Scissors mode and effects of the low-lying E1 excitations on the dipole distributions in 175Lu

Abstract

The low-lying magnetic (M1) and electric (E1) dipole modes in well-deformed odd-proton 175Lu have been investigated in the framework of the Rotational, Translational, and Galilean Invariant-Quasiparticle Phonon Nuclear Model (RTGI-QPNM) for the first time. In this model, the single-particle basis obtained from an axially symmetric Woods-Saxon potential, E1 and M1 excitations are assumed to be generated by isovector dipole-dipole and spin-spin interactions between nucleons, respectively. It also includes the restoration forces for breaking the Rotational, Translational and Galilean symmetries of the nuclear Hamiltonian. The transition probabilities, radiation widths and the structure for both M1 and E1 transitions in 175Lu have been calculated. The theory has satisfactorily reproduced the observed fragmentation in dipole spectra. However, the individual dipole strength of the states is higher than the experimental ones, which may be attributed to the lack of multiphonon configurations in the model used. Besides, the predicted total dipole radiation width and its reduced value are almost twice the experimental data. This difference is a well-known phenomenon for odd-mass deformed nuclei, called ‘missing strength’, arising in the Nuclear Resonance Flouracanse experiment due to the high-level densities.