Impact of Tensor Interaction on Beta-Delayed Neutron Emission from Neutron-Rich Nickel Isotopes
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CLEI Theory
Impact of Tensor Interaction on Beta-Delayed Neutron Emission from Neutron-Rich Nickel Isotopes E. O. Sushenok1), 2)* , A. P. Severyukhin1), 2)** , N. N. Arsenyev1)*** , and I. N. Borzov3), 1)**** Received August 2, 2017
Abstract—The Skyrme energy density functional including tensor interaction is used to describe microscopically multineutron delayed-neutron emission accompanying beta decay of even–even neutron-rich nickel isotopes of mass number in the range of A = 74−80. The respective calculations are performed in the quasiparticle random-phase approximation with allowance for the two-phonon components of the wave function for states of the daughter nucleus. The properties of the lowest quadrupole excitation of 74,76,78,80 Ni are also studied. It is shown that a decrease in the strength of neutron–proton tensor interaction leads to a substantial hindrance of beta decay and to an increase in the probability for delayedneutron emission. DOI: 10.1134/S1063778818010192
nucleus of 78 Ni, the idea of the possible existence of a so-called weak r-process responsible for the formation of elements in the region of the А = 80 peak [3] also nourishes interest in nuclides near the Z = 28, N = 50 shells. Its mechanism differs from the mechanism of the “basic” r-process, which is operative for A > 120 nuclides. Since the problem of possible scenarios of the r-process is presently far from being solved, a refinement upon beta-decay data in this region of the nuclear map is of importance. The quasiparticle random-phase approximation (QRPA) involving effective Skyrme forces is one of the basic approaches to describing charge-exchange nuclear excitations and beta decay (see, for example, [4–7]). Calculations within this conceptual framework do not require introducing new parameters, since one obtains here the residual interaction self-consistently with the same energy density functional as the mean field. Data on beta decay and delayed-neutron emission are frequently the only source of information about the respective beta strength function [8, 9]. Interest in semimagic isotopes of nickel and tin is caused by the fact that attempts at describing them on the basis of modern QRPA models run into difficulties [10]. In particular, the description in [10] of the contribution of the firstforbidden half-lives to the total half-lives of nuclei containing Z = 28 and 50 protons is at odds with the experimental beta-decay scheme from [11]. The inclusion of the tensor nucleon–nucleon interaction has a substantial impact on Gamow–Teller (GT) transitions in the beta-decay window [12]. In order to study the multineutron-emission process accompanying the beta decay of nuclei, it is necessary
1. INTRODUCTION Investigations into the structure of neutron-rich nuclei are among the lines of research in low-energy nuclear physics that are of great topical interest. A strong neutron–proton asymmetry of such nuclei overburdened with neutrons may lead to the appearance of new subshells and even to a change in magic numbers, affecting their beta-deca
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