Fig. 4: Longitudinal and transverse sound velocities.
From: Depletion of two-level systems in highly stable glasses with different molecular ordering
Sound velocity as a function of temperature for the differently prepared glasses, as indicated in the legend: a longitudinal sound velocity vL; b transverse sound velocity vT. In the case of the conventional glass the darker symbols represent a cooling run and the less dark ones represent a heating run. In the case of the anisotropic ultrastable glasses (USG), both symbols (darker and less dark ones) represent two different cooling runs. It is to be stressed that data in anisotropic glasses refers only to the sound velocity measured in the direction of the acoustic vector (see the Sound velocity subsection for more details). Errors associated with the data points are calculated from the frequency error values obtained from the non-linear fits to the peaks in the Brillouin spectra and are below 1% for vL and about 2.5% for vT, making them smaller than the symbols in the plot.
