Exchange currents in electric transitions and the role of Siegert's theorem: A case study in deuteron photodisintegration

The size of exchange corrections to electric transitions is investigated for deuteron photodisintegration. Large contributions are found in E1 transitions, which become dominant above 40 MeV. Most of them are already included by using Siegert's theorem together with classical one-body operators. Higher multipoles are only little affected except for rather high energies. The Born approximation for the final states gives in general a poor description. (orig.)