(y, n) studies of the giant isovector E2 resonance in lead, cadmium, and calcium

The angular asymmetry in the (..gamma..,n) reaction on natural lead, cadmium, and calcium has been measured in the energy region of the isovector quadrupole resonance (20 to 40 MeV). The asymmetry increases from low values, about 0.2, to high values, 0.6 to 0.8, where this resonance is expected. This increasing asymmetry interference is interpreted as resulting from the between the E1 and E2 isovector amplitudes. We have done direct-semidirect calculations for lead and cadmium and obtain resonance energies of 23.5 +- 1.5 and 26.5 +- 1.5 MeV for those elements, respectively. For calcium, preliminary results indicate a resonance energy of 34 +- 2 MeV. The widths are found to be considerably larger than those of the E1 resonance. 10 refs., 10 figs., 1 tab.

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[2]  G. Breit,et al.  Nuclear Structure, Vol. 1 , 1970 .