Elastic backscattering analysis

A correction for matrix effects is usually required. Difficulties in PIXE quantitation may be relieved by complementary information from RBS [290], or FTIR and elastic backscattering (EBS) analysis [291], FTIR can give a rough estimation of the elemental composition, while EBS or RBS can deliver information on the major-element composition. 

The use of elastic backscattering, which is the primary technique for energetic ion beam analysis, is the normal method of choice when it will produce satisfactory results. Some other ion beam techniques which may be useful in supplementing backscattering in specific cases will be discussed later in this paper. 

Cox R P, Leavitt J A and McIntyre L C Jr 1995 Non-Rutherford elastic backscattering cross sections Handbook of Modern Ion Beam Materials Analysis ed J R Tesmerand M Nastasi (Pittsburgh, PA Materials Research Society) ch A7, p 481... 

Several experimental techniques can be used to study surfaces. X-ray Photoelectron Spectroscopy (XPS), Auger Spectroscopy, X-ray Absorption Spectroscopy, Low Energy Electron Diffraction (LEED), Infra-Red spectroscopy (IR), Raman spectroscopy. Time of Flight Secondary Ionization Mass Spectroscopy (ToF-SIMS), different microscopy techniques, cyclic voltammetry and many other methods have been used to understand the chemical composition and also the reactivity of many sulfide surfaces. However, any analysis using these methodologies are not limited to surface atoms and contributions from the bulk phase are also included. In LEED, for example, in which the incident electrons are elastically backscattered from a surface and subjected to diffraction, the electrons can travel around 5-20 A into the solid. This will make any spectra analysis very difficult and, sometimes, not conclusive. 

The use of nuclear techniques allows the determination of C, N, H, O, and heavier contaminants relative fractions with great accuracy, and of the elements depth profile with moderate resolution (typically 10 nm). Rutherford backscattering spectroscopy (RBS) of light ions (like alpha particles) is used for the determination of carbon and heavier elements. Hydrogen contents are measured by forward scattering of protons by incident alpha particles (ERDA) elastic recoil detection analysis [44,47]. 

The application of neutron spin-echo spectroscopy to the analysis of the slow dynamics of biomolecules is still in its infancy, but developing fast. The few published investigations either pertain to the diffusion of globular proteins in solution [332-334] or focus on the internal subnanosecond dynamics on the length scale, <10 A as measured on wet powders [335,336]. The latter regime overlaps with other quasi-elastic neutron scattering methods as backscattering and TOE spectrometry [337-339]. 

Appearance potential spectroscopy involves detection of electronic transitions not of the backscattered electrons as in ELS, but of secondary processes. The latter include increase in soft X-ray (SXAPS) or Auger electron (AEAPS) emission or decrease in elastically scattered primary electrons (DAPS) (382). SXAPS is not as sensitive as AES for surface chemical analysis. However, SXAPS and IS spectra are easier to analyze than AES, since only one core transition is involved. This makes SXAPS and IS quite convenient for detecting heavy elements on catalyst surfaces. 

X-ray emission (PIXE), heavy ion-induced X-ray emission (HIXE), particle-induced y-ray emission (PIGE), Rutherford backscattering spectrometry (RBS), and elastic recoil detection analysis (ERDA). These methods are also multielemental and nondestructive. In general, when ion beam methods are used it should be kept in mind that sulfur-containing matter may be lost during the irradiation, and therefore sufficiently low beam currents should be employed. Also, sample homogeneity is vital since the volume probed by the ions is rather small. 

The most commonly used accelerator-based techniques for depth profiling are Rutherford Backscattering (RBS) which will be discussed in Chap. 2, Elastic Recoil Detection (ERD) which will be discussed in Chap. 3, and Nuclear Reaction Analysis (NRA) which will be discussed in Chap. 7. PIXE analysis has the advantage of a very good sensitivity and possible simultaneous detection of all heavier elements. 

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