A technique for analysing the chemical structure of a solid by bombarding it with ions. A sample of the solid to be analysed is bombarded with ions, referred to as primary ions, having energies between 5 and 20 keV. A number of different types of entity are detached from the surface of the solid, including neutral atoms and molecules, electrons, photons, and negative and positive ions. The negative and positive ions given off, called the secondary ions, can be identified using mass spectrometry. Using this technique solid samples can be characterized with great accuracy.