Low-energy M1 states in deformed nuclei: spin-scissors or spin-flip?

Abstract

The low-energy $M1$ states in deformed ${}^{164}$Dy and spherical ${}^{58}$Ni are explored in the framework of fully self-consistent Quasiparticle Random-Phase Approximation (QRPA) with various Skyrme forces. The main attention is paid to orbital and spin $M1$ excitations. The obtained results are compared with the prediction of the low-energy {\it spin-scissors} $M1$ resonance suggested within Wigner Function Moments (WFM) approach. A possible relation of this resonance to low-energy spin-flip excitations is analyzed. In connection with recent WFM studies, we consider evolution of the low-energy spin-flip states in ${}^{164}$Dy with deformation (from the equilibrium value to the spherical limit). The effect of tensor forces is briefly discussed. It is shown that two groups of $1^{+}$ states observed at 2.4-4 MeV in ${}^{164}$Dy are rather explained by fragmentation of the orbital $M1$ strength than by the occurrence of the collective spin-scissors resonance. In general, our calculations do not confirm the existence of this resonance.

arXiv comment7 pages, 7 figures, submitted to Physics of Atomic Nuclei. arXiv admin note: text overlap with arXiv:2102.13580. As compared with the previous version, Ref. [1] was removed, Ref [33] was replaced, description of Fig. 3 was modified

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Cited by in corpus (2)

• QRPA calculations for M1 transitions with the noniterative finite amplitude method and the application to neutron radiative capture cross sections
• Microscopic analysis of dipole electric and magnetic strengths in ${}^{156}$Gd