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- Jacobsson, Per, et al.
(författare)
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Reorientational motion of the NO3− ion through the liquid-glass transition in Ca0.4K0.6(NO3)1.4 and Ca(NO3)2 + 8H2O
- 1994
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier. - 0022-3093 .- 1873-4812. ; 172-174:Part 1, s. 161-166
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Tidskriftsartikel (refereegranskat)abstract
- The reorientational correlation function of the NO3- ion in Ca0.4K0.6(NO3)1.4 and in Ca(NO3)2 + 8H2O has been investigated by Raman spectroscopy from the low viscosity liquid at high temperatures through the liquid-glass transformation region and into the frozen glassy state. It was obtained from the reorientational contribution to the 1050 cm-1 symmetric stretch of the NO3- ion, determined from a comparison of the anisotropic and isotropic parts of the Raman band. It was found that the NO3- ion displays rapid reorientational motion over the entire temperature range studied, i.e., also well below the glass transition temperature, Tg. Two types of rotational motion were revealed from the time evolution of the reorientational correlation function which shows a change of behaviour around 0.2 ps. The fast process was attributed to a free-rotor-type motion and the slower process to reorientational diffusion. The relaxation time of the latter, τor, was observed to follow an Arrhenius temperature dependence over the range from above the melting temperature to well below Tg. It was found that τor decouples from the structural relaxation time at temperatures below ∼1.7Tg in the two systems studied.
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