Cold electron attachment to atomic hydrogen on liquid helium surface

Surface state electrons (SSE) on liquid helium have been applied to cold electron-atom/molecule collision experiments. In a two-dimensional mixture of SSE and adsorbed atomic hydrogen below 1 K, we found a chemical reaction reduces the SSE density. From the SSE density decay kinetics measurement, we found that the reaction is expressed as H + H + e(-) H- + H. As a possible explanation, we propose a dissociative attachment mechanism to a highly rovibrationally excited hydrogen molecule which is an early product of atomic hydrogen recombination. (C) 2003 Elsevier Science B.V. All rights reserved.