Search

The nucleus 212Po has been produced through the fragmentation of a 238U primary beam at 1 GeV/nucleon at GSI, separated with the FRagment Separator, FRS, and studied via isomer γ-decay spectroscopy with the RISING setup. Two delayed previously unknown γ rays have been observed. One has been attributed to the E3 decay of a 21− isomeric state feeding the α-emitting 45-s (18+) high-spin isomer. The other γ-ray line has been assigned to the decay of a higher-lying 23+ metastable state. These are the first observations of high-spin states above the 212Po (18+) isomer, by virtue of the selectivity obtained via ion-by-ion identification of 238U fragmentation products. Comparison with shell-model calculations points to shortfalls in the nuclear interactions involving high-j proton and neutron orbitals, to which the region around Z∼100 is sensitive.

The decay of the 21.47-MeV stretched resonance in 13C, arising from p3/2→d5/2 nucleon excitation coupled to maximum spin, was investigated in a (p,p′) experiment at 135 MeV proton bombarding energy, performed at the Cyclotron Centre Bronowice (CCB) at IFJ PAN in Krakow. First experimental information on the proton and neutron decay branches from this state was obtained by using coincidence measurement of protons inelastically scattered on a 13C target and γ rays from daughter nuclei, namely, 12B (proton decay) and 12C (neutron decay). The main branches lead to the Jπ=2+, first-excited state at 0.953 MeV in 12B, and to the Jπ=1+, T=1 level at 15.110 MeV in 12C. The results were compared with predictions from the Gamow Shell Model (GSM), which was used to describe the stretched resonance in terms of its energy, width, electromagnetic transition strengths and decay pattern. A very good agreement was obtained between the measured and calculated properties of the 21.47-MeV stretched resonance in 13C, demonstrating the high-quality and precision of the GSM wave function calculations, which include coupling to the resonant and non-resonant particle continuum.