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Abstracts
P4.16
Head-on collision of xenon atoms against superfluid 4-helium droplets.
Coppens Fran¸cois, Leal Antonio, Barranco Manuel, Halberstadt Nadine, Pi Mart´ı
1)Universit´e Paul Sabatier, Physics, LCAR/IRSAMC, 118 route de Narbonne,
31062 Toulouse
2)Universitat de Barcelona, Facultat de F´ısica, Departament FQA, Diagonal
645, 08028 Barcelona
We study the head-on collision of a heliophilic xenon atom with a superfluid
helium droplet made of 1000 atoms. At variance with previous findings for a
heliophobic cesium atom of similar atomic weight, it is found that the xenon
atom has to hit the droplet with a large kinetic energy to get across it without
being captured. When this happens the xenon impurity does not emerge as a
bare atom; instead, due to its heliophilic character, it carries away some helium
atoms whose number depends on the collision energy.
P4.17
Dissipative superfluidity and mesoscale confinement
Adrian Del Maestro(1) and Bernd Rosenow(2)
1) Department of Physics, University of Vermont, Burlington, VT 05405, USA
2) Institut f¨ur Theoretische Physik, Universit¨at Leipzig, D-04103, Leipzig,
Germany
Pressure driven flow of a superfluid inside a narrow channel can be maintained
by the nucleation of vortices and their resulting motion across the flow lines. The
maximum velocity of the superfluid is set by a nucleation rate which crucially
depends on the microscopic details of the vortex cores and flow profile. Within
the kinetic vortex theory, we have determined the critical superfluid velocity
inside mesoscale constrictions and obtain agreement with experimental results
for superfluid helium-4 in nanopores. In the small pore limit, when the ratio of
pore radius to correlation length is of order unity, we find a drastic suppression of
the superfluid velocity due to a reduction in the energy barrier of flow reducing
excitations.
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