A system of two electrons and two positrons is shown to possess dynamic stability. The variational calculation performed leads to a binding energy of at least 0.11 ev for this cluster. The approximate wave function which yields this value depends on the four electron-positron distances only. Neglect of the two distances between particles of the same kind permits an essential mathematical simplification which might be of interest in other problems.

• Received 26 December 1946

DOI:https://doi.org/10.1103/PhysRev.71.493