KAPITZA RESISTANCE IN H-DOWN GAS AT LIMITING SURFACE-DENSITY

The energy exchange between a gas of spin-polarized atomic hydrogen (H↓) and a liquid helium surface under the conditions of limiting surface density of adsorbed hydrogen atoms is discussed. It is found that the leading mechanisms of energy exchange are due to capture of gas particles into the condensate of an adsorbed H↓ phase. The process accompanied by emission of a ripplon turns out to be effective only under a strong limitation imposed on the size of the limiting density region. The relations for the rate of energy exchange via the ripplon channel and for the Kapitza resistance at the gas-helium interface differ appreciably from those in the case of a low surface density, discussed earlier. It is shown that for T > 0.1 K the mechanism of adsorption into the surface condensate with simultaneous phonon emission in helium becomes dominant. © 1990.