Emission of phonons into liquid helium
Danil'chenko B. A., Poroshin V. V., Sarbei O. G.
The flux density of thermal energy from a metal film into liquid helium has been measured. Although the propagation of phonons in helium is of a diffusive nature, the ballistic emission law (?Cu-He ~ a(^cu ~ holds at flux densities up to those which would cause the He to boil. The coefficient a is discontinuous near the λ point.