Local structural rearrangement in deeply undercooled liquid Ge probed by subsecond time-resolved x-ray-absorption spectroscopy

Abstract

The local structure in deeply undercooled Ge has been probed by time-resolved x-ray-absorption spectroscopy (XAS). By using a technique that allows us to collect full x-ray-absorption spectra in less than a second, snapshots of the electronic and local structure in the metallic phase of Ge were taken at temperatures much lower than had been possible with previous static XAS investigations. Upon a rapid freezing of the melt, and prior to the occurrence of the solidification transition, we observe a sharpening of the pair correlation function $g(r),$ and a slight shift of $g(r)$ towards smaller distances. We interpret this phenomenon in terms of increased stability of the covalent bonds that are continuously formed and destroyed in the liquid.