Mass Spectrometric Study of Heats of Sublimation of Dysprosium, Samarium, Thulium, and Ytterbium

Abstract

The flux of atoms from a Knudsen-type effusion cell has been studied by means of a mass spectrometer. The heat of sublimation was obtained from the dependence of the ion current upon the cell temperature by means of the Clausius-Clapeyron equation. The method was used to obtain heat of sublimation values for dysprosium, samarium, thulium, and ytterbium. The results were: Dy, 69.3±0.6 kcal/mole for vaporization at 1215°K; Sm, 48.7±0.4 kcal/mole for vaporization at 811°K; Tm, 56.2±0.4 kcal/mole for vaporization at 937°K; and Yb, 39.5±0.5 kcal/mole for vaporization at 667°K.