Beta-delayed proton activities:Dy147andEr149

The $\beta$-delayed proton spectra of ${}_{}{}^{147}{}_{}{}^{}\mathrm{Dy}$ and the hitherto unknown isotope ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}$ were investigated in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ bombardments of ${}_{}{}^{142}{}_{}{}^{}\mathrm{Nd}$ and ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$., respectively. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{142}{}_{}{}^{}\mathrm{Nd}$ data confirm preliminary results of Klepper et al. that the ${}_{}{}^{147}{}_{}{}^{}\mathrm{Dy}$ delayed-proton spectrum has a high-energy cutoff at ∼5 MeV and is dominated by distinct peaks below 4 MeV in excitation. The proton spectrum following ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}$ decay has a half-life of 9±1 sec and extends from about 2.0 to 6.5 MeV; it has less of the sharp structure observed for ${}_{}{}^{147}{}_{}{}^{}\mathrm{Dy}$. The difference probably arises from the expected lower level density in ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tb}$, a nucleus with one proton outside the ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ core.