Experimental cross sections ofHo165(α,n)Tm

Abstract

Background: Optical potentials are crucial ingredients for the prediction of nuclear reaction rates needed in simulations of the astrophysical γ process. Associated uncertainties are particularly large for reactions involving α particles. This includes (γ,α) reactions which are of special importance in the γ process. Purpose: The measurement of (α,n) reactions allows for an optimization of currently used α-nucleus potentials. The reactions 165 Ho(α,n) and 166 Er(α,n) probe the optical model in a mass region where γ process calculations exhibit an underproduction of p nuclei which is not yet understood. Method: To investigate the energy-dependent cross sections of the reactions 165 Ho(α,n) and 166 Er(α,n) close to the reaction threshold, self-supporting metallic foils were irradiated with α particles using the FN tandem Van de Graaff accelerator at University of Notre Dame. The induced activity was determined afterwards by monitoring the specific β-decay channels. Results: Hauser-Feshbach predictions with a widely used global α potential describe the data well at energies where the cross sections are almost exclusively sensitive to the α widths. Increasing discrepancies appear towards the reaction threshold at lower energy. Conclusions: The tested global α potential is suitable at energies above 14 MeV, while a modification seems necessary close to the reaction threshold. Since the γ-and neutron width show non-negligible impact on the predictions, complementary data are required to judge whether or not the discrepancies found can to be solely assigned to the α width.

Measurement of (α,n) reaction cross sections of erbium isotopes for testing astrophysical rate predictions

“…The agreement between the two data sets is almost perfect, this fact strengthens further the conclusions of [28].…”

“…A similar situation as in [28] is encountered here. Figure 5 shows a comparison of our data to Hauser-Feshbach predictions performed with the code SMARAGD [41].…”

“…169 Yb reaction was studied at energies overlapping with the results of a recent measurement performed by [28]. The agreement between the two data sets is almost perfect, this fact strengthens further the conclusions of [28].…”

“…Towards lower energy approaching the reaction threshold, the neutron width strongly decreases and the cross sections become increasingly sensitive to the neutron-and γ-widths in addition to the α-widths. It was already pointed out in [28] that this behavior does not allow for an unambiguous identification of the source of discrepancy closer to the threshold from (α,n) data alone, if such a discrepancy between cross section measurements and prediction were found.…”

Total and partial cross sections of theSn112(α,γ)Te116Netterdon1, Mayer2, Scholz3 et al. 2015Phys. Rev. C300310View full textAdd to dashboardCite

“…Up to now, the activation technique has been the most widely used method to measure absolute reaction cross sections for charged-particle induced reactions [13][14][15][16][17][18][19]. In addition, the 4jr-summing technique is available for the in vestigation of certain a-and proton-capture reactions [20,21 ].…”