Shape of the $0^{+}$ → $0^{+}$ Positron Spectrum in ${\mathrm{Ga}}^{66}$

A detailed study of the beta spectrum of ${\mathrm{Ga}}^{66}$ with emphasis on the shape of the positron spectrum of the $0^{+}$ → $0^{+}$ transition has been made with a magnetic spectrometer. The ground-state to ground-state transition is found to have a nonstatistical shape. The shape factor is fitted by the equation $S\left(W\right)=K(1+0.0328W+\frac{0.354}{W}-0.000419\mathrm{}{W}^2)$ based upon a ratio of matrix elements $\lambda =\frac{〈i\alpha ·\hat{r}〉}{〈1〉}=-21.3\mathrm{}$. An additional factor of the form ($1+\frac{0.4}{W}$) is needed to obtain the best fit. The nonstatistical shape for this group leads to an end-point energy of 4.153±0.003 MeV and an intensity of 51.2%. The $log\mathrm{ft}$ is 7.903 and from this the amount of $T=3\mathrm{}$ admixture in the $T=2\mathrm{}$ ground state of ${\mathrm{Ga}}^{66}$ is found to be 4.00×${10}^{-5\mathrm{}}$.