Induced Radioactivity of the Lighter Elements

Abstract

WE have been investigating the phenomenon of induced radioactivity in aluminium, boron and magnesium recently reported by Curie and Joliot¹, and have been able fully to confirm their observations, and also to add further details. Using radium C-particles reduced in range to 6.1 cm., we find the relative yields of positrons during the entire decay from aluminium, boron and magnesium to be approximately 30, 10 and 7. Since the periods are respectively 3¼, 14 and 2¼ minutes, the initial effects are in the ratio 6, 0.5, 2. With all materials we find an effect with a period of about 1 minute and of initial activity comparable with that of boron. This must be due to some impurity which is always present, such as carbon, nitrogen or oxygen.