Decay of giant resonances following excitation by inelastic electron scattering

Experiments have been initiated to study the decay of giant resonances following excitation by inelastic electron scattering. The program at Stanford is concentrated on the detection of charged particles using conventional solid state detectors. Data have been accumulated on proton and alpha decay from 12C following excitation by scattering 86 and 126 MeV electrons at 400. The results provide the first measurement of proton decay leaving 11B in the first and higher excited states. In addition measurements of the angular correlations and their variation with increasing momentum transfer q have provided possible evidence for a spin-flip component to the electric dipole resonance and for an electric monopole resonance in 12C. The integrated alpha yield from 12C amounts to less than 10% of that for the protons and shows no structure indicative of the giant dipole resonance. Experiments are underway at both Stanford and Illinois to study the decay be fission from the giant resonances in the transuranium elements. First results on 238U at low q give a fission branching ratio consistent with photonuclear results in the giant dipole region but indicate there may be some excess at lower excitation energies. (author)