Atomization enthalpies and enthalpies of formation of Ge3 and Ge4 by Knudsen effusion mass spectrometry Original Research Article

The high-temperature mass spectrometric method was employed to measure the equilibrium partial pressures of Ge3 and Ge4 above liquid germanium contained in a graphite Knudsen cell. These data were combined with thermal functions for Ge3 and Ge4, calculated from recent theoretical and spectroscopic molecular parameters, to evaluate the atomization enthalpies and enthalpies of formation. Mass spectrometric equilibrium data for Ge3 and Ge4 available in literature were also re-evaluated. The following atomization enthalpies, ΔaHo0 (Gen,g) and enthalpies of formation ΔfHo298.15 (Gen,g), in kJ mol−1, are overall assessed values: Ge3, 589.8±19 and 531.9±19; Ge4, 969.4±24 and 527.7±24. The atomization energies are in very good agreement with predictions by Deutsch et al. [Chem. Phys. Lett. 270 (1997) 413] using Gaussian-2 theory.