RESUMO
We study by electron-spin-resonance spin-polarized atomic hydrogen adsorbed on the surface of superfluid helium at temperatures T(S) from 50 to 110 mK. The average dipolar field in this 2D system shifts the electron-spin-resonance peak of the adsorbed atoms relative to that of bulk atoms. The shift is directly proportional to surface density. The role of longitudinal magnetization relaxation is played by particle exchange between the 2D and the 3D phases, which diminishes exponentially with decreasing T(S). Therefore at T(S) less, similar 80 mK an excitation field of 0.1 mG disturbs the equilibrium surface density and leads to a magnetization instability observed as sawtooth shaped resonance lines.
RESUMO
We present the first systematic measurement of the binding energy E(a) of hydrogen atoms to the surface of saturated 3He- 4He mixture films at temperatures 70-400 mK. E(a) is found to decrease almost linearly from 1.14(1) K down to 0.39(1) K, when the population of the ground surface state of 3He grows from zero to 6x10(14) cm(-2), yielding the value 1.2(1)x10(-15) K cm(2) for the mean-field parameter of H- 3He interaction in 2D. Measuring by ESR the rate constants K(aa) and K(ab) for second-order recombination of hydrogen atoms in hyperfine states a and b, we find the ratio K(ab)/K(aa) to be independent of the 3He content and to grow with temperature.
