The process of held evaporation of rhodium in an atmosphere of 10(-6) Pa hydrogen at a temperature of 30 K was investigated using the high-resolution pulsed-laser time-of-flight atom-probe field-ion microscope. It is found that under these conditions the rhodium evaporates in most part as RhH22- which is subsequently field dissociated as rhodium and hydrogen. By employing theoretical values of the binding energy and ionization potentials of rhodium hydrides, as calculated by an ab initio method. and using measurements of the energy distribution of the rhodium ions. the binding energy of RhH2 onto the emitter surface is estimated to be 5.09 eV. (C) 2002 Elsevier Science B.V. All rights reserved.