Internal Pair Production Associated with the Emission of High-Energy Gamma Rays

The theory of inner pair production associated with the radiative capture of ${\pi }^{-}$ mesons and with the decay of the ${\pi }^0$ meson is discussed. Appropriate distribution functions are derived and compared with recently obtained experimental results. The weak dependence of the theoretical predictions upon the details of meson theory is emphasized. The possible utility of the double conversion process, in which the ${\pi }^0$ meson decays into two electron-positron pairs, for the determination of the ${\pi }^0$ parity is also discussed.