Spontaneous Single-Photon Decay of 2 ³S₁ in Helium-Like Ions

Transition probabilities for 1 1S0_2 3S1 lines in helium-like ions are estimated from hydrogen 1 2S112_ 2 2S112 magnetic-dipole transition probabilities obtained by Breit and Teller from Dirac theory. For C V and higher members of the isoelectronic sequence the new transition rates are sufficiently large (when compared with collisional rates) to explain the strong emission of these lines by the corona and to make two-photon decay negligible for Z < 20