A study of the gamma radiation produced in the alpha-particle bombardment of O16

Background: The nuclear structure of the cluster bands in 20 Ne presents a challenge for many theoretical approaches. It is especially difficult to explain the broad 0 + and 2 + states, both at around 9 MeV excitation energy. More reliable experimental data for these levels is important for proper quantitative assessment and development of theoretical methods.Purpose: To obtain new data on 20 Ne α-cluster structure.Method: Thick target inverse kinematics technique was used to study the 16 O+α resonance elastic scattering and the data were analyzed using an R-matrix approach. The 20 Ne spectrum, the cluster and nucleon spectroscopic factors were calculated using cluster-nucleon configuration interaction model (CNCIM). Conclusions: Our experimental results obtained by the TTIK method generally confirm the adopted data on α cluster levels in 20 Ne. The CNCIM gives a good description of the 20 Ne positive parity states up to an excitation energy of ∼ 7 MeV, predicting reasonably well the excitation energy of the states and their cluster and single particle properties. At higher excitations, a qualitative disagreement with the experimentally observed structure is evident, especially for broad resonances.

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“…The authors of Ref. [22] observed a weak γ decay of this state in the presence of a large background. A broader level than in Ref.…”

Section: Resultsmentioning

confidence: 99%

“…For this state the adopted data in Ref. [6] are based on the results of a single older work [22]. The authors of Ref.…”

Section: Resultsmentioning

confidence: 99%

Structure of Ne20 states in resonance O16+α elastic scattering

et al. 2017

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“…However, in view of technical problems in the j3-ray measurements we have preferred to make our analysis in terms of the superallowed transition of Na 20 to its analog in Ne 20 at 10.270±0.009 MeV. 7 For the Fermi part of this transition we have taken 8 ft-3060 ± 20 sec; for the Gamow-Teller part we have based ourselves on local systematics and taken the range ft = 6.3 xl0 4 -°° sec; this leads toft = 2990 ± 70 sec for the two together. For the Na 20 mass excess we have taken 6 The half-life of F 20 has been determined as 11.03 ±0.06 sec and J3 branches have been measured in the decay of Na 25 .…”

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confidence: 99%

Mirror Symmetry in theβDecay of theA=20and 25 Systems

Wilkinson

Alburger

1970

Phys. Rev. Lett.

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10 The importance of imaginary contributions to the phase shifts by dispersion corrections has been recog-The simplest expectation for mirror /3 decays is that they should have identical/£ values. It has, however, been known for some time that the ft value for N 12 decay to the ground state of C 12 is some 10% greater than that for the mirror decay of B 12 . Careful analysis 1 suggests that the discrepancy may well be a significant one, not explicable in terms of electromagnetic, secondforbidden, isospin-mixing, and binding-energy corrections, and that its resolution may lie in the reality of second-class currents, specifically the induced tensor interaction, 2 ' 3 i.e., that the 0 interaction does not respect G parity. 2 Before accepting this fundamental conclusion one must be sure both that the known corrections have been properly evaluated and that there are not others of a "structural" nature that may fluctuate from case to case.It is therefore important to investigate other cases of mirror decay to see whether or not they fall systematically into line with A = 12. If the discrepancy in ft values was due solely to an induced tensor term its magnitude, for light nuclei and W Q * » 1, should be proportional to W 0 + + W 0~ and approximately state independent. 3 * 4 We have carried out measurements on the systems A = 20 and 25 that enable us to extend the mirror test to nized previously by Rawitscher (Ref. 6). Using a model of pure monopole excitation he was able to show that the imaginary contributions to the phase shifts are bigger than the corrections of the real part by about one order of magnitude. Assuming then that the real part of the correction may be neglected, our Eq. (1) may be derived directly from the Appendix of Ref. 6. n F. Wo J. Olver, Phil. Trans 0 Roy. Soc D London A247, 307 (1954), and to be published. these cases. We find that A = 25 shows a large departure from mirror symmetry in the same sense as for A = 12; the evidence on A = 20 is conflicting but suggests that the departure from mirror symmetry could have the opposite sense. These results emphasize the caution that must be used in interpreting the failure of mirror symmetry in terms of second-class currents.The P~ decay of F 20 is 99.92% to the first excited state of Ne 20 at 1.63 MeV. 5 The /3 + decay of Na 20 has been extensively investigated 6 by measurement of its j3 rays and the subsequent y decay and a decay of Ne 20 . The Na 20 half-life is reported 6 as 408 ± 6 msec and the /3 branch to the first excited state of Ne 20 as 90.0%. However, in view of technical problems in the j3-ray measurements we have preferred to make our analysis in terms of the superallowed transition of Na 20 to its analog in Ne 20 at 10.270±0.009 MeV. 7 For the Fermi part of this transition we have taken 8 ft-3060 ± 20 sec; for the Gamow-Teller part we have based ourselves on local systematics and taken the range ft = 6.3 xl0 4 -°° sec; this leads toft = 2990 ± 70 sec for the two together.The half-life of F 20 has been determined as 11.03 ±0.06 sec and J3...

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“…[6] in the widths is marginally exceeds the error bars, the influence on the better fit is evident. The adopted data [6] for this level are based on the results of a single older work [22]. The authors [22] observed a weak γ decay of this state in the presence of a large background.…”

Section: Resultsmentioning

confidence: 99%

“…The adopted data [6] for this level are based on the results of a single older work [22]. The authors [22] observed a weak γ decay of this state in the presence of a large background. A broader level than in Ref.…”

Section: Resultsmentioning

confidence: 99%

Structure of $^{20}$Ne states in the resonance $^{16}$O+$α$ elastic scattering

Nauruzbayev,

Goldberg,

Nurmukhanbetova

et al. 2017

Preprint

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Background: The nuclear structure of the cluster bands in 20 Ne presents a challenge for different theoretical approaches. It is especially difficult to explain the broad 0 + , 2 + states at 9 MeV excitation energy. Simultaneously, it is important to obtain more reliable experimental data for these levels in order to quantitatively assess the theoretical framework.Purpose: To obtain new data on 20 Ne α cluster structure.Method: Thick target inverse kinematics technique was used to study the 16 O+α resonance elastic scattering and the data were analyzed using an R matrix approach. The 20 Ne spectrum, the cluster and nucleon spectroscopic factors were calculated using cluster-nucleon configuration interaction model (CNCIM).Results: We determined the parameters of the broad resonances in 20 Ne: 0 + level at 8.77 ± 0.150 MeV with a width of 750 (+500/-220) keV; 2 + level at 8.75 ± 0.100 MeV with the width of 695 ± 120 keV; the width of 9.48 MeV level of 65 ± 20 keV and showed that 9.19 MeV, 2 + level (if exists) should have width ≤ 10 keV. The detailed comparison of the theoretical CNCIM predictions with the experimental data on cluster states was made.Conclusions: Our experimental results by the TTIK method generally confirm the adopted data on α cluster levels in 20 Ne. The CNCIM gives a good description of the 20 Ne positive parity states up to an excitation energy of ∼ 7 MeV, predicting reasonably well the excitation energy of the states and their cluster and single particle properties. At higher excitations, the qualitative disagreement with the experimentally observed structure is evident, especially for broad resonances.

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A study of the gamma radiation produced in the alpha-particle bombardment of O16

Abstract: This thesis describes an investigation of gamma rays from the d 6 20 reaction (a., y)Ne • The excitation function for gamma radiation has been studied for laboratory alpha-particle energies Ea. from 4. 8

Cited by 53 publications

References 28 publications

Structure of Ne20 states in resonance O16+α elastic scattering

Structure of Ne20 states in resonance O16+α elastic scattering

Mirror Symmetry in theβDecay of theA=20and 25 Systems

Structure of $^{20}$Ne states in the resonance $^{16}$O+$α$ elastic scattering

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