Lifetime of the 462-keV Level inTe125

Resonance scattering from ${\mathrm{Te}}^{125}$ has been investigated with ${\mathrm{Sb}}^{125}$ as the source of the exciting gamma radiation. The centrifuge technique was used for the compensation of the recoil energy losses. Appreciable resonance scattering was observed only from the 462-keV ${\frac{5}{2}}^{+}$ level. With a branching ratio $\frac{{\Gamma }_0}{\Gamma }=0.24\mathrm{}$, the observed scattering corresponds to a partial width ${\Gamma }_0=(8.5\mathrm{}\pm 0.9)\times {10}^{-6\mathrm{}}$ eV for the 462-keV $E2\mathrm{}$ ground-state transition. The mean life of the 462-keV level is thus (1.9±0.3) × ${10}^{-11\mathrm{}}$ sec. The absence of resonance scattering from ${\mathrm{Te}}^{125}$ levels reported at 633-, 640-, 652-, and 688-keV excitation energy is consistent with the assignment of spin values $\ge \frac{7}{2}$ to the first two of these states, an upper limit of 0.03% per ${\mathrm{Sb}}^{125}$ decay for the intensity of the 652-keV transition, and a lower limit of ${10}^{-11\mathrm{}}$ sec for the mean life of the 668-keV ground-state transition.