The investigation of giant resonances, other than electric dipole, has been accomplished with various nuclear probes. Electron scattering and hadron scattering have been used most often for this purpose. The photonuclear cross sections associated with multipoles higher than dipole are very small so that photon scattering would seem an unlikely method of studying the electric quadrupole giant resonance. However, an appreciable E1-E2 interference term in the angular distribution permits the observation of E2 strength. In this Letter, we report on the use of elastically Phys. Rev. Lett. _36, 307 (1976).scattered photons to determine the location and magnitude of the E2 strength in 12 C. Scattering cross sections were measured at 90° and 135° in the energy range from 23.5 to 39 MeV and the results compared to the predicted values derived from the measured photonuclear absorption cross section. 1 The results show that for excitation energies below 24 MeV only electric dipole transitions need be considered, but in the energy range from 24 to 40 MeV, the magnitude of the electric quadrupole absorption is surprisingly large. The elastic-scattering cross section is meas-The elastic-photon-scattering cross section for 2 C has been measured at 90° and 135° in the energy range from 23.5 to 39 MeV. These data disagree with the predicted scattering, derived from the measured photonuclear absorption cross section, if only El transitions are assumed. To explain the difference in these cross sections, a large component of electric quadrupole absorption between 24 and 40 MeV is inferred.

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