Spectroscopic study of oxygen and fluorine isotopes with the (α,3He) and (α,t) reactions on O16,17,18

The (α,3He) and (α,t) reactions on O16,17,18 were studied at Eα=65 MeV. Measured cross sections for the states up to 15 MeV in the residual nuclei were analyzed with the distorted wave Born approximation theory. Many spin-parity and isospin assignments were proposed based on the strengths, angular distributions, and excitation energies. Nearly equal spectroscopic factors were obtained for bound and unbound analog pairs except for the 21+, T=1 states in O18 and F18. Almost full strengths were observed for the 0d5/2, 1s1/2, and 0d3/2 transfers. The obtained spectroscopic factors for the 0d5/2 and 1s1/2 transfers were in good agreement with shell-model calculations, while the agreement was unsatisfactory for the 0d3/2 transfer in many respects. The d3/2 strengths in O17 and F17 were more fragmented than the shell-model prediction, while only half of the expected 0d3/2 strength was found in O18 and O19. The strength to the first excited 3/2+, T=1/2 state in F19 was twice that predicted. Spectroscopic factors for many 0f7/2 transitions were also deduced. The 14.1 and 14.3 MeV states in O18, in particular, proposed to be the stretched 6- states in a recent (e,e') experiment, were found to be excited by pure l=3 transfer with spectroscopic factors 0.16 and 0.05, respectively.