Micro-Ionoluminescence and micro-PIXE in natural diopside: activators and ion damaging effects

Diopside is a mineral belonging to the pyroxene family, in particular it is an inosilicate with a single calcium and magnesium chain, whose chemical formula is CaMgSi 2 O 6 . Natural diopside displays a large variety of luminescence centers: at room tempertaure main features are a 450 nm band, that can be ascribed to the silicate- based network [1-3] and an intense band at 585 nm that can be ascribed to Mn 2+ ions in M2 (Ca 2+ ) sites [4]. Also Ti 3+ and Ferelated impurities have a role as activators of luminescence [5,6]. The main purpose of the present work is to study the radiation hardness of several of such centers by following the evolution of ionoluminescence upon proton and helium irradiation at different energies and fluences. Moreover an attempt was made to correlate the trace elements to the centers of luminescence by means of micro-PIXE. As this work falls in the framework of the provenance study of lapis lazuli used for artworks we are carrying on since 2008 [7] all analysed natural diopside crystals were found in lapis lazuli rocks. [1] L.H. Abu-Hassan, P.D. Townsend, Nucl. Instr. Meth. B, 32(1988)293-298. [2] K. Moritani, I. Takagi, H. Moriyama, J. of Nuclear Materials, 312(2003)97-102 [3] S.I. Kitazawa, S. Yamamoto, M. Asano, S. Ishiyama, Physica B, 349(2004)159-165 [4] A.L. Smith, Journal of The Electrochemical Society, 96(5) (1949) 287-296 [5] A. Quaranta A. et al. Nucl. Instr. Meth. B, 254 (2007) 289-294 [6] C.D.K. Herd, R.C. Peterson, G.R. Rossman The Canadian Mineralogist, 38 (2000) 1193-1199 [7] A. Lo Giudice et al., Analytical and Bioanalytical Chemistry 395 (2009) 2211-2217