β-delayed neutron emission in theNi78region

Abstract

A systematic study of the total β-decay half-lives and β-delayed neutron emission probabilities is performed. The β-strength function is treated within a self-consistent density-functional + continuum-quasiparticle-randomphase-approximation framework including the Gamow-Teller and first-forbidden transitions. The experimental total β-decay half-lives for the Ni isotopes with A 76 are described satisfactorily. The half-lives predicted from A = 70 up to A = 86 reveal fairly regular A behavior which results from simultaneous account for the Gamow-Teller and first-forbidden transitions. For Z ≈ 28 nuclei, a suppression of the delayed neutron emission probability is found when the N = 50 neutron closed shell is crossed and the neutron excess becomes more than one major shell. The effect originates from the high-energy first-forbidden transitions to the states outside the Q β -B n window in the daughter nuclei.

Reexamining Gamow-Teller decays nearNi78

“…For sufficiently exotic nuclei, the GT decay becomes dominant, resulting in the observation of large β-delayed neutron branching ratios [30,[32][33][34][35] in this region [33,35]. The experimental results presented here show evidence for the GT transitions to the bound states in the decay daughter, thus providing insight into the role of the N = 50 shell gap in these decays.…”

β-decay measurements forN>40Mn nuclei and inference of collectivity for neutron-rich Fe isotopes

“…A χ 2 -minimization was used for nuclei observed with more than 400 β correlation events, whereas the likelihood normalization method is used for lower correlation yields. For very neutron-rich nuclei a strong β-delayed neutron branch is expected [23]. This branch for Co and Ni isotopes is of the order of 10% [24].…”

Multi-neutron emission of Cd isotopes

“…In the last years a renewed attention has been attracted to the delayed multi-neutron emission (βxn) with x = 2, 3.... The β2n emission has been predicted in early 60-s [2] and later observed in for the cases of 11 Li [3] and 30−32 Na [4]. It has also been considered for heavier nuclei in Ref.…”

“…Assuming an amplification of the intensity distribution by the integral Fermi factor, the most important contributions come from the allowed Gamow-Teller (GT) and high-energy first-forbidden β-decays. Importantly, they should be treated employing the one and the same self-consistent framework [10,11].…”