[en] A model is proposed for the charge exchange behaviour of low energy noble gas ions and atoms scattering from a metal surface. The model takes into account two types of charge transfer processes. Firstly ions can be neutralized by an Auger process in which only conduction electrons are involved. Secondly transitions between quasi molecular states can occur when the distance between the incoming particle and a surface atom becomes small. This process may result in the neutralization of an ion and in the ionization of an incoming atom or an incoming ion which has been neutralized before by an Auger process. An expression is derived for the ion yield of singly or quasi singly scattered particles. The assumptions on which the model is based and the limitations for using the model are discussed