Proton-threshold states in 28Si

doi:10.1016/0375-9474(86)90065-5

Nuclear Physics A

Volume 459, Issue 1, 27 October 1986, Pages 239-252

https://doi.org/10.1016/0375-9474(86)90065-5 Get rights and content

Abstract

The ²⁷Al(³He, d)²⁸Si reaction has been used to locate candidates for resonances in the ²⁷Al + p system residing near the proton-capture threshold in the energy region characteristic of quiescent stellar hydrogen burning. Two such states are observed at excitation energies E_x = 11.658 MeV(J^π = 2⁺) and 11.671 MeV (J^π = 1⁻). A comparison of the cross sections for the ²⁷Al(³He, d)²⁸Si and the ²⁷Al(α, t)²⁸Si reactions implies angular-momentum transfers of l = 2 and l = 3, respectively, for the two states of interest. Using this result, an astrophysically significant upper limit on the thermonuclear reaction rate has been calculated for the ²⁷Al(p, γ)²⁸Si reaction which is found to be too slow to affect the ²⁷Al abundance in red giants.

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Cited by (15)

Nuclear data sheets for A = 28
2013, Nuclear Data Sheets
A compilation of charged-particle induced thermonuclear reaction rates
1999, Nuclear Physics A
Low-energy cross section data for 86 charged-particle induced reactions involving light (1 ⩽ Z ⩽ 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10⁶ K to 10¹⁰ K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states.
Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided.
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.
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.
Thermonuclear reaction rates V
1988, Atomic Data and Nuclear Data Tables
Particle decays in 28Si: The destruction of 27Al in red giants and novae
1988, Nuclear Physics, Section A
The ²⁷Al(³He, d)²⁸Si reaction has been used to populate states near the ²⁷Al+p threshold and the ensuing proton and alpha decay has been measured. No evidence for new $^{27} Al(p, α)^{24} Mg$ resonance strength was observed and consequently revised limits have been placed on the thermonuclear reaction rate. As a result, the $^{27} Al(p, α)^{24} Mg$ reaction is found to be astrophysically unimportant at red-giant and nova temperatures.

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^☆: Work supported in part by the National Science Foundation and in part by the US Department of Energy.

¹: Permanent address: Institute of Atomic Energy, Academia Sinica, Beijing, PO 27548, PRC.

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Nuclear Physics A

Abstract

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Cited by (15)

Nuclear data sheets for A = 28

A compilation of charged-particle induced thermonuclear reaction rates

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

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

Thermonuclear reaction rates V

Particle decays in <sup>28</sup>Si: The destruction of <sup>27</sup>Al in red giants and novae

Proton-threshold states in 28Si☆

Abstract

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

J. Phys. Soc. Japan

Phys. Rev.

Nucl. Phys.

Ann. Rev. Astron. Astrophys.

Proton-threshold states in ²⁸Si☆