Secondary relaxation in<i>o</i>-terphenyl glass

Abstract

We have measured the dielectric response, \ensuremath{\varepsilon}\ifmmode \tilde{}\else \~{}\fi{}(\ensuremath{\omega}), in o-terphenyl due to the secondary relaxations that occur below the glass-transition temperature. We have found that the imaginary part of \ensuremath{\varepsilon}\ifmmode \tilde{}\else \~{}\fi{}(\ensuremath{\omega}) has a log-normal shape that can be ascribed to a Gaussian distribution of barrier heights. The width of this distribution increases slightly as the temperature is lowered. The peak position shifts in an Arrhenius manner with temperature as was reported previously by Johari and Goldstein. The data appear to be of different origin from what has also been called \ensuremath{\beta} relaxation in mode-coupling theories and light-scattering experiments.