Lifetime and branching measurements on the Kπ = 0+ and Kπ = 2+24Mg rotational levels

doi:10.1016/0375-9474(75)90324-3

Nuclear Physics A

Volume 241, Issue 2, 7 April 1975, Pages 349-364

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Abstract

The ²⁴Mg ground state K^π = 0⁺ rotattonal band and the K^π = 2⁺ band built on the 4.24 MeV 2⁺ level have been studied using the ¹²C(¹⁶O, α)²⁴Mg reaction. The results of lifetime measurements, made using the Doppler shift attenuation method, and γ-branching ratio determinations are reported. These give an unambiguous assignment of J^π = 6⁺ to the 8.11 and 9.53 MeV levels. The results for the 13.21 MeV (8⁺, 6⁺) level and a new level at 12.35 MeV support assignments of J^π, K = 8⁺, 0 and (7⁺, 2) to these levels, respectively. All the intraband itE2 transition strengths are in reasonable agreement with both the rotational model and recent shell model calculations although the interband E2 strengths are in poor agreement. No evidence for band mixing was observed and an upper limit of 2.5% is given for the fractional amplitude of the 2⁺, 0 state mixed into the 2⁺, 2 state.

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Nuclear Data Sheets for A=24
2022, Nuclear Data Sheets
Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for ²⁴N, ²⁴O, ²⁴F, ²⁴Ne, ²⁴Na, ²⁴Mg, ²⁴Al, and ²⁴Si. This evaluation for A=24 supersedes the earlier one by R. B. Firestone (2007Fi14).
Highlights of this evaluation are the following:
In ²⁴O, the 7.4- and 7.65-MeV groups reported in ¹H(²⁴O,p′) (2012Ts03) and ⁹Be(²⁶F,nX) (2011Ho05), respectively, are considered as separate states in this evaluation, since the former one was observed to decay by only one neutron emission to ²³O, while the latter one by two sequential neutrons to ²²O. Based on assigned configurations, the 7.4- and 7.6-MeV groups are tentatively assigned negative and positive parities, respectively. Additional study would be useful to determine if these states are same or different.
In ²⁴Na, 2014Fi01 (n,γ) proposed J^π=(0,1,2)⁻ for 4048.8 keV level based on weaker population from the capture state (J^π=1⁺,2⁺) and mentioned to reexamine the J^π=0⁺ assignment, suggested in earlier evaluations (1990En08, 2007Fi02).
This evaluation includes the first observation of E0 transition, strength ρ²(E0)=0.380 70, for the 6432 keV transition from 0⁺ state at 6432 to 0⁺ g.s. in ²⁴Mg reported in 2020Do10. Authors proposed the first-excited 0⁺ state of ²⁴Mg to be superdeformed.
In ²⁴Al, the excited level energies deduced from (³He,t) measurements reported by different research groups vary significantly and it was not clear if some of those levels were same or different. Additional measurements are needed.
Nuclear Data Sheets for A = 24
2007, Nuclear Data Sheets
This evaluation of A = 24 has been updated from previous evaluations published in 1998En04, 1990En08, and 1978En02. Coverage includes properties of adopted levels and γ rays, decay-scheme data (energies, intensities and placement of radiations), and cross reference entries. The following tables continue the tradition of showing the systematic relationships between levels in A = 24. These assignments are based on energy differences for states with the same J^π values, γ-ray strengths, spectroscopic factors in analog single particle (T = 1) or two particle (T = 2) transfer reactions. Isospin is not a perfect quantum number and the adopted T-value may correspond to a small component in the wavefunction.
Semimicroscopic algebraic cluster model of light nuclei. I. Two-cluster-systems with spin-isospin-free interactions
1994, Annals of Physics
The relation of the phenomenological algebraic cluster model, i.e., of the vibron model and its extensions, to the microscopic description is discussed. Based on this connection a semimicroscopic approach is formulated, in which the internal cluster degrees of freedom are treated in terms of the SU(3) shell model, and the relative motion is described by the vibron model. For a two-cluster system this model has a group structure of U^ST_C₁(4)⊗U_C₁(3)⊗U_R(4)⊗U_C₂(3)⊗U^ST_C₂(4), and the phenomenological interactions are obtained in terms of the group generators. The model space is constructed to be free from the Pauli-forbidden states and spurious center of mass motion, similar to that of the SU(3) cluster model. Three examples, the ¹²C + α, the ¹²C + ¹²C and the ¹⁴C + α systems are presented to demonstrate various aspects of the semimicroscopic algebraic cluster model.
Energy levels of A = 21-44 nuclei (VII)
1990, Nuclear Physics, Section A
The experimentally determined properties of A = 21–44 nuclides are complied and evaluated with special emphasis on nuclear spectroscopy.
Separate tables for each of the nuclides reviewed present the available information about the following properties (in this order):
- •
  - excitation energies E_x,
- •
  - γ-ray branching ratios b(γ),
- •
  - γ-ray mixing ratios σ,
- •
  - lifetimes γ_m or widths Λ,
- •
  - neutron, proton, or α-particle resonances,
- •
  - partial widths,
- •
  - single-nucleon transfer reactions,
- •
  - beta-decay,
- •
  - arguments for spin and parity (J^π) and isospin (T) assignments.
For each nuclide a master table summarizing the “best” or adopted values for E_x, J^π; T and τ_m or Λ precedes the auxiliary tables listed above.
The review of each A-chain concludes with a discussion of isospin multiplets.
Figures are presented of the level schemes of all nuclei and, for each A-chain, an overview of the relative energies of the ground states and lowest analogue states of all nuclei in the chain.
A 12C+12C cluster model of 24Mg
1990, Nuclear Physics, Section A
A recently proposed cluster model of ²⁴Mg based on two ¹²C component nuclei is re-examined with a view to justifying some of its assumptions and parameter values. The ¹²C clusters are allowed to occupy their 0₁⁺ (0.00 MeV), 2₁⁺ (4.44 MeV), O₂⁺ (7.65 MeV), 3₁⁻ (9.64 MeV) or 1₁⁻ (10.84 MeV) states, and hence give rise to a variety of bands of states of both positive and negative parity in ²⁴Mg. Coupled-channels calculations, invoking the bound-state diagonalisation approximation, are performed to evaluate the energies and wave functions of these states up to excitation energies of about 16 MeV and are found to describe almost the entire experimentally known T = 0 spectrum in this region. Reduced E2 electromagnetic strengths for transitions between the low-lying positiveparity states are also calculated in good agreement with measured values, without the need to introduce effective charges. Finally, form factors for elastic and inelastic electron scattering (the latter via the 2₁⁺ and unresolved 4₁⁺ + 2₂⁺ states) from ²⁴Mg are examined, and found to imply a charge radius somewhat larger than that deduced from other analyses, and a breakdown of the applicability of the plane-wave Born approximation at the higher values of the momentum transfer.
Spectroscopic information on 24Mg and 28Si from proton capture
1990, Nuclear Physics, Section A
Gamma-ray spectra with good statistics have been measured at three ²³Na(p, γ)²⁴Mg and five ²⁷Al(p, γ)²⁸Si resonances. The E_x = 9.30 MeV level of ²⁴Mg is proved to be a triplet, and those at 9.53 and 10.66 MeV of ²⁴Mg and at 10.67 MeV of ²⁸Si are found to be doublets. Substantial improvements over previous work are obtained in the γ-ray branchings of the resonances and bound states, in excitation energies, and in lifetimes of ²⁸Si levels (from observed Doppler shifts). The new information has led to new J^π; T assignments (or restrictions) for 16 levels of ²⁴Mg and 16 of ²⁸Si. A shell-model calculation has helped to clarify the level schemes of both nuclei, in particular with regard to the T = 1 states. New information has also been obtained on levels close above the α-particle binding energy, which are important in nucleosynthesis.

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^†: Present address: Physics Department, The University, Edinburgh, Scotland.

^††: Present address: John Fisher School, Purley, Surrey, England.

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Nuclear Physics A

Abstract

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Nuclear Data Sheets for A=24

Nuclear Data Sheets for A = 24

Semimicroscopic algebraic cluster model of light nuclei. I. Two-cluster-systems with spin-isospin-free interactions

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

A <sup>12</sup>C+<sup>12</sup>C cluster model of <sup>24</sup>Mg

Spectroscopic information on <sup>24</sup>Mg and <sup>28</sup>Si from proton capture