Abstract. Luminescence techniques are powerful and sensitive probes to study imperfections, impurities and modifications of insulating materials. They are used in a wide range of disciplines from condensed matter physics to archaeology and mineralogy and the methods have developed over nearly a century. Early equipment was often not quantitative and data were collected in formats that were difficult to process and manipulate, and so signals were frequently presented in terms of the initial signals without corrections for equipment spectral sensitivity. Unfortunately not only did this distort the information but often it resulted in incorrect interpretations. Further, the incorrect data handling has persisted into modern usage both by physicists and those in other fields who merely use luminescence as a sensitive technique. Several main types of problem are considered. These include temperature errors in thermoluminescence dosimetry; subtleties in the signal intensity corrections for the responses of both the spectrometer and detectors; grating polarization effects; sample anisotropy; and common errors in spectral deconvolution, especially failure to transform from wavelength to energy plots. IntroductionLuminescence signals provide information on relaxation processes in both inorganic and biological materials and the photon energy of the transition is primarily defined by the electronic structure around the emission site. Subtle variations in the structure will then influence the transition energy and excited state lifetime. Such variations have been successfully used to track changes over volumes as large as 50 neighbouring shells. Luminescence is therefore a powerful probe of defect structures in insulators, as well as responding to impurities, phase changes and distortions such as those caused by stress or nanoparticle inclusions. Equally, the changes induced by local distortion make luminescence a useful probe to distinguish between healthy and diseased biological material and it is used in the emerging field of Optical Biopsy. Luminescence signals have been studied for more than a century with techniques from simple visual observation to black and white or colour photography. By the 1960s more quantitative detectors, such as photomultiplier tubes became available. However the spectral information was generally displayed on a chart recording as a monochromator swept through the wavelength range of the system. Such raw data were then published and used as the basis for discussion and interpretation of the luminescence. For some applications this was acceptable, for example in mineralogical applications changes in spectra revealed different component materials and the presence of rare earth ions were easily identified by characteristic line spectra. It must be recalled that in the 1960s attempts to remove the background dark current, and then scale the signals to correct for the transmission efficiency of the monochromator and sensitivity of the PM tube involved tedious manual processing (N.B. on line computer...

Luminescence data have often been used to study imperfections and to characterize lattice distortions because the signals are sensitive to changes of structure and composition. Previous studies have included intentionally added probe ions such as rare earth ions to sense distortions in local crystal fields caused by modified structural environments. An under-exploited extension of this approach was to use luminescence to monitor crystalline phase changes. A current overview of this new and powerful technique shows that continuous scanning of the sample temperatures immediately offered at least three types of signatures for phase transitions. Because of high sensitivity, luminescence signals were equally responsive to structural changes from inclusions and nanoparticles. These coupled to the host material via long-range interactions and modified the host signals. Two frequently observed examples that are normally overlooked are from nanoparticle inclusions of water and CO2. Examples also indicated that phase transitions were detected in more diverse materials such as superconductors and fullerenes. Finally, luminescence studies have shown that in some crystalline examples, high dose ion implantation of surface layers could induce relaxations and/or structural changes of the entire underlying bulk material. This was an unexpected result and therefore such a possibility has not previously been explored. However, the implications for ion implication are significant and could be far more general than the examples mentioned here.