Anomaly of the Nonergodicity Parameter and Crossover to White Noise in the Fast Relaxation Spectrum of a Simple Glass Former
We present quasielastic light scattering and dielectric spectra of the glass former α-picoline. At high temperatures the evolution of the susceptibility minimum is well described by the mode coupling theory (MCT). Below the critical temperature Tc the simple scaling laws of MCT fail due to the appearance of the excess wing of the α process, which shows a universal evolution as a function of 10τα. Taking this into account, however, we observe the predicted cusplike anomaly of the nonergodicity parameter as well as a crossover to ``white noise.''