Thermal ($n,{\gamma}$) cross section and resonance integral of $^{171}\mathrm{Tm}$

Background: About 50% of the heavy elements are produced in stars during the slow neutron capture process. The analysis of branching points allows us to set constraints on the temperature and the neutron density in the interior of stars. Purpose: The temperature dependence of the branch point Tm171 is weak. Hence, the Tm171 neutron capture cross section can be used to constrain the neutron density during the main component of the s process in thermally pulsing asymptotic giant branch (TP-AGB) stars. Methods: A Tm171 sample produced at the ILL was activated with thermal and epithermal neutrons at the TRIGA research reactor at the Johannes Gutenberg-Universitat Mainz. Results: The thermal neutron capture cross section and the resonance integral have been measured for the first time to be σth=9.9±0.9b and σRI=193±14b. Conclusions: Based on our results, new estimations of the direct capture components' impact on the Maxwellian-nAveraged cross sections (MACS) are possible.