Homodyne photon-correlation spectroscopy of a supercooled liquid: 1,3,5-Tri-α-naphthyl benzene

Homodyne depolarized photon-correlation functions of 1,3,5-tri-α- naphthyl benzene (TαNB) have been measured at the 90° scattering angle in the temperature range of 75-110°C. The correlation functions are analyzed in terms of a fractional exponential function and a modified constrained regularization method originally developed by Provencher. The results from both methods of data analysis are in agreement. The temperature dependence of the mean orientational relaxation time when fitted to the Arrhenius equation gives an apparent activation energy E=85.3 kcal/mol. The Antoine-WLF equation provides a better fit of the mean reorientational relaxation time data. It is also found that orientational time τ is linearly proportional to η/T, indicating that the Debye-Stokes-Einstein equation is applicable to describe molecular reorientation in the supercooled TαNB liquid.