Lifetimes of Metastable $2\;^3{\rm S}_1$ States of Heliumlike Ions

The lifetime of the $2\,^3{\rm S}_1$ state of helium is unusually long. This property is useful in astrophysical observations of nebulae to determine their temperature and density conditions. Calculations of relativistic magnetic dipole (M1) transitions, including corrections to the magnetic dipole transition operator, are performed and the lifetimes for the metastable $2\,^3{\rm S}_1$ state are evaluated. These decay rates for heliumlike ions have been calculated by Drake [1]. The present work provides an update to the calculations using significantly larger basis sizes in the calculation, yielding more accurate results. M1 decay rates are presented for all the heliumlike ions through the isoelectronic sequence up to Fe XXV. These results can be compared with measurement by Moos and Woodworth [2], and the electron beam ion trap results tabulated by Tr\"abert [3].\\[6pt] \mbox{}[1] G.W.F. Drake, Phys. Rev. A {\bf 3}, 3 (1971).\\ \mbox{}[2] H.W. Moos and J.R. Woodworth, Phys. Rev. A {\bf 12}, 2455 (1975).\\ \mbox{}[3] E. Tr\"abert, Can. J. Phys. {\bf 86}, 73 (2008).