We have investigated the radiative decay of the metastable level $5d{}^{4}D_{7∕2}$ in ${\mathrm{Xe}}^{+}$. Theoretically we find the decay to be heavily dominated by an $M2$ transition and not by $M1∕E2$ transitions. Lifetime measurements of $5d{}^{4}D_{7∕2}$ in a storage ring are difficult since magnetic mixing of the metastable with a short-lived level quenches its population. Decay rates were determined at different magnetic field strengths $\left(B\right)$ in order to allow a nonlinear extrapolation to $B=0$. The experimental lifetime of $2.4\pm 0.8\mathrm{s}$ was in agreement with the calculated value, but much smaller than previously estimated.

• Received 9 March 2005

DOI:https://doi.org/10.1103/PhysRevA.72.020501