Gamma-Ray Circular Polarization and Nuclear Spin Orientation inO16on Ni Reactions at 100 MeV

The circular polarization of the energy-integrated $\gamma$-ray spectra and the angular correlation of discrete $\gamma$ transitions in coincidence with the light fragments detected at 35° were measured for the reaction 100-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + Ni. A large nuclear spin polarization and at least 80% negative-angle scattering are deduced for deep-inelastic events. The decrease of the circular polarization observed at $Q>-30\mathrm{}$ MeV is ascribed to increasing positiveangle contributions to the cross section.