Stabilities of Gaseous Molecules in the Pb–Se and Pb–Te Systems

Mass spectrometric analyses of the vaporization products of phases near compositions PbSe and PbTe indicate that these substances vaporize primarily as molecular PbSe(g) and PbTe(g), respectively. Ion fragmentation processes originating from electron bombardment of vapors effusing from a conventional Knudsen cell interfere with quantitative determination of thermochemical dissociation energies of PbSe(g) and PbTe(g). The use of double oven-type Knudsen cells provided a means for the study of the dissociation of PbSe(g) and PbTe(g) into the gaseous elements. Dissociation energies of PbSe(g) and PbTe(g) were found to be 61.5±2.5 and 51.4±2.0 kcal/mole, respectively. The dissociation energy of Te2(g) was found to lie close to the published spectroscopic value.