Shell model and mean-field description of band termination in theA∼44 nuclei

Abstract

We study nuclear high-spin states undergoing the transition to the fully stretched configuration with maximum angular momentum I max within the space of valence nucleons. To this end, we perform a systematic theoretical analysis of non-fully-stretched I max − 2 and I max − 1 f n 7/2 seniority isomers and d −1 3/2 f n+1 7/2 intruder states in the A∼44 nuclei from the lower-fp shell. We employ two theoretical approaches: (i) the density functional theory based on the cranked self-consistent Skyrme-Hartree-Fock method, and (ii) the nuclear shell model in the full sdfp configuration space allowing for 1p-1h cross-shell excitations. We emphasize the importance of restoration of broken angular momentum symmetry inherently obscuring the mean-field treatment of high-spin states. Overall good agreement with experimental data is obtained.

Loss of collectivity in the transitionalEr156nucleus at high spin

“…This was discussed for close-to-spherical states built on a few valence particles in Ref. [56]. The problems should be less severe in the present case given the larger deformation with particles distributed over several j shells.…”

STUDIES OF 44Ti AND 48Cr NUCLEI WITHIN VARIATIONAL MEAN FIELD THEORY

“…The middle of this valence space turns out to be unique workbench where several interesting concepts related to collective phenomena can be studied. Existence of rotational bands at low to intermediate spins confirmed by experiments, 1,2,[9][10][11][12] backbending of the yrast band, band termination 13 and the appearance of superdeformed as well as axially symmetric shape triaxiality [14][15][16] find their microscopic explanation in terms of Spherical Shell Model calculations within this valence space.…”

Isospin-symmetry restoration within the nuclear density functional theory: Formalism and applications

“…Hence, they can be regarded as extreme cases of an almost undisturbed s.p. motion, thus offering an excellent playground to study, among others, timeodd densities and fields, spin-orbit force [23,72,73], tensor interactions [74], and the isospin dependence of cross-shell (sd − fp) p-h matrix elements [73,75].…”

“…configurations of odd-odd N = Z nuclei and in all other but isoscalar excited states. Two prominent examples are discussed in this work: superdeformed (SD) bands in a doubly magic nucleus 56 Ni [22] and terminating states in N = Z A ∼40 nuclei [23]. In the present work, we neglect pairing, because our applications concern high-spin and/or high-seniority states in medium mass nuclei, in which static pairing is expected to be weak or negligible, except for some cases [22].…”