Evolution of collectivity in the⁷⁸Ni region: Coulomb excitation of⁷⁴Ni at intermediate energies.

Abstract

Abstract. The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic observables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope ( 64 Ni) towards the 78 Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently performed an experiment with the goal to extract the B(E2; 0 + → 2 + ) value for the 74 Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed.

Dipole and quadrupole moments of Cu73–78 as a test of the robustness of the Z=28 shell closure near Groote1, Goodacre2, Flanagan3 et al. 2017Phys. Rev. C

“…In recent years, evidence interpreted as an evolution of the magic numbers when going away from the valley of stability has steadily grown, making the study of shell evolution one of the challenges in nuclear physics [3,4]. The very exotic 78 Ni (Z = 28,N = 50) nucleus is a cornerstone in this investigation, and a large volume of theoretical and experimental work has already been devoted to testing these magic numbers [4][5][6][7][8][9][10][11][12][13][14][15][16]. However, low production rates of isotopes in the vicinity of 78 Ni (and, in particular, low production rates of the nickel isotopes themselves) have slowed experimental progress.…”

Single-neutron orbits near 78 Ni: Spectroscopy of theN=49isotope 79 Zn

“…The region of isotopes near 78 Ni is the focus of intense experimental and theoretical research (cf., for example, [7][8][9][10][11][12] and references therein). Whether 78 Ni can be considered a doubly-magic spherical nucleus depends ultimately on the size of the Z = 28 and N = 50 shell gaps.…”

Persistence of the Z=28 shell gap in A=75 isobars: Identification of a possible (1/2Escrig1, Morales2, Nishimura3 et al. 2021Phys. Rev. CSelf Cite3020View full textAdd to dashboardCite

“…The robustness of the Z = 28 closed shell and the coexistence of deformed and spherical shapes in the neutronrich νg 9/2 Ni isotopes have been a matter of debate in a number of recent experimental and theoretical works [11,[19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Particularly important is the conservation of the seniority quantum number υ -the number of protons or neutrons that are not coupled in pairs to J = 0 [33,34]-as it is a good indicator of gap stability.…”