Abstract
The low-lying M1 strength of the open-shell nucleus Cr-50 has been studied with the method of nuclear resonance fluorescence up to 9.7 MeV using bremsstrahlung at the superconducting Darmstadt linear electron accelerator S-DALINAC and Compton backscattered photons at the High Intensity gamma-ray Source (HI gamma S) facility between 6 and 9.7 MeV of the initial photon energy. Fifteen 1(+) states have been observed between 3.6 and 9.7 MeV.
Following our analysis the lowest 1(+) state at 3.6 MeV can be considered as an isovector orbital mode with some spin admixture. The obtained results generally match the estimations and trends typical for the scissors-like mode.
Detailed calculations within the Skyrme quasiparticle random-phase-approximation method and the large-scale shell model justify our conclusions. The calculated distributions of the orbital current for the lowest 1(+)-state suggest the schematic view of Lipparini and Stringari (isovector rotation-like oscillations inside the rigid surface) rather than the scissors-like picture of Lo Iudice and Palumbo.
The spin M1 resonance is shown to be mainly generated by spin-flip transitions between the orbitals of the fp shell.