Constraints on the α+ nucleus optical-model potential via α-induced reaction studies on 108Cd

Scholz, Philipp; Heim, F.; Mayer, J.; Münker, Carsten; Netterdon, L.; Wombacher, Frank; Zilges, A.

doi:10.1016/j.physletb.2016.08.040

Cited by 31 publications

(40 citation statements)

References 34 publications

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“…It was recently suggested in [10] that the real part of this potential should be multiplied by a factor of about N DGG ≈ 1.1 − 1.2 for a better description of reaction data for heavy targets (A > ∼ 100). For 64 Zn it will be shown that the best fit is achieved by a reduction of the real part by a factor of about 0.9 (instead of an increased potential as found for A > ∼ 100 in [10]). The latest global A-OMP by Su and Han [33] is not yet implemented in TALYS.…”

Section: α-Nucleus Optical Model Potentialsmentioning

confidence: 99%

Statistical model analysis of α -induced reaction cross sections of Zn64 at low energies

2017

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Background α-nucleus potentials play an essential role for the calculation of α-induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions (typically at higher energies) and to the energy dependence of the effective α-nucleus potentials.Purpose The present work studies cross sections of α-induced reactions for 64 Zn at low energies and their dependence on the chosen input parameters of the statistical model calculations. The new experimental data from the recent Atomki experiments allow for a χ 2 -based estimate of the uncertainties of calculated cross sections at very low energies.Method The recently measured data for the (α,γ), (α,n), and (α,p) reactions on 64 Zn are compared to calculations in the statistical model. A survey of the parameter space of the widely used computer code TALYS is given, and the properties of the obtained χ 2 landscape are discussed.Results The best fit to the experimental data at low energies shows χ 2 /F ≈ 7.7 per data point which corresponds to an average deviation of about 30 % between the best fit and the experimental data. Several combinations of the various ingredients of the statistical model are able to reach a reasonably small χ 2 /F , not exceeding the best-fit result by more than a factor of two.Conclusions The present experimental data for 64 Zn in combination with the statistical model calculations allow to constrain the astrophysical reaction rate within about a factor of 2. However, the significant excess of χ 2 /F of the best-fit from unity asks for further improvement of the statistical model calculations and in particular the α-nucleus potential.

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Section: α-Nucleus Optical Model Potentialsmentioning

confidence: 99%

Statistical model analysis of α -induced reaction cross sections of Zn64 at low energies

2017

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“…It has turned out over the years that standard α-nucleus potentials like the extremely simple McFadden-Satchler potential [11] are able to reproduce (α,n) and (α,γ ) cross sections around and above the Coulomb barrier, whereas at very low energies below the Coulomb barrier (i.e., in the astrophysically relevant energy range) an increasing overestimation of the experimental reaction cross sections has been found in many cases (e.g., [12][13][14][15][16][17][18][19][20][21][22][23][24][25]). Interestingly, in the A ≈ 20-50 mass range, experimental (α,p) and (α,n) data are well described using the McFadden-Satchler potential [26].…”

mentioning

confidence: 99%

α scattering and α -induced reaction cross sections of Zn64 at low energies

Ornelas¹,

Mohr²,

Gyürky³

et al. 2016

Phys. Rev. C

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Background: α-nucleus potentials play an essential role for the calculation of α-induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions and to the energy dependence of the effective α-nucleus potentials. Purpose: The present work studies the total reaction cross section σ reac of α-induced reactions at low energies which can be determined from the elastic scattering angular distribution or from the sum over the cross sections of all open nonelastic channels. Method: Elastic and inelastic64 Zn(α,α) 64 Zn angular distributions were measured at two energies around the Coulomb barrier, at 12.1 and 16.1 MeV. Reaction cross sections of the (α,γ ), (α,n), and (α,p) reactions were measured at the same energies using the activation technique. The contributions of missing nonelastic channels were estimated from statistical model calculations. Results: The total reaction cross sections from elastic scattering and from the sum of the cross sections over all open nonelastic channels agree well within the uncertainties. This finding confirms the consistency of the experimental data. At the higher energy of 16.1 MeV, the predicted significant contribution of compound-inelastic scattering to the total reaction cross section is confirmed experimentally. As a by-product it is found that most recent global α-nucleus potentials are able to describe the reaction cross sections for 64 Zn around the Coulomb barrier. Conclusions: Total reaction cross sections of α-induced reactions can be well determined from elastic scattering angular distributions. The present study proves experimentally that the total cross section from elastic scattering is identical to the sum of nonelastic reaction cross sections. Thus, the statistical model can reliably be used to distribute the total reaction cross section among the different open channels.

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“…TALYS [33] provides 8 different options for the α-potential which is the basic ingredient for the calculation of (α,X) cross sections. In addition, we have implemented the Atomki-V1 potential in TALYS, and we have used scaling factors between 0.7 and 1.2 for the Demetriou potential as suggested by [64].…”

Section: B χ 2 -Based Assessment Of the Calculationsmentioning

confidence: 99%

α -induced reactions on In115 : Cross section measurements and statistical model analysis

et al. 2018

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Background: α-nucleus optical potentials are basic ingredients of statistical model calculations used in nucleosynthesis simulations. While the nucleon+nucleus optical potential is fairly well known, for the α+nucleus optical potential several different parameter sets exist and large deviations, reaching sometimes even an order of magnitude, are found between the cross section predictions calculated using different parameter sets. Purpose: A measurement of the radiative α-capture and the α-induced reaction cross sections on the nucleus 115 In at low energies allows a stringent test of statistical model predictions. Since experimental data are scarce in this mass region, this measurement can be an important input to test the global applicability of α+nucleus optical model potentials and further ingredients of the statistical model. Methods: The reaction cross sections were measured by means of the activation method. The produced activities were determined by off-line detection of the γ rays and characteristic x rays emitted during the electron capture decay of the produced Sb isotopes. Results:The simultaneous measurement of the (α,γ ) and (α,n) cross sections allowed us to determine a best-fit combination of all parameters for the statistical model. The α+nucleus optical potential is identified as the most important input for the statistical model. The best fit is obtained for the new Atomki-V1 potential, and good reproduction of the experimental data is also achieved for the first version of the Demetriou potentials and the simple McFadden-Satchler potential. The nucleon optical potential, the γ -ray strength function, and the level density parametrization are also constrained by the data although there is no unique best-fit combination. Conclusions:The best-fit calculations allow us to extrapolate the low-energy (α,γ ) cross section of 115 In to the astrophysical Gamow window with reasonable uncertainties. However, still further improvements of the α-nucleus potential are required for a global description of elastic (α,α) scattering and α-induced reactions in a wide range of masses and energies.

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Constraints on the α+ nucleus optical-model potential via α-induced reaction studies on 108Cd

Cited by 31 publications

References 34 publications

Statistical model analysis of α -induced reaction cross sections of Zn64 at low energies

Statistical model analysis of α -induced reaction cross sections of Zn64 at low energies

α scattering and α -induced reaction cross sections of Zn64 at low energies

α -induced reactions on In115 : Cross section measurements and statistical model analysis

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