Particle-induced X-ray emission (PIXE)

What is PIXE used for?

PIXE can be used to analyze the elemental composition of geological samples, archeological specimens, thin films, and proteins. The method is often used in archaeology and art conservation for dating objects, as it is a non-destructive method and does not harm the artifact. MicroPIXE (X-ray emission with a micro-focused beam) is also used in protein analysis to determine the elemental composition of liquid and crystalline proteins.

PIXE can be combined with RBS measurements (Rutherford backscattering spectrometry) to help identify heavy elements. Due to their similar masses, heavy elements may have only small differences in RBS backscattered energies, making identifying different elements challenging. However, these elements might be seen in a PIXE spectrum, which helps determine the elemental composition.

How does PIXE work?

PIXE works by bombarding the sample with small ionic particles, such as H+ or He2+. The focused ion beam removes a low-energy electron from the atom's inner shell. To maintain stability, a higher energy electron fills the spots that the low energy electron left behind. During this process, excess energy is released from the atom in the form of an X-ray.

The X-rays are detected and their individual energies are recorded. The energies are independent of the excitation process but are characteristic of the different elements. The X-ray's specific energy indicates the atom's type and can therefore identify the elements present in the sample. By recording and combining data, this process can be used to accurately determine the sample's elemental composition.

X-ray analysis can also be combined with backscattering analysis. Backscattered ions are scattered elastically from the sample's atomic nuclei back to their original direction. The detected energy of the backscattered ions is dependent on the mass of the target nucleus and the depth of the scattering event. Hence, backscattering can also provide information about the depth of the elements.

What are the limitations of PIXE?

Typically, elements lighter than magnesium (atomic number 12) will not appear in a PIXE spectrum. For this reason, PIXE is generally more suitable for determining the concentrations of heavier metals rather than organic components.

Do you need a PIXE analysis?

Measurlabs offers high-quality PIXE analyses for delicate samples. If you have any questions related to the method or your samples, our experts are happy to answer them and help find a solution to your analysis needs. Contact us through the form below or by emailing us at info@measurlabs.com.