Deducing neutron capture cross sections with recoil mass separators

Shuya Ota (Brookhaven National Laboratory, USA)

While reaction cross sections for short-lived nuclei have been sought after but have only been available from theory calculations for many years, experiments with radioactive ion (RI) beams can replace or drastically improve these predicted cross sections. Exceptions are neutron-induced reactions because they require reliable indirect measurement techniques, as no neutron is available as a target. In particular, radiative neutron capture ((n,g)) cross sections are significantly difficult to constrain since compound nuclear decays via g-ray emissions are very sensitive to the reaction mechanisms, while these cross sections are vital for basic (e.g., nuclear astrophysics) and applied nuclear science.

In this talk, I will discuss a new possible indirect technique using transfer reactions with VAMOS++. Within the technique, sensitivity to the reaction mechanism suffered by all existing indirect techniques may be removed. Related to the new technique, I will introduce three experiments we have performed at the Texas A&M University cyclotron: 1) ²²Ne(a,n) cross sections with the TIARA Si array + MDM spectrometer [1,2], 2) ⁹⁴Zr(n,g) cross sections with the DAPPER BaF₂ total absorption g-ray detector, and 3) ¹²C(¹¹Be,¹¹Be) with the BlueSTEAl Si array [3]. Our idea for the new technique with VAMOS++ was inspired mainly by the first two experiments. Meanwhile, the third experiment, though the experimental technique is similar, is more about our recent effort to establish a new technique to constrain nuclear halo properties from elastic and one neutron breakup angular distributions.

[1] S. Ota et al. Phys. Lett. B 802, 135256 (2020).
[2] S. Ota et al., Phys. Rev. C 104, 055806 (2021).
[3] S. Ota et al., Nucl. Instr. Meth. A 1059, 168946 (2024).