Long range correlations and photo effect in nuclei

Abstract

A detailed quantum mechanical treatment of the collective model for the giant dipole resonance in the low energy nuclear photo effect is presented. A relation ω D = c k D for the resonance energy ω D is derived from sum rule considerations, where k D is related to the nuclear radius by k D ≈ π 2R and c to the structure factor s( k) of nuclear matter at small momenta k by s( k) = k 2mc . The velocity c is calculated and the semiclassical expresssion for c in terms of the symmetry energy K (c = ( 2K m ) 1 2 ) is found to be valid only for extremely strong interactions. For weaker forces one obtains a larger value of c than indicated by this relation and a value of ω D in better agreement with the results of shell model configuration mixing calculations.