Accelerator Mass Spectrometry (AMS) is today the most selective and sensitive analytical techniques stellar-nucleosynthesis for determination of isotopic abundances ranging down to below 10^-15. The principle and examples of the method are described. We now apply the technique to measurements of nuclear cross sections of stellar-nucleosynthesis reactions leading to long-lived nuclides. Recent measurements and experimental results for the important ⁶²Ni(n,\gamma )⁶³Ni (t_1/2=100 yrs) and ⁴⁰Ca(\alpha ,\gamma )⁴⁴Ti (59 yrs) reactions are presented.

PACS numbers: 07.75.+h, 29.20.–c, 26.20.Kn, 26.30.–k