Shell-model calculations in A = 23−28 nuclei

doi:10.1016/0375-9474(74)90369-8

Nuclear Physics A

Volume 225, Issue 1, 4 June 1974, Pages 119-136

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Abstract

Energy levels, electromagnetic transition rates and multipole moments have been calculated for positive parity states in A = 23−28 nuclei in an untruncated $ld_{52} 2 s_{12}$ . configuration space. The results obtained by considering all two-body matrix elements as free parameters (FP) are compared with those obtained with matrix elements derived from the modified surface-delta interaction (MSDI), as well as with matrix elements from a realistic Hamada-Johnston interaction (HJ). The binding and excitation energies as well as strong B(E2) values calculated with FP and MSDI are found to be rather similar and in good agreement with experiment, in contrast to the B(M1) values. Poor agreement with experiment is obtained for HJ matrix elements.

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The quasi-SU(3) symmetry, as found in shell-model calculations, refers to the dominance of the single-particle plus quadrupole–quadrupole terms in the Hamiltonian used to describe well-deformed nuclei, and to the subspace relevant in its diagonalization. It provides a very efficient basis truncation scheme. It is shown that a small number of SU(3) coupled irreps, those with the largest C₂ values within the direct product of the proton and neutron SU(3) irreps with spin 0 and 1 (for even number of particles), and spin 1/2 and 3/2 for (for odd number of nucleons), are enough to describe the low-energy spectra, B(E2) transition strengths and band structure of ²¹Ne, ²³Na and ²⁵Mg odd-mass and ²²Na, ²⁴Na, ²⁶Al and ²⁸Al odd–odd nuclei. A simple but realistic Hamiltonian is employed. Results compare favorably both with experimental data and with full shell-model calculations. Limitations and possible improvements of the schematic Hamiltonian are discussed.
Short lifetimes in 26Al
1983, Nuclear Physics, Section A
Mean lifetimes of levels in ²⁶Al have been measured using the Doppler-shift attenuation (DSA) method and the reaction ²⁵Mg(p, γ)²⁶Al. The lifetime values or limits were determined for 34 bound levels below the excitation energy of 6 MeV; the lifetimes of 13 levels and upper limits of 3 levels are reported for the first time. For the effective stopping of recoils, the targets were prepared by implanting ²⁵Mg into Ta backings. The Monte Carlo method and the experimental stopping power were used in the DSA analysis.
The quadrupole moment of 26Mg as a test of shell-model interactions
1982, Nuclear Physics, Section A
The static quadrupole moment Q_2₁⁺, and the B(E2; 0₁⁺ → 2⁺₁) value of the first excited state of²⁶Mg have been measured using the reorientation effect in Coulomb excitation of ²⁶Mg projectiles. It is found that Q_2₁⁺ = −13.6±3.0 (−9.5±3.0) e ·fm² and B(E2; 0⁺₁ → 2⁺₁) = 322±16 (328±16) e² ·fm⁴ for constructive (destructive) interference from higher states. The result for Q₂ clearly differentiates among several alternative effective interactions which have been used in shell-model calculations.
Static quadrupole moments of first 2+ states in the 2s1d shell: A review of experiment and theory
1981, Physics Reports
Available experimental information on the static electric quadrupole moments Q₂₊ of the 2⁺ first excited states of even-mass nuclei in the 2s1d shell is tabulated and critically reviewed, and “adopted values” are presented. The results reveal a well defined pattern for the variation of Q_2⁺ through the shell. Predictions of Q_2⁺ made from various nuclear models are tabulated and compared with experiment. For each nucleus the qua ty and quality of the existing data for Q_2⁺, together with the current theoretical significance of the result, are used as criteria to determi whether new experimental work is desirable.
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Energy levels of A = 21-44 nuclei (VI)
1978, Nuclear Physics, Section A
The experimentally determined properties of the A = 21–44 nuclei are compiled and evaluated, special emphasis being given to nuclear structure.
Separate tables for each of the nuclides reviewed give all available information about the following properties in this order: - excitation energies (E_x),
1. •
  - γ-ray branching ratios,
2. •
  - γ-ray mixing ratios (δ),
3. •
  - lifetimes (τ_m) or widths (Λ),
4. •
  - spin and parity (J^π) and isospin (T) assignments, and
5. •
  - any other data, on single-particle transfer, resonance levels, etc.
The “best” (or adopted) values for E_x, τ_m or Λ, J^π and T are summarized in a master table.
The review of each A-chain concludes with - a discussion of isospin multiplets,
1. •
  - a few remarks about the experimental situation, and
2. •
  - a compilation of references to relevant theoretical papers.

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Nuclear Physics A

Abstract

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Cited by (25)

Quasi-SU(3) truncation scheme for odd-even and odd-odd sd-shell nuclei

Short lifetimes in <sup>26</sup>Al

The quadrupole moment of <sup>26</sup>Mg as a test of shell-model interactions

Static quadrupole moments of first 2<sup>+</sup> states in the 2s1d shell: A review of experiment and theory

Quadrupole moments of even-even (sd) shell nuclei in the band-mixed Hartree-Fock model

Energy levels of A = 21-44 nuclei (VI)