Nuclear Scattering of Plane-Polarized Photons

A beam of plane-polarized monochromatic photons has been produced by the resonance fluorescence of the well-known $1^{+}$ state at 15.1 MeV in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. These have been scattered a second time from natural targets of Cd, Sn, Ta, W, Pt, Au, and Bi. Measurements were made with poor energy resolution of the relative number of photons scattered at 90° parallel and perpendicular to the polarization vector in the incident 15.1-MeV beam. The observation of photons scattered along the polarization vector reflects the contribution of incoherent scattering to the dominant coherent-scattering process and results either from permanent nuclear deformation or from the dynamic deformation produced by the coupling of the giant dipole resonance with the quadrupole oscillations of the nuclear surface. The observed intensities of incoherent scattering are of the same order of magnitude for the deformed nuclei and the spherical vibrators and agree roughly with the predictions of the dynamic collective model. No incoherent scattering was observed from the rigid sphere ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$.