Many innocuous materials are also primarily composed of the same elements. These elements, however, are found in each material with very different elemental ratios and concentrations. It is thus possible to identify and differentiate, e.g. TNT from other innocuous materials that have the same density. I below shows the atomic density of elements for various materials along with the atomic ratios. The problem of identifying explosives is thus reduced to the problem of elemental identification.
Nuclear techniques show a number of advantages for non-destructive elemental characterization.
These include the ability to examine bulk quantities with speed, high elemental specificity, and no memory effects from the previously measured object. These qualities are important for an effective detection system for explosives. Table I. Elemental densities and ratios of two classes of substances. The PDF file can be viewed using the free Adobe Acrobat Reader.