The theory of decay in radioactive luminous compounds

Abstract

It has been found that the luminosity of radium luminous compound at first rises rapidly to a maximum and then decreases, according to an exponential law, for about 200 days from manufacture. From this time on, however, the rate of luminosity decrease becomes slower and slower, so that the brightness tends to approach a limiting value which is not zero. The following paper is the .result of an attempt to find some explanation of this behaviour such as will furnish grounds for the prediction of the ultimate behaviour of compounds of varying composition. The theory of destruction of “active centres,” put forward by Rutherford to explain the fact of decay, leads to a simple exponential which, as has been said, represents the results to a sufficiently close approximation during the first part of the life, but fails increasingly at the later period.