Adsorption and Two-Body Recombination of Atomic Hydrogen onH3e−H4

Abstract

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.

Cold Collision Frequency Shift in Two-Dimensional Atomic Hydrogen

“…To verify such possibility we attempted to modify the interaction of the adsorbed atoms with the film by admixing some small amount of 3 He. The presence of 3 He on the surface reduces the adsorption energy and increases delocalization l of the adsorbed atoms [26]. This should lead to a l ÿ3 reduction of the wall shift [21] and to a l ÿ1 reduction of the clock shift [Eq.…”

Thermal compression of two-dimensional atomic hydrogen gas

“…By independent measurements of the surface density and its decay rate we make the first direct determination of the three-body recombination rate constant and get the upper bound L 3b 2 × 10 −25 cm 4 /s which is an order of magnitude smaller than previously reported experimental results.PACS numbers: 05.30.Jp, 67.65.+z, 82.20.Pm When adsorbed on the surface of superfluid helium spin-polarized atomic hydrogen (H↓) is an ideal realization of a two-dimensional (2D) boson gas [1]. Helium provides a translationally invariant substrate and its surfacenormal potential supports only one bound state for hydrogen with the binding energy E a =1.14(1) K [2]. Even for such a weak interaction, lowering the surface temperature T s well below 1 K leads to a large adsorbate density σ.…”

Electron-Spin-Resonance Instability in Two-Dimensional Atomic Hydrogen Gas

“…where is the thermal de Broglie wavelength and E b =k B 1:14 K [12] is the binding energy of hydrogen to liquid 4 He. For T S < 100 mK the exponential factor in Eq.…”

“…The adsorption and desorption rates are, respectively, nvs=4 and = s , where s is the sticking probability, v is the thermal speed of the bulk atoms, and the surface residency time is given by s 4=vs expE b =k B T S . For surface densities of interest, > 10 11 cm ÿ2 , the characteristic recombination time of a spin-flipped atom is bc & 3 s [12]. On the other hand, at temperatures below 110 mK, s * 100 s bc , and therefore each spin flip instantly removes two particles from the 2D sample.…”