A 'mass-anomalous' vapor-pressure isotope effect for SF_6

Abstract

Large mass-anomalous isotope fractionations of O and S are commonly attributed to photochemical reactions. It is unclear whether more subtle mass-anomalous fractionations of O and S can arise from exchange equilibria or other nonphotochemical reactions. Statistical thermodynamic models of a simple harmonic oscillator may [1] or may not [2] predict mass-anomalous equilibrium fractionations of light elements. Experimental devolatilization of carbonate [3] and sulfate [4] reveal mass-anomalous net fractionations of O and S, respectively, but have unconstrained reaction mechanisms and may reflect mixing and/or distillation rather than novel chemical isotope effects.

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