The subshell closure at N = 56 and the deformation of neutron-rich isotopes from Ge to Zr

doi:10.1016/0375-9474(81)90237-2

Nuclear Physics A

Volume 359, Issue 2, 27 April 1981, Pages 278-288

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Abstract

The microscopic energy density method is applied to the study of nuclei with N ⩾ 50 and Z = 32−40. The experimental Subshell effect at N = 56, which is not found in many previous works about this region, is well reproduced by the present self-consistent calculation. The existence of strongly deformed prolate isotopes of Zr and Sr for N ⩾ 60 is also explained. A wide region of oblate shapes is predicted for N ⩾ 60 and Z ⩽ 36. The results also support the interpretation of low-energy isomers in the shape transition region as shape isomers.

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A systematic study of shell closures around N and $Z = 40 – 60$ through beta decay Q-values, one nucleon separation energies and excited states is presented for different isospin chains. Shell closure at $N = 40$ is found to be absent in neutron-rich nuclei (contrary to some existing discussions) but is indicated in nuclei with $T_{z} ⩽ 1$ within errors. The persistence of the N and $Z = 50$ shell closure is observed, together with evidence of sub-shell closure at $N = 56$ in neutron-rich nuclei. The sub-shell closure at $Z = 40$ , that exists for neutron-rich nuclei, is found to disappear for $T_{z} = 2$ .
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1993, Nuclear Physics, Section A
Collective quadrupole and octupole excitations in even ⁹⁴⁻⁰⁰Zr nuclei are studied within the fully microscopic generator-coordinate method using a basis generated by the selfconsistent Hartree-Fock BCS method. Results with the effective interaction SkM^∗ correctly describe the experimentally observed spherical to deformed shape transition at A = 100. Properties of low-lying O⁺, 2⁺ and 3⁻ states are analysed. The measured B(E3) value of 65 single-particle units in ⁹⁶Zr is underestimated in our calculations. Various aspects of our theoretical approach are discussed, including Skyrme force parametrization, treatment of pairing and one- versus two-dimensional description of octupole excitations.
Thomas-Fermi approach to nuclear mass formula. (III). Force fitting and construction of mass table
1991, Nuclear Physics, Section A
The ETFSI method, developed in two earlier papers, is here used to construct a complete mass table. Since the method allows for interpolation both in the (N, Z) plane and with respect to deformations, without losing the characteristic shell-model fluctuations, it is some 2000 times faster than the HF-BCS method for a given force. The present table is calculated using a preliminary Skyrme-type force with δ-function pairing, fitted to a restricted data set of 491 spherical nuclei. The resulting rms error for all 1492 measured nuclei, spherical and deformed, with A ⩾ 36 is ε_rms = 0.868 MeV, achieved with just 9 parameters. The main experimental trends in ground-state deformations are well followed. The symmetry coefficient of nuclear matter corresponding to our force is 27.5 MeV. Ways of rapidly improving the fit are indicated.
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The 1974 evaluation of A=100 mass chain (74Ko37) has been revised. The evaluated experimental data are presented for 13 known nuclides of mass 100 (Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In). Excited state data are nonexistent for ¹⁰⁰Rb and ¹⁰⁰In. High spin excitations are known for ¹⁰⁰Mo, ¹⁰⁰Ru, ¹⁰⁰Rh, ¹⁰⁰Pd and ¹⁰⁰Cd. The neutron capture data are available for ¹⁰⁰Tc and ¹⁰⁰Ru. Particle transfer data exist for ¹⁰⁰Nb, ¹⁰⁰Mo, ¹⁰⁰Tc and ¹⁰⁰Ru. In terms of a variety of experimental studies, the ¹⁰⁰Mo and ¹⁰⁰Ru are the ones most extensively investigated. No. experimental data exist for ¹⁰⁰Ge, ¹⁰⁰Se, ¹⁰⁰Kr and ¹⁰⁰Sn, but amongst other nuclides in this region, these have been included in calculations dealing with nuclear structure, β⁻ strength functions, half-lives etc. (81Al25 for ¹⁰⁰Ge, ¹⁰⁰Se and ¹⁰⁰Kr; 80Ca23 and 85Bo36 for ¹⁰⁰Kr; 88Do04, 88De29, 85St14, 85B104, 88BaZS, 84Zv01, 84Le12, 74Ca10 and 73Da35 for ¹⁰⁰Sn).
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Nuclear Physics A

Abstract

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Cited by (23)

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Deformation and shape coexistence of 0<sup>+</sup> states in <sup>98</sup>Sr and <sup>100</sup>Zr

A shell-model description of 0<sup>+</sup> intruder states in even-even nuclei