Self-consistent 13 C pocket in low mass AGB stars and related nucleosynthesis

We present new results concerning the self-consistent formation of a tiny 13 C pocket in a star with initial mass M = 3 M and solar metallicity during the Asymptotic Giant Branch phase. The introduction of an exponentially decaying profile of velocity below the convective envelope during third dredge up episodes allows a small amount of protons to di use in the 4 He- and 12 C- rich zone, leading to the formation of a 13 C-rich layer, whose extension varies from pulse to pulse. The resulting s-process nucleosynthesis is discussed and compared with previous models. Moreover, new models show an enhancement factor of about 50% in the e ciency of Third dredge up, which starts when the core mass MH' 0.58 M , in better agreement with the observed C-star luminosity function.