ION BEAM ANALYTICAL GROUP
The currently applied methods in the laboratory are based on the physical interactions of energetic ions with matter
Depending on the type of interaction, the bombarding particles may scatter, decelerate, be absorbed in the sample while the atoms are excited, ionized or nuclear reactions occur.
These processes lead to electromagnetic radiation (optical, X-ray, gamma-ray) and / or the emission of particles, such as electrons, protons, alpha-particles. The energy of the electromagnetic radiation and particles reaching the various detectors depends on the atoms or nuclei in the sample which are the sources of these emissions, that means on the elements in the investigated material, while the intensity is related to the concentration of these elements. With the measurements, qualitative and quantitative information can be obtained about the elemental, in some cases chemical, composition of the sample.
THE MOST WIDESPREAD ION BEAM ANALYTICAL (IBA) TECHNIQUES
- Particle Induced X-ray Emission (PIXE): The most prevalent IBA technique in heritage science, it is based on the detection of the so called characteristic x-rays emitted by the atoms (through processes involving the electron shells). The energy of the radiation depends on the given element (atomic number). The method is applicable from magnesium or even carbon to uranium, depending on the detectors and the experimental set-up.
- Rutherford Backscattering Spectrometry (RBS): A portion of the bombarding ions, passing through the electron cloud, is scattered back from the nuclei, without changing the state of the target atom. The energy of the backscattered ion depends on the mass of the target nucleus. The method is especially suitable to determine a compositional depth profile in the surface layers of the sample. RBS is used for the investigation of surface alterations, corrosion, and coatings.
- Particle Induced Gamma-ray Emission (PIGE): Some of the incident ions interact with the target nuclei in a way that the collision results in a nuclear reaction. The consequent gamma or particle radiation gives information on the elemental (isotopic) composition of the sample. The PIGE method is suitable for the quantitative analysis of elements with low or medium atomic number (from lithium to sulphur), the sensitivity varies greatly depending on the element.