On the annihilation radiation of the positron

Boron and carbon activated by diplon and proton bombardment have been used as positron emitting sources in experiments on the annihilation radiation. By coincidence counting with two Geiger-Müller tubes it has been established that the radiation is emitted in pairs. By the coincidence method of Becker and Bothe it has been shown that the annihilation radiation consists only of “soft” quanta. By ordinary absorption measurements it has been shown that the annihilation radiation is homogeneous with a hardness corresponding to 0·5 million e -volt.