Fifty-four-point angular distributions in the angular range 2.5° to 170° have been measured for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}({}_{}{}^6{}_{}{}^{}\mathrm{Li},\alpha ){}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ reaction to the $1^{+}$ (0.0 MeV), $3^{+}$ (0.937 MeV), and $0^{-}$ + $5^{+}$ (1.1 MeV) states in ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ at a bombarding energy of 34 MeV. In addition, forward angle data have been measured for the $2^{-}$ (2.101 MeV), $1^{+}$ (3.725 MeV), $3^{-}$ (3.791 MeV), and $2^{+}$ (3.836 MeV) states. The angular distributions for all of the above states are forward peaked and have little structure at back angles. The general structure of the first 60° of the angular distributions can be reproduced by zero-range two-particle transfer distorted-wave Born-approximation calculations; however, the calculations are generally 3° and as much as 10° out of phase with the data past the first maximum. A zero-range distorted-wave Born-approximation normalization factor of 100 is obtained assuming the $5^{+}$ state to be a pure ${\left(d_{\frac{5}{2}}\right)}^2$ configuration. Finite-range distorted-wave Born-approximation calculations which include the $2S$ and $1D$ components of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ do not improve the fits to the data and are similar to zero-range calculations at forward angles. The $1D$ component was shown to have little effect on the calculated angular distributions. The absolute magnitudes of the cross sections are predicted to within a factor of 2 when the ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ shell model wave functions of Kuo and Brown are used in the finite-range distorted-wave Born-approximation calculations. Two-particle and cluster form factors used in the finite-range calculations gave equivalent fits to the data. The magnitude of the cross section at angles greater than 90° and the phase of the forward angle data could not be reproduced by any of the calculations. The failure of the distorted-wave Born-approximation calculations at back angles suggests that a more complete description of the reaction mechanism which includes the exchange of an $\alpha$ particle in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ with the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ projectile is necessary.

NUCLEAR REACTIONS ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}({}_{}{}^6{}_{}{}^{}\mathrm{Li},\alpha ){}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, $E=34\mathrm{}$ MeV; measured $\sigma \left(\theta \right) \theta =2.5\mathrm{}°-170\mathrm{}°$ lab, $\Delta \theta =2.5\mathrm{}°$; compared data to zero-range and finite-range DWBA calculations using shell model wave functions. Extracted (${}_{}{}^6{}_{}{}^{}\mathrm{Li},\alpha$) zero-range normalization factor.

• Received 1 March 1976

DOI:https://doi.org/10.1103/PhysRevC.14.977