High Energy Secondaries for the Quantitative Secondary Ion Mass Spectrometric Analysis of Minerals

The major hurdle in quantitative analysis by SIMS is the inconsistency and non-predictability of ion yields, particularly their sensitivity to sample matrix. High energy (100-500 eV) secondary ions have been shown to be considerably less susceptible to matrix effects than low energy secondary ions, particularly in mineral analysis. Therefore ion yields of some sixty elements were measured utilizing very high energy secondaries (~ 500 eV), from a standard silicate glass. They show a broad ionization potential dependence and a mass (or velocity) dependency which is not removed by the application of a M½ or M factor. The modification of yields with conventional thermodynamic partition functions, improves but does not clearly define agreement with the inverse exponential relationship observed by others, for low energy secondaries sputtered from oxygen rich matrices. The reproducibility of ion yields of high energy secondaries suggests empirical approaches to quantitative analysis are well justified; however the poor agreement of ion yields with an inverse exponential relationship, suggests that ion yielding mechanisms are somewhat different to those proposed in the low energy regime