NUCLEAR PHOTOABSORPTION IN 208Pb BETWEEN THRESHOLD AND 140 MeV

We have investigated photonuclear reactions in 208 Pb from the reaction threshold to pion production threshold. In the Giant Dipole Resonance energy region we have considered the results of a recent 1− 1p-1h continuum calculation and multiplied them, heuristically, by a factor, which includes the effect of neglected nucleon-nucleon correlations, through the occupation number probabilities of the single particle and hole energy levels. We have thus obtained a much better agreement with experiment. In the energy region above the Giant Dipole Resonance we have considered a quasi deuteron model, which contains the effect of nucleon swelling. Both this model and corresponding integrated sum rules yield a satisfactory agreement with experiment.