Decay of the high-spin isomers inHo150,151,152

The electron-capture decay properties of the high-spin isomers in ${}_{}{}^{150,151,152}{}_{}{}^{}\mathrm{Ho}$ were investigated. The nuclides were produced in ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ bombardments of samarium and then transported to shielded areas with the use of gasjet systems. Singles and coincidence $\gamma$-ray measurements were made. Each isomer decays primarily to one excited state in its dysprosium daughter by means of an allowed $\beta$ transition ($log\mathrm{ft}$ values are ∼4.5). The following explanations are proposed. For ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$ and ${}_{}{}^{152}{}_{}{}^{}\mathrm{Ho}$ the transitions connect $9^{+}$($\pi h_{\frac{11}{2}}$,$\nu f_{\frac{7}{2}}$) levels with $8^{+}$($\nu h_{\frac{9}{2}}$,$\nu f_{\frac{7}{2}}$) levels in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}$(2401.8 keV) and ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$(2437.6 keV). Deexcitation to the ground states then follows via a cascade of four $E2$ $\gamma$ rays. In ${}_{}{}^{151}{}_{}{}^{}\mathrm{Ho}$ the $\beta$ transition represents the changeover of an $h_{\frac{11}{2}}$ proton orbital to an $h_{\frac{9}{2}}$ neutron orbital in ${}_{}{}^{151}{}_{}{}^{}\mathrm{Dy}$. This single neutron state lies at 527.4 keV and deexcites directly to the ground state. The $\alpha$ decay of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Ho}$ was also investigated with the use of an on-line isotope separator. Its $\alpha$-decay branching ratio was determined to be 10.5±3.0%.