Beta decay of the new isotopesK52,Ca52, andSc52; a test of the shell model far from stability

The nuclides ${}_{}{}^{52}{}_{}{}^{}\mathrm{K}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Sc}$ have been produced by fragmentation of a uranium target with a 600 MeV proton beam. The subsequent β decays to the daughter nuclei ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Sc}$, and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ti}$ have been studied by neutron and γ spectroscopy on sources obtained from on-line mass separation. β decay energies have been determined by β-γ coincidence spectroscopy. In addition to the short half-life of ${}_{}{}^{52}{}_{}{}^{}\mathrm{K}$ ($T_{1/2}$=110±30 ms), we attributed two different half-lives ($T_{1/2}$=4.6±0.3 s and $T_{1/2}$=8.2±0.2 s) to ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Sc}$, respectively. A decay scheme has been established for ${}_{}{}^{52}{}_{}{}^{}\mathrm{K}$ involving five β branches to delayed neutron emitting states between 6.6 and 10.3 MeV and one β branch to a bound level at $E_x$=2.56 MeV. The ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ca}$ decay scheme accounts for β branches to four levels at 1.64, 2.75, 3.46, and 4.27 MeV for which the deduced logft values restrict the angular momentum and parity to $J^{\pi }$ ${=1\mathrm{}}^{+}$. For the ${}_{}{}^{52}{}_{}{}^{}\mathrm{Sc}$ ground state, strong β transitions to the $2^{+}$ (1.05 MeV) and the ($4^{+}$) (2.32 MeV) levels in ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ti}$ strongly favor a $J^{\pi }$ ${=3\mathrm{}}^{+}$ attribution. The measured $Q_{\beta }$ values for the ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ca}$ (5.7±0.2 MeV) and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Sc}$ (8.02±0.25 MeV) decay are noticeably lower than expected from mass systematics. The energy level diagrams of ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Sc}$, and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Ti}$ nuclei have been calculated in the framework of the shell model with a realistic interaction. Good agreement between theory and experiment is achieved as well for excitation energies as for mass excesses, assuring then the applicability of the theory to this region of nuclei far from stability.