Adsorption and two-body recombination of atomic hydrogen on He-3-He-4 mixture films

We present the first systematic measurement of the binding energy E-a of hy drogen atoms to the surface of saturated He-3-He-4 mixture films at tempera tures 70-400 mK. E-a is found to decrease almost linearly from 1.14(1) K do wn to 0.39(1) K, when the population of the ground surface state of He-3 gr ows from zero to 6 X 10(14) cm(-2), yielding the value 1.2(1) X 10(-15) Kcm (2) for the mean-field parameter of H-He-3 interaction in 2D. Measuring by ESR the rate constants K-aa and K-ab for second-order recombination of hydr ogen atoms in hyperfine states a and b, we find the ratio K-ab/K-aa to he i ndependent of the He-3 content and to grow with temperature.