Large Parity Admixture inNe21?

Abstract

In ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ there are two levels of the same spin and opposite parity separated by 8 keV. This suggests that a parity-nonconserving nucleon-nucleon potential will give rise to large parity admixtures in these states. In our calculation the standard Cabibbo parity-nonconserving potential gives a circular polarization of at least ${10}^{-3\mathrm{}}$ for the 2.79-MeV transition ${\frac{1}{2}}^{-}\to {\frac{3}{2}}^{+}$ ground state. Strong neutral-current effects would lead to $P_{\gamma }$ in excess of 1% in contradiction with a recent experiment.