Stellar Nucleosynthesis: s-Process in Massive Stars

The s-process nucleosynthesis is relatively well understood, at least from the nuclear physics point of view. The site of this important process is believed to be linked to AGB stars and to massive stars. In both cases, the physical conditions underlying the stellar environments where the s-process occurs are still not fully understood and need further elaboration. In this contribution, we give an updated brief overview on the s-process in massive stars pointing out several physical uncertainties still under debate. In particular, we describe the effect of the still uncertain C-12(alpha, gamma)O-16 reaction on the s-process. We emphasize the behavior of the s-process during core helium burning and during shell carbon burning.