Systematics of the excitation energy of the 1+ scissors mode and its empirical dependence on the nuclear deformation parameter

From the data on dipole excitations obtained in photon scattering experiments we extract and tabulate the mean values of the excitation energy of the 1(+) scisssors mode in nuclei of the mass region 130<A<200. The centers of gravity of the observed M1 strength distributions are always close to 3 MeV including several moderately deformed transitional nuclei. In particular, the data exhibit a weak dependence of the scissors made energy on the deformation parameter. Including roughly the deformation dependence of pairing effects we could modify an earlier estimate based on a schematic random phase approximation and get a simple formula which yields qualitative agreement with the data.