Current models of s-nucleosynthesis in massive stars ( M \sim 15 M _ { \odot } to \sim 30 M _ { \odot } ) are able to reproduce some main features of the abundance distributions of heavy isotopes in the solar system , at least in the A \sim 60 - 90 mass range .
The efficiency of the process and the above specified mass range for the s-nuclei are still heavily uncertain due to both nuclear reaction rates and stellar models uncertainties .
A series of s-process simulations with stellar models in the 15 - 30 M _ { \odot } ( mass at ZAMS ) and metallicity Z = 0.02 mass have been performed to analyse the impact of the overshooting model used on the s-process yields .
As in a previous exploratory work performed with stellar models having M _ { ZAMS } = 25 M _ { \odot } and Z = 0.02 , enhancements factors in the range 2-5 are found in the final s-process efficiency when overshooting is inserted in the models .