Test of the singly magic character of theN=50isotoneAs83populated inGe83decay

The first information obtained on excited states of the N=50 isotone ${}_{}{}^{83}{}_{}{}^{}\mathrm{As}$ populated in the β decay of neutron-rich ${}_{}{}^{83}{}_{}{}^{}\mathrm{Ge}$ is presented. The ${}_{}{}^{83}{}_{}{}^{}\mathrm{Ge}$ half-life was measured to be 1.85±0.06 s. Using γ singles and γγ coincidence measurements, a total of 51 γ rays were placed in a level scheme for ${}_{}{}^{83}{}_{}{}^{}\mathrm{As}$ corresponding to 28 levels in a range of excitation energy up to 4.84 MeV. The density of levels up to 2.0 MeV excitation energy is reasonably well reproduced by shell-model calculations, indicating that ${}_{}{}^{78}{}_{}{}^{}\mathrm{Ni}$ is probably a doubly magic nucleus. Approximately half of the β intensity to excited states in ${}_{}{}^{83}{}_{}{}^{}\mathrm{As}$ populates a group of levels above 3.5 MeV excitation energy which can be interpreted as primarily core polarization neutron particle-neutron hole states.