Data for inelastic pion scattering from ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ at $T_{\pi }$=164 MeV, exciting the lowest $2^{+}$, $3^{\mathrm{-}}$, and $1^{\mathrm{-}}$ states, were analyzed by distorted-wave impulse approximation and coupled-channel calculations using transition densities derived from shell model calculations. Coupled-channels effects were found to be relatively unimportant for the $2^{+}$ and $3^{\mathrm{-}}$ states, but non-negligible for the excitation of the $1^{\mathrm{-}}$ state. Nevertheless, the inclusion of multistep excitation paths is not sufficient to generate a fit to the $1^{\mathrm{-}}$ data with the shell model wave functions. Major modifications are needed in the radial dependence of the neutron and proton parts of the transition density for the $0^{+}$→$1^{\mathrm{-}}$ one-step process.

• Received 4 March 1987

DOI:https://doi.org/10.1103/PhysRevC.35.2197