Mathematical-modeling of secondary-ion energy-spectra
Faculty of Sciences. Chemistry
International journal of mass spectrometry and ion processes. - Amsterdam
, p. 173-179
An attempt has been made to compose a mathematical model of secondary ion energy spectra, taking into account the sputter process, the ionization process and the transmission of the secondary ion mass spectrometer. In this model a new equation for the transmission of the instrument was formulated. The percentage fit of the model was equal to 99.9+% for 80% of the tested cases and 99+% for all measured energy distributions. A total of 59 energy distributions were tested. It was hoped that the various mathematical parameters used in the expressions to describe the above processes and characteristics will provide a direct link with the variation of the measured isotopic ratios and hence a better insight into the reasons for this variation. Unfortunately, this objective was not achieved since the uncertainty of the calculated ratio by model-fitting the energy distributions is larger than the measured uncertainty. However, the model provides some insight into the energy dependent fractionation observed within individual measurements.