Se(d,pγ) with GODDESS for weak r-process nucleosynthesis *

The mass 80 peak of the r-process abundance pattern is believed to be the product of multiple possible astrophysical environments. Among these is a possible weak r-process that could occur in hot (~1GK) environments such as core-collapse supernovae. Neutron-capture rates on Se isotopes have been identified by Surman et al. [1] to have significant impact on final calculated abundance patterns. Stable ⁸²Se lies between the 81 and 83 Se isotopes, which have significant impact on final abundances. However, the evaluated ⁸²Se(n,γ) cross sections are inconsistent. Due to the close proximity to the N=50 shell closure, neutron-capture on ⁸²Se probably proceeds via both direct and a compound nucleus (CN) processes. Direct-capture contributions can be deduced from spectroscopic factors of low-lying states in ⁸³Se. To inform capture via a CN, the (d,pγ) reaction has recently be validated as surrogate for (n,γ) by Ratkiewicz et al [2]. To inform the competition between direct and compound nucleus (n,γ) processes near the weak r-process path, the (d,pγ) reaction was measured with GODDESS using ⁸²Se beams from the ATLAS facility at ANL. Preliminary results will be presented.

[1]  R. Surman et al., AIP Advances 4, 041008 (2014)

[2]  A. Ratkiewicz et al., Phys. Rev. Let., 122 052502 (2019).