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Raulin K.,Laboratoire Of Spectrochimie Infrarouge Et Raman Lasir | Gobeltz N.,Holliday Pigments S.A.S. | Vezin H.,Laboratoire Of Spectrochimie Infrarouge Et Raman Lasir | Touati N.,Laboratoire Of Spectrochimie Infrarouge Et Raman Lasir | And 2 more authors.
Physical Chemistry Chemical Physics | Year: 2011

Green and blue ultramarine pigments are characterized by the sodalite structure Na6(Al6Si6O24) and colored inserted species. These chromophores are sulfur species: S3 - (blue) and S2 - (yellow). Both radicals are encapsulated inside the β-cages. They contribute to the EPR spectrum of ultramarine pigments. The well-known strong EPR signal observed in all ultramarine pigments Continuous-Wave (CW) spectra has long been assigned to S3 - (g = 2.029). In contrast, the S2 - contribution is still subject to controversy because its signal in ultramarine pigments was not resolved even at low temperature in CW-EPR experiments. In this study, we identify unambiguously for the first time by CW-EPR and field sweep-echo detected (FS-ED) EPR the signal of S 2 - in ultramarine pigments and we determine its tensor components: g1 = 2.69(6), g2 = 2.03(4) and g3 = 1.86(4). © 2011 the Owner Societies. Source

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