Ag ion formation mechanisms in molten glass ion emitters

Experimental and computational studies were conducted on silver/molten boro silicate glass (silica gel) ion emitters to better understand the physical and chemical processes associated with them, and in particular the chemistr y of the molten glass solution that enhances ion emission. Based on the res ults of these studies and previous work, a model is proposed that explains the major features of the observed phenomena. It is believed that the molte n glass dissolves both the analyte element and some Re from the filament. R henium is oxidized by the B2O3 of the borosilicate glass producing a rheniu m oxide that migrates to the surface of the glass, providing a high work fu nction surface that enhances cation emission. Last, we believe the analyte element (in this case Ag) resides in the glass primarily in the zero oxidat ion state (reduced by thermal decomposition of the oxide or nitrate) and vo latilizes from the surface with a percentage of Ag atoms volatilizing as ca tions determined by the difference between the work function of the surface and the ionization potential of the analyte atom. This explanation may be applicable to other elements analyzed by silica gel technology that are rea dily reduced to the elemental form (by thermal decomposition or by reductio n by the Re filament). Selected features of this explanation, such as analy te solubility and a high work function surface, may be applicable to analyt e elements that are not readily reduced to elemental form. (C) 2001 Elsevie r Science B.V.