C-12/C-13 ratios and Li abundances in C stars: evidence for deep mixing?

High-resolution spectra are used to derive Li abundances and C-12/C-13 ratios for 44 Galactic C stars. It is found that Li-rich stars [log epsilon (Li) > 1] usually have low C-12/C-13 ratios (< 15). The great majority of the Li-rich and low C-12/C-13 stars are of J type, although this correlation can also be found in normal (N-type) C stars. If these stars were indeed low-mass C stars, these results would require the existence of a deep-mixing mechanism able to operate in low-mass (M less than or similar to 2 M-.) C stars as an alternative for Li production by the hot bottom burning mechanism proposed in asymptotic giant branch stars with larger mass. We show observational evidence suggesting that high mass loss appears to act against such a mechanism.