6. Measuring a composition

6.1 Quantitativity

One of the strengths of atomic probes is their quantitative nature. Unlike many other microanalysis methods (such as SIMS, Secondary Ion Mass Spectrometry), no calibration or ionization yield is involved in calculating compositions. Unlike most chemical analysis techniques, composition measurement is very direct. The number of ions collected from each species (N _A , N _B ) is proportional to the atomic fractions (A, B):