Spectrometry of elastic collisions and nuclear reactions. Theory

Whatever its origin, a mineral or organic solid undergoes various transformations or constraints throughout its history. From their synthesis to their eventual disappearance, natural materials such as minerals, rocks, organic molecules and biological edifices contained in living beings, as well as man-made materials such as metals, alloys, semiconductors, ceramics and polymers, undergo changes in their chemical composition. These compositional changes may be only superficial, or may involve a significant thickness of material.

The spatial distribution of one or more constituents of the solid under consideration may have been altered, and new elements, absent from the material at the outset, may have been incorporated. Knowledge of a material's initial composition and its evolution as a function of the key parameters of the transformations and stresses undergone is a decisive source of information for understanding the major physico-chemical phenomena likely to occur during its production, its use or its natural ageing. A wide range of scientific disciplines are involved: materials science, earth and universe sciences, life sciences (biology, medicine, botany), environmental sciences, human sciences (archaeology, works of art), and so on. Of course, measuring composition alone is not usually able to completely solve the problem posed, and additional data on the morphology and structure of the material, as well as on the chemical environment of its constituents, are often required.

• Numerous elemental analysis methods, both destructive and non-destructive, have been developed, providing access to average composition for a quantity of material ranging from a milligram to a gram, to surface composition, to local contents in a volume of material of a few µm ³ or to concentration profiles as a function of depth. Since the early 1960s, Ion Beam Analysis (IBA) methods have become increasingly popular, thanks to their analytical flexibility, intrinsic sensitivity and relative independence from the chemical environment of the element(s) to be characterized. In the early 1970s, the birth of ion beam microanalysis, where the incident beam of a few mm ² was replaced by a beam focused to a few µm ² that could be automatically moved over the surface of the sample, reinforced the interest in these techniques for technicians, engineers and researchers of all disciplines. Rapid scanning (kHz) over the target surface enables the construction of elementary images of 2D or even 3D distribution, combined with energy slicing of the signals detected.

  The major problems for analysts are often related...