Li abundance evolution as probe of extra-mixing in 47 Tuc RGB stars

Fundamental parameters and lithium abundances, ALi, have been derived for a sample of evolved stars in the globular cluster 47 Tuc (from GIRAFFE spectra and MARCS models of atmosphere). These data sample a complete evolutionary sequence from subgiant stage to the tip of the Asymptotic Giant Branch. With this unique observational data set we have analyzed the evolution of ALi along the Red Giant Branch (RGB) using non-standard stellar evolution models, so as to explore the occurence and the efficiency of extra-mixing processes in low mass stars at the so-called Red Giant bump.