This technique is similar to SIMS and is also known as 'Sputtered Neutral Mass Spectrometry'. The neutral atoms are detected by post-ionising any atoms that are ejected from the surface. This post-ionisation can be accomplished by using lasers or electron bombardment of the atoms entering the mass analyser.

Ionization probabilities for particles sputtered from a surface can vary between 10^-5 to 10^-1. The remaining particles are neutral and thus vary between 90% and 99.9999% which is a much smaller variation in total flux. This fact leads to much better quantitative estimations using SNMS than SIMS.