Electron Pair Creation by a Spherically Symmetrical Field

Abstract

IN the nuclear reaction F19(p,α)O16, the oxygen nucleus can be produced in an excited state with an excitation energy of 5·9 MeV. The transition from this state to the ground state of O16 does not occur, as normally, by the emission of γ-radiation, but by the creation of electron-positron pairs1, this fact being interpreted as meaning that its excited state has zero total angular momentum (J), and since its ground state also has zero J, a single γ-radiation transition between the two states is impossible2. Alternative, competitive processes such as emission of two quanta or a two-step transition via a state of oxygen-16 intermediate between the ground state and that at 5·9 MeV. have not been observed ; the absence of the latter possibility is consistent with the absence of any evidence for an excited state of O16 below 5·9 MeV.