We measured the dynamic structure factor S(Q,w) of liquid and undercooled water down to 253 K in the Q \apporx 0,02–0,1 nm-1 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, c1, matches with the results obtained in the high momentum transfer limit by inelastic neutron and x-ray scattering. These results strongly support the viscoelastic interpre- tation of the dynamics of water. Hence, we propose to call c\infty 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.
Is There Any Fast Sound in Water?
SANTUCCI, Silvia;FIORETTO, Daniele;COMEZ, Lucia;
2006
Abstract
We measured the dynamic structure factor S(Q,w) of liquid and undercooled water down to 253 K in the Q \apporx 0,02–0,1 nm-1 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, c1, matches with the results obtained in the high momentum transfer limit by inelastic neutron and x-ray scattering. These results strongly support the viscoelastic interpre- tation of the dynamics of water. Hence, we propose to call c\infty 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
