Nature of the low-lying 1+ isovector states in deformed nuclei

At the Technische Hochschule in Darmstadt the group of Richter and coworkers found in 1983/84 in deformed rare earth nuclei low-lying isovector 1+ states. Such states have been predicted in the generalized Bohr-Mottelson model and in the interacting boson model no. 2(IBA2). They describe the excitation energy of these states in good agreement with the data but overestimate the magnetic dipole transition probabilities. A microscopic description is needed to describe the spreading of the scissors strength over several states. For a microscopic determination of these scissors states one uses the Quasi-particle Random Phase Approximation (QRPA)