Rates of an intercombination transition and several electric-dipole forbidden transitions between the levels of the ground complex in C-like ions of O and F and in N-like ions of S have been measured optically at a heavy-ion storage ring. The lifetime results, 1.250(13) ms for the ${2s2p}^3$ ${}^5{S}_2^o$ level in ${\mathrm{O}}^{2+},$ 530(25) and 304(5) ms for the ${2s}^2$ ${2p}^2$ ${}^1{S}_o$ level in ${\mathrm{O}}^{2+}$ and ${\mathrm{F}}^{3+},$ respectively, and 5.20(15) and 2.10(6) ms for the ${2s}^2{2p}^3$ ${}^2{P}_{1/2,3/2}^o$ levels of $S^{9+},$ agree with only some of the theoretical predictions, while they have a lower estimated uncertainty than all of them.

• Received 17 March 2000

DOI:https://doi.org/10.1103/PhysRevA.62.022507