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

A. I. Safonov·S. A. Vasilyev·A. A. Kharitonov·S. T. Boldarev·I. I. Lukashevich·S. Jaakkola
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Abstract

We present the first systematic measurement of the binding energy $E_a$ of hydrogen atoms to the surface of saturated $^3$He-$^4$He mixture films. $E_a$ 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 $^3$He grows from zero to $6\times10^{14}$ cm$^{-2}$, yielding the value $1.2(1)\times 10^{-15}$ K cm$^2$ for the mean-field parameter of H-$^3$He interaction in 2D. The experiments were carried out with overall $^3$He concentrations ranging from 0.1 ppm to 5 % as well as with commercial and isotopically purified $^4$He at temperatures 70...400 mK. 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 $^3$He content and to grow with temperature.

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A. I. Safonov, S. A. Vasilyev, A. A. Kharitonov, S. T. Boldarev, I. I. Lukashevich, S. Jaakkola. 2000-10-07. Adsorption and two-body recombination of atomic hydrogen on $^3$He-$^4$He mixture films. https://doi.org/10.1103/physrevlett.86.3356

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