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

Abstract

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.

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

“…It is found that the 6720 combinations under study show a wide range of χ 2 /F per data point from slightly below 8 to more than 4000 for all 43 experimental values for σ reac and the (α,n), (α,γ), and (α,p) reactions in [7,8]. These χ 2 /F correspond to an average deviation factor f dev between experiment and theory for all data points from about 1.3 for the best fits up to 2.6 for the worst cases.…”

“…The latest global A-OMP by Su and Han [33] is not yet implemented in TALYS. It has been shown in [7] that this potential overestimates the total reaction cross sections for 64 Zn at low energies. Thus, no efforts have been made to implement this potential into TALYS for the present study.…”

“…The data labeled σreac (shown in red) are total reaction cross sections and have been derived from elastic scattering angular distributions [7]. The thresholds for the different channels are indicated by arrows on top.…”

“…In particular, this means 4 data points for the (α,γ) reaction, 10 data points for the (α,n) reaction, 27 data points for the (α,p) reaction, and 2 data points for the total reaction cross section σ reac from the analysis of the elastic scattering angular distributions [7,8]; in total, 43 experimental data points are used to determine the χ 2 landscape. The χ 2 adjustment procedure will be discussed in detail in the following section.…”

“…Our recent study of α-induced reaction cross sections for the target nucleus 64 Zn [7,8] was focused on total reaction cross sections σ reac and its determination from either elastic scattering angular distributions or from the sum over the cross sections of all open nonelastic channels (including inelastic scattering). It was found that there is excellent agreement at the lower energy of 12.1 MeV (428 ± 7 mb from elastic scattering vs. 447 ± 41 mb from the sum over non-elastic channels).…”