Shape coexistence in the microscopically guided interacting boson model

Abstract

Abstract. Shape coexistence has been a subject of great interest in nuclear physics for many decades. In the context of the nuclear shell model, intruder excitations may give rise to remarkably low-lying excited 0 + states associated with different intrinsic shapes. In heavy open-shell nuclei, the dimension of the shell-model configuration space that includes such intruder excitations becomes exceedingly large, thus requiring a drastic truncation scheme. Such a framework has been provided by the interacting boson model (IBM). In this article we address the phenomenon of shape coexistence and its relevant spectroscopy from the point of view of the IBM. A special focus is placed on the method developed recently which makes use of the link between the IBM and the self-consistent mean-field approach based on the nuclear energy density functional. The method is extended to deal with various intruder configurations associated with different equilibrium shapes. We assess the predictive power of the method and suggest possible improvements and extensions, by considering illustrative examples in the neutron-deficient Pb region, where shape coexistence has been experimentally studied.

Structural evolution inA≈100nuclei within the mapped interacting boson model based on the Gogny energy density functional

“…The method allows a computationally feasible as well as quantitative description of the low-energy collective excitations. It has already been applied to study the quadrupole [29,[31][32][33] and octupole [34] modes in atomic nuclei as well as to describe shape coexistence phenomena [35][36][37]. In the present study we extend the method of Ref.…”

Structural evolution in germanium and selenium nuclei within the mapped interacting boson model based on the Gogny energy density functional

“…The IBM Hamiltonian is then diagonalized and the resulting wave functions are used to compute the spectroscopic properties of 66−94 Ge and 68−96 Se. The fermion-to-boson mapping procedure has allowed an arXiv:1702.04879v2 [nucl-th] 14 Jun 2017 accurate, computationally economic and systematic description of the shape coexistence [35], the structural evolution in A ≈ 100 nuclei [36], the quadrupole and octupole transitions in the light actinide and rare-earth regions [37,38] as well as odd-mass nuclei [39]. In this work, we demonstrate the ability of the mapping scheme to account for the properties of the nuclei on the neutrondeficient side (N ≤ 50), where there are enough experimental data to compare with.…”

Large-scale shell-model calculations on the spectroscopy ofN<126Pb isotopes

“…One prominent example is the study of the systematics of the low-lying 0 + states and the possible coexistence of states with different shapes in nuclei around the neutron mid-shell nucleus 186 Pb for which substantial experimental and theoretical efforts have been devoted from different perspectives (for reviews see Refs. [1][2][3][4][5][6][7] and references therein) both experimentally [1,[8][9][10][11][12][13][14][15][16][17][18] and theoretically [2,[19][20][21][22][23][24][25][26][27][28][29][30]. Another interesting aspect is the gradual increase in empirical pairing gaps in nuclei in that region when leaving the N = 126 shell closure.…”