Decay ofV50

A. 4.25-kg sample of vanadium metal was counted with a high purity Ge detector for 135.5 d. Ninety-six peaks were observed in the $\gamma$-ray spectrum between 220 and 2615 keV, all but one of which could be assigned to known contaminant radioactivities mostly contained in the V sample itself. After making a 4.0% calculated correction for the intensity of a ${}_{}{}^{234}{}_{}{}^{}\mathrm{Pa}_{}^m{}_{}{}^{} \gamma$ ray of 1554.1(5) keV, the unassigned peak had an energy of 1553.77(6) keV and contained 1020(70) counts. This energy agrees with a recent precision determination of 1553.768(8) keV for the $\gamma$ ray from the first excited state of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ following the ${\beta }^{-}$ decay of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Sc}$. The 1554-keV $\gamma$ ray from the V sample is assigned to the electron capture decay of ${}_{}{}^{50}{}_{}{}^{}\mathrm{V}$ to ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$. Based on an absolute $\gamma$-ray efficiency calibration of the system, a partial half-life $T_{\frac{1}{2}}=1.5\mathrm{}\left(3\right)\mathrm{}\times {10}^{17}$ yr and $log{f}_{0}t=23.4\mathrm{}\left(1\right)\mathrm{}$ were derived for the ${}_{}{}^{50}{}_{}{}^{}\mathrm{V}$ e.c. branch. The expected 783.3-keV $\gamma$ ray, which would follow the ${\beta }^{-}$ decay of ${}_{}{}^{50}{}_{}{}^{}\mathrm{V}$ to ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, was in an unresolved region of contaminant peaks allowing only an upper limit of $T_{\frac{1}{2}}>4.3\mathrm{}\times {10}^{17}$ yr and $log{f}_{0}t>\mathrm{}24.0\mathrm{}$ for the ${\beta }^{-}$ branch. The total half-life derived for ${}_{}{}^{50}{}_{}{}^{}\mathrm{V}$ is $T_{\frac{1}{2}}={1.5}_{-0.7\mathrm{}}^{+0.3\mathrm{}}\times {10}^{17}$ yr.