The deformed, fissionable nucleus 238U was studied with inelastic scattering of 87.5 MeV electrons between 5 and 40 MeV excitation energy with inelastic momentum transfers ranging from 0.32 fm ' to 0.58 fm ' for an excitation energy of 15 MeV. Resonance cross sections extracted were compared with distorted-wave
Born-approximation calculations using the Goldhaber-Teller, Steinwedel-Jensen, and Myers-Swiatecki
models of the giant resonance. It is demonstrated that up to the first minimum of the form factor the cross
section is nearly completely determined by one parameter, the transition radius Rt„. Using the known
systematics of various multipole resonances in other, nonfissionable nuclei as a guide, it was found that the
assumed ground state radius of ' U had to be enlarged by about 10% for all multipolarities, to bring the
strength found into agreement with the systematics and with other experiments in 238U. In particular, while the model-independent values for position and width of the giant dipole resonance agree well with photon
experiments, a scaled version of the Myers-Swiatecki model had to be used to produce agreement in strength. Similarly a scaled Goldhaber-Teller model was used for the isoscalar E2 resonance at 9.9 MeV. The situation for the isovector states above the giant dipole resonance, E2, and E3 (or EO) is even more complicated. It is argued that with proper caution and consideration of other available data the use of the collective models mentioned above may give valuable insight into the charge distribution of 238U at higher excitation energies.This work was supported in part by the Naval Postgraduate School Research Foundation and the National Science FoundationApproved for public release; distribution is unlimited
