Electron attachment reaction rates in 2D atomic hydrogen-electron mixed system on liquid helium surface

We have measured the temperature dependence of the electron attachment reaction rate of atomic hydrogen (H) on a liquid ⁴He surface in applied magnetic fields of 0-5 T at 0.2-0.6 K. The measured surface state electron (SSE) losses are faster at lower temperatures for a given magnetic field. This behavior can be qualitatively understood, since the surface coverage of adsorbed H is large at low temperature and the collisions between H and SSE are frequent. However, the reaction is faster than expected based on the collision frequency argument. The measured reaction rate coefficient K _e is strongly temperature dependent. We observe that, as the temperature is lowered, K_e increases by several orders of magnitude. This indicates that some additional effect enhances electron attachment at low temperature. We discuss a possible reaction mechanism between H and SSE.