Stellar production cross section ofLum176

The partial neutron capture cross section of ${}_{}{}^{175}{}_{}{}^{}\mathrm{Lu}$ to the isomer ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}_{}^{\mathit{m}}{}_{}{}^{}$ has been measured at kT=25 keV via the activation technique. Systematic uncertainties were carefully evaluated by two independent methods for determination of the induced activities and by variation of the relevant experimental parameters. The final cross section of 1135±30 mb was derived from six different activations. With this result, the production of the long-lived ground state ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}_{}^{\mathit{g}}{}_{}{}^{}$ (${\mathit{t}}_{1/2}$=41 Gyr) by s process neutron captures would not be sufficient to account even for the observed lutetium abundance. Consequently, other mechanisms, e.g., thermally induced transitions from the isomer to the ground state must have enhanced the yield of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}_{}^{\mathit{g}}{}_{}{}^{}$ during the s process.