Atomization enthalpies and enthalpies of formation of the germanium clusters, Ge-5, Ge-6, Ge-7, and Ge-8 by Knudsen effusion mass spectrometry

The high-temperature mass spectrometric method was employed to measure the equilibrium partial pressures of small germanium clusters above liquid germ anium contained in a graphite Knudsen cell. These data were combined with n ew thermal functions, calculated from recent theoretical and spectroscopic molecular parameters, to evaluate the atomization enthalpies and enthalpies of formation of Ge-5-Ge-8. Mass spectrometric equilibrium data available i n literature were also reevaluated. The following atomization enthalpies, D elta(a)H(0)(o)(Ge-n,g) and enthalpies of formation Delta(f)H(298.15)(o)(Ge- n,g), in kJ mol(-1), have been obtained: Ge-5, 1313 +/- 27 and 548 +/- 27, Ge-6, 1649 +/- 33 and 583 +/- 33, Ge-7, 2008 +/- 42 and 598 +/- 42, Ge-8, 2 359 +/- 60 and 618 +/- 60. The atomization energies are compared with avail able theoretical values. (C) 2000 American Institute of Physics. [S0021-960 6(00)00517-1].