Spin scissors mode and the fine structure of M1 states in nuclei

The coupled dynamics of low lying modes, including the scissors mode, and various giant quadrupole resonances are studied with the help of the Wigner Function Moments method generalized to take into account spin degrees of freedom. Equations of motion for collective variables are derived on the basis of Time Dependent Hartree–Fock equations in the harmonic oscillator model including spin–orbit potential plus quadrupole–quadrupole residual interaction. Introducing spin allows one to consider new types of nuclear collective motion where the nucleons with spin ‘up’ oscillate against nucleons with spin ‘down’.