PIXE in an external microbeam arrangement for the study of finely decorated tartesic gold jewellery items

Narrow regions on Tartesic (Spain, 6th century B.C.) gold jewellery items h ave been studied by PIXE, An external microbeam (250 mu m) of 2.3 MeV proto ns has been used in order to determine the elemental concentrations in the various tiny elements and specially at places of solders. The comparison wi th results on jewellery items of Etruscan origin (same period as Tartesic b ut coming from the North of Italy) allows us to identify the differences in the workmanship of goldsmiths of these geographic regions. The details on the surface topography of wires, granulations, filigrees were observed with an electron microbeam in order to complement the micro-PIXE results. Accurate quantitative elemental analyses have been obtained from PIXE spect ra by a comparison with reference samples and an extensive calculation of t hick target parameters. The background has been carefully calculated by usi ng a physical approach and not only computer adjustment. The necessary corr ections to take the topography of these very irregular surfaces into accoun t were calculated. They include the secondary fluorescence effects and the variation of K alpha/ K beta (for Cu and Ag) or L alpha/L beta (for Au) X-r ay intensity ratios as a function of the surface orientation relative to th e incident beam and the detector positions. (C) 1999 Elsevier Science B.V. All rights reserved.