ABSTRACT Though the presence of hybrid Fen+ states with 2<n<3 have been recognised in tourmalines, no attempt has been done to quantify the degree of hybridisation. In this work we attempt to estimate the Fe-Fe charge transfer between the two octahedral sites in two tourmalines from Örnö, Central Sweden and Räkevik, Norway. Mössbauer spectra were taken at temperatures sufficiently low to quench the hopping of electrons and quantify the amount of Fe involved in electron transfer. Depending on the asymmetry of Fe-Fe charge interactions, two different fitting models were used. The symmetrical spectrum of the sample from Räkevik was fitted using simple Lorentzian lines for the entire temperature range, while the asymmetrical spectrum of the sample from Örnö was fitted with Lorentzian lines for only the 5K measurement. The Mössbauer parameters obtained from the 5K measurement for the Örnö sample were used to model the 295 K spectra, assuming that quadrupole splitting and centre shift are distributed and linearly correlated. From these data we were able to calculate the thermal population fraction, f, of the itinerant electron involved in the Fe-Fe interaction. We found that the two sites sharing the electron have an average charge of Fe2.4+ and Fe2.6+ in the Z and Y sites, respectively, for the Örnö sample and Fe2.5 for the Räkevik sample.
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