The radiative decay rate of ${\mathrm{C}}^{4+}$ ions in the metastable 1s2${\mathit{s}}^3$${\mathit{S}}_1$ state has been measured at the ion storage ring TSR in Heidelberg, observing the time dependence of the dielectronic recombination rate on resonances characteristic for this metastable state. The very accurate result of 48.57±0.11 ${\mathit{s}}^{\mathrm{-}1}$ allows us to distinguish between different theoretical approaches. Our result is in excellent agreement with a calculation of the magnetic-dipole decay rate using nonrelativistic radial wave functions for the heliumlike carbon ion.

• Received 29 September 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.1616