beta-Molecular rearrangement process, but not an alpha-process, as governing the homogeneous crystal-nucleation rate in a supercooled liquid

The time dependence of the growth rate of homogeneous-nucleation-based (HNB) crystallization in o-terphenyl was tracked by a temperature-jump method through microscopic observations, and HNB crystallization was found to proceed at a steady rate, specified by the tracking temperature just after the jump. Two sets of numerical computations were carried out according to a classical homogeneous nucleation theory for the temperature-jump experiment on alternative assumptions that the homogeneous nucleation process is governed by the alpha-molecular rearrangement process or by the beta-process in the liquid. From a comparison between the experimental and calculated results, the homogeneous nucleation, and thus the crystal growth as well, were concluded to be governed by the beta-rearrangement process rather than the alpha-process, differently from the common recognition that they are governed by the latter.