Separation of the $1^{+}/1^{-}$ parity doublet in ²⁰Ne

Abstract

The $(J,T)=(1,1)$ parity doublet in ²⁰Ne at 11.26 MeV is a good candidate to study parity violation in nuclei. However, its energy splitting is known with insufficient accuracy for quantitative estimates of parity violating effects. To improve on this unsatisfactory situation, nuclear resonance fluorescence experiments using linearly and circularly polarized γ-ray beams were used to determine the energy difference of the parity doublet $\mathrm{\Delta }E=E(1^{-})-E(1^{+})=-3.2{(\pm 0.7)}_{\text{stat}}{({}_{-1.2}^{+0.6})}_{\mathrm{sys}}\text{keV}$ and the ratio of their integrated cross sections $I_{s,0}^{(+)}/I_{s,0}^{(-)}=29{(\pm 3)}_{\text{stat}}{({}_{-7}^{+14})}_{\mathrm{sys}}$. Shell-model calculations predict a parity-violating matrix element having a value in the range 0.46–0.83 eV for the parity doublet. The small energy difference of the parity doublet makes ²⁰Ne an excellent candidate to study parity violation in nuclear excitations.