title: Neutron Brillouin scattering study of collective dynamics in a dense He-Ne gaseous mixture.
abstract: The dynamic structure factor S(k,omega) of a 77% He and 23% Ne gaseous mixture at T = 39.3 K and total number density n = 15.8 nm(-3) has been measured by inelastic neutron scattering at small angles. In the range of wave vectors studied, 0.7<k/nm(-1)<1.8, we find clear side peaks at frequencies following the hydrodynamic sound dispersion c k of the binary mixture (with c the adiabatic sound speed in the mixture). Surprisingly, neither fast modes nor a transition from normal to fast sound are observed in the above low- k region, indicating that hydrodynamic behavior persists up to k values which are larger than those predicted by theories and computer simulations.
authors.affiliation: Istituto di Electronica Quantistica, Consiglio Nazionale delle Ricerche, Firenze, Italy.
authors.forename: U
authors.initials: U
authors.lastname: Bafile
authors.forename: P
authors.initials: P
authors.lastname: Verkerk
authors.forename: E
authors.initials: E
authors.lastname: Guarini
authors.forename: F
authors.initials: F
authors.lastname: Barocchi