Multipole Assignment of the 8.9-MeV Resonance inPb208

Abstract

High-resolution inelastic electron scattering [full width at half-maximum (FWHM) ≃ 38 keV] with 50-MeV electrons on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ yields a width $\Gamma =1.3\mathrm{}\pm 0.2$ MeV for the 8.9-MeV resonance. This result together with the results from a reanalysis of older data with moderate energy resolution (FWHM ≃ 300 keV) shows that the previous identification of the 8.9-MeV resonance as a monopole excitation is not conclusive. The excitation of this state may as well be $E2\mathrm{}$. The giant quadrupole resonance at 10.8 MeV seen in former measurements has been reanalyzed.