Toroidal quadrupole transitions associated with collective rotational-vibrational motions of the nucleus

In the framework of the collective model the longitudinal, transverse and toroidal multipoles corresponding to the excitations of low-lying levels in the ground-state band of several even-even nuclei are computed by inelastic electron scattering (e,e'). In connection with these transitions a new quantity, which accounts for the deviations from the Siegert theorem, is introduced in the framework of the Riemann rotational model with non-vanishing vorticity. Inelastic differential cross sections calculated at backscattering angles show the dominance of toroidal form factors over a broad range of momentum transfer.