## 4 UV-VIS-IR Radiation Detectors
### Luminescence Induced by Electrons, Ions and X-rays
This feature offers a great advantage over measurements with a monochromator, scanning one wavelength at a time, and in addition, enables avoiding spectral distortions due to the creation of luminescence centers during irradiation in small areas in some materials. The detected wavelength range frequently extends up to 1000-1100 nm, to reveal the features in the NIR region (typically with a 1 nm resolution). The implementation of an IL setup on a scanning apparatus gives the opportunity to acquire wavelength-selective bidimensional IL maps, similar to the PIXE elemental maps, a feature which enhances the complementarity of the two techniques. Considering that X-ray based analytical techniques are very popular in the archaeometric community, especially X-ray fluorescence (XRF) for elemental analysis and Radiography (RX) or X-ray Computed Tomography (XCT) for structural information, the use of X-rays also as source of luminescence excitation is starting to take hold. X-ray luminescence (XRL) can be recorded as image, for example as an easy tool, complementary to RX, for discrimi  
Figure 12: IL spectrum of a diopside crystal contained in lapis lazuli, acquired at the Legnaro National Laboratories of INFN with an Ocean Optics QEPro thermoelectrically cooled spectrometer. nating saltwater and freshwater cultivated pearls [199]; otherwise an XRL spectrum can be acquired with a setup similar to IL one, composed by an optical fiber system for signal collection and transportation to the spectrometer. Very few applications to CH items have been performed so far, finding some examples in lapis lazuli characterization [200,201]. The INFN-CHNet network instrumentation covers most of the techniques presented above. For IL, in particular, several setups have been developed, to exploit both the broad- and the micro-beams available at the INFN accelerators. IL microscopy and imaging can be performed at INFN-LABEC, where, working in air with a broad beam (with \(\sim\)6 mm\({}^{2}\) area, obtained defocusing a micro-beam), the image is captured by a Prosilica GC2450C CCD color camera equipped with a zoom lens set at a 45\({}^{\circ}\) angle with the beam direction. The objective, a TECHSPEC VZM 1000 Zoom Imaging Lens, enables magnifications from 2.5\(\times\) to 10\(\times\), with a working distance of 35 mm [202]. The components employed to implement this setup have been selected in order to obtain information of the same kind of that provided by in-vacuum CL microscopy, but with the great advantage of performing the analysis in air without any sample pre-treatment. This setup has already proven its potential in the study of lapis lazuli provenance, both on semi-thin sections (approximately 100 \(\upmu\)m) and on artworks. On the same external scanning microbeam line, \(\upmu\)-IL spectroscopy has also been developed. The optical system is based on a collimating lens set at \(\sim\)60\({}^{\circ}\) with respect to the incident beam while the collected photons are focused on the common end of a Y-shape optical fiber with diameter of 200 \(\upmu\)m. The luminescent signal is then split in two different paths: the 85% of the signal reaches a CCD based OO USB2000 spectrometer (bandwidth 200-900 nm, spectral resolution 2 nm) for spectra acquisition, whereas the remaining 15% follows the other branch of the fiber to a PMT HAMAMATSU R376 photomultiplier, connected to the microbeam acquisition system. This second setup can produce panchromatic IL maps, or monochromatic ones if wavelength-selective filters are interposed between the fiber and the PMT [203,204].