Decay ofA35

The positron decay of ${\mathrm{A}}^{35}$ has been investigated with a magnetic lens beta-ray spectrometer and a NaI(Tl) scintillation spectrometer. A maximum beta-ray energy of 4.96±0.04 Mev was found, which is 0.5 Mev higher than the previous values determined by cloud-chamber measurements. The new value is in good agreement with the end point predicted from Coulomb energy considerations. Two weak gamma rays were found with energies of 0.19±0.04 and 1.73±0.04 Mev; both are in good agreement with reported levels in ${\mathrm{Cl}}^{35}$. Analysis of the complex beta spectrum shows that approximately 7% of the ${\mathrm{A}}^{35}$ decays to two excited states in ${\mathrm{Cl}}^{35}$. The $\mathrm{ft}$ value of the ground-state, mirror transition is 6200±400 seconds. From this $\mathrm{ft}$ value and the $\mathrm{ft}$ value of ${\mathrm{O}}^{14}$, the ${\left|\int \sigma \right|}^2$ for this transition was estimated to be less than 0.13; the $e-\nu$ angular correlation coefficients were calculated to be +0.96±0.04 and -0.93±0.09 for the $V$, $T$ and $S$, $T$ beta interactions, respectively. These coefficients are indistinguishable from those expected in the case of a pure Fermi transition, indicating that ${\mathrm{A}}^{35}$ would be very suitable for identifying the Fermi invariant in the beta-decay interaction by an angular correlation experiment.