Particle-induced X-ray emission spectrometry PIXE

Principles and Characteristics Particle-induced X-ray emission spectrometry (PIXE) is a high-energy ion beam analysis technique, which is often considered as a complement to XRF. PIXE analysis is typically carried out with a proton beam (proton-induced X-ray emission) and requires nuclear physics facilities such as a Van der Graaff accelerator, or otherwise a small electrostatic particle accelerator. As the highest sensitivity is obtained at rather low proton energies (2-4 MeV), recently, small and relatively inexpensive tandem accelerators have been developed for PIXE applications, which are commercially available. Compact cyclotrons are also often used. 

S. A.E. Johansson, J.L. Campbell and K.G. Malmqvist (eds), Particle-Induced X-Ray Emission Spectrometry (PIXE), John Wiley Sons, Inc., New York, NY (1995). 

Johansson SAL (1995) Introduction to PIXE. In Johansson SAL, Campbell JL and Malmqvist KG, eds. Particle-induced X-ray emission spectrometry (PIXE) (Vol 133 in Chemical Analysis), pp. 1-17. John Wiley Sons, New York. 

Particle-Induced X-ray Emission Spectrometry (PIXE)-, Johansson, S. A. E. ... 

Since the mid-1960s, a variety of analytical chemistry techniques have been used to characterize obsidian sources and artifacts for provenance research (4, 32-36). The most common of these methods include optical emission spectroscopy (OES), atomic absorption spectroscopy (AAS), particle-induced X-ray emission spectroscopy (PIXE), inductively coupled plasma-mass spectrometry (ICP-MS), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray fluorescence spectroscopy (XRF), and neutron activation analysis (NAA). When selecting a method of analysis for obsidian, one must consider accuracy, precision, cost, promptness of results, existence of comparative data, and availability. Most of the above-mentioned techniques are capable of determining a number of elements, but some of the methods are more labor-intensive, more destructive, and less precise than others. The two methods with the longest and most successful histoty of success for obsidian provenance research are XRF and NAA. 

PIXE particle induced X-ray emission spectrometry (variant of XRF for thin surface layers)... 

To measure Pb concentrations in small particles such as aerosols, or to study the variation in Pb concentrations within sohds such as mineral grains, there is a range in available techniques such as micro-beam XRF (including synchrotron methods), proton induced X-ray emission spectrometry (PIXE), secondary ionization mass spectrometry (SIMS), and laser ablation ICP-MS (LA-ICP-MS). These methods have been used for high spatial resolution even in 3-D, as well as for rapid analyses of biological or geological structures growing incrementally [39-43] or small, specihc phases [44]. 

Substances sampled using a sampler are usually determined directly or after sample preparation using an instrumental analysis technique such as gas chromatography (GC), liquid chromatography (LC), ion chromatography (IC), gas chromatography-mass spectrometry (GC-MS), particle-induced X-ray emission analysis (PIXE), or instrumental neutron activation analysis (INAA), among others. 

Figure 1 Energy dispersed X-ray spectra from the same sample excited by 20 keV electrons (top) and 2.5 MeV protons (bottom). The enhancement of the detection limit for the trace elements caused by the absence of primary Bremsstrahlung in the PIXE spectrum can be seen clearly. Reproduced with permission of Wiley from Johansson SAE, Campbell JL and Malmqvist KG (1995) Particle-Induced X-ray Emission Spectrometry. New York Wiley.

Neutron Activation Analysis X-Ray Fluorescence Particle-Induced X-Ray Emission Particle-Induced Nuclear Reaction Analysis Rutherford Backscattering Spectrometry Spark Source Mass Spectrometry Glow Discharge Mass Spectrometry Electron Microprobe Analysis Laser Microprobe Analysis Secondary Ion Mass Analysis Micro-PIXE... 

There are now several different types of machines that are all capable of microanalysis. All have advantages and disadvantages, but the choice of which to use is often governed by expense and availability to a particular institution. Electron probe microanalysis is by far the most popular, but here particle-induced X-ray emission (PIXE), the laser microprobe mass analyzer (LAMMA), electron energy loss spectroscopy (EELS), and secondary ion mass spectrometry (SIMS) are also considered. 

Another important characteristic is that ion beams can produce a variety of the secondary particles/photons such as secondary ions/atoms, electrons, positrons. X-rays, gamma rays, and so on, which enable us to use ion beams as analytical probes. Ion beam analyses are characterized by the respectively detected secondary species, such as secondary ion mass spectrometry (SIMS), sputtered neutral mass spectrometry (SNMS), electron spectroscopy, particle-induced X-ray emission (PIXE), nuclear reaction analyses (NRA), positron emission tomography (PET), and so on. 

Until now, little attention has been given to the analysis of ancient copper alloys with LA-ICP-MS. This type of material is usually analyzed with fast or instrumental neutron activation analysis (FNAA or INAA), particle induced X-ray emission (PIXE), X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectrometry or inductively coupled plasma-atomic absorption spectrometry (ICP-AES or ICP-AAS). Some of these techniques are destructive and involve extensive sample preparation, some measure only surface compositions, and some require access to a cyclotron or a reactor. LA-ICP-MS is riot affected by any of these inconveniences. We propose here an analytical protocol for copper alloys using LA-ICP-MS and present its application to the study of Matisse bronze sculptures. 

The same equipment as for X-ray spectrometry is used for X-ray fluorescence analysis (XFA). In this method, emission of characteristic X rays is induced by excitation with X-ray sources (X-ray tubes or X-ray emitting radionuclides) or with charged particles (PIXE, i.e. particle-induced X-ray emission). 

Particle-Induced X-ray Emission, PIXE Nuclear Reaction Analysis, NRA Hydrogen Mass Spectrometry, HMS Noble Gas Mass Spectrometry, NGMS... 

A review appeared on speciation of trace elements using radioanalytical methods . Particle-induced X-ray emission (PKE) combined with X-ray spectrometry affords a sensitive multielement analytical method. An advantage of this radiation method is its capability to combine with microbeam techniques, allowing elemental mapping with 1 pm spatial resolution. Applications of PIXE in biology, medicine, geology, air pollution research, archeology and art have been demonstrated . 

IPM can be used simultaneously with RBS (Rutherford backscattering spectrometry), NRA (nuclear reaction analysis), PIXE (particle induced X-ray emission) or PIGE (particle induced gamma ray emission). More specialized examples include the field ion microscope (FIM), which gives better then atomic resolution in the study of high melting point materials. 

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