HEAVY ELEMENT DIFFUSION AND GLOBULAR-CLUSTER AGES

This paper discusses low mass, metal poor stars, presenting new evolut ionary computations which take into account the inward diffusion of bo th He and heavy elements during the H burning phase. The investigation has been extended to He burning models, discussing the luminosity of the Zero Age Horizontal Branch (ZAHB) models originated from progenito rs with efficient element diffusion. We find that diffusion of heavy e lements plays a non-negligible role in the evolutionary paths of the m odel. One finds that element diffusion has a sensitive influence on ev olutionary models, a less significant effect on the isochrone turn off and, finally, a rather marginal impact on the difference in luminosit y between the ZAHB and the isochrone Turn-Off (TO). The consequences o f these results on current evaluations of globular cluster ages are di scussed in connection with possible sources of errors.