SAIP2025

Indirect experimental technique for constraining the 193,194Ir(n,γ) cross sections

9 Jul 2025, 15:00

20m

Solomon Mahlangu House (University of the Witwatersrand, Johannesburg)

Oral Presentation Track B - Nuclear, Particle and Radiation Physics Nuclear, Particle and Radiation Physics-1

Speaker

Sebenzile Magagula (University of the Witwatersrand)

Description

The formation of elements, particularly those heavier than iron,
predominantly occurs through two neutron capture processes: slow
neutron capture process and rapid neutron capture process, each
contributing approximately 50%. These are known as the s- and
r-processes, respectively [1].
The neutron capture reactions 192Ir(n,γ)193Ir and 193Ir(n,γ)194Ir
were indirectly studied by analyzing data obtained from the Oslo
Cyclotron Laboratory (OCL). These data enabled the study of the
193,194Ir isotopes, originating from the 192Os(α,tγ) and 192Os(α,dγ)
reactions, respectively. The 193Ir(n,γ)194Ir cross sections constrained
by our measurements provided a comparison to existing (n,γ) mea-
surement data [2]. Additionally, the 192Ir(n,γ)193Ir reaction maps a
branching point in the s-process, making it highly significant. How-
ever, directly measuring the (n,γ) cross section is challenging due to
the instability of 192Ir. Therefore, the OCL data provided valuable
information on the 192Ir(n,γ)193Ir cross section by indirectly con-
straining it using the experimental nuclear level density (NLD) and
γ-strength function (γSF).
An array of Sodium Iodine (NaI)Tl detectors, called CACTUS,
detected γ-rays, while the silicon particle telescope array, called SiRi,
was used to detect charged particles in coincidence. The NLDs and
γSFs were extracted below the neutron separation energy, Sn, using
the Oslo Method [3]. Furthermore, the NLDs and γSFs were used as inputs in the open-source code TALYS to calculate the neutron cap-
ture cross-sections and Maxwellian averaged neutron capture cross
sections (MACS) for 193,194Ir. Final results of this study will be
presented in comparison to existing data.

[1] Arnould, M., Goriely, S., and Takahashi, K. (2007). Physics
Reports, 450(4-6), 97-213.
[2] Zerkin, V. V., and Pritychenko, B. (2018). The experimental
nuclear reaction data (EXFOR) 888, 31-43.
[3] Schiller, A., Bergholt, L., Guttormsen, M., Melby, E., Rekstad,
J., and Siem, S. (2000). Nuclear Instruments and Methods in Physics
Research Section A: Accelerators, Spectrometers, Detectors and As-
sociated Equipment, 447(3), 498-511.

This work is based on research supported in part by the National Re-
search Foundation of South Africa (Grant Number:PMDS22070734847),
SAINTS Prestigious Doctoral Scholarship, U.S. Department of Energy,
Office of Science, Office of Nuclear Physics under Contract No. DE-AC02-
05CH11231 and the SARChI under grant No REP-SARC180529336567. The experiment was financed through ERC-STG-2014 under Grant Agreement No. 637686