We have measured the ionization probabilities of Ag, Cs and AgCs sputtered from a Cs covered silver surface by simultaneously registrating the sputtered neutral and charged species. As the main result, we find that AgCs molecules are predominantly emitted as neutrals. Moreover, it is found that the dependence of the AgCs ion fraction on the cesium surface concentration does not follow the ionization probability of sputtered Cs atoms. (C) 2002 Elsevier Science B.V. All rights reserved.