Net Charge on a Noble Gas Atom Adsorbed on a Metallic Surface
  Adsorbed noble gas atoms donate (on the average) a fraction of an electronic charge to the substrate metal. The effect has been experimentally observed as an adsorptive change in the electronic work function. The connection between the effective net atomic charge and the binding energy of the atom to the metal is theoretically explored. 
A. Widom, M.S. Tomassone, Y.N. Srivastava, M. Hannout