A mass-independent sulfur isotope effect in the nonthermal formation of S2F1

Abstract

A non-mass-dependent sulfur isotope effect is present in the rotationally symmetric S2F10 molecule, produced in an electrical discharge through sulfur tetrafluoride. A similar isotopic fractionation was observed in the product S2F10 from the electrodissociation of SF5Cl, and reaction between fluorine atoms produced by F2 photolysis and SF4, collectively ruling out the SF5 formation process as the source of the mass-independent fractionation. The mass-independent mechanism is shown to occur in the SF5+SF5→S2F10 formation step. The secondary dissociation of S2F10 as a source of the mass-independent fractionation is ruled out by control S2F10 dissociation experiments which are shown to produce small mass-dependent fractionations. Mass-dependent effects such as sulfur isotopic exchange and secondary dissociation reactions are significant processes for the system under study and have been quantitatively accounted for. The role of symmetry in non-mass-dependent isotope effects is strengthened by the present experiments, and the search and characterization of mass-independent effects is extended to sulfur-containing molecules.