Inelastic Electron Scattering Studies:Cu63,In115,Ta181,Pb208, andBi209

Abstract

Measurements were made of the cross sections for scattering of electrons of primary energies from 183 MeV to 600 MeV from ${\mathrm{Cu}}^{63}$, ${\mathrm{In}}^{115}$, ${\mathrm{Ta}}^{181}$, ${\mathrm{Pb}}^{208}$, and ${\mathrm{Bi}}^{209}$, using high-resolution detectors. A number of $E2$, $E3$, $E4$, and two $E5$ transitions were induced with nuclear excitations up to 7 MeV. The levels excited have enhanced gamma-decay rates to the nuclear ground states. In the odd-$A$ nuclei most of the observed transitions were to clusters of near-similar states. The results are compared in detail to studies of ($p,{p}^{\ensuremath{'}}$), ($d,{d}^{\ensuremath{'}}$), ($\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}$), and ($n,{n}^{\ensuremath{'}}$) reactions in the same nuclei. Great similarities between these and the ($e,{e}^{\ensuremath{'}}$) are established. It is shown how the combined results can be used to determine the disposition and intensities of the levels within the clusters and how these are related to the discrete-energy core excitations in neighboring even-even nuclei. Data taken at high momentum transfer show that inelastic electron scattering continues to be dominated by excitation of collective states in disagreement with predictions based on present understanding of the process. Excitations seen in both ${\mathrm{Bi}}^{209}$ and ${\mathrm{Pb}}^{208}$ at about 5.8 MeV are identified as leading to collective states in these nuclei. They are probably E5 transitions although $E4$ assignments cannot be excluded. The collective states are not seen in ${\mathrm{Ta}}^{181}$ and ${\mathrm{Au}}^{197}$ in ($e,{e}^{\ensuremath{'}}$).