γ -soft rotor with configuration mixing in the O(6) limit of the interacting boson model

Abstract

In order to describe obvious intruder states and nonzero quadrupole moments of γsoft nuclei such as 194 Pt, a rotor extension plus intruder configuration mixing with 2n-particle and 2n-hole configurations from n = 0 up to n → ∞ in the O(6) (γ-unstable) limit of the interacting boson model is proposed. It is shown that the configuration mixing scheme keeps lower part of the γ-unstable spectrum unchanged and generates the intruder states due to the mixing. It is further shown that almost all low-lying levels below 2.17MeV in 194 Pt can be well described by modifying the O(6) quadrupole-quadrupole interaction into an exponential form. The third order term needed for a rotor realization in the IBM seems necessary to produce nonzero quadrupole moments with the correct sign.

Exact solution of U(5)–O(6) transitional description in interacting boson model with two-particle and two-hole configuration mixing *

“…Similar to that in Ref. [13], the level energies up to the three-phonon states in the normal bands and the intruder states , , and of deduced in Ref. [20]…”

“…tinction between neutron-type and proton-type bosons, as shown in [7][8][9][10][13][14][15][16]. In this study, we demonstrate that the U( 5) ↔O(6) transitional Hamiltonian of the IBM-I with two-particle and two-hole configuration mixing is also exactly solvable based on the Bethe ansatz approach.…”

“…In contrast, configuration mixing due to multi-particle-hole excitations was considered to gain an understanding of the shape coexistence phenomena by assuming different symmetry limits of the IBM for different configurations [6][7][8][9][10][11][12], which has proven to be successful in describing intruder states and shape coexistence phenomena in near closed shell nuclei, typically those around proton numbers Z~50 and Z~82 [2-4]. Recently, the intruder configuration mixing schemes with -particle and -hole configurations from up to in the U(5) (vibrational) and the O(6) (γ-unstable) limits of the IBM-I were proposed [13,14], whose simple Hamiltonians, suitable to describe the intruder and normal configuration mixing, prove to be exactly solvable based on the SU(1,1) coherent states.…”

New γ-soft rotation in the interacting boson model with SU(3) higher-order interactions *

“…The combination of the two parts can describe the shape transitions from spherical to traditional γ-soft nuclei. The critical point of this transitional region can be described using dynamical symmetry [48]. A typical feature of γsoftness is the level degeneracy between the ground-band and quasi-γ rotational band due to the common symmetry, such as or (Fig.…”

Band mixing in 96,98Mo isotopes *

“…A linear combination of the basis states in the two-state model is common. Recently, it has been shown [3][4][5][6][7][8] that precise evidence exists for the presence of band mixing in medium mass nuclei such as those of Zr, Pd, Mo, Cd, Te, and Xe isotopes. Due to the large space configuration, shellmodel calculations with multi particle-hole excitations are not simple.…”