PIXE-alpha and micro-raman analysis for a non-destructive characterisation of the salerno exultet

The collaboration between Istituto Centrale per la Patologia del Libro, Rome, Dipartimento di Fisica, Università Roma Tre - Sezione INFM and LNS/INFN LANDIS laboratory, Catania, allowed the complete characterization of the Salerno Exultet, a XIII century parchment scroll. PIXE measurements were obtained using the portable PIXE-??system, entirely designed and realised by the LNS/INFN LANDIS laboratory. It consists of a sealed 210Po source emitting ? particles at energy of about 4.5 MeV, enough to investigate the sample up to a thickness of about 10-40 ?m. The activity of the 210Po source is 1 mCi while the spot diameter is about 1 cm. The PIXE system was completed with a germanium detector with energy resolution of 130 eV at 5.9 keV. Its good resolution allowed us to separate the S-K line at 2.30 keV, Hg-M line at 2.19 keV and Pb-M line at 2.34 keV. Raman analysis were performed with a Dilor Labram spectrometer, equipped with two different laser sources at 632.8 nm (He-Ne) and at 785.5 nm (diode laser). The illumination and collecting optics of the system consists in a microscope in confocal configuration. This configuration limits the dimensions of the analysed sample. For this reason, to investigate larger samples, we realised a special hand-piece that was equipped with an external laser source at 632.8 nm and connected to the Labram system by optical fibres. We tried to perform all measurements in the same points both with the PIXE-??system and with the Raman spectrometer. Due to the different nature and spatial resolution of the two techniques it was not always possible perform measurements in the same point: sometimes Raman spectra gave no information because of the intense fluorescence of the sample; sometimes the analysed zone was too small for carrying out PIXE measurements. In any case the whole analysis allowed us to reveal the Salerno Exultet palette.