We have used x-ray diffraction and ultrasound techniques to study the structure of mesoporous impurity-helium solids created after the injection of impurity particles (D2, Ne, N2, Kr) into a volume of superfluid 4He. Clusters of impurities with size of order 50±20 Å and density ∼1020 impurities/cm3 were observed by x-ray diffraction. The presence of a wide distribution of pore sizes in Im-He solids was revealed by ultrasound (80 to 8600 Å) and by small-angle x-ray scattering (80 to > 400 Å). Both x-ray and ultrasound methods detected irreversible structural changes when samples were warmed above Tλ=2.17 K. This is ascribed to the aggregation of small clusters caused by thermally activated diffusion. In addition to being of fundamental interest, the properties of the unique porous media studied in this work may be relevant to investigations of low temperature chemical reactions, storage of free radicals, matrix isolation spectroscopy, and superfluid 4He contained in the pores of an extremely compliant medium.
|Original language||English (US)|
|Number of pages||2206542|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jan 1 2002|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics