Mass Spectrometric Study of the Evaporation Products of Strontium Oxide on Platinum

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Abstract
The vapor above the SrO–Pt system was bombarded with electrons and the ion fragments analyzed by a mass spectrometer. Evaporator temperatures ranged from 1600°K to 1800°K. Log Sr+ vs 1/T plots were found to be time dependent initially. Eventually the plots became stable, and could be represented by two straight lines having a slope of 60 kcal/mole at the higher temperatures and of 138 kcal/mole at the lower temperatures. The appearance potential for Sr+ was approximately 5 volts. The ratio of Sr+ to SrO+ was between 10 and 100. These results indicate that thermal dissociation of SrO took place. An explanation based on a diffusion‐limited mechanism is offered for the smaller slope of the upper part of the log Sr+ vs 1/T plot. The behavior of the SrO–Pt system is compared with that of the BaO–Pt system. The latter system does not appear to exhibit thermal dissociation.