H-He: effets de l'interaction gaz-surface

A hydrogen atom, adsorbed on liquid helium, slightly polarizes the substrate. Hence a self-energy Σ, associated with an effective mass m * a few percent larger than m. From the gas-surface coupling, we estimate: Σ≃−0.3 K• |Σ| contributes to the adsorption energy e a and this figure agrees rather well with the measured e a . On the other hand, it leads to a low-temperature «plateau» for the sticking coefficient α which we discuss by reference with available experiments. Again at low temperature, we predict a surface/volume decoupling for the a-atom (↓↑−e↑↓) population, which opens the possibility of an independent measurement of α. Finally, we give a few remarks on the liquid- 3 He «substrate» Par adsorption d'un atome H a la surface de He liquide, mise en evidence d'une legere polarisation du support conduisant a une energie propre Σ, associee a une masse effective m * un peu superieure a m et que l'on evalue a partir du couplage gaz-surface: Σ∼−0,3 K, en accord avec sa contribution a l'energie d'adsorption sur 4 He et a la formation d'un plateau pour le coefficient de collage α a basse temperature. Prevision d'un decouplage surface/volume pour la population d'atomes a (etat hyperfin); deduction du principe d'une mesure independante de α. Cas du support 3 He