Evidence for the Isoscalar Giant Dipole Resonance in208PbUsing InelasticαScattering at and near 0°

The isoscalar giant dipole resonance (ISGDR) in ${}^{208}\mathrm{Pb}$ has been investigated using inelastic scattering of 200 MeV $\ensuremath{\alpha}$ particles at and near 0\ifmmode^\circ\else\textdegree\fi{} where the angular distribution of the ISGDR can be clearly differentiated from those of other modes. The ``difference of spectra'' technique was employed to separate the ISGDR from the high-energy octupole resonance (HEOR). These data provide the clearest evidence yet for the ISGDR adjacent to the HEOR. With these results, all expected isoscalar $\ensuremath{\lambda}\ensuremath{\le}3$ resonances in ${}^{208}\mathrm{Pb}$ have been identified.