The Evaporation Products of Barium Oxide from Various Base Metals and of Strontium Oxide from Platinum

Abstract

The evaporation products of BaO heated on ribbon filaments of Pt, Ta, Ni, Mo, and W, and of SrO on Pt have been studied using a high resolution mass spectrometer for positive ion analyses. The ratio Ba⁺/BaO⁺, was measured for each base material as a function of temperature and of the energy of the ionizing electrons to determine the origin of each ion peak observed. The results indicate: (a) Only on systems BaO on Pt and BaO on Ni, and SrO on Pt were the evaporation processes reproducible without particular attention to procedure. (b) The two systems BaO on Pt and SrO on Pt differ markedly in their evaporation mechanisms. (c) At high temperatures peaks are found due to Ba₂O⁺⁺, Ba₂O⁺, Ba₂O₂⁺, and other barium compounds depending on the base metals used. (d) A measurable ion current was found due to Sr⁺ ions evaporated from Pt.