Splitting of the Giant Resonance for Deformed Nuclei

Photoneutron yield measurements have been made for terbium, tantalum, and gold with good energy resolution from threshold up to 25 Mev. Neutron-production cross sections were obtained directly from the experimental points without smoothing the raw data. Corrections were made for the multiple production of neutrons above the ($\gamma , 2n$) thresholds. The giant resonances for terbium and tantalum were found to be split into two resonances as predicted by Okamoto and Danos. The giant resonances for all three nuclei were fitted by the superposition of two Lorentz shape resonance lines. The intrinsic quadrupole moments determined from these fits to the experimental data were: terbium, +5.6±0.6 barns; tantalum, +5.7±0.3 barns; and gold, +1.6±0.6 barns.