Particle-hole excitations in the interacting boson model (I) General structure and symmetries

The Pt isotopes: Comparing the Interacting Boson Model with configuration mixing and the extended consistent-Q formalism

“…The energy spectrum remains remarkably constant in the mass interval 178 ≤ A ≤ 186, contrasting with a different structure that shows a number of up sloping levels with increasing mass number A beyond mass A = 186. excitations [29]. On the basis of intruder spin symmetry [33,73], no distinction is made between particle and hole bosons. Hence, the model space which includes the regular proton 4h configurations and a number of valence neutrons outside of the N = 82 closed shell (corresponding to the standard IBM treatment for the Pt even-even nuclei) as well as the proton 6h-2p configurations and the same number of valence neutrons corresponds to a [N] ⊕ [N + 2] boson space (N, being the number of active protons, counting both, proton holes and particles, plus the number of valence neutrons outside the N = 126 or the N = 82 closed shell (depending on the nearest closed shell), divided by 2 as the boson number).…”

“…The truncation of the model space, however, by concentrating on nucleon pair modes (mainly 0 + and 2 + coupled pairs, to be treated as bosons within the Interacting Boson Approximation (IBM) [28]), has made the calculations feasible, even including pair excitations across the Z = 82 shell closure [29] in the Pb region. More in particular, the Pb nuclei have been extensively studied giving rise to bands with varying collectivity depending on the nature of the excitations treated in the model space [11,30,31,32,33,34,35,36,37].…”

Shell-model-based deformation analysis of light cadmium isotopes

“…The Cd nuclei have been studied using shell-model calculations for the lighter mass region [7-12, 14, 18, 69] and also using the Interacting Boson Model (IBM) [17,18,21,23,51,64,[70][71][72][73][74][75][76][77]. Besides that, other studies, starting from a general collective Bohr Hamiltonian, derived from a microscopic starting point using a Skyrme force, calculations using the Adiabatic Time-Dependent Hartree-Fock-Bogoliubov (ATDHFB) method (for the nuclei 106−116 Cd) [78], as well as using a self-consistent HFB approach, starting from the finite range Gogny interaction [79] have been carried out.…”

Shape coexistence in the light Po isotopes

“…An equivalence between particle-like and hole-like excitations, which is the idea behind the intruder spin (I-spin) symmetry, deduced within the framework of the Extended protonneutron Interacting Boson Model (EIBM) [16,17,18,19], will imply the existence of intruder con gurations for the Z > 82 nuclei as well. Predictions for the structure of intruder bands in the very light P o and Rn nuclei, which will be due to (np-2h) excitations across the closed shell, can be made [20] using the analogy with (2p-nh) intruder bands in the Hg and Pt nuclei with the same neutron number.…”

“…The study of the coexistence of regular and intruder con gurations and their mixing can beembedded in a larger framework using particle-hole symmetry concepts and intruder spin [17,18,19]. The intruder 4p-2h structure in Po and the regular 6h excitations in the Os isotopes with the same neutron numberbelong both to the I=3/2 multiplet (I z = 1=2 and 3=2, respectively) and are thus expected to bevery similar.…”