出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present the results of nucleosynthesis computations in mass transport phenomena affecting
the final evolutionary stages of a low mass star. We assume that the process starts near the
H-burning shell, and is driven by magnetic mechanisms, according to recent suggestions [1].
This is due to the fact that magnetized bubbles are subject to a fast buoyancy, accompanied by
a downward flow induced by the settling of the heavier non-magnetized envelope material. During
its downward journey toward the H shell this envelope material can undergo further proton
captures, so that the mixing process ultimately induces changes in the envelope isotopic ratios
12C/13C,17O/16O,18O/16O,26Al/27Al. In most conditions the circulation is such that 7Li is destroyed.
Production of this nucleus can however occur in a region of the parameter space, if the
fast-rising magnetic structures provide a rapid upward transport of the Be abundance, as present
near the H shell or produced in the downflow. In normal low mass red giants (i.e. excluding the
anomalous CJ stars and the super-Li rich objects) Li seems to be created only on the RGB, and
then to undergo a slow destruction through extra-mixing processes
