We report the first observation of the rare pion capture mode in beryllium consisting in the emission of an electron-position pair. Rate, angular distribution, and energy-spectrum are in quantitative agreement with the ones expected assuming internal pair-creation from single radiative capture.

[NUCLEAR REACTIONS (${\pi }^{-},ee$) on beryllium for stopped pions. Rate, angular correlation, energy spectra measured.]

• Received 6 March 1981

DOI:https://doi.org/10.1103/PhysRevC.24.754