title: Dynamics of normal and superfluid fogs using diffusing-wave spectroscopy.
abstract: The dynamics of normal and superfluid fogs are studied using the technique of diffusing-wave spectroscopy. For a water fog generated with a 1.75 MHz piezoelectric driver below the liquid surface, the 7 microm diameter droplets are found to have diffusive dynamics for correlation times long compared to the viscous time. For a fog of 10 microm diameter superfluid helium droplets in helium vapor at 1.5 K the motion appears to be ballistic for correlation times short compared to the viscous time. The velocity correlations between the helium droplets are found to depend on the initial velocity with which the droplets are injected from the helium surface into the fog.
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA.
authors.forename: Heetae
authors.initials: H
authors.lastname: Kim
authors.forename: Pierre-Anthony
authors.initials: PA
authors.lastname: Lemieux
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Durian
authors.forename: Gary A
authors.initials: GA
authors.lastname: Williams