A reassessment of the quasi-simultaneous arrival effect in secondary ion mass spectrometry

Quasi-simultaneous arrival (QSA) effects in secondary ion mass spectrometry can create mass-indepedent inaccuracies isotope measurements when using electron multiplier detectors (EMs). The simple Poisson statistical model of QSA does not explain most experimental data. We present pulse-height distributions (PHDs) and time-series to better study QSA. Our data show that PHDs the distribution multiple arrivals on EM are consistent with model. Multiple over-dispersed compared closer a negative binomial distribution. Through an emission-transmission-detection we correction depends non-Poisson emission ions, energy distribution, other factors, making analytical impractical. A standards-based for is best approach, proper way calculate standards-normalized $\delta$ values minimize effect