Direct measurement of the astrophysical reaction 14O (α, p) 17F

The stellar reaction O-14(alpha,p)F-17, that critically determines the onset of the high-temperature rp-process, has been studied through a direct measurement with a low-energy radioactive O-14 beam and a gaseous helium target cooled down to 30 K. The reaction cross section was measured directly by means of a thick target technique in the energy range of E-c.m(O-14+alpha) = 0.8-3.8 MeV. The O-14(alpha,p)F-17* reaction leading to the first excited state in F-17 was clearly observed for the first time, suggesting an increase of about 50% for the stellar reaction rate through resonance at around 7.1 MeV in Ne-18.