Nuclear magnetic dipole properties and the triaxial deformation

Nuclear magnetic dipole properties of ground bands and γ-vibrational bands are studied for the first time using the triaxial projected shell model approach. The study is carried out for the Dy and Er isotopic chains, ranging from transitional to well-deformed region. It is found that the g-factor ratio of the 2 state in ground bands to that of γ-bands, r = g(2, γ-vib)/g(2, ground), varies along an isotopic chain. With the γ-deformations, which best reproduce the energy levels for both bands, we obtain a qualitative agreement with the experimental data. This result thus suggests that study of the ratio may provide an important information on the triaxial deformation of a nuclear system. The angular-momentum dependence of the ground band g-factor on the triaxial deformation is also investigated. The importance of triaxial deformation has been a long-standing problem in the studies of atomic nuclei. Although it is known from several model studies that nuclei in the transitional regions acquire a stable triaxial mean-field deformation, consequences of it on the measurable electromagnetic transition probabilities have remained less clear. Nuclear magnetic dipole properties are very sensitive to the single-particle aspects of the nuclear wave-function and hence can provide valuable information on the microscopic structure of a nuclear system. As the single-particle orbits can be strongly modified by triaxiality, the interesting question is whether the triaxial deformation will have observable effects in the magnetic dipole properties. The study of nuclear magnetic properties has been an active field of research in nuclear structure physics. On the experimental side, considerable progress in the g-factor experiment has recently been made by taking advantages of modern experimental techniques and sensitive detectors, for a recent example, see Ref. [1]. There have been new measurements on the ground band and the γ-band g-factors for some rare earth nuclei [2,3]. On the theoretical side, several early calculations were devoted to the study of g-factors.