Liquefaction of 4He in aerogel

Abstract

Liquefaction dynamics of 4He in a silica aerogel with porosity of 90% was studied optically at 2.4 K. At low condensation rate of gas into a sample cell the aerogel became opaque during the condensation and then finally cleared up. Liquid outside of the aerogel appeared after the liquefaction in the aerogel was completed. At high condensation rate liquid appeared outside of the aerogel first and filled the lower part of the sample cell. When the surface of the liquid reached the bottom of the aerogel, the aerogel sucked up the liquid and made a visible interface in the aerogel. The height of the interface was proportional to the square root of time. This behaviour was consistent with the Washburn model and the effective pore radius obtained was 9.4 nm.