Determination of tin equilibrium isotope fractionation factors from synchrotron radiation experiments

A method of determination of the reduced isotopic partition function ratio (β-factor) from the partial density of state (PDOS) obtained by inelastic nuclear resonant X-ray scattering (INRXS) in synchrotron radiation experiments has been established. The method has been demonstrated by the example of tin isotopes. The tin β-factors for CaSnO3, SnO2, SnO have been computed from the INRXS-derived PDOSs. ln⁡βSn122/116=(0.390±0.0076)x−(0.00160±0.0000242)x2+(1.099±0.0573)⋅10−5x3)  for SnOln⁡βSn122/116=(0.771±0.0150)x−(0.00392±0.000061)x2+(3.548±0.287)⋅10−5x3 for SnO2ln⁡βSn122/116=(0.776±0.0157)x−(0.00334±0.000064)x2+(2.561±0.157)⋅10−5x3 for CaSnO3Equilibrium 122/116Sn isotope fractionation between di- and tetravalent tin compounds is about 0.4‰ at 1000 K and about 4.1‰ at room temperature and can be measured by modern multicollector inductively-coupled plasma mass-spectrometers. Tin β-factors reveal dependence on oxidation state previously detected for iron isotopes.A comparison of the tin β-factors for SnO2 obtained on the basis of the INRXS-derived PDOS with those obtained by the Mössbauer spectroscopy method shows that both methods give similar results, but application of synchrotron radiation provides more accurate and reliable data.Equilibrium stable isotope fractionation of transition metals between different oxidation state compounds is not negligible even for elements as heavy as tin.