STUDIES OF (E-],E'GAMMA-]1GAMMA-]2=) REACTIONS AND ELECTROMAGNETIC CURRENTS IN ROTATIONAL NUCLEI

The general formalism is presented for electron scattering studies involving excitation of a discrete state followed by the emission of any number of real photons which are detected in coincidence with the scattered electron. Special limited situations are discussed in which only a single real photon is emitted and in which one multipole dominates in the γ-decay. The formalism is applied in a treatment of low-lying collective excitations in nuclei. Observables which become accessible from measurements of angular distributions in the (e, e′γ) reaction permit the determination of transverse multipole matrix elements through sensitivity to transverse/longitudinal interferences, and so yield information on intrinsic nuclear electromagnetic current distributions where heretofore in almost all cases only charge distribution information has been available. Illustrative examples of vibrational and rotational excitations are presented to help elucidate the degreee of sensitivity to the nature of the current flow. Detailed results are given for rotational bands described within the context of the deformed Hartree-Fock method (using projected Hartree-Fock and cranking approximations, and using several effective forces) applied to two selected nuclei, a light nucleus, 20Ne and a rare-earth nucleus, 166Er. © 1990.