Lifetime of the Second Excited Levels inNi60andTi46

The lifetime of the second excited levels in ${\mathrm{Ni}}^{60}$ and ${\mathrm{Ti}}^{46}$ was measured by beta-gamma delayed coincidence method employing a time-to-amplitude converter. The centroid shift of the beta-gamma delayed time distribution was measured with respect to the prompt time distribution due to a prompt gamma-gamma cascade which is present in each isotope. Simultaneous accumulation of the delayed and prompt time distribution on a split memory of a multichannel analyzer was made possible by the use of a third sorting detector. An upper limit of 5×${10}^{-12\mathrm{}}$ sec was established for the mean life of both ${\mathrm{Ni}}^{60}$ and ${\mathrm{Ti}}^{46}$. The mean life of the first excited state of ${\mathrm{Pb}}^{207}$ was also measured to be (1.60±0.1)×${10}^{-10\mathrm{}}$ sec from the slope of the delayed time distribution.