Abstract
The low-lying strength of the open-shell nucleus 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 -ray Source facility between 6 and 9.7 MeV of the initial photon energy. Fifteen states have been observed between 3.6 and 9.7 MeV. Following our analysis the lowest 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 -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 resonance is shown to be mainly generated by spin-flip transitions between the orbitals of the shell.
3 More- Received 16 November 2015
DOI:https://doi.org/10.1103/PhysRevC.93.014318
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