Nucleon-pair approximation to the nuclear shell model

Zhao, Y. M.; Arima, A.

doi:10.1016/j.physrep.2014.07.002

Cited by 79 publications

(65 citation statements)

References 266 publications

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“…The nucleon-pair approximation (NPA) is a pairtruncation scheme for the nuclear shell model [83][84][85]. The building blocks of the NPA are collective nucleon pairs with given spin and parity.…”

Section: The Nucleon-pair Approximation Of the Shell Modelmentioning

confidence: 99%

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

Jia

2016

Phys. Rev. C

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Large-scale shell-model calculations are carried out in the model space including neutron-hole orbitals 2p 1/2 , 1f 5/2 , 2p 3/2 , 0i 13/2 , 1f 7/2 and 0h 9/2 to study the structure and electromagnetic properties of neutron deficient Pb isotopes. An optimized effective interaction is used. Good agreement between full shell-model calculations and experimental data is obtained for the spherical states in isotopes 194−206 Pb. The lighter isotopes are calculated with an importance-truncation approach constructed based on the monopole Hamiltonian. The full shell-model results also agree well with our generalized seniority and nucleon-pair-approximation truncation calculations. The deviations between theory and experiment concerning the excitation energies and electromagnetic properties of low-lying 0 + and 2 + excited states and isomeric states may provide a constraint on our understanding of nuclear deformation and intruder configuration in this region.

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Section: The Nucleon-pair Approximation Of the Shell Modelmentioning

confidence: 99%

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

Jia

2016

Phys. Rev. C

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“…[6,15]. Our formalism is based on the nucleon-pair approximation of the shell model with isospin symmetry [22][23][24]. The building * Corresponding author: ymzhao@sjtu.edu.cn blocks of this model are collective nucleon pairs with good quantum numbers of both spins and isospins, and a quartet is written in terms of two such pairs, viz.,…”

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confidence: 99%

Quartet structure in atomic nuclei

Zhao

2015

Phys. Rev. C

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A quartet is a tightly bound cluster of two protons and two neutrons, similar to the α particle but occasionally with nonzero spin and/or isospin. If the interaction between two quartets is weak in given states, such states are concluded to be well represented by a quartet structure. In this paper, we study the quartet structure of eight valence nucleons in two cases. The first is a single j shell, demonstrating that the so-called stretch scheme [M. Danos and V. Gillet, Phys. Rev. Lett. 17, 703 (1966)] is very good for low-spin states with a quadruplequadruple interaction, and is reasonably good under realistic interactions. The second case is the ground state of 92 Pd in the p 1/2 p 3/2 f 5/2 g 9/2 shell with the JUN45 effective interaction. We show that the quartet correlation is essential in the ground state of 92 Pd.The α particle (namely, 4 He) is a very tightly bound system of two protons and two neutrons. Therefore α correlation in low-lying states of atomic nuclei has been conjectured and studied extensively [1]. One of the most famous examples is the Hoyle state [2] (weak coupling of the α particle and 8 Be in the 12 C nucleus). The work in Ref. [3] suggests that the Hoyle state has a deformed shape accompanied by a rotational band. Similar structure was also studied in 8 Be, 16 O, 20 Ne, and 24 Mg.There has been much work done towards quartet correlations in N = Z nuclei [4][5][6][7][8][9][10][11]. In the literature a cluster with two protons and two neutrons coupled to a given spin and isospin is usually called a quartet. It is a tightly bound cluster, similar to the α particle but occasionally with nonzero spin and/or isospin. If the interaction between two quartets is weak in given states, such states are concluded to be well represented by quartet structure. Among various efforts along this line, here we mention work involving antisymmetrized molecular dynamics (AMD) [12][13][14] and "quartet truncation" models [6,[15][16][17][18][19]. In AMD, the wave function is constructed by using multicenter configurations, similar to the idea in molecular physics. Not only the quartet structure but also other types of clustering structures are taken into account in the configuration space of the AMD. The quartet truncation models are based on the quartet truncation scheme of the nuclear shell model. In the quartet truncation models, the building blocks of wave functions are quartets. It has been shown that pairing correlation energies in the full shell model space and those in the quartet-truncated space are very close to each other under a simple phenomenological interaction [15][16][17][18][19]. The connection between the AMD and the quartet (or many-body cluster) truncation scheme is discussed in Refs. [20,21].In this paper we study structures consisting of two quartets (namely, eight valence nucleons). The framework we use here is a quartet truncation model similar to that in Refs. [6,15]. Our formalism is based on the nucleon-pair approximation of the shell model with isospin symmetry [22][23][24]. The bu...

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“…A detailed investigation on the applications of the nucleon-pair approximation of the shell model on this subject is presented in Ref. [76]. In any case the isospin symmetry is exactly conserved, as it is included in the interaction matrix elements that we use [63].…”

Section: Seniority and Np Coupling Schemesmentioning

confidence: 99%

“…[106]. The influence of the np pairing and deformation on the neutrinoless double-β decay in 76 Ge is calculated in Ref. [107].…”

Section: The Np Pairing Correlation Within the Deformed Shell-model Fmentioning

confidence: 99%

N=Znuclei: a laboratory for neutron–proton collective mode

Qi¹,

Wyss²

2015

Phys. Scr.

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The neutron-neutron and proton-proton pairing correlations have long been recognized to be the dominant many-body correlation beyond the nuclear mean field since the introduction of pairing mechanism by Bohr, Mottelson and Pines nearly 60 year ago. Nevertheless, few conclusion has been reached concerning the existence of analogous neutron-proton (np) pair correlated state. One can see a renaissance in np correlation studies in relation to the significant progress in radioactive ion beam facilities and detection techniques.The np pairs can couple isospin T = 1 (isovector) or 0 (isoscalar).In the isovector channel, the angular momentum zero component is expected to be the most importance one. On the other hand, as one may infer from the general properties of the np two-body interaction, in the isoscalar channel, both the np pairs with minimum (J=1) and maximum (J=2j) spin values can be important. In this contribution, we will discuss the possible evidence for np pair coupling from different perspective and analyze its influence on interesting phenomena including the Wigner effect and mass correlations in odd-odd nuclei. In particular, we will explain the spin-aligned pair coupling scheme and quartet coupling involving pairs with maximum (J=2j) spin values.

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Nucleon-pair approximation to the nuclear shell model

Cited by 79 publications

References 266 publications

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

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

Quartet structure in atomic nuclei

N=Znuclei: a laboratory for neutron–proton collective mode

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