Radioactivity of Neodymium and Samarium

Abstract

Descriptions of methods for determining (a) absolute activity of an element, (b) the penetrating power of its radiation, (c) the deflectability in a magnetic field and (d) the sign of the charge of the radiation are given. The methods involve the use of Geiger-Müller counters with screen walls. Neodymium emits beta-rays of maximum $\mathrm{H}\rho$ value 355 and 2.4 mm of air penetrating power. The half-life is slightly less than 1.5×${10}^{12}$ years. The range of the samarium alpha-particle has been found to be 1.23±0.05 cm in air at N.T.P. and its half-life 6.3×${10}^{11}$ years. Gadolinium, praseodymium, tin, iodine and beryllium have been found inactive. They cannot have half-lives less than ${10}^{14}$ years if they emit particles of ranges greater than 1 cm. The limit for Be is ${10}^{15}$ years.