High-resolution neutron scattering measurement of the dynamic structure factor of heavy water
The low momentum collective dynamics of heavy water has been investigated by means of neutron three-axis spectroscopy. Working at the resolution limit of this instrument, an energy resolution of 2.6 meV was achieved for a constant analyzer energy of 120 meV. This good resolution allowed us to establish definitely that the collective dynamics of water is dominated by the presence and interaction of opticlike and acousticlike branches, coupling at wave-vector transfers of 0.3 to 0.35 A(-1). The transition from slow to fast sound has been attributed to the interaction between opticlike modes and a solidlike fast acoustic mode.
Petrillo
C
Istituto Nazionale per la Fisica della Materia, Unita di Perugia, Perugia, Italy and Dipartimento di Fisica, Universita di Perugia, Via A. Pascoli, I-06123 Perugia, Italy.
Sacchetti
F
Dorner
B
Suck
JB