Note on the electric quadrupole absorption in the nuclear photo-reaction

Abstract

The behavior of the EQ absorption cross section in the « Giant resonance » region is discussed through the analysis of the angular distributions of emitted particles by using the direct interaction model. The difference between proton’s and neutron’s angular distributions is attributed to the difference between the effective charges of the proton and the neutron for EQ radiation. The excitation functions for the EQ absorption are computed for40A(γp)39Cl and59Co(γ p)58Fe. It is pointed out that the integrated cross sections for the EQ absorption are favorable to explain the feature of the angular distributions and the excitation curves have a peak near the maximum energy of the « Giant resonance ». The agreement between our results and the experiments for the angular distributions of the above reactions is good in part. On the whole, however, the ratio of the ED to the EQ absorption cross section is too small in comparison to that required from the experiments. The results of this model are closely discussed and the direction of the modification is also indicated.