Atomization enthalpy and enthalpy of formation of gaseous Si2 and Si3 from mass spectrometric equilibrium measurements

Abstract

Recent experimental and theoretical studies have allowed us to calculate new thermal functions for the Si2 and Si3 molecules. We have determined the atomization enthalpies and enthalpies of formation of Si2 and Si3 from mass spectrometric data and have combined them with reevaluated previously published mass spectrometric data using a consistent set of ionization cross sections and thermal functions. The selected atomization enthalpy and enthalpy of formation for the Si2 molecule are ΔHa,0=319±7 and ΔHf,0=584±7 kJ mol−1, the corresponding values for Si3 are 705±16 and 649±16 kJ mol−1. Reevaluated values for Si4 are 1151±22 and 654±22 kJ mol−1. Experimental literature values (Neumark and co-workers) for the electron affinities of Si2–Si4 have been combined with the present results to obtain enthalpies of formation and binding energies for the anions Si−2–Si−4. The experimental atomization enthalpies are compared to recent theoretical studies.