Testing mode-coupling predictions for α and β relaxation in Ca0.4K0.6(NO3)1.4 near the liquid-glass transition by light scattering

Abstract

Light-scattering studies of the liquid-glass transition of ${\mathrm{Ca}}_{0.4}$ ${\mathrm{K}}_{0.6}$(${\mathrm{NO}}_3$ ${)}_{1.4}$ have been carried out from 305 to 23°C. Composite spectra covering over four decades in frequency were obtained by combining data obtained with a Sandercock tandem Fabry-Pérot interferometer and Raman spectra. Two-step relaxation processes were observed in the supercooled liquid near the glass transition. The α relaxation exhibits a temperature-independent stretching for T>${\mathit{T}}_{\mathit{c}}$ with ${\mathit{T}}_{\mathit{c}}$≊105 °C, which is about 45°C above the glass transition temperature. The β-relaxation frequency scale indicates critical slowing down when the temperature approaches ${\mathit{T}}_{\mathit{c}}$ from either above or below. Scaling analyses for both α and β relaxations provide good agreement with the predictions of mode-coupling theory.