EELS and PIXE Studies

Particle- or proton-induced. X-ray emission (PIXE) is another modern powerful yet non-destructive elemental analysis technique used to determine the elemental make-up of a sample material. When a material is exposed to a particle or proton beam, atomic interactions occur that give off electromagnetic radiation of wavelengths in the X-ray part of the electromagnetic spectrum characteristic of an element. Three different types of spectra can be collected from a PIXE experiment an X-ray emission spectrum, a Rutherford (proton) backscattering spectrum and a proton transmission spectrum. 

Quantum theory states that orbiting electrons of an atom must occupy discrete energy levels in order to be stable. Bombardment with ions of sufficient energy (usually megaelectronvolt protons) produced by an ion accelerator will cause inner-shell ionisation of atoms in a specimen. Outer-shell electrons drop down to replace inner shell vacancies, however only certain transitions are allowed. X-rays of a characteristic energy of the element are emitted. An energy dispersive detector is used to record and measure these X-rays. Only elements heavier than fluorine can be detected. 

In Rutherford backscattering mode, protons can also interact with the nucleus of the atoms in the sample through elastic collisions, often repelling the proton at angles close to 180°. The degree and angle of backscatter reveals information on the sample thickness and composition. The bulk sample properties allow for the correction of X-ray photon loss within the sample. The transmission of protons through a sample can also be used to get information about 

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