Electromagnetic Structure of the Giant Resonance in Oxygen-16

Abstract

The transverse inelastic form factor for excitation of the giant resonance in oxygen-16 is calculated by means of the particle-hole theory of the giant resonance. The calculation is done in such a way that no free parameters are involved. In addition, calculations similar to those of Brown, Castillejo, and Evans have been carried out and the form factor has also been calculated for the Goldhaber-Teller model. The results are compared with 180\ifmmode^\circ\else\textdegree\fi{} electron-scattering experiments and with photoabsorption data. It is found that the particle-hole calculations predict the observed behavior for the squared form factor, and also the change in the shape of the giant resonance cross section which is seen experimentally as the momentum transfer $q$ is varied. Neither of these effects is predicted by the Goldhaber-Teller model. Numerical results are presented for all of the different theoretical models, and it is found that the calculations involving no free parameters predict essentially the observed energy levels for the giant resonance and yield form factors which are consistent with all of the experiments considered.