The reaction ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}(\overrightarrow{p}, {\alpha }_0){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ was used to study a parity and isospin forbidden $\alpha$ transition. The $1^{+}$, 1 state in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ ($E_x=13.482\mathrm{}$ MeV, $\Gamma =6\mathrm{}$ keV) was populated by capture of transversally polarized protons. Placing the quantization axis in the reaction plane, the "irregular" analyzying power $A^{\mathrm{PNC}}$ was determined. No relevant deviation from zero was observed within a statistical accuracy of $\Delta A^{\mathrm{PNC}}=1.1\mathrm{}\times {10}^{-3\mathrm{}}$. An upper limit for the irregular width of the $1^{+}$ level ${\Gamma }_{\alpha }^{\mathrm{PNC}}<6\mathrm{}\times {10}^{-6\mathrm{}}$ eV was determined.

NUCLEAR REACTIONS ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}(\overrightarrow{p}, {\alpha }_0){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, measured parity nonconserving analyzing power, deduced irregular ${\alpha }_0$ decay width of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ ($1^{+}$, 1) state at $E_x=13.482\mathrm{}$ MeV.

• Received 31 August 1982

DOI:https://doi.org/10.1103/PhysRevC.27.906