M1 strengths (scissors and twist modes) in heavy deformed nuclei (Gd156-160)

The Elliott SU(3) Model, extended for heavy nuclei using pseudo-spin, is us ed to study low-lying magnetic dipole excitations in deformed nuclei. The H amiltonian includes single-particle energies as well as quadrupole-quadrupo le and pairing interaction terms. Since the quadrupole-quadrupole interacti on dominates, a strong SU(3)-dictated truncation of the model space is used . With interaction strengths fixed by systematics, good agreement with expe rimental results is found for the excitation and M1 transition spectra of t he well-deformed Gd156-160 isotopes.