Isotopic spin selection rules XIII: The 6.92 MeV state of16O revisited

Abstract

The status of the possible E1-E3 cascade between the 2 + state at 6.92 mev, the 3- state at 6.14 mev and the 0+ ground state of ¹⁶O is reviewed in the light of recent improvements in our knowledge of radiative transitions and isotopic spin impurities. It is concluded that the present limit of 5 × 10⁻³ on the relative intensity, although clearly demonstrating the efficacy of the isotopic spin selection rule, is not sharp enough to be a significant test for detailed models of the nuclear structure, for which purpose an improvement by an order of magnitude would be required. It is shown by a coincidence method, wing the reaction ¹⁹F(p, α)¹⁶O, that the relative intensity is less than 4 × 10⁻⁴. This corresponds to α₀ ²(1) < 2 × 10⁻³, a low figure.