Experimental observation of the liquid-liquid transition in bulk supercooled water under pressure

We prepared bulk samples of supercooled liquid water under pressure by isochoric heating of high-density amorphous ice to temperatures of 205 ± 10 kelvin, using an infrared femtosecond laser. Because the sample density is preserved during the ultrafast heating, we could estimate an initial internal pressure of 2.5 to 3.5 kilobar in the high-density liquid phase. After heating, the sample expanded rapidly, and we captured the resulting decompression process with femtosecond x-ray laser pulses at different pump-probe delay times. A discontinuous structural change occurred in which low-density liquid domains appeared and grew on time scales between 20 nanoseconds to 3 microseconds, whereas crystallization occurs on time scales of 3 to 50 microseconds. The dynamics of the two processes being separated by more than one order of magnitude provides support for a liquid-liquid transition in bulk supercooled water.

Source: ScienceNOW - November 19, 2020 Category: Science Authors: Kim, K. H., Amann-Winkel, K., Giovambattista, N., Späh, A., Perakis, F., Pathak, H., Parada, M. L., Yang, C., Mariedahl, D., Eklund, T., Lane, T. J., You, S., Jeong, S., Weston, M., Lee, J. H., Eom, I., Kim, M., Park, J., Chun, S. H., Poole, P. H. Tags: Chemistry, Physics reports Source Type: news