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The present research concerns the characterization of samples of corundum (Al2O3), varieties of sapphire, by micro-Raman spectroscopy. Ten samples of natural corundum from Australia, Madagascar, Sri Lanka, Thailand, Tanzania, and Vietnam were studied. After standard gemmological analysis, micro-Raman analysis was also performed in order to identify mineral inclusions within the sapphire samples and to obtain information on the geological genres of the minerals. Several inclusions were evidenced within the sapphires and identified by Raman spectroscopy thanks to a confocal spectrometer, which allowed detection also below the external surface of the gem. Finally, the Raman spectra are discussed taking into account the provenance of the samples and their optical absorption. Copyright © 2008 John Wiley & Sons, Ltd.

Silica glasses containing SnO 2 nanocrystals and Er 3 + ions were prepared by the sol-gel route and proper annealing treatments. A few samples were prepared with fluorinated Si precursors. Er 3 + transitions from the ground 4 I 1 5 / 2 to the 4 I 1 3 / 2 , 4 I 1 1 / 2 , 4 I 9 / 2 , 4 F 9 / 2 , 4 S 3 / 2 , 2 H 1 1 / 2 , and 4 F 7 / 2 excited manifolds were monitored by means of high resolution (as fine as 0.1 cm - 1 ) Fourier Transform spectroscopy in the wave number (6000-22000 cm - 1 ) and temperature (9-300 K) range, respectively. Broad absorption spectra were observed in silica samples simply doped with Er 3 + , as expected for Er 3 + in a glassy environment. In samples containing also SnO 2 nanocrystals, complex, narrow line Er 3 + related spectra were monitored. The lines become sharper and sharper by lowering the temperature to 9 K, as expected for Er 3 + ions embedded in an ordered (crystalline) environment. The nature and origin of different surroundings probed by the Er 3 + line spectra are discussed.

Radio-luminescence, time resolved photo-luminescence and Raman spectroscopy measurements were performed on Ce-doped sol-gel silica glasses. Quenching of the 5d-4f Ce3+ emission transition was observed by increasing Ce3+ concentration above 0.04 mol%, evidenced by a decrease of the emission intensity accompanied by the appearance of a fast component in the photoluminescence time decay. Raman measurements revealed the formation of CeO2 clusters, which can be considered a cause of the observed luminescence quenching. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The changes in the absorption spectra induced by Co-60 irradiation and high temperature annealing was studied for selected PbWO4 crystals. Based on radiation and annealings induced absorption spectra, four color centers are proposed, which could be responsible for shaping the absorption spectrum of PbWO4 crystals below 3.6 eV, namely Pb3+, O-, F, and F+ centers. Thermoluminescence (TSL) glow curves above room temperature were also studied on these samples to determine further the trap levels resulting from irradiation. Correlation between the results obtained by TSL and Co-60 irradiation induced absorption changes is discussed. (C) 1997 American Institute of Physics.

Temperature-programmed desorption (TPD) and differential-scanning calorimetry (DSC) analyses were performed on synthetic crystalline quartz, both ''as received'' and ''hydrogen swept'', from 200 to 600 degrees C. The TPD measurements allowed us to establish that interstitial hydrogen ions, present as charge compensators near trivalent aluminium ions substitutional for silicon, are removed from the crystal in the considered temperature range, mostly in the form of H-2 molecules. In 2 the hydrogen-swept samples, release of small amounts of other molecular groups, namely SiH4 and NaOH, was also observed. The DSC studies revealed the existence of a weak exothermic peak (enthalpy change similar or equal to 0.90 J g(-1)) in the temperature range from 350 to 400 degrees C. The exothermic process, only observable in hydrogen-swept samples, may tentatively be attributed to the total-energy variation involved in processes leading to H-2 formation and to SiO4 tetrahedra relaxation after H-2 release. The above results have been compared with the intensity variations, following annealing treatments, of near-infrared OH stretching vibrations and with time-transient effects observed in ionic conductivity measurements. The analysis contributes to a deeper understanding of the hydrogen-impurity dynamics in crystalline quartz. Copyright (C) 1996 Elsevier Science Ltd

The paper presents the current density peaks during the heating-up phase for different kind of quartzes: clear natural from Brazil, smoky natural, and synthetic quartz from Sawyer Research Product (Electronic and Premium Q), Toyo, romanian and polish ones, and compares the phenomenon in vacuum and in air for the same applied electric field and gives a model, with which the process could be described. Die Arbeit stellt fur verschiedene Arten von Quarzkristallen (durchsichtiger Quarz von Brasilien, Rauchquarz und synthetischer Quarz von Sawyer Research Product, Toyo, rumanischer und polnischer Quarz), die Maxima der Stromdichte wahrend der Erwarmungsphase der Elektrodiffusion dar und unter denselben Bedingungen des angewandten Stromfeldes das im Vakuum durchgefuhrte Phanomen - dem in Luft durchgefuhrten gegenuber und schlagt ein Modell vor, das den Vorgang beschreiben kann.

Photoluminescence in various types of silica (a-SiO 2 ) both unirradiated and neutron irradiated has been studied in the range 10–300 K. The already reported α emissions at 4.25 eV and at 4.35 eV, whose respective excitation bands peak at 5.10 eV and 4.96 eV, have been found to be excited also in a band peaking at ∼ 7.6 eV; the temperature dependence of their intensities has also been investigated for both excitations. Time resolved emission spectroscopy excited by KrF excimer laser (5 eV) allowed the detection of the different lifetimes of the two a emissions. Similar studies on neutron irradiated quartz (c-SiO 2 ) have evidenced the presence of the center emitting at 4.35 eV up to now observed only in a-SiO 2 .

Corundum is a crystalline form of aluminum oxide (Al2O 3) and is one of the rock-forming minerals. When aluminum oxide is pure, the mineral is colorless, but the presence of trace amounts of other elements such as iron, titanium, and chromium in the crystal lattice gives the typical colors (including blue, red, violet, pink, green, yellow, orange, gray, white, colorless, and black) of gemstone varieties. The starting point for our work is the quantitative evaluation of the concentration of chromophore chemical elements with a precision as good as possible to match the data obtained by different techniques as such as optical absorption photoluminescence. The aim is to give an interpretation of the absorption bands present in the NIR and visible ranges which do not involve intervalence charge transfer transitions (Fe2+ → Fe3+ and Fe2+ → Ti 4+), commonly considered responsible of the important features of the blue sapphire absorption spectra. So, we developed a method to evaluate as accurately as possible the autoabsorption effects and the secondary excitation effects which frequently are sources of relevant errors in the quantitative EDXRF analysis. © 2009 Springer-Verlag.

Low iron, pale blue natural and synthetic sapphire samples were studied by low temperature absorption and luminescence spectroscopy. For comparison, a bicolour pink and blue corundum from Vietnam was also considered. From radioluminescence and photoluminescence excitation spectra of both Cr 3+ and Ti3+, experimental evidence was obtained for attributing an absorption band at 17 500cm-1, currently interpreted as intervalence charge transfer, to overlapping crystal field transitions of Cr3+ and Ti3+. An important role was also proposed for Cr2+; indeed, it is possible to propose that the colour of pale blue sapphires is mainly determined by chromium in its two valence states while Ti3+ and Fe3+ have a minor role. © IOP Publishing Ltd.

Radio-luminescence (RL) and wavelength resolved thermally stimulated luminescence (TSL) measurements have been performed on sol-gel SiO2 glasses, undoped (with high OH- or low OH-content) and rare-earth (Ce, Gd and Tb) doped in the temperature range 10-310K. Moreover, a comparison has been performed between undoped sol-gel and commercial glasses. In undoped samples RL spectra are characterized by emissions at 1.9eV, 2.4 eV (only in high OH-content glasses) and 2.7 eV at 10K.; their nature is discussed and related to different intrinsic defects. Strong emission quenching is observed by temperature increasing. Besides similar intrinsic bands, the doped glasses RL emission spectra display typical emissions related to 5d-4f (Ce3+), 6P-8S (Gd3+) and 5D 3-7Fj, 5D4- 7Fj (Tb3+) transitions respectively, whose amplitudes increase by increasing the temperature above 150K. TSL measurements show the existence of glow peaks at ≈100 K and 220 K. The observed increase of RL rare-earth emission amplitudes above 150 K can be explained by considering (i) the progressive decrease of competitive host matrix recombination channels and (ii) the free carriers trapping at defect sites during irradiation (monitored by TSL), whose stability strongly depends upon temperature. © 2004 Elsevier B.V. All rights reserved.

Radio-, photo- and thermally stimulated - luminescence (RL, PL, TSL) measurements have been performed on SiO2 sol-gel glasses doped by 0.1 mol% Ce and 3 mol% Gd, and on (0.1 mol% Ce, 3 mol% Gd) co-doped samples. Ce3 5d-4f emission F caking at about 2.7 eV has been observed in the RL of SiO2: 0.1 mol% CC, while the typical (6)p-S-8 emission of Gd3 centred at 3.97 eV has been detected in SiO2: 3 mol% Gd. The co-doped sample displays both 5d-4f Ce3 and P-6-S-8 Gd3 emissions with reduced intensities with respect to those observed in the singly doped glasses. Moreover, in co-doped glasses the PL time decay patterns of both rare earth ions show a non exponential dependence and are significantly shortened. To explain such an effect non radiative de-excitation of both RE ions excited states involving energy transfers to defect levels is suggested. Bidirectional Gd3 Ce3 energy transfers could also occur. Complementary TSL measurements put in evidence the existence of broad glow peaks at about 100 K and 220 K. The TSL spectra feature the RE ions emissions.

Silica glasses with substitutional Sn-doping or with dispersion of SnO2 nanoclusters were prepared by the sol–gel method. The occurrence of SnO2 clustering was investigated by optical absorption, Raman scattering and electron paramagnetic resonance spectroscopies, varying both the tin concentration and the densification temperature of Sn-doped silica xerogels. The 3.7 eV absorption edge of SnO2 and the A1g Raman mode at 630 cm−1 of the SnO2 phonon spectrum were used to assess the presence of SnO2 nanoclusters; the yield of X-ray induced paramagnetic E′ Sn centres was monitored to probe the variation in the amount of substitutional Sn centres. The results indicate that the clustering of SnO2 becomes effective for Sn concentrations ≥ 0.8 mol% and it is competitive with the substitutional doping in xerogels densified at T ≥ 900 °C. No evidence of pre-existent clustering was observed in xerogels densified at lower temperatures in the investigated doping range.

The thermally stimulated luminescence ~TSL! properties of lead tungstate in the temperature range 10–250 K have been investigated by wavelength-resolved measurements performed on undoped and lanthanum doped crystals after x irradiation at 10 K. Glow peaks at around 10 and 20 K have been observed, followed by a strong and composite structure in the 40–70 K region. At higher temperatures TSL emission in the 85–100 K range has also been detected, whose intensity is higher in the lanthanum doped crystal with respect to the undoped one. Additionally, the undoped crystal displays a composite glow peak in the 180–200 K region. The emission spectrum of the TSL varies both as a function of temperature and doping: a band centered at 2.85 eV is found in the undoped sample below 70 K; a similar emission is found in the case of the lanthanum doped crystal, with the exception of a limited temperature interval around 60 K where another band at lower energy (E52.63 eV) is found. In the 200 K region, the emission is centered at 2.5 eV. These results are discussed in comparison with literature photoluminescence and scintillation data. A detailed investigation of the composite TSL structure in the 40–70 K range has been performed through several partial heating treatments: three distinct TSL peaks have been found at 50, 55, and 67 K, characterized by trap depths of 48, 65, and 104 meV, respectively. The comparison with recent literature electron paramagnetic resonance studies allows us to propose that the TSL peak at 50 K is related to the thermal disintegration of (WO4)32 electron centers followed by radiative recombination. Spatial correlation between traps and luminescent centers is suggested, leading to localized recombination not involving the conduction band

Sn centers are point defects easily formed by X-ray irradiation of Sn-doped silica. Point defects are a tool for assessing the substitutional character of the dopant in Sn-doped SiO2 glasses with different Sn content (SnO2/SiO2 ratio from 0.01 to 10.0 % w/w) and prepared by two sol-gel methods differing in tin precursors (tin tetraterbutoxide and tin dibutyldiacetate). The former method produced transparent crack-free monolithic glasses of Sn-doped silica with maximum tin content of 0.1 % (SnO2/SiO2 % w/w). The latter method is more efficient and produced transparent glasses with a tin content of 1%.

Physical review / B 57, 3718 (1998). doi:10.1103/PhysRevB.57.3718, Published by APS, College Park, Md.

We present an observation of the photoluminescence features introduced by Sn doping in the SiO2:Ge core of an optical fiber preform, excited in the vacuum-ultraviolet energy region by synchrotron radiation. Detailed measurements as a function of the excitation energy indicate the presence of two specific emissions around 3.5 and 3.7 eV related to two excitation channels at 5.7 and 5.9 eV, underlying an absorption band centered at about 6 eV. These data put in evidence the capability of Sn to introduce specific optically active defect configurations, contrary to Ge, which mainly introduces perturbations on otherwise intrinsic oxygen-deficient-center sites.

A study of the thermally stimulated luminescence (TSL) and conductivity (TSC) properties of PbWO4 crystals was performed on a selected set of samples. Under X-ray irradiations at 90 K TSL peaks are observed in three temperature regions, (100–130 K, 160–200 K, 220–300 K) with corresponding TSC structures. Room temperature irradiations put in evidence a weak TSL peak around 360 K. The emission spectra of the TSL signals are also presented. On the basis of these measurements, the possible nature of the defects involved in the TSL processes is discussed.

Optical absorption measurements in the 3.5--6.5 eV spectral range and photoluminescence spectra, excited in the 4--8 eV range have been performed on neutron irradiated synthetic crystalline quartz as a function of temperature and of neutron fluence. The Gaussian deconvolution of the radiation-induced absorption spectrum in the 4.5--6 eV region reveals a complex structure: five distinct components, peaking at 4.85, 5.06, 5.35, 5.62, and 5.96 eV are detected. The complexity of the absorption pattern finds a correspondence in photoluminescence spectra excited in the 5 eV region: a detailed analysis of the emission spectra as a function of excitation energy indicates the presence of three emission bands centered at 3.91, 4.23, and 4.46 eV, excited at 5.25, 4.83, and 5.03 eV respectively. Excitation in the 5.62 and 5.96 eV absorption peaks does not produce emission. The features of the 4.23 eV and of the 4.46 eV bands are very similar to those of the ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{intrinsic}}$ emission, already well studied in amorphous ${\mathrm{SiO}}_{2}$: this suggests a possible correlation between these bands and the ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{}\mathrm{intrinsic}}$ center. The 3.91 eV band does not find a correspondence in amorphous ${\mathrm{SiO}}_{2}$, and so the responsible defect appears specifically related to the crystalline structure. The emission spectra excited in the E absorption band (\ensuremath{\approxeq}7.6 eV) present a weak band centered at 4.83 eV: its dependence on neutron irradiation dose suggests the attribution to an intrinsic center different from those responsible for the emission in the 3.8 -- 4.5 eV region. \textcopyright{} 1996 The American Physical Society.

X-ray excited luminescence, photoluminescence decay and thermally stimulated luminescence (TSL) measurements have been performed on a selected set of PbWO 4 single crystals. At room temperature the X-ray excited emission spectrum is characterized by two components peaking at about 2.5 and 3.1 eV. The photoluminescence decay indicates the presence of a slow recombination component extending up to a ms timescale and related mainly to the 2.5 eV emission. Different TSL peaks have been observed in the 100–300 K range: direct correlation has been found between integrated intensities of TSL peaks detected above 200 K, the intensity of the slow decay component and steady state emission intensity measured at 2.5 eV. These results suggest that thermal detrapping from TSL traps and free carrier diffusion followed by their radiative recombination at luminescent centers are responsible for the slow decay processes observed.

A wavelength resolved thermally stimulated luminescence (TSL) study has been carried out for the first time on X-irradiated chemical vapor deposition SiO2 films deposited on a silicon substrate, from room temperature, to 400 degrees C. Upon irradiation, the TSL glow curve features a prominent structure at a maximum temperature, T-max, of approximately 62 degrees C (heating rate = 1 degrees C/s); the analysis of the emission wavelength shows a peak at 457 nm (2.71 eV). The shape of the TSL peak is complex, and cannot be described in the frame of classical first- or second-order kinetics. Moreover, T-max has a strong and monotonic shift to higher temperatures after partial pre-heating treatments while the spectral emission is not modified: a similar phenomenon has already been observed in bulk fused silica of various types, different from crystalline quartz which does not present any shift of T-max as a function of pre-heating. These results suggest that the TSL peak is characterized by a distribution of trap parameters: specifically, a continuous distribution of trap energy or of the frequency factor can be taken into account. Considerations on the characteristics of the trap parameter distribution are made.

The effect of prolonged annealing treatments at elevated temperatures (900-1700 K) on the a.c. ionic conductivity of Sawyer PQ 'hydrogen swept' quartz has been investigated by impedance spectroscopy measurements. Transient and irreversible effects have been observed during the annealings: specifically, a monotonic enhancement of the conductivity is detected in the 900-1300 K temperature range, while at higher annealing temperatures an opposite effect is evidenced. The experimental results can be interpreted in the frame of a phenomenological model featuring two equilibrium reactions; an indirect role of hydrogen impurity in the ionic transport dynamics is evidenced, also by means of infrared spectroscopy measurements.

Spectrally resolved thermostimulated-luminescence (TSL) measurements have been carried out on samples of synthetic quartz, submitted to different treatments in order to change the type of charge compensation at the substitutional aluminum sites. Near-infrared (NIR) optical absorption, electron paramagnetic resonance (EPR), and ac ionic conductivity measurements have been performed to monitor the kinetics of defects involved in the treatments. A specific treatment, consisting in a prolonged high-temperature annealing of the samples in vacuum (10 h at 1400 C°, 1 Pa), is shown to reduce the presence of ionic charge compensators at the Al sites and, at the same time, to induce an intense 380-nm TSL, undetected before the treatment. The assignment of the 380-nm emisson to [AlO4]0 centers is proposed and is seen to be in good agreement with a number of experimental results presented so far. © 1995 The American Physical Society.

The ionic conductivity of synthetic quartz (both untreated and ''hydrogen swept''), due to the migration of alkali-metal ions (M(+)) dissociated from [AlO4-M](0) centers, has been investigated in an extended temperature range (550-1700 K) by impedance spectroscopy measurements. Two time-dependent effects, important for the overall interpretative framework, have been observed during high-temperature annealings: (a) during thermal treatments performed in the 900-1300 K temperature range, a monotonic enhancement of the conductivity is detected, more evident in ''hydrogen swept'' samples; (b) thermal treatments in the 1400-1700 K range induce a monotonic decrease of the conductivity. The interpretation of the former effect is based on the indirect role of hydrogen impurity in ionic transport, also supported by infrared spectroscopy measurements on the [AlO4-H](0) centers; the latter effect is attributed to alkali-metal ion desorption. The experimental results are interpreted in the framework of a model featuring two interacting dissociation reactions, of the [AlO4-M](0) and of the [AlO4-H](0) defects, respectively. Following this model, a satisfactory fit of the experimental data is performed, leading to the determination of the dissociation and migration energies of the alkali-metal ions as 1.19 eV and 0.25 eV, respectively.

A comparative and simultaneous study of TSL and TSC above room temperature (20-400 degrees C) has been performed on ''as-grown'' and ''hydrogen-swept'' synthetic quartz crystals. Following X-irradiations, TSL spectra (heating rate = 1 degrees C/s) feature a number of peaks: at 75 degrees C an intense structure is observed (the well-known ''100 degrees C'' peak of quartz); the analysis of this peak obtained by numerical methods has shown that it follows monomolecular kinetics, giving a value of 0.83 eV for the trap depth. Additional peaks are observed at 110 degrees C and 160 degrees C, followed by weaker and less resolved emissions above 200 degrees C. TSC peaks at 80 degrees C, 120 degrees C and 160 degrees C, particularly evident in as-grown samples when measured with the electric field applied along the x-axis, can be associated to the corresponding TSL peaks. However, spectra performed with the electric field applied along the z-axis evidence different features. In as-grown samples a strong and broad peak at approximately 132 degrees C is observed, while hydrogen-swept samples are characterized by two peaks at 180 degrees C and 275 degrees C. Such an anisotropic character, and the fact that no TSL structures are observed in the same temperature range, support the hypothesis of an ionic nature for the latter peaks. TSC ''pre-dose'' measurements of the 75 degrees C peak show that no current enhancement is observed upon irradiation and heating treatment: this result is in accordance with previous radioluminescence and thermally stimulated exoelectron emission experiments and supports the proposed model of the dynamics of this effect.

Thermally Stimulated Luminescence (TSL) and phosphorescence measurements excited by X- and beta rays have been performed above room temperature on fused quartz and on thin SiO2 films deposited on a silicon substrate by the technique of chemical vapour deposition. Although in these types of SiO2 the basic TSL features, noticeably the prominent glow peak at 60 < T < 120°C, are similar to those already studied in quartz, some behaviours are different. Specifically, the maximum temperature of the glow peak shifts linearly to higher temperatures as a consequence of partial pre-heating treatments and the phosphorescence decay shows a t-1 power law. The implications of these results are discussed also in comparison with the corresponding ones of crystalline quartz and with preliminary data on thermally stimulated currents measurements. © 1994.

AC (102-3*105 Hz) measurements have been performed on Sawyer premium-quality synthetic quartz oriented along the z axis, in the temperature range between 240 and 1500 K. The samples were both 'as-received' and X-rayed, in the case of the lower-temperature measurements. The results confirm that the conductivity, in the temperature range considered, is essentially due to extrinsic phenomena, i.e. to the dissociation of Al-Na substitutional centres and to the migration process of alkali ions. An interpretative scheme is proposed, which involves the detailed structure of the attractive potential of Na+ ion in the vicinity of an aluminium impurity and the increase in the radius of the z-axis channels in the beta -quartz-to-tridymite transition.

The cover picture of this issue relates to the article by G. Spinolo et al. on optical absorption spectra of Fe ions in beryl crystals [1]. It shows the low temperature polarized light absorption spectrum of a gem-quality natural aquamarine, i.e. an iron rich beryl. The relevant achievement is that satisfactory attributions of the numerous peaks of the spectrum may be obtained only assuming that both Fe2+ and Fe3+ are substituted for Al in an octahedral oxygen environment. This result excludes the possibility, proposed by several authors, of alternative locations (tetrahedral or “channel“ sites) for iron in beryl. The paper also discusses the ligand-to-metal (probably Fe3+) charge transfer spectrum which was measured in beryl for the first time. The corresponding author Giorgio Spinolo is a Professor of Physics at Milano–Bicocca University, Italy. After early studies on color centers in alkali halides, he became interested in intrinsic optical properties of transition metal halides and later in silica for electronic and photonic applications. Nowadays, his research is devoted to promote a solid state physics approach to study minerals of gemological interest. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The pre-dose effect has been investigated in SiO//2 for various ionizing particles and specifically p, d, alpha , e** minus and X-rays. The general features are qualitatively similar; the effect intensity is however rather different for particles with different specific ionization and changes monotonically with s/ rho . At the same time data on the relative thermoluminescence efficiency (K factor) have been obtained. A microdosimetric approach to the energy release along the track has been considered and the interpretation of the phenomenology in terms of those concepts is discussed.

DC and AC (102-105 Hz) conductivity measurements both parallel and perpendicular to the z-axis have been performed on synthetic quartz (Sawyer PQ) extending the temperature range up to 950° C. In the lower temperature range (250 < T < 500° C) as-received samples show an activation energy for the process of AC conduction in the z-direction, E = 1.32 eV while at higher temperatures (500 < T < 950° C), a lower energy is found, E = 0.67 eV. Experimental results concerning electrodiffused samples (either "vacuum swept out" and "Na swept in") have also been considered. The interpretation proposed for the ionic conduction mechanism is consistent both with AC and DC data, considers a wide T range, and allows a comprehensive view of the ionic transport in quartz. © 1988.

TSL and pre-dose studies on the 110°C peak in quartz crystals and powders put in evidence an anti-correlation between TSL intensity and TSL sensitivity increase. The results together with recent observations on the decay of RT phosphorescence and radiation induced a.c. conductance promote the proposal of a phenomenological model on the dynamics of traps, carriers and luminescent centers responsible for the TSL and the pre-dose effect in crystalline SiO2.

In the thermally stimulated luminescence (TSL) of quartz there is always a glow peak at T=100 °C, whose sensitivity (response to a unit irradiation dose) increases after repeated irradiations followed by heating. This phenomenon, known as predose, has been studied in synthetic quartzes, both as grown and deprived of alkali ions, this latter process being obtained by electrodiffusion (‘‘sweeping out’’). Evidence is given that only unswept or partially swept quartzes show the predose effect. Through the study of the combined effects of irradiation and thermal annealing, following two different procedures, a relation between the formation of Al‐OH− centers and the 100 °C TSL intensity is established. We propose that the enhancement of luminescence happens through the modification of oxygen hole centers from precursors containing hydrogen to peroxy radicals (e.g., O−2 ions) which are responsible for the luminescence. The H+ ions, made available in such a process, are responsible for the Al‐OH− centers formation.

Thermally stimulated luminescence (TSL) studies have been performed on x-irradiated Sawyer PQ quartz, both “as received” and “vacuum swept out”. The variation of the 100°C TSL peak after irradiation and subsequent thermal treatments (pre-dose effect) has been studied as a function of the irradiation temperature.

Single crystals of PbWO 4 have been studied in connection with their application for high energy physics experiments. A comprehensive characterization of PbWO 4 by means of transmission, thermoluminescence and emission spectra measurements will be described. Annealing procedures in the air and vacuum atmospheres at high temperatures were used to study induced changes in the transmission. The gamma radiation induced changes in the absorption spectra of several PbWO 4 crystals of different origin, and intentionally doped will be illustrated.