Blue toruses = 13 protons
Red toruses = 5 nuclear electrons
Atomic number of O (8) = protons (13) - nuclear electrons (5)
Oxygen 13 transformed by positron emission from a source of a photon by decomposition of photon,
while the electron component of the photon captured to central part of Oxygen 13 and Nitrogen 13 nucleus produced.
Nitrogen 13 decays by an other positron emission with the aid of decomposition of a light photon (= pair production !) and
the remnant electron captured by Nitrogen 13 recombinant form, and Carbon 13 nucleus finally formed.
Click on image for Carbon 13 (stable) nuclear structure.
Light photon modell