Microscopic observation of hidden Johari-Goldstein-beta process in glycerol

The Johari-Goldstein-beta (JG-beta) process is widely observed in a variety of glass-forming systems and recognized as an intrinsic process in deeply supercooled and glassy states. However, in some systems, e.g., glycerol, a clear sign of the JG-beta process is often not apparent; for example, an isolated JG-beta peak may not be observed in the dielectric relaxation spectrum. In this study, we directly investigated the angstrom-scale dynamics of glycerol through quasielastic scattering experiments using time-domain interferometry. The relaxation times of the local motions start to decouple from the timescale of the diffusion process and follow the established behavior of the JG-beta process. This finding microscopically indicates the existence of the hidden JG-beta process in glycerol. In addition, we succeeded in determining the decoupling temperature of the JG-beta process by using the spatial-scale selectivity of the quasielastic scattering technique.