Fundamentals of the RBS Technique and its Characteristics

Rutherford backscattering occurs when 1-3 MeV ions are deflected through an obtuse angle (close to 180°) by the repulsive electrostatic field of an atomic nucleus. A beam of a-particles from a radioactive source strikes the foil and gets scattered. The number of flashes seen, as the a-particles hit a fluorescent screen, are then measured at different angles of scattering (6). The profound observation of backscattering of a-particles by Ernest Rutherford in 1910 paved the way for discovery of the nucleus. 

Energy transfer from a projectile to a target nucleus in an elastic two-body collision - concept of kinematic factor K = Ei/Eq i.e., ratio of energy of the scattered particle to the energy of the incident particle). 

Probability of occurrence of such a two-body collision - concept of scattering cross-section. 

Statistical fluctuations in the energy loss of an atom moving through a dense medium - concept of energy straggling and to a limitation in the ultimate mass and depth resolution of RBS. 

nondestructive and multielemental analysis technique for elements from Be to U. No light element can be detected on heavy substrates. Matrix independent (unaffected by chemical bonding states). Quantitative without standards. 

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