Orbital rotational vibrations in theA=130 mass region

The rotational vibrations (${\mathit{K}}^{\mathrm{\pi }}$=$1^{+}$ states) in 16 even-even Xe, Ba, and Ce nuclei are studied in the quasiparticle random-phase approximation with a mean field given by a deformed Woods-Saxon potential and residual forces: a self-consistent quadrupole-quadrupole interaction, a spin-spin interaction, and a force that restores the rotational invariance of the Hamiltonian. A shell effect is found which is typical for this mass region: a strong orbital character of almost all low-energy (2.5–5 MeV) excitations, while the higher-energy ones are predominantly spin flip. The comparison of random-phase approximation M1 transition densities and (e,e’) form factors with the microscopic realization of the two-rotor model $1^{+}$ state allow us to conclude that the strongly orbital low-energy random-phase approximation states perform the scissor-type motion described by the two-rotor model, but only few particles are involved in this motion.