Di Sun

The cross sections of ¹²⁷ I( n , γ ) ¹²⁸ I and ¹³³ Cs( n , γ ) ¹³⁴ Cs play a critical role in the s -process of nuclear astrophysics, the iodine–xenon chronometer on early meteorite evolution, and understanding the performance of CsI crystal detectors for Dark Matter Detection Experiment and Coherent Elastic Neutrino-Nucleus Scattering (CE ν NS) experiments. The neutron capture cross sections of ¹²⁷ I and ¹³³ Cs were measured from 1 eV to 1 MeV using the time-of-flight method at China Spallation Neutron Source Back-n facility. The neutron capture yield was derived via the pulse-height weighting technique based on the total energy detection principle of C ₆ D ₆ detectors. In the resolved resonance region (RRR), some new resonance peaks of ¹³³ Cs( n , γ ) were observed for the first time. Resonance parameters for the neutron capture cross section were extracted using the SAMMY code from 1 eV to 4 keV, while averaged capture cross sections in the unresolved resonance region (URR) from 4 keV to 1 MeV were analyzed with TALYS. Results were compared with evaluated libraries and previous work in both RRR and URR. Astrophysical Maxwellian-averaged cross sections (MACS) were calculated for kT = 5–100 keV. At kT = 30 keV, the MACS of both ¹²⁷ I( n , γ ) ¹²⁸ I and ¹³³ Cs( n , γ ) ¹³⁴ Cs were slightly higher than those of the KADoNiS v0.3 recommended value. And the reaction rates were derived over the astrophysically relevant temperature range of s -process nucleosynthesis models. The uncertainties of present reaction rates are significantly reduced.

The ( n , γ ) cross section of silver is crucial for the nucleosynthesis process of nuclear astrophysics, the design of silver-indium-cadmium absorber rod in the nuclear reactors, and neutron resonance capture analysis for determining the elemental and isotopic composition of cultural heritage. The high-precision Ag ( n , γ ) cross section was measured from 1 eV to 1 MeV at the Back-n facility of the Chinese Spallation Neutron Source using the time-of-flight method and pulse height weighting technique. The resonance parameters were accurately extracted in the resolved resonance region by the multilevel multichannel R -matrix code . The code was used to describe the average cross sections in the unresolved resonance region, and the Maxwellian-averaged cross sections (MACSs) of Ag 107 and Ag 109 were further given in the 5–100 keV range. The MACS values at k T = 30 keV for Ag 107 ( 887 ± 89 mb ) and Ag 109 ( 903 ± 90 mb ) are slightly higher than the recommended values in the Karlsruhe Astrophysical Database of Stellar Nucleosynthesis.