Disintegration of Slow Mesotrons

The disintegration of mesotrons at the end of their range was investigated by means of an improved arrangenxent of the type already described by the author. The absorption of a mesotron by a block of aluminum or iron is recorded by a system of coincidence and anticoincidence counters. Another system of counters and circuits registers the delayed emission of a particle, which is interpreted as the disintegration electron associated with the absorbed mesotron. The present apparatus enables one to determine the time distribution of the emitted particles and hence the mean life of the decay process, independently of the effects produced by the scattering of mesotrons. The mean life is found to be 1.5&0.3 microseconds, in substantial agreement with the value deduced from the atmospheric absorption effect. The absolute number of disintegration electrons per absorbed mesotron has also been determined (for an Al absorber) and found to be about one-half. This result suggests that, in agreement with theoretical predictions, positive mesotrons undergo spontaneous decay, while the negative ones react with nuclear particles.