Differential cross sections and analyzing powers for polarized ($p,p^{\prime }$) scattering on ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ have been measured at an incident proton energy of 24.5 MeV, using the Saclay AVF cyclotron. Data have been taken for nine levels, up to 7.11 MeV excitation energy. The analysis has been carried out in the distorted wave Born approximation within the framework of the macroscopic and microscopic models. For the latter the available wave functions of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ and an approximate description of the nucleon-nucleon interaction, derived from the Hamada-Johnston potential, have been used. The macroscopic model, with just a simple deformation parameter $\beta$, accounts reasonably well for some even-parity transitions, and also for the excitation of the $3^{-}$ level at 5.09 MeV. Furthermore, coupled-channel calculations support evidence for a rotational band based on the ground state and including the $2^{+}$ at 1.98 MeV and the $4^{+}$ at 7.11 MeV. The analysis also supports a collective character of the $3^{-}$ level at 5.09 MeV and accounts for the observed strong excitation of this state. Satisfactory fits are obtained for some levels within the microscopic model, even though the absolute values of the cross sections are usually underestimated and large normalization factors needed. The use of an imaginary form factor adds some structure to the calculated angular distributions and improves the agreement between theory and experiment for those transitions for which the real form factor is collective like, i.e., peaked at the nuclear surface.

NUCLEAR REACTIONS ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}(p,p^{\prime }){}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, $E=24.5\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$ and analyzing power for nine levels. Macroscopic and microscopic DWBA calculations.

• Received 5 November 1973

DOI:https://doi.org/10.1103/PhysRevC.10.1645