Spectroscopic factors in nuclear astrophysics: The Ca-39(p, gamma)Sc-40 reaction as an example

The Ca-39(p, gamma)Sc-40 reaction is investigated in a microscopic cluster model. Spectroscopic properties of (SC)-S-40 are calculated and tested from K-40 properties, for which experimental data are available. The reaction r ate is much larger than previously accepted, which arises from different pr oton widths of the 2(1)(-), resonance in (SC)-S-40. In a more general conte xt, we draw attention to possible inaccuracies of the use of spectroscopic factors in nuclear astrophysics. Owing to strong differences between theore tical approaches, a direct measurement using a radioactive beam is desirabl e.