Answers are grounded in this paper and cite their sources.
The electric dipole oscillator strengths and transition probabilities of the spin-forbidden transitions among the 1'S, 21S, 21P, and 23P levels of the heliumlike ions from He i to Ne ix are evaluated to high accuracy by purely theoretical methods
No takes yet. Share an insight, caveat, or question.
Drake et al. (1969) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: