Orientational dynamics on glassformer 2 [Ca(NO3)2]⋅3[KNO3]: A study by transient optical Kerr effect

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Abstract
The fast orientational dynamics of molten 2[Ca(NO3)2]⋅3[KNO3] is investigated by time‐ resolved optical Kerr effect (OKE) with subpicosecond resolution in the temperature range 380–620 K. Apart from the instantaneous electronic response and a very fast decay, the OKE intensity profiles show clearly the presence of a nonexponential decay. The simplest function which fits the experimental data is a biexponential with time constants ranging from 120 to 15 and 10 to 3 ps, respectively. The results are discussed in terms of an integrated correlation time τc that does not show a diverging behavior approaching the glass transition. At high temperatures τc follows a typical Arrhenius law with activation energy of 1.5 kcal/M. Different possible interpretations of the observed behavior (α–β bifurcation, domain size effect) are discussed. The main conclusion is that rotational motions are decoupled from translational ones even for temperatures well above the liquid–glass transition.