Condensed water in superfluid He-II

Abstract

The formation of semi-transparent irreversible water “clouds” suspended in bulk superfluid He-II by condensation of gaseous He contaminated with water vapour has been observed. While lowering the level of He-II below the upper edge of a dense cloud (“iceberg”), it can jump down to the liquid due to irradiation of the cold He gas from its surface. Segregation of helium from icebergs with initial dimensions of a few mm collected at the bottom of the cell, containing no He-II, has resulted in reducing the volume of the “dry” icebergs by more than an order of magnitude. It can be supposed that the clouds are composed of water clusters surrounded by a layer of solidified He, which should result in the formation of a porous matter – “watergel”, soaked with superfluid helium. Observations of the creation of a well pronounced meniscus at the initially flat free surface of He-II inside the glass tube during the process of the gas condensation confirm the suggestion that these water clouds are well wetted by He-II.