The mobility of the actinium a recoil atom measured by the cloud method

Abstract

This paper describes the measurement of the mobility of a single atom of actinium A immediately after it reaches the end of its recoil track. Such a measurement is of importance for two main reasons. Firstly, it is of interest to obtain measurements of the mobility of individual atoms in order to ascertain whether the mobility has always a constant value, or whether a recoil atom possesses sometimes a mobility which is a multiple of the usually accepted value, namely, 1.56 cm./sec./volt/cm. Also, statistical experiments should give much better values of the relative numbers of recoil atoms of differ­ent mobilities than can be obtained from activity measurements as made by Erikson.