The Isotopic Constitution of Europium, Gadolinium, and Terbium

Abstract

The isotopic abundances of europium, gadolinium, and terbium have been determined electrometrically by means of a mass spectrometer. The abundances of europium isotopes of masses 151 and 153 were found to be 47.77 and 52.23 percent, respectively. For gadolinium, masses 152, 154, 155, 156, 157, 158, and 160 were found to have abundances of 0.20, 2.15, 14.78, 20.59, 15.71, 24.78, and 21.79 percent, respectively. Upper limits for the existence of other isotopes of these elements were determined.