The low frequency phonons dynamics in supercooled LiCl, 6H2O

We report the results of a series of ultrasound, Brillouin scattering, and optical heterodyne detected transient grating experiments performed on a LiCl, 6H(2)O solution from room temperature down to the vicinity of its liquid-glass transition, T-g similar to 138 K. Down to T similar to 215 K, the supercooled liquid has a behavior similar to what is expected for supercooled water: its zero frequency sound velocity, C-0, continuously decreases while the corresponding infinite frequency velocity, C-infinity, sharply increases, reflecting the increasing importance of H bonding when temperature is lowered. Below 215 K, specific aspects of the solution, presumably related to the role of the Li+ and Cl- ions, modify the thermal behavior of C-0, while a beta relaxation process also appears and couples to the sound propagation. The origin of those two effects is briefly discussed. (C) 2009 American Institute of Physics. [doi:10.1063/1.3197851]