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

The stellar reaction 14 O( α ,p) 1 7F, that critically determines the onset of the high-temperature rp-process, has been studied through a direct measurement with a low-energy radioactive 14 O 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. ( 14 O+ α ) = 0.8-3.8 MeV. The 14 O( α ,p) 17 F * reaction leading to the first excited state in 17 F 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 18 Ne.