Spin and orbital scissors modes in $^{166}$Er

Abstract

Recently, low-energy dipole excitations in $^{166}$Er were investigated via nuclear resonance fluorescence [T. Shizuma {\it et al}, Phys. Rev. C {\bf 113}, 044325 (2026)]. The magnetic dipole strength associated with the nuclear scissors mode was extracted for excitation energies between 2.2 and 3.5 MeV. It was found that the $M1$ strength distribution is separated into two groups. We interpret this splitting as caused by the spin degrees of freedom instead of the nucleus nonaxiality suggested by authors.