Mass-Spectrometric Studies at High Temperatures. II. The Dissociation Energies of the Monofluorides and Difluorides of Silicon and Germanium

Abstract

Calcium fluoride has been used to fluorinate silicon and germanium in a heated Knudsen cell in a mass spectrometer. Second- and third-law calculations using effusion data for the gaseous monofluoride and difluoride species produced at temperatures up to 1575°K are in good agreement and lead to the following atomization energies: D°298[SiF(g)]=5.61±0.2 eV, ΔH°a,298[SiF2(g)]=12.33±0.2 eV, D°298[GeF(g)]=5.04±0.2 eV, and ΔH°a,298[GeF2(g)]=10.0±0.8 eV.