Lifetime of the 11-keV Level inCs134

The mean life of the 11-keV level following the decay of ${\mathrm{Cs}}^{134m}$ has been measured by a delayed-coincidence technique and found to be 69±1 nsec. An indirect measurement of the total-internal-conversion coefficient for this transition ($\alpha =105\mathrm{}$) agrees closely with the theoretical value for a pure $M1\mathrm{}$ transition. This implies that the mean life for radiative decay is ${\tau }_0=7314\mathrm{}$ nsec. This is about 1.8 times the radiative mean life calculated with the odd-group model with the aid of the magnetic moments of neighboring nuclei.