Measurement of effective atomic number of gunshot residues using scattering of gamma rays

by Kenneth Ujevich

Better understanding of gunshot residues and the major elemental composition would be valuable to forensic scientists for their analysis work and interpretation of results. In this experiment, the atomic numbers of gunshot residue-containing items (cartridge case, bullet core, bullet jacket and gunpowder) were analyzed using energy dispersive X-ray analysis (EDX). The scattering of 59.54 keV gamma rays is studied using a high-resolution HPGe (high-purity germanium) detector. The experiment is performed on various elements with atomic number (Z) in the range of 4 to 82. The results, which is the intensity ratio of coherent to Compton scattered peaks, are plotted as a function of atomic number and constituted a best-fit-curve. From this fit-curve, the respective effective atomic numbers of gunshot residues are determined. Based on the data, the theoretical atomic numbers match up nicely with the calculated atomic numbers that resulted from the curve. This shows that the method used in this experiment is a simple, non-destructive technique that accurately determines the atomic numbers of gunshot residues.

Demet Yılmaz, Ahmet Turşucu, Zeynep Uzunoğlu, Demet Korucu. “Measurement of effective atomic number of gunshot residues using scattering of gamma rays.” Radiation Physics and Chemistry, Volume 102, September 2014, Pages 68-71, ISSN 0969-806X, http://dx.doi.org/10.1016/j.radphyschem.2014.04.012.

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