Isotopic abundances in RGB- and AGB-stars

Asymptotic Giant Branch stars contribute significantly to the chemical evolution of their host galaxies. All stars with a main-sequence mass = 8M ? will return eventually 30-80% of their mass to the interstellar medium. In parallel to the He-burning phase, which follows the original main sequence H-burning, AGB stars are known to produce heavy elements. He-burning is accompanied by a strong neutron flux which in turn breeds heavy nuclei in the so called s-process. Convective mixing of the entire star outside of the degenerate C/O core (dredge-up) ensures, that the s-process produced material becomes part of the outer shells which are being expelled in the mass-loss phase on the AGB. In spite of the importance of this process for understanding chemical evolution precious little observational constraints exist for the various models describing thermo-nuclear evolution. Fully resolved infrared spectroscopy of rotation-vibrational molecular transitions may contribute substantially to a better understanding of the thermo-nuclear evolution. Π2006 Springer-Verlag Berlin Heidelberg.