Abstract
We measured the dynamic structure factor of liquid and undercooled water down to 253 K in the momentum transfer region. We observe the neat departure of the apparent speed of sound from the adiabatic regime as a function of decreasing temperature. Our evaluation of the infinite-frequency limit of sound velocity, , matches with the results obtained in the high momentum transfer limit by inelastic neutron and x-ray scattering. These results strongly support the viscoelastic interpretation of the dynamics of water. Hence, we propose to call the high-frequency speed of sound and to abandon the term fast sound, which recalls a propagation mechanism through lighter atoms, like in gas mixtures.
- Received 3 October 2006
DOI:https://doi.org/10.1103/PhysRevLett.97.225701
©2006 American Physical Society