Elastic Properties of Guanidine Hydrochloride Solutions with Various Concentrations in the Gigahertz Frequency Range

The temperature dependences of the veloсity of hypersound ( V ( T )) in solutions with various concentrations of guanidine hydrochloride (GndHCl) are studied by Brillouin–Mandelstam light scattering spectroscopy in the temperature range from 263 to 353 K. It is shown that the temperature dependence of the sound velocity has a pronounced maximum at low concentrations of GndHCl. An increase in the concentration of GndHCl in a solution is accompanied by a shift of the maximum to the low-temperature region and an increase in the absolute values of the sound velocity, which means a decrease in the adiabatic compressibility over the entire range of studied temperatures. The temperature dependence of the adiabatic compressibility is constructed at low concentrations of GndHCl. The contribution of relaxation processes to the temperature behavior of the attenuation of hypersound in solutions of GndHCl is determined. It is shown that their behavior is activated thermally and described by the Arrhenius law. The values of the activation energy of relaxation processes are calculated. Possible mechanisms that underlie the observed phenomena are discussed.