We use neutron scattering and optical Kerr effect data to demonstrate that Johari-Goldstein (βJG) relaxation events in liquids are collective reorganizations of small groups of molecules which answer to the description of metabasin transitions on a potential energy lanscape. From this understanding, we are able to develop simlple but quantitative relations for macroscopic diffusion, alpha relaxation, and βJG relaxation from only picosecond dynamics information. In addition to resolving the 50-year old mystery regarding the origin of the βJG relaxation, we provide a direct experimental window on the microscopic dynamic processes that are the subject of many theories of glass formation. We will show that these direct measurements help to constrain those theories.

Relaxation and self-diffusion of liquids and supercooled liquids derived from picosecond timescale dynamics

253rd National Meeting (2017)

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