Alternatively, "static SIMS" uses a much lower energy primary ion beam (usually Ga or Cs). This technique is used for "bulk" analysis of elements and isotopes, and is particularly well-suited for analysis of isotopes and trace elements in minerals (e.g. In "dynamic SIMS" mode the primary ion beam exceeds the "static limit" (~1E12 ions/cm 2) producing a high yield of secondary ions. These ions are then accelerated, focused, and analyzed by a mass spectrometer. Although most atoms and molecules removed from the sample by the interaction of the primary beam and the sample surface (referred to as sputtering) are neutral, a percentage of these are ionized. If the primary beam is composed of positively charged ions, the resultant ionization favors production of negative ions primary beams of negative ions favor generation of positive ions. ![]() The interaction of the primary ion beam with the sample (under vacuum) provides sufficient energy to ionize many elements. ![]() Schematic depiction of SIMS source region.
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