Isoscalar quadrupole giant resonance in 208Pb: A statistical analysis of high-resolution inelastic electron scattering spectra

The fine structure observed in high resolution inelastic electron scattering spectra for 208Pb in the excitation energy range of the isoscalar giant quadrupole resonance has been analysed with a fluctuation analysis technique. The obtained density of levels as a function of excitation energy Ex has then been used as a constraint for the shape and magnitude of the (radiative) background subtracted spectra subjected to a multipole decomposition. The derived E2 strength in the region 8.0≤Ex≤11.5 MeV exhausts (50(±12))% of the energy weighted sum rule. The E2 strength found is considerably larger than previously estimated from the same spectra and it is now both in shape and magnitude in good agreement with results from a recent 208Pb(e,e'n) coincidence experiment. (orig./HSI)