values, Hy-CI, oscillators strengths, Slater-type orbitals (STOs), transition moments, upper and lower bounds.

Citation

Sims, J. , Ruiz, M. and Padhy, B. (2026), Exponentially correlated Hylleraas-Configuration Interaction studies of atomic systems. IV. The Five Lowest singlet S and Five Lowest singlet P States of He and Oscillator Strengths, including Upper and Lower Bounds, for their Allowed Transitions, Atoms, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=962494 (Accessed October 8, 2026)

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