Spectroscopic study of oxygen and fluorine isotopes with the ( alpha,3He) and ( alpha,t) reactions on 16,17,18O.

The ({alpha},{sup 3}He) and ({alpha},{ital t}) reactions on {sup 16,17,18}O were studied at {ital E}{sub {alpha}}=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 2{sub 1}{sup +}, {ital T}=1 states in {sup 18}O and {sup 18}F. Almost full strengths were observed for the 0{ital d}{sub 5/2}, 1{ital s}{sub 1/2}, and 0{ital d}{sub 3/2} transfers. The obtained spectroscopic factors for the 0{ital d}{sub 5/2} and 1{ital s}{sub 1/2} transfers were in good agreement with shell-model calculations, while the agreement was unsatisfactory for the 0{ital d}{sub 3/2} transfer in many respects. The {ital d}{sub 3/2} strengths in {sup 17}O and {sup 17}F were more fragmented than the shell-model prediction, while only half of the expected 0{ital d}{sub 3/2} strength was found in {sup 18}O and {sup 19}O. The strength to the first excited 3/2{sup +}, {ital T}=1/2 state in {sup 19}F was twice that predicted. Spectroscopic factors for many 0{ital f}{sub 7/2} transitions were alsomore » deduced. The 14.1 and 14.3 MeV states in {sup 18}O, in particular, proposed to be the stretched 6{sup {minus}} states in a recent ({ital e},{ital e}{prime}) experiment, were found to be excited by pure {ital l}=3 transfer with spectroscopic factors 0.16 and 0.05, respectively.« less