pixe

PIXE, or Particle-Induced X-ray Emission, is an analytical technique used to determine the elemental composition of a material. In PIXE, a specimen is irradiated with charged particles, typically protons from a particle accelerator. The incident ions ionize inner-shell electrons of atoms in the sample; as electrons from higher shells fill the vacancies, characteristic X-rays are emitted. The energies of these X-rays identify the elements, while their intensities—after corrections for detector efficiency, geometry, and matrix effects—relate to element concentrations.

Instrumentation commonly includes a particle accelerator (often a cyclotron), a beam transport system, and an X-ray detector such as a silicon drift detector (SDD), a Si(Li) detector, or a high-purity germanium detector. PIXE can be performed in total- or external-beam mode and, with beam focusing, in micro-PIXE to achieve micron-scale spatial resolution. Data analysis relies on calibrations with reference samples and models to correct for self-absorption, secondary excitation, and viewing geometry.

Applications span archaeology and cultural heritage (pigments and glazing), environmental science (aerosol, soils, sediments), materials science (metals and semiconductors), and forensics. PIXE is valued for rapid, multi-element, non- or minimally destructive analysis with good sensitivity for most elements from potassium onward to heavier elements; detection limits typically range from parts per million to parts per billion, depending on element, matrix, and measurement time.

Limitations include the need for particle accelerators, potential radiation damage for sensitive samples, and reduced sensitivity for light elements such as carbon, nitrogen, and oxygen. Quantitative accuracy requires careful handling of matrix effects and standards. PIXE has a long history dating to the 1960s and remains a widely used tool in qualitative and quantitative elemental analysis.