Reexamining Gamow-Teller decays nearNi78

Abstract

Decays of neutron-rich nuclei 82,83 Zn and 82,83 Ga produced in proton-induced fission of 238 U were studied at the Holifield Radioactive Ion Beam Facility (HRIBF) using on-line mass separation and β-γ spectroscopy techniques. New γ-ray transitions were identified and level schemes, which include states at high excitation energies in the range between 3 to 7 MeV were constructed. These high energy levels were identified to be populated through allowed Gamow-Teller β-transitions, and their structure was interpreted with new shell model calculations. A β-delayed neutron branching ratio of 69±7% was deduced for 82 Zn and revised β-decay half-life values of 82 Zn (155(17)(20) ms) and 83 Zn (122(28) ms) were determined.

Pygmy Gamow-Teller resonance in the N=50 region: New evidence from staggering of β -delayed neutron-emission probabilities

“…This value is compatible within error bars with all previous measurements (see Refs. [24,25]) with the exception of the one at 308(1) ms from Ref. [17] (but very close to it).…”

Evidence for Gamow-Teller Decay ofNi78Core from Beta-Delayed Neutron Emission Studies

“…In the case of 84 Ga our calculations predict quasidegenerate 2 − and 3 − states. We used the ground state configuration corresponding to the 2 − state following the observation of the same ground state spin parity in 82 Ga [29,38]. For both 83;84 Ga the resulting calculated β-strength distributions were 2 orders of magnitude smaller than large strength observed in the experimentally accessible region.…”

“…The quenching is necessary due to the incomplete neutron configuration space in our model affecting the normalization of the wave functions after diagonalization [44]. For completeness, we included the strength feeding neutron bound states, taken from [29,30]. These matrix elements to bound states are 1 order of magnitude smaller and therefore likely to be forbidden transitions and are not included in our calculations.…”

“…An additional set of matrix elements was added to build the new hybrid interactions in a schematic way, utilizing interactions for the f 5=2 orbital. Our hybrid interaction has also been tested to interpret the β-decay gamma spectroscopy from decays of other N > 50 nuclei [29,43].…”

Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga86,87Yokoyama1, Grzywacz2, Rasco3 et al. 2019Phys. Rev. CSelf Cite16030View full textAdd to dashboardCite

“…The model we adopt to estimate the GT decay strength distribution for Ga isotopes [16] was based on a shell-model calculation using the NUSHELLX code [31] with hybrid interactions and the truncation described previously in [16,32,33]. In this model, the β-decay properties are dominated by the Gamow-Teller decay of the 78 Ni-core states, leaving the nucleus in the highly excited state because of the N = 50 shell gap.…”