Radioactivity ofScandium44

Because of the unusual beta-ray spectrum previously reported by Smith, a study of the ${\mathrm{Sc}}^{44}$ radioactivity has been made. ${\mathrm{Sc}}^{44}$ was prepared according to the reaction $K^{41}(\alpha ,n){\mathrm{Sc}}^{44}$, and the activity was examined in two 180° focusing, shaped magnetic field spectrometers. A single positron group ($E_0=1.463\mathrm{}\pm 0.005$ Mev; $T_{\frac{1}{2}}=4.0\mathrm{}\pm 0.1$ hr.) was found; the Fermi plot of its momentum distribution has the allowed shape. The positron decay is fed by an isomeric transition ($E=271.3\mathrm{}\pm 0.7$ kev; $T_{\frac{1}{2}}=57\mathrm{}\pm 2$ hr.) and is followed by a gamma-ray ($E=1.16\mathrm{}\pm 0.01$ Mev) to the ground state of ${\mathrm{Ca}}^{44}$. No positron transition directly to the ground state was observed. Evidence was found for a high proportion of $K$-capture to the excited state of ${\mathrm{Ca}}^{44}$.