Affiliations: Dipartimento di Fisica e Scienze della Terra,
Università di Messina, Messina, Italy | INFN, Sez. CT, Gruppo Coll. ME, Messina, Italy | Dipartimento di Fisica, Università di Catania,
Catania, Italy
Abstract: The investigation on the differences occurring in the manufacture of
silver coins allows to get information on their elemental composition and
represents a powerful support to the methodology to identify the producing
technologies, workshops being also instrumental to distinguish between original
and counterfeit ones. Aim of the present work is to study recent and old silver
coins through non-destructive X-Ray Fluorescence (XRF) analysis. The XRF was
applied to extend the analysis to the deepest layers of the coins; for surface
layers an X-ray tube or an electron beam were employed to induce the atom
fluorescence to obtain information on the surface elemental composition.
Moreover, a detailed study has been performed to evaluate the influence of the
surface curvature on the measurement, by deducing a proper corrective factor to
keep into account in the data analysis. The elemental atomic composition was
measured for each coin, mainly by means of the X-ray tube excitation for the
bulk and the electron Scanning Electron Microscope (SEM) microbeam probe for
the surface patina analysis. Ionization was induced by an X-ray tube using an
Ag anode for the bulk and by an electron microprobe for the surface
composition. X-ray detection was performed by using a semiconductor Si device
cooled by a Peltier system. The Ag L-lines X-ray yield is affected by coin
surface morphology and geometry. The comparison between coin spectra and
standard samples, shows that the Ag quantitative analysis is influenced by
error of the atomic concentration lower that 10%.
