A mass spectrometric study of the vaporization of cerium tribromide under Knudsen and Langmuir conditions

The molecular and ionic vaporization of cerium tribromide from the effusion cell (Knudsen conditions) and the open surface of a CeBr3 single crystal (Langmuir conditions) were studied by high-temperature mass spectrometry. The CeBr3 and Ce2Br6 molecules and the CeBr4− and Ce2Br7− negative ions were observed as vapor constituents. The partial pressures of the molecules in saturated vapor and the ratio between the vaporization coefficients of monomers and dimers under free vaporization conditions were determined. The enthalpies and the activation energies of sublimation in the form of monomers and dimers were measured. Ion-molecular equilibria with the participation of negative ions were studied. The enthalpies of formation of molecules and ions in the gas phase were obtained.