The 24Mg(16O, 16O') reaction and triaxial structures in 24Mg

doi:10.1016/0375-9474(83)90607-3

Nuclear Physics A

Volume 399, Issue 1, 9 May 1983, Pages 259-274

https://doi.org/10.1016/0375-9474(83)90607-3 Get rights and content

Abstract

Angular distributions for the elastic and inelastic scattering of ¹⁶O from ²⁴Mg, exciting the 2₁⁺ (1.37 MeV), 4₁⁺ (4.12 MeV) and 2₂⁺ (4.24 MeV) states, have been measured at E_c.m. = 43.5 MeV, an energy at which resonance-like structure has been observed previously in the related ²⁴Mg(¹⁶O, ¹²C)²⁸Si reaction. In particular, the 4₁⁺, 2₂⁺ doublet has been resolved for the first time for heavy-ion projectiles. The data have been well described by coupled-channels calculations within the framework of a Davydov-Filippov asymmetric rotor model for the low-lying states of ²⁴Mg, which has been extended to include a symmetric hexadecapole shape component. The optical model potential for the ¹⁶O + ²⁴Mg interaction was found to have a moderate real well depth and some surface transparency. The shape parameters for the nuclear potential were determined to be β^(N)₂ = 0.25, γ = 22° and β₄^(N) = −0.065 and the corresponding deformation lengths are in good agreement with earlier light-ion results. The inclusion of a negative symmetric hexadecapole component leads to an improved description of the reduced transition rates. The triaxial structure of ²⁴Mg is discussed.

References (42)

A.V. Cohen et al.
Nucl. Phys.
(1962)
R. Batchelor et al.
Nucl. Phys.
(1960)
A.S. Davydov et al.
Nucl. Phys.
(1958)
D. Branford et al.
Nucl. Phys.
(1975)
O. Aspelund
Phys. Lett.
(1982)
Y. Abgrall et al.
Phys. Lett.
(1969)
J. Eenmaa et al.
Nucl. Phys.
(1974)
I. Lovas et al.
Nucl. Phys.
(1977)
T. Tamura
Nucl. Phys.
(1965)
J. Kokame et al.
Phys. Lett.
(1964)

K. van der Borg et al.

Nucl. Phys.

(1979)

B. Imanishi

Phys. Lett.

(1968)

Nucl. Phys.

(1969)

W. Scheid et al.

Phys. Rev. Lett.

(1970)

Y. Abe et al.

Prog. Theor. Phys. Suppl.

(1980)

J.R. Leigh et al.

Nucl. Instr.

(1982)

A.S. Davydov et al.

ZhETF (USSR)

(1959)

JETP (Sov. Phys.)

(1959)

J. Raynal

Saclay Report D Ph-T/24/80

(1980)

D. Dehnhard et al.

Phys. Rev. Lett.

(1978)

R.A. Chatwin et al.

Phys. Rev.

(1970)

S.W. Robinson et al.

Phys. Rev.

(1968)

A. Faessler et al.

Z. Phys.

(1962)

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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.
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.
The α+20Ne cluster structure of 24Mg in a microscopic three-cluster model
1987, Nuclear Physics, Section A
With the generator-coordinate method, the ²⁴Mg spectrum is studied microscopically in a three-cluster model involving an ¹⁶O core and two α-particles. The wave functions are projected out on the 0⁺ and 2⁺ internal states of ²⁰Ne and on the total angular momentum and parity. We discuss the band structure of²⁴Mg and suggest the existence of an α + ²⁰Ne molecular band starting at 10.7 MeV. The $α +^{20} Ne (0^{+}, 2^{+})$ collision matrices are calculated with the microscopic R-matrix method. Reduced E2 transition probabilities in the ²⁴Mg spectrum are presented and compared with experiment. Finally, the ²⁰Ne(α, γ)²⁴Mg capture reaction is discussed.
Inelastic scattering of 32S on 28Si
1985, Nuclear Physics, Section A
The elastic and inelastic cross sections of ³²S on ²⁸Si at 77, 90 and 97.09 MeV incident energies have been measured. The excitation of the first 2⁺ and 3⁻ levels in both nuclei as well as the [2₁⁺, 2₁⁺] mutual excitation were studied. The angular distributions are reproduced by coupled-channel calculations. The influence of various reaction mechanisms have been studied. Strong high-order effects are predicted. Total reaction and inelastic cross sections for low-lying excited states have been extracted.
Coupled-channel description of resonant structures in the 16O + 20Ne system
1985, Nuclear Physics, Section A
Gross resonant structures observed in elastic scattering, inelastic scattering and the total reaction cross section for the ¹⁶O + ²⁰Ne system have been studied successfully using a coupled-channel approach, within a symmetric rotor model, with the diagonal potential modified to include both a parity-dependent real interaction and an angular-momentum (J)-dependent absorptive term. It is shown that the inclusion of both these terms is essential for the prediction of the four correlated gross structures observed in the energy range 23 MeV ≦ E_c.m ≦ 38 MeV for both elastic and inelastic scattering excitation functions at backward angles. Each of the gross structures is modelled as a doublet of even-parity plus odd-parity resonances, which arise as a consequence of the parity-dependent interaction and which are enhanced by the J-dependent absorptive form. The elastic and inelastic scattering angular distributions at a number of energies are also well described. It is demonstrated that the inclusion of strong coupling overcomes a number of inadequacies noted in previous optical-model calculations for the ¹⁶O + ²⁰Ne system. The total angular momenta of the resonant states obtained in the coupled-channel calculations are higher than those extracted from calculations which ignore coupling.
Resonant structures in the 16O + 20Ne system
1983, Nuclear Physics, Section A
Gross resonant structures observed in ¹⁶O + ²⁰Ne elastic scattering and the ²⁰Ne(¹⁶O, ¹²C)²⁴Mg(g.s.) reaction for $22.8 MeV ≦ E_{c.m.} (^{16} O +^{20} Ne) ≦ 38.6 MeV$ have been studied successfully using an extended optical model and an exact finite-range (EFR) DWBA approach, respectively. The ion-ion potentials employed include both a real parity-dependent interaction and an angular momentum (J) dependent absorptive term. It is demonstrated that the inclusion of both these terms is essential for the prediction of the four gross structures observed in the ¹⁶O + ²⁰Ne elastic scattering excitation function at θ_c.m. = 154°, with each of those structures being modelled as a doublet of even parity plus odd parity shape resonances. The doublet structure is a consequence of the parity-dependent interaction and is enhanced by the J-dependent absorptive form. The ¹⁶O + ²⁰Ne elastic scattering angular distributions at E_c.m. = 24.5, 27.9, 31.7, 32.1, 33.0 and 35.5 MeV are also generally well reproduced. The ¹²C + ²⁴Mg potential is determined by fitting available elastic scattering data, with the constraint that the shape resonances of the ¹²C + ²⁴Mg interaction overlap approximately the corresponding ¹⁶O + ²⁰Ne shape resonances. EFR-DWBA calculations using optical potentials which describe the elastic scattering data do not reproduce the observed resonant gross structures of the ²⁰Ne(¹⁶O, ¹²C)²⁴Mg(g.s.) excitation function at θ_lab = 13°. However, it is shown that these gross structures, their previously assigned J^π values and the measured angular distribution data at $E_{c.m.} (^{16} O +^{20} Ne) = 24.5, 27.9, 31.7, 32.1, 33.0 and 35.5 MeV$ can be well described by making the optical potentials more surface transparent. This different degree of transparency required to describe the elastic scattering and transfer reaction is discussed. The role of elastic transfer, the sign of the parity-dependent interaction and the possibility of shape resonances with different numbers of nodes are also considered.

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^†: Present address: Chemistry Department, The University of Georgia, Athens, Georgia 30602, USA.

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Nuclear Physics A

Abstract

References (42)

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Phys. Lett.

Phys. Lett.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Phys. Lett.

Nucl. Phys.

Phys. Lett.

Nucl. Phys.

Phys. Rev. Lett.

Prog. Theor. Phys. Suppl.

Nucl. Instr.

ZhETF (USSR)

JETP (Sov. Phys.)

Saclay Report D Ph-T/24/80

Phys. Rev. Lett.

Phys. Rev.

Phys. Rev.

Z. Phys.

Cited by (10)

Nuclear Data Sheets for A=24

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

The α+<sup>20</sup>Ne cluster structure of <sup>24</sup>Mg in a microscopic three-cluster model

Inelastic scattering of <sup>32</sup>S on <sup>28</sup>Si

Coupled-channel description of resonant structures in the <sup>16</sup>O + <sup>20</sup>Ne system

Resonant structures in the <sup>16</sup>O + <sup>20</sup>Ne system