Energy Separation Of The 1(+)/1(-) Parity Doublet In Ne-20

The parity doublet of 1(+)/1(-) states of Ne-20 at 11.26 MeV excitation energy is one of the best known test cases to study the weak part of the nuclear Hamiltonian. The feasibility of parity violation experiments depend on the effective nuclear enhancement factor (R-N/vertical bar E(1(+))-E(1(-))vertical bar) which amplifies the impact of the matrix element of the weak interaction on observables indicating parity mixing. An extreme large value of R-N/vertical bar E(1(+)) - E(1(-))vertical bar = (670 +/- 7000) MeV-1 was reported for the doublet in Ne-20. The large uncertainty depends amongst others on the large uncertainty of vertical bar E(1(+))-E(1(-))vertical bar = 7.7 +/- 5.5 keV of the parity doublet. Nuclear resonance fluorescence (NRF) experiments with linearly and circularly polarized photon beams were performed at the High Intensity Gamma-Ray Source at Duke University, Durham, NC, USA, to determine the energy difference of the parity doublet with higher precision. The different angular distributions for 0(+) -> 1(-) -> 0(+) and 0(+) -> 1(+) -> 0(+) NRF cascades in polarized gamma-ray beams were used to determine the energy difference of the parity doublet to 2.9(13) keV.