The lifetime of the $1s2s{}^3{S}_1$ level of the He-like ${\mathrm{O}}^{6+}$ ion has been measured using the Electron Beam Ion Trap in the magnetic trapping mode. A value of ${956}_{-4}^{+5\mathrm{}}$ $\mu \mathrm{s}$ is found, which corresponds to a radiative transition rate of ${1046}_{-5}^{+4\mathrm{}}$ ${\mathrm{s}}^{-1}$ for the magnetic dipole transition to the ${1s}^2{}^1{S}_0$ ground state. This value is in excellent agreement with recent theoretical predictions and distinguishes among different treatments of negative energy states and correlation in multiconfiguration Dirac-Fock calculations.

• Received 29 December 1997

DOI:https://doi.org/10.1103/PhysRevA.58.238