page_title: Elastic recoil detection
section_title: Multiple scattering scheme in Forward Recoil Spectrometry
hierarchical_section_title: Elastic recoil detection / Physical Processes of Elastic Recoil Detection Analysis / Multiple scattering scheme in Forward Recoil Spectrometry
caption_attribution_description: English: Multiple-scattering scheme
context_page_description: Elastic Recoil Detection Analysis, also referred to as forward recoil scattering, is an Ion Beam Analysis technique in materials science to obtain elemental concentration depth profiles in thin films. This technique is known by several different names. These names are listed below. In the technique of ERDA, an energetic ion beam is directed at a sample to be characterized and there is an elastic nuclear interaction between the ions of beam and the atoms of the target sample. Such interactions are commonly of Coulomb nature. Depending on the kinetics of the ions, cross section area, and the loss of energy of the ions in the matter, Elastic Recoil Detection Analysis helps determine the quantification of the elemental analysis. It also provides information about the depth profile of the sample.
  The incident energetic ions can have a wide range of energy from 2 MeV to 200 MeV. The energy of the beam depends on the sample to be studied. The energy of the beam should be enough to kick out the atoms of the sample. Thus, ERD usually employs appropriate source and detectors to detect recoiled atoms.
context_section_description: When an Ion beam penetrating in to matter, ions undergo successive scattering events and deviates from original direction. The beam of ions in initial stage are well collimated(single direction), but after passing through a thickness of Δx in a random medium their direction of light propagation certainly differs from normal direction . As a result, both angular and lateral deviations from the initial direction can occur. These two parameters are discussed below. Hence, path length will be increased than expected causing fluctuations in ion beam. This process is called multiple scattering, and it is statistical in nature due to the large number of collisions.
  Lateral displacement Case 1
  Ion beam fluctuations because of lateral deviations on Target surface is explained by considering Multiple scattering of an ion beam which is directed in x – direction.
  Angular deviation Case 2
  In the below figure there is a considerable difference between in the shape area of Gaussian peak (ideal condition) and angularly deviated peak.  and α is an angle due to angular deviation of a penetrated ion beam through matter.
caption: Multiple scattering scheme where the ion beam is directed in x direction. Lateral displacement perpendicular to the beam direction is ρ(y,z),and α is the total angular deviation after the penetrated depth x
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