Numerical modelling of mineral impact ionisation spectra

We present model mass spectra of fayalite, forsterite, enstatite, ferrosilite, magnesiohornblende, ferrohornblende, anorthites, albite and Mg–Al spinel, as would be generated by a medium resolution impact ionisation cosmic dust mass spectrometer. Spectral peak intensities are found using ion relative sensitivity factors (RSFs) derived for TOF-SIMS mineral analysis. We demonstrate that, although TOF-SIMS RSFs are a reasonable approximation for the RSFs of impact ionisation, the RSFs for some important elements, such as Si, may differ by up to a factor of four. However, the TOF-SIMS RSFs are in general a valuable tool for predicting the peak intensities of inorganic species in impact ionisation mass spectra of minerals and mineral mixtures. The model spectra are used to estimate the ability of a medium resolution mass spectrometer to discriminate between different mineral compositions, and compared with impact ionisation mass spectra of anorthite cosmic dust analogue particles.