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Uneven micron-sized pores on the surface of the polycrystalline alumina (Al 2 O 3) substrates can affect their performance as electrical insulating plates. In this study, we investigated the sealing of these pores with amorphous Al 2 O 3 films deposited via atmospheric chemical vapor deposition. Furthermore, we conducted annealing treatments on the samples. The color change of the deposited Al 2 O 3 films was investigated using the Commission Internationale de I'Eclairage color space. Notably, the deposited films initially changed the sample color from white to orange or brown. However, increasing the annealing temperature and duration reversed this discoloration effectively and restored the original white (colorless) appearance of the sample. We measured thermal conductivity using the flame flash method with the H 2 -O 2 flame to assess the influence of sealing. While the unsealed substrate exhibited a thermal conductivity of 4.66 W/mK in the range of 400–500 °C, the annealed and flattened Al 2 O 3 film deposited on the substrate maintained a comparable thermal conductivity of 4.67 W/mK within the same temperature range. This finding demonstrates that our sealing method successfully filled the pores while having minimal influence on thermal conductivity, which is a crucial property for electrical insulation applications. [ABSTRACT FROM AUTHOR]

• Creation of color centers in a LiF crystal by proton irradiation with a SOBP setup. • First successful visualization of proton SOBP via luminescent color centers in LiF. • Proton-beam energy spectrum reconstruction from measured photoluminescence profiles. • Preliminary comparison between SOBPs measured in LiF and expected in water. The 35 MeV proton beam produced by a modular linear accelerator was used to irradiate at grazing incidence a LiF crystal through a spinning Mylar multi-sector range modulation wheel and a Pyrex range shifter. Starting from a measured pristine depth dose curve, these energy-modulation devices were designed to plan a test shallow spread-out Bragg peak in water. The irradiation of the LiF crystal produced in its lattice a volume distribution of color centers, which could be visualized in a fluorescence microscope as a fluorescent image under blue-light illumination. Since the intensity of this fluorescent image was proportional point-by-point to the absorbed energy, it was elaborated to obtain an experimental depth dose curve in the LiF crystal, from which the proton beam energy distribution was estimated. This latter was finally used to evaluate the corresponding spread-out Bragg peak that would be obtained in water and compare it to the designed one. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental observation of two types of stimulated emission (SE) under pulsed laser pumping at 532 nm in diamond with NV centers. A comprehensive spectroscopic characterization of multisectorial HPHT diamond plate was performed. At low pumping power, the stimulated emission from NV¯ centers was recorded as a broad (≥80 nm wide) band with a maximum at 706 nm in the {111} and {311} sectors of the diamond plate. As the pump power increased in the {111} sector, narrow-band stimulated emission (<10 nm wide) was detected, with a maximum at 716 nm and a luminescence impulse duration of 1.5–3 ns. As the pump density increased, a fine structure in the spectrum of narrow-band stimulated emission was revealed for the first time. The concentration of NV¯ centers in the {111} and {311} growth sectors was ≈10 ppm. However, there were considerable differences in the concentrations of C (35 and 3.5 ppm) and C+ centers (6.1 and 3.2 ppm, respectively). It was demonstrated that the presence of a high concentration of NV¯ centers is not the only necessary condition for the initiation of narrow-band SE in the 710–720 nm range. In the {311} sector, lighting at 360, 405, and 488 nm reduced the concentration of NV¯ centers by 15 % while increasing the concentration of C+ centers in the {311} sector. This effect is weak in the {111} sector. The authors suggested a model for narrow-band SE at the transition Valence Band → C+ with charge-state conversion of C↔C+ and NV0↔NV¯ centers. Further research on the dynamic processes is required in order to a detailed understanding of the operation of NV centers in diamond during SE generation. [Display omitted] [ABSTRACT FROM AUTHOR]

The incorporation of impurity atoms into diamonds has been an important issue for the application in the area of electronics, opto-electrics, and quantum optics with color centers. To date, it remains a challenge to explore the impurity distribution in diamond films owing to the low incorporation efficiency. In this work, Si-doped diamond films were deposited in microwave CVD system. Thermal oxidation was employed to selectively etch the non-diamond phase to study the impurity distribution and evolution. For micro-/nano-sized diamond films, the micro-sized grains remain intact, while the diamond nanocrystals are oxidized into porous oxides. The diamond needles exhibit strong silicon-vacancy center optical emission at 738 nm, implying that the Si atoms are incorporated into the lattice. Detailed microstructure characterizations reveal that the porous oxides are crystallized in amorphous state, consisting of silicon, oxygen, and carbon elements. Such abundance of Si in the amorphous porous oxides suggests that the Si atoms segregate at the grain boundaries. Therefore, this work provides a new path to reveal the impurity distribution along diamond crystalline defects. Moreover, the in-situ formed silicon oxide can act as an anti-reflection coating to enhance the optical emission of color centers, which is important for their optical applications. [Display omitted] • A new approach is used to reveal the distribution of impurity atoms in diamond films. • Porous silicon oxides are formed when grain boundaries are oxidized in Si doped diamond films. • It is confirmed that Si atoms segregate along grain boundaries in diamond films. • The in-situ formed oxide film act as an anti-reflection film to enhance the optical collection efficiency of SiV centers. [ABSTRACT FROM AUTHOR]

Diamond synthesis with silicon-vacancy (SiV) color centers is of high interest to nanophotonics and optical quantum technologies. The methods to control and/or maximize concentration of Si atoms incorporated in diamond lattice, and coupled to vacancies, together with improving crystallinity of diamond structure, are in demand. Here, we studied the effect of heat treatment of electron-irradiated single crystal CVD diamond doped with 28S isotope, on evolution of the neutral SiV0 and negatively charged SiV− centers. The crystal subjected to stepwise annealing at temperatures T ann from 200 °C to 1640 °C has been analyzed with photoluminescence (PL) and optical absorption spectroscopies at room and low-temperature (T = 5 K). We found a complex non-monotonous behavior of SiV0 and SiV− intensity both in absorption and PL, with sharp rise at T ann > 600 °C, reaching a maximum concentration peak, decline at 850 °C, and a repeated elevation to higher T ann , reflecting creation and annihilation processes of these defects. Moreover, we detected a group of seven lines of a Si-related defect in the range 828–871 nm, which strongly correlate with annealing dynamics of the SiV− and, especially, of SiV0 centers, and estimated the isotope spectral shift. In parallel, dynamics of other optical centers such as NV, R11 and GR1, in course of the annealing is traced. The controlled annealing opens the way to preparation of the SiV color centers with optimized optical properties, promising for quantum technologies. [Display omitted] • Epitaxial diamond films are doped in situ from SiH 4 by MPCVD to form SiV centers. • Heat treatment of electron-irradiated single crystal diamond in steps up to T = 1640 °C. • Nonmonotonic evolution of SiV0 and SiV− centers with T in luminescence and absorption. • Annealing dynamics of Si-related defect (lines set 828–871 nm) correlates with SiV0. • Isotopic shift between 28Si and 29Si in SiV0 absorption spectral positions. [ABSTRACT FROM AUTHOR]

In order to estimate the stability of the light output of the scintillation detector, the Lu 2 SiO 5 :Ce scintillation crystals, additionally doped with Ca2+ ions at concentrations of 0 ÷ 0.4 at%, were studied. The spectra of optical absorption, gamma-luminescence, thermal luminescence, dose and temperature dependences of luminescence were measured. Gamma-luminescence in the dose range 10 - 5·107 Gy was recorded using 60Co gamma-source at the temperature range of 310–460 K. In contrast to the initial sample (non-doped with Ca), in the sample doped with 0.1 at% of Ca, an increase in the luminescence intensity was observed in the range of 390–425 nm, but further with an increase in the concentration of Ca (0.3–0.4 at%), the intensity of this band decreased to the initial level (undoped). At Ca concentrations of 0.3 and 0.4 at%, the intensity of the Ce1 center band remains practically unchanged up to a dose of 5·107 Gy. LSO crystals doped with Ce 0.1 at% and co-doped with Ca 0.1 at% can be recommended as a scintillation detector up to a gamma-dose of 105 Gy at room temperature. • Ca-codoped Lu 2 SiO 5 :Ce crystals are studied as a material for scintillation detector. • At Ca 0.1 at% an increase in the luminescence at 390–425 nm was observed. • At Ca 0.3 at% the Ce1 center emission doesn't change up to a γ-dose of 5·107 Gy. • Defect complexes completely discolor at room temperature in two days. [ABSTRACT FROM AUTHOR]

The annealing treatment plays a crucial role in tailoring the properties of synthetic diamond materials, especially those doped with various elements in order to form specific color centers like nitrogen-vacancy (NV), silicon-vacancy (Si-V), germanium-vacancy (Ge-V), etc. This study delves into the annealing of 175 μm-thick Ge-doped polycrystalline diamond (PCD) films grown by microwave plasma-assisted chemical vapor deposition (MPCVD). Large-area PCD plate was cut into smaller equivalent 5 × 5 mm2 pieces, which were separately subjected to annealing in microwave plasma in H 2 atmosphere, to annealing in vacuum or to annealing under high-pressure high-temperature conditions (HPHT, 5.9 GPa, 2000 °C). The structure, phase composition and photoluminescence (PL) of samples before and after various annealing processes were investigated. All applied types of annealing enhance both the Si-V and Ge-V lines in PL at room temperature. Increasing annealing temperature leads to gradual decrease of full widths at half-maxima (FWHM) of diamond Raman peak (1332.5 cm−1), as well as Si-V (738 nm) and Ge-V (602 nm) PL peaks. In addition, the limitations for each type of annealing are established. The obtained results are crucial for the design of CVD-grown Ge-doped and Si-doped PCD materials that can be used for applications in photonics such as single photon sources, biomarkers, as well as for the fabrication of optical diamond thermometers. [Display omitted] • Ge-doped PCD film was grown by MPCVD and cut into series of equivalent samples. • Different samples were subjected to different types of annealing: in H 2 plasma, in vacuum, and in HPHT conditions. • The annealing resulted in lowering FWHM of Raman, XRD and PL peaks of samples. [ABSTRACT FROM AUTHOR]

Lithium fluoride doped with Mg and Ti (LiF:Mg,Ti) has been used for several decades as thermoluminescent dosimeter material, but recently also its radiophotoluminescence has been investigated for applications in dosimetry. In this work, LiF:Mg,Ti pellets (TLD-100) were irradiated in a water phantom at CNAO (Pavia, Italy) with therapeutic proton beams at five energies from 70 to 200 MeV in the dose range from 2 to 20 Gy. After irradiation, their visible radiophotoluminescence spectra were measured in controlled conditions and the spectrally-integrated red emission response of radiation-induced color centers has been investigated. The radiophotoluminescence signal, excited by a 445 nm continuous wave laser, was integrated within a 50 nm-wide band around the emission peak of the F 2 color centers, located around 670 nm in LiF. The spectrally-integrated signal of the samples irradiated at the energy of 147.7 MeV exhibited a linear dependence with dose. Moreover, this radiophotoluminescence response appears independent from Linear Energy Transfer in the range from 0.8 to 1.6 keV/μm in all the samples irradiated at the dose of 5 Gy. Such independence was found up to 10.3 keV/μm in samples irradiated within two spread out Bragg peaks made of 36 energy components in the entire investigated proton energy range. The radiophotoluminescence response of the TLD-100 pellets was compared to that of nominally-pure LiF crystals irradiated in the same conditions, which show a similar behavior. The results are encouraging for the exploitation of TLD-100 pellets as passive solid-state radiophotoluminescent dosimeters for proton therapy. • Experimental study of RPL response of TLD-100 irradiated with clinical proton beams. • RPL of F 2 color centers in TLD-100 pellets linear vs dose in 2–20 Gy at E p = 148 MeV. • RPL of F 2 color centers in TLD-100 pellets independent from proton beam energy. • Same RPL behavior measured also in undoped LiF crystals identically irradiated. • Laser-excited visible RPL of TLD-100 promising for dosimetry in protontherapy. [ABSTRACT FROM AUTHOR]

The exploitation of visible radiophotoluminescence in lithium fluoride (LiF) crystals, due to local aggregate point defects produced by ionizing radiation in the crystal lattice, is demonstrated for fluorescent imaging of single tracks of protons at low energies. LiF crystals were irradiated perpendicularly with respect to nearly monochromatic, collimated proton beams at the energies of about 1 MeV in a fluence range from ∼5.8 × 105 p/cm2 up to ∼3.4 × 107 p/cm2 and of about 2.6 MeV in a fluence range from ∼9.6 × 105 p/cm2 up to ∼4.7 × 106 p/cm2. The fluence values were estimated by detecting and automatically counting the tracks on the images acquired with a fluorescence microscope at high magnification; they were found to be in agreement with those obtained using CR39 plastic detectors irradiated under the same experimental conditions. Despite the very short range in matter of these charged particles, by focusing the excitation blue light at discrete depths in the irradiated LiF crystals, an estimate of the proton energies was also obtained. These first results are encouraging for the utilization of LiF crystals as fluorescent nuclear track detectors under typical conditions employed in ion radiobiology. • Imaging of fluorescent tracks of 1 and 2.6 MeV protons in LiF crystals. • Proton beam energy estimated by fluorescent track image analysis at different depth. • Automatic counting of the tracks in the fluorescence images at high magnification. • Beam fluence of 1.4 × 106 p/cm2 in LiF in good agreement with that in CR39 detector. • Fluence in LiF crystals estimated up to 2.2 × 107 p/cm2 without track superposition. [ABSTRACT FROM AUTHOR]

• Kinetics of color centers, being created by swift ions in lithium fluoride crystals, is considered. • Ion track morphology is analyzed, taking into account diffusion and drift of point defects. • Possible mechanism of the track core formation by swift heavy ions is suggested. Radiation defect kinetics modeling is used to describe ion tracks in lithium fluoride crystals. According to the track geometry, suggested model takes into account diffusion currents of point defects and their drift in the temperature and elastic fields, caused by thermal spike. Due to the different dilatation signs of vacancies and interstitials, the induced stress field produces the opposite forces, squeezing out the interstitials, whereas the vacancies are rather confined. Resulting anion depletion in the track center can explain formation of the track core, which was observed with SAXS, chemical etching, AFM and other techniques, for heavy projectiles when the linear energy transfer exceeds a threshold of ~10 keV/nm. The anion interstitials can form aggregates, which were observed with VUV absorption spectroscopy and NMR studies, aside the track center. [ABSTRACT FROM AUTHOR]

We present thermal conductivity measurements of lithium fluoride single crystals irradiated by 710 MeV Bi ions at fluences ranging between 1010 and 1013 cm−2. The thermal transport degradation due to irradiation damage was examined across two depths regions, on nanometer and micrometer scales, by picosecond time-domain thermoreflectance and modulated continuum wave thermoreflectance methods, respectively. The proliferation of swift heavy ion-induced structural defects (color centers) was characterized using optical absorption and photoluminescence spectroscopies. Klemens thermal model was applied to correlate the concentrations of color center defects to thermal conductivity reduction in irradiated LiF crystals. [ABSTRACT FROM AUTHOR]

• In-situ ion beam induced luminescence measurments on LiF. • Insight on F-type centers kenitics and its correlation with the self-trapped exciton. • Evolution of F 3 + and F 2 centers reveals three kinetics stages. • The behavior revealed in LiF may find application in radiation dosimetry/detector. The present work reports the in-situ ion beam induced luminescence measurements using 2 MeV proton excitation of LiF single crystal with the aim of obtaining a further insight on F-type centers kinetics and its correlation with the self-trapped exciton (STE). It is found that the STE luminescence intensity decreases from the beginning of irradiation. While the dose-dependent evolution of F 3 + and F 2 centers reveals three kinetic stages: (i) linear increase from the beginning of irradiation up to 10.1 MGy, followed by (ii) monotonic decrease to 18.1 MGy, and (iii) steady state from 18.1 to 26.2 MGy where the luminescence intensity remains constant. The STE luminescence completely extinguished at high dose; 18.1 MGy in our case. Whereas, the F 3 + and F 2 luminescence persist and remain constant above 18.1 MGy. The latter behavior revealed in the present study can be useful for LiF application in radiation dosimetry and an imaging detector. [ABSTRACT FROM AUTHOR]

• Photoluminescence behavior of color centers in LiF irradiated by 18 MeV protons. • Proton beam imaging by visible photoluminescence of color centers in LiF crystals. • Photoluminescence saturation dose from Bragg curve profiles reconstruction. • Photoluminescence saturation dose from proton beam transversal intensity maps. • Reliable method for proton-beam diagnostics and LiF dose response investigation. The paper concerns the analysis of spatial distributions of visible photoluminescence of optically active F 2 and F 3 + color centers created in lithium fluoride crystals by irradiation with proton beams. Spectrally integrated photoluminescent maps are detected in a fluorescence microscope and numerically elaborated to gather pieces of information regarding both the beam characteristics and the material response. A method based on two independent measurements (Bragg curve and beam transversal map) is developed to evaluate the saturation dose defined as the value above which the photoluminescence intensity begins saturating up to an asymptotic maximum. The paper describes the procedure and demonstrates its application to the experimental case of LiF crystals irradiated by a proton beam of 18 MeV nominal energy. [ABSTRACT FROM AUTHOR]

• The photoformation and separation of charge carriers in traps in VLA titania ceramics and titania powder were examined. • Thermoprogrammed annealing (TPA) spectra of Ti3+ color centers photoinduced in VLA TiO 2 displayed temperature dependencies. • Highest rate of recombination of holes released into the valence band with Ti3+ centers was due to extra charged centers. • Rate of photodesorption of O 2 occurrence in specific channel to activate VLA TiO 2 by photoexcitation of Ti3+ centers. We herein report on the photophysics of color centers in visible-light-active (VLA) rutile titania ceramics and titania powder resulting from the photoformation and separation of charge carriers explored by a diffuse reflectance (DR) spectroscopic and kinetic study using a cryostat-type accessory for a Cary 5000 spectrophotometer after exposure of the titanias to UV radiation and Vis-light illumination. The action spectrum of the photoformation of Ti3+ at 90 K accorded fully with the absorption spectrum of intrinsic defects in the as-synthesized TiO 2. The photoinduced absorption spectra consisted of a set of individual absorption bands attributable to several different Ti3+ centers. Analysis of the dependencies of the photoformation of separate centers on the wavelength of illumination and light exposure provided extraction of specific Ti3+ centers putatively attributed to centers with excess negative charge {2Ti3+ + V o 2+} ⟵→ {Tiδ+ + V o 2+} with 3 > δ > 2 formed at significantly high concentration upon maximal exposure to Vis-light illumination. Thermoprogrammed annealing (TPA) spectra of Ti3+ color centers photoinduced in VLA TiO 2 displayed temperature dependencies of the rate of detrapping of the photoinduced holes observed optically through annihilation of the Ti3+ centers. The TPA spectra in the range 90–500 K consisted of a set of first-order peaks corresponding to the traps, whose depths ranged from ∼0.2 eV (peak at 130 K in powder specimen) to 1.06 eV (peak at 455 K in the ceramics). The highest rate of recombination of holes released to the valence band with Ti3+ centers, an event attributable to the Tiδ+ centers, provided TPA spectra that clearly manifested the existence of shallow traps. We also report mass spectrometric evidence of the photoformation of electrons and holes in VLA TiO 2 under Vis-light illumination through an examination of the photoadsorption of molecular oxygen and the photodesorption of photoadsorbed oxygen from the surface of powdered VLA titania specimens. Moreover, kinetics of the photodesorption of O 2 under orange light illumination, after the photoadsorption of O 2 stimulated by blue light excitation, provided experimental proof of the occurrence of an additional specific channel toward the photoactivation of VLA TiO 2 via the photoexcitation of photoinduced Ti3+ color centers. [ABSTRACT FROM AUTHOR]

Er3+-doped xK 0.5 Na 0.5 NbO 3 -(1-x)Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (x = 0.04, 0.05, 0.06 and 0.07) translucent ceramics have been first prepared by conventional pressureless sintering. Owing to the effective suppression of grain growth induced by both Er3+ and K 0.5 Na 0.5 NbO 3 , the ceramics possess dense and fine-grained microstructure. The XRD patterns demonstrate cubic-like phase structure with minimal optical anisotropy. The ceramics perform good photochormic (PC) properties under 407-nm light irradiation and superior reproducibility after heat treatment (200 °C, 5 min). And PC reaction is responsible for coloration and decoloration processes. The up-conversion photoluminescence before and after irradiation have been studied. With increasing the K 0.5 Na 0.5 NbO 3 content or elevating the sintering temperature of the ceramics, the luminescent quenching degree (ΔR t) gradually increases. The color centers induced by irradiation can be reversibly created or eliminated, resulting in invertible luminescent modulations. This work can guide other multifunctional PC transparent ferroelectric materials for optoelectronic applications. [ABSTRACT FROM AUTHOR]

• Proton-LiF interaction creates color centers that photoluminesce in the visible. • LiF crystals are used as detectors for multienergetic proton beams. • Luminescent Bragg curves in LiF contain information on the proton energy spectrum. • A novel algorithm gives the proton energy spectrum from luminescent Bragg curves. • A novel algorithm gives the proton energy spectrum for target spread-out Bragg peak. In a recent paper, an analytical expression for proton Bragg curves was introduced and utilized to best fit photoluminescent depth distributions of optically active F 2 and F 3 + color centers in lithium fluoride, with the purpose of evaluating the energy spectrum of a proton beam, assumed to consist of the superposition of Gaussian components. Here, an original alternative method is introduced by means of which the same energy spectrum analysis can be performed by iteratively applying a suitable mathematical operator to the photoluminescent depth distribution, no best fitting operation being needed. [ABSTRACT FROM AUTHOR]

• An analytical formula is obtained for proton Bragg curves in LiF. • Simulated proton LET curves in LiF are successfully analytically reproduced. • Proton-LiF interaction creates color centers that photoluminesce in the visible. • LiF crystals are used as detectors for multienergetic proton beams. • Proton energy spectra are estimated from photoluminescence profiles in LiF. An analytical model that approximates Bragg curves due to protons in water is extended to lithium fluoride (LiF), both in bulk and lower-density homogeneous thin film form. To that purpose, Monte Carlo simulations of proton range for energies from 5 to 65 MeV are best fitted so that optimal values of the model parameters are deduced for LiF. Tests are performed by comparing analytically computed Bragg curves with corresponding ones simulated by Monte Carlo software in LiF, bulk and lower density, at two example proton energies and energy-straggling widths. The model is then applied to the reconstruction of the energy spectra of proton beams by best fitting experimental Bragg profiles due to visible photoluminescence of optically-active F 2 and F 3 + color centers created in LiF crystals by the ionizing interaction of protons with the material. [ABSTRACT FROM AUTHOR]

Rate equations are employed to the kinetic description of lattice defects, created in lithium fluoride by ion irradiation. The F centers are assumed to be created in a mobile state (anion vacancies or excited F* centers), having a certain relaxation time to become stable at room temperature. Concentrations of the F centers and their aggregates are analyzed depending on the irradiation conditions and model parameters. Comparison of the swift ion and electron/gamma irradiations using the suggested model captures the prominent experimental results of a higher complex defect fraction, which created under irradiation with the heavier projectiles. [ABSTRACT FROM AUTHOR]

Abstract In the last few years, the peculiar photoluminescence properties of radiation-induced color centers in lithium fluoride (LiF) films have been successfully used for advanced diagnostics of low-energy proton beams produced by the TOP-IMPLART linear accelerator for protontheraphy under development at ENEA C.R. Frascati. The two-dimensional spatial dose map of the transversal section of proton beams was fully reconstructed in a wide interval of doses. In this work the optical emission properties of LiF thin films, grown by thermal evaporation on glass and Si(100) substrates and subsequently irradiated by proton beams of nominal energy 3 MeV at doses higher than 105 Gy, were carefully investigated. Their structural and morphological analyses were performed by X-ray diffraction and atomic force microscopy. A careful comparison of the photoluminescence and photoluminescence-excitation spectra of F 2 and F 3 + electronic defects was performed. Substrate-enhanced photoluminescence intensity increase up to 100% was observed in colored LiF films grown on Si substrates with respect to glass ones. This behavior can be substantially ascribed to the reflective properties of the Si substrate at the emission wavelengths of F 2 and F 3 + CCs, although other complex effects due to the polycrystalline nature of the films cannot be excluded. Highlights • Photoluminescence of color centers in LiF thin films successfully used for advanced diagnostics of low-energy proton beam. • Color centers emission properties investigated in LiF thin films irradiated by 3 MeV proton beams at high doses. • Polycrystalline LiF thin films thermally-evaporated on glass and silicon substrates for low-energy proton beam detectors. • Morphological and structural analysis together with optical investigation by photoluminescence and photoexcitation spectra. • Substrate-enhanced PL up to 100% measured in colored LiF films grown on Si substrates with respect to glass ones. [ABSTRACT FROM AUTHOR]

Abstract Pure and PbF 2 doped CaF 2 crystals were obtained in our crystal research laboratory. The influence of PbF 2 concentration on the color centers induced by γ-and x-rays irradiation were studied. Two broad absorption bands with maxima peaked at 410 and 730 nm appear in the optical absorption spectra; the spectra are quite similar in band structure for all samples and for the both radiation. Different bands showed different responses to the irradiation and to the long-term recovery. The most stable color centers are (F i 0) and the dimer P-P (Pb+(1)-Pb2+). These absorption bands remain stable even for trace amount of Pb2+ ions, so CaF 2 :PbF 2 is not a good material for applications in which the new optical absorption bands are undesirable. Highlights • PbF2 doped CaF2 single crystals were grown by Bridgman technique. • The optical properties of γ and x-rays irradiated crystals were investigated. • The induced color centers depend on the PbF2 concentration and the radiation dose. • The irradiation induced color centers remain stable even for trace amount of PbF2. [ABSTRACT FROM AUTHOR]

Here we report in situ formation of tin-vacancy color centers in microcrystalline and aggregated diamonds synthesized in Sn-C growth system at pressure of 8–9 GPa and temperatures of 1700–2000 K. Bright zero phonon line at 620 nm and a broad line at 660 nm in its sideband were only features in luminescence of the center in single microcrystals at room temperature. Diluting the growth system by lighter chemical elements, such as hydrogen and oxygen, with higher chemical affinity to carbon was shown to prevent doping of diamond with Sn. Synthesis of diamond crystals with SnV center in double Sn-C growth system under pressure is very important for understanding the nature of this new color center as well as perspectives of its practical usage. [ABSTRACT FROM AUTHOR]

Scintillation glass doped with Tb 3+ and Pr 3+ ions with different concentrations were prepared by the melt-quenching method. Optical, photoluminescence and decay kinetic characteristics of the pulse cathodoluminescence (PCL) were investigated. It was shown that the absorption coefficient of the induced absorption in the visible range of the spectrum decreases significantly with the increase of the Pr 2 O 3 content starting from 0.2 to 1 wt%. There was the difference in the luminescence spectra of the glass at a selective and non-selective type of excitation. The “green” emission (λ em = 542 nm, 5 D 4 → 7 F 5 radiative transition of Tb 3+ ions) was excited an electron beam. The “red” emission (λ em = 600 nm, 3 P 0 → 3 H 6 radiative transition of Pr 3+ ion) was observed under selective excitation action (λ exc = 450 nm). It was demonstrated that decreasing of intensity the main bands of Tb 3+ ions at 487, 544, 622 nm connected with increases of concentration Pr 3+ ions. The luminescence decay time of terbium ions at 487, 544, 622 nm emission bands depend on Pr 3+ concentration. The tendency of reducing the luminescence decay time in the main luminescence bands of Tb 3+ ions at increasing the Pr 3+ concentration was presented. The results showed that Tb 3+ / Pr 3+ co-doped phosphate-borate-fluoride glasses are promising non-crystalline scintillation materials. [ABSTRACT FROM AUTHOR]

Optical properties of color centers in diamond have been the subject of intense research due to their promising applications in quantum photonics. In this work we study the optical properties of Xe related color centers implanted into nitrogen rich (type IIA) and an ultrapure, electronic grade diamond. The Xe defect has two zero phonon lines at ∼ 794 nm and 811 nm, which can be effectively excited using both green and red excitation, however, its emission in the nitrogen rich diamond is brighter. Near resonant excitation is performed at cryogenic temperatures and luminescence is probed under strong magnetic field. Our results are important towards the understanding of the Xe related defect and other near infrared color centers in diamond. [ABSTRACT FROM AUTHOR]

Optical absorption, photo-excitation, gamma-ray and thermally stimulated luminescence of a cerium-doped scintillation crystal Lu 2 SiO 5 :Ce were studied prior and after irradiating with fast neutrons fluencies of 1015-5∙1017 cm−2 in reactor, and after gamma-irradiation from 60Co for comparison. It is shown that at neutron fluencies >1015 cm−2 F centers (absorption band 5.2 eV), Ce3+/Ce4+ (4.75 eV) and Ce3+/F + (4.25 eV), as well as Ce4++V O (2.85 eV) and V Lu or V Si (2.3 eV) centers are generated in the LSO:Ce crystal structure. These induced defects are generated more intensively under neutron irradiation than when irradiated with gamma-quanta to dose of 5·107 Gy. Basing on the analysis of the gamma-excited luminescence of Ce3+ centers after various neutron fluencies and the results of thermal and photo impacting, several energy transfer mechanisms were suggested: reabsorption of activator luminescence by color centers, as well as charge capture with the formation of hole and electronic centers. LSO:Ce crystals can be recommended as a scintillation detector of fast neutron up to a fluency of 1016 cm−2 with a gamma-ray up to a dose of 106 Gy. Additional doping of LSO:Ce with Ca2+ ions results in the stabilization of visible optical transparency to gamma-irradiation up to a dose of 107 Gy. • Neutron irradiation of LSO:Ce leads to a decrease of the Ce activator luminescence. • When Ca is introduced the γ-dose up to 107Gy do not change the optical transparency. • Neutron fluency 1015cm−2 generates color centers more effective than γ-dose 5·107Gy. • Annealing of neutron-induced defects recovers the Ce3+ activator gamma-luminescence. [ABSTRACT FROM AUTHOR]

Germanium-Vacancy (Ge-V) color centers in diamond have narrow-band photoluminescence (PL) at room temperature (RT) and attract considerable attention due to their possible application in quantum information technologies, biomedicine, and local optical thermometry. In this work, we used microwave plasma chemical vapor deposition (MPCVD) to synthesize Ge-doped polycrystalline diamond (PCD) films and single-crystal diamond (SCD) epitaxial layers in hydrogen-methane-germane gas mixtures. Thick (>100 μm) layers of both types were grown to analyze their structure and luminescence characteristics. The first demonstration of the absorption of Ge-V centers in both PCD and SCD materials at low temperatures is presented. The sufficient narrowing of the Ge-V PL line for the SCD sample in comparison with the PCD sample was observed. On the other hand, the intensity of the Ge-V signal was an order of magnitude higher in the PCD sample compared to the SCD sample. A set of single Ge-V centers formed during CVD has been demonstrated. The results obtained can be used to manufacture and design various photonic devices based on Ge-V color centers. [Display omitted] • Synthesis of Ge-doped poly- and monocrystalline diamond is realized by MPCVD using GeH 4 impurity source. • Ge-V color center formation is evidenced both in photoluminescence and absorption spectra. • Single Ge-V emitters are detected in the plasma-thinned Ge-doped diamond layers. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (hBN) is promising for applications in neutron detection and quantum sensing. Here we created spin-dependent luminescence defects in hBN using 50 keV helium ion beam. The irradiated hBN flakes with a dose around 2 × 1014–1 × 1015/cm2 have the maximum photoluminescence (PL) intensity. The PL spectra are in the range of 700–1000 nm with a peak around 818 nm at 297 K after irradiation with a dose of less than 2 × 1014/cm2, which can be eliminated by high temperature annealing at 1097 K due to defects repair according to Raman spectra. However, the PL peaks exhibit a redshift from 818 nm to 830 nm when the irradiation dose is no less than 1 × 1015/cm2. Combining with constrained density functional theory calculations, it is found that high dose irradiation can cause local lattice swelling and further induce the redshift of PL spectra by 12 nm/0.33% strain. Furthermore, we proposal a novel optical neutron detection method by recording the intensity and position of PL signal of luminescence defects induced by neutron-10B nuclear reaction daughter particles. This work would be helpful to create luminescence defects in hBN for quantum sensing, and develop a novel neutron detector. • The optimum irradiation dose for fabrication of color centers in hBN is obtained. • Irradiation swelling effects on PL of V B −1 color centers in hBN are identified. • The ODMR contrast of V B −1 defects in hBN is as high as 4%. • High temperature annealing at 1097 K can repair V B −1 color centers in hBN. • Proposing an optical neutron detection method based on luminescence defects. [ABSTRACT FROM AUTHOR]

The existence of thermally induced diffusion of F 2 + centers was shown by measuring the coefficient of optical absorption dichroism of gamma-irradiated LiF crystals. An elementary act of diffusion is a rotation of an F 2 + center with the shift of one of the vacancies in the neighbor lattice site, thus, there is a displacement of the center as a whole. The measured activation energy of rotation is 1.0 eV, which is in a good agreement with the energies of​​ the activation process of F 2 + centers thermal destruction obtained before. [ABSTRACT FROM AUTHOR]

Halites are one of the interesting material due to its color variations. Natural halites whose color ranges from transparent to dark blue were studied by UV–VIS and Raman spectroscopy. The halite crystals were irradiated with 3 MeV proton micro-beam (∼20 μm beam width with ∼80 PA beam current) for 10 and 90 min to study the radiation damage. After 10 mins of irradiation, small spot developed on the surface of transparent halite crystal whereas after 90 mins of irradiation the spot spread inside the bulk leading to a brown coloration (20 µm initial size to ∼2.0 mm final size). The irradiated portion and the un-irradiated portion of the halites was characterized by Raman spectroscopic technique. The variation in the population density was observed from the UV–Vis spectra. The change in the Raman band intensities was observed for transparent, blue colored and proton beam irradiation halites. Such variation of spectroscopic characteristics due to proton irradiation suggests that the halite can be used for the radiation monitoring. [ABSTRACT FROM AUTHOR]

Parameters of point defects halos ( F -color centers) created due to decays of self-trapped valence holes generated in nanometric vicinities of trajectories of gold ions of 275 MeV and 2187 MeV in LiF are estimated in absorption spectroscopy experiments. Such ions have approximately the same electronic stopping: 24.6 keV/nm and 22.9 keV / nm, respectively. In contrast to the usual concept of the velocity effect that a slower ion produces larger structure changes due to a higher density of the deposited energy, the opposite effect occurs for the defect halo revealing a larger radius and a larger defect concentration for an ion of the higher velocity realizing the same energy loss. Spatial spreading of generated valence holes before their self-trapping (500 fs) forms the size of the defect halos around the trajectories of the applied ions. Simulations with Monte-Carlo code TREKIS show no significant difference in the initial spatial distributions of these valence holes by the times of finishing of ionization cascades (∼10 fs after the projectile passage) within the radii of the defect halos deduced from the experiments. Using these distributions as initial conditions for spatial spreading of generated valence holes and taking into account the difference between the defect halo radii, the diffusion coefficients of these holes near the trajectories of 275 and 2187 MeV Au ions in LiF are estimated showing about six times larger value in tracks of the faster ion for irradiations at room temperatures. Presence of H -color centers changes considerably the kinetics of the created defect ensemble in the defect halo resulting in differences between the defect halo parameters in LiF crystals irradiated at 8 K vs. 300 K. [ABSTRACT FROM AUTHOR]

Crystal growth and structure solution of new Ba 3 (BO 3 ) 2– x F 3 x solid solution with x = 0.2 ( Pbam , a = 13.60119 Å, b = 13.65014 Å, c = 14.87279 Å) were performed. The solved structure demonstrate an unusual for borates feature – the presence of [Ba 12 (BO 3 ) 6 ] 6+ cation pattern with channels filled by disordered anions. We identify the same cation pattern also in two recently described LiBa 12 (BO 3 ) 7 F 4 and NaBa 12 (BO 3 ) 7 F 4 borates, where additional (LiF 4 ) 3– and (NaF 4 ) 3– anionic clusters are situated inside the channels as well. The unit cell metrics of the new solid solution fits well that reported for Ba 3 (BO 3 ) 2 compound, indicating that the latter may represent the orthoborate end-member of Ba 3 (BO 3 ) 2– x F 3 x . [ABSTRACT FROM AUTHOR]

Mixed garnet crystals with nominal stoichiometry Gd 3 Al 2.5 Ga 2.5 O 12 undoped, single doped with Sm 3+ , Ho 3+ , Er 3+ and Yb 3+ and co-doped with Ho 3+ + Yb 3+ and Er 3+ + Yb 3+ were grown by the Czochralski method. Optical spectra and thermal conductivity of obtained single crystal samples were measured and analyzed. Recorded optical absorption spectra revealed that the intensity and spectral characteristics of color centre absorption in the UV region, close to the UV absorption edge of the host, are affected by the type of incorporated rare earth ions. On the other hand, spectral characteristics of stable color centers induced by an intense UV irradiation of crystals depend weakly on the rare earth admixture. Low temperature optical spectra provided the evidence that Sm 3+ ions and Er 3+ ions occupy at least two different types of sites in this host but Yb 3+ ions seem to be located preferentially in identical sites. Thermal conductivity of the crystals at 300 K, weakly affected by incorporated rare earth ions, is comparable to that reported for ordered gallium gadolinium garnet crystals. At cryogenic temperatures, i.e. below ca 80 K, thermal conductivities of the crystals containing rare earth ions are markedly smaller than that of undoped one, however. [ABSTRACT FROM AUTHOR]

In this paper, we present the thermoluminescence and optical absorption studies of Dy-doped LiF phosphors. The phosphors were synthesized via co-precipitation method, in which the reactions were carried out at fixed pH value 8.00. X-ray diffraction (XRD) patterns revealed single phase structure of phosphors up to concentration (0.04 mol%) of Dy in the host lattice of LiF. The field emission scanning electron microscope (FE-SEM) images showed micro-cubical morphologies. The incorporation of Dy in LiF was confirmed from the results of electron dispersive spectroscopy (EDS) and XRD. The thermoluminescence (TL) glow curves of γ-irradiated samples in the dose range (0.1–50 kGy) revealed a main dosimetric glow peak positioned at 417 K. Moreover, at irradiation dose of 10 kGy and above, a broad TL band towards higher temperature side of main dosimetric peak also appeared. Using TLanal program, the complex TL glow curves were deconvoluted and TL kinetics parameters namely; the activation energies, frequency factors and order of kinetics were evaluated. The results revealed the formation of additional localized trapping sites of different values of activation energy and frequency factor in the forbidden band. The optical absorption study revealed the formation of radiation induced stable color centers (CCs) at room temperature. The concentrations of CCs were evaluated using Smakula's formula. [ABSTRACT FROM AUTHOR]

Thermodynamically stable α- MoO 3 thin film is prepared without any other phases of the molybdenum oxides. Simple and low coast spray pyrolysis technique is used. Growth conditions are optimized to produce pure α- MoO 3 with controlled crystallite size and surface morphology. Small angle (GAXRD) diffractometer is used to elucidate the structure. Profile shape function (PSF) model is made for the experimental data. WinFit software is going first to fit (PSF) to use the refined profile parameters for determination of crystallite size and internal residual strain. The (GAXRD) patterns prove the existence of α- MoO 3 only with layered structure, indicated by the appearance of only (0k0). The calculated crystallite sizes and the strain are found to range from 10 to 28 nm and 0.28%–0.05% respectively. Ultraviolet and Visible transmission measurements were performed over a wavelength range 190–2500 nm on the MoO 3 thin films synthesized by spray pyrolysis technique at different substrate temperature. The two sub-bands corresponds to the electronic transition between the molybdenum oxidation states Mo 4+ , Mo 5+ and Mo 6+ are observed. Quantitative information on the temperature-induced blue shift of the sub-bands was obtained by fitting the spectra with Lorentz functions. The transition from Mo 5+ to Mo 6+ oxidation states show a blue shift up to Tc = 325 °C. Above Tc, the transition Mo 5+ to Mo 6+ increases more drastically, resulting in an anomaly in the temperature-induced shift at Tc. The anomaly can be attributed to the amorphous-to-crystalline phase transition at 325 °C. In addition, both refractive index and extinction coefficient are calculated as a function of substrate temperature. [ABSTRACT FROM AUTHOR]

A laser can operate in regular but also in nuclear ionizing radiation environments. This paper presents the results of a real time measuring method used to detect the laser induced damage threshold (LIDT) in the optical surfaces/volumes of TEMPAX borosilicate glasses operating in high gamma rays fields. The laser damage quantification technique is applied by using of an automated station intended to measure the damage threshold of optical components, according to the International Standard ISO 21254. Single and multiple pulses laser damage thresholds were determined. For an optical material, life time when it is subjected to multiple pulses of high power laser radiation can be predicted. A few ns pulses shooting laser, operating in regular conditions, inflects damage to a target by its intense electrical component but also in a lower manner by local absorption of its transported thermal energy. When the beam is passing thru optical glass elements affected by ionizing radiation fields, the thermal component is starting to have a more important role, because of the increased thermal absorption in the material's volume caused by the radiation induced color centers. LIDT results on TEMPAX optical glass windows, with the contribution due to the gamma radiation effects (ionization mainly by Compton effect in this case), are presented. This contribution was highlighted and quantified. Energetic, temporal and spatial beam characterizations (according to ISO 11554 standards) and LIDT tests were performed using a high power Nd: YAG laser (1064 nm), before passing the beam through each irradiated glass sample (0 kGy, 1.3 kGy and 21.2 kGy). [ABSTRACT FROM AUTHOR]

The commented article contains numerous errors. The presentation of experimental data is slipshod and biased. They are not credible. The author had no reason to write about the scientific achievements outlined in the sections Abstract and Conclusion. One of the main conclusions of the work, that the author for the first time experimentally observed relation between orbital angular momentum of femtosecond laser radiation and induced by this radiation helicity of the tracks in crystals, has not been confirmed by direct check experiments. No orbital angular momentum of the exciting radiation nor the twisted tracks has been observed in the experiments. Other conclusions are also baseless. [ABSTRACT FROM AUTHOR]

• In this paper the role of point and complex, intrinsic and extrinsic defects on the electronic structure and thermodynamics of LiF:Mg have been investigated by density functional theory. • The role of these defects in luminescence has been analyzed. • the defect complex formed by an Mg impurity with an adjacent F vacancy capturing two electrons, which forms a Z 2 center, cannot contribute to thermoluminescence or to luminescence in general. • These findings suggest that to maximize the thermoluminescence response, it would be important to maximize the number of Mg atoms isolated from F vacancies. Thermoluminescence properties of the most widely used thermoluminescence dosimeter, namely LiF: Mg, Ti, are controlled by the concentration of the Mg dopant. The origin of the thermoluminescence peaks and the optical absorption peaks of irradiated LiF: Mg is still not fully understood. In this work, the role of point and complex, intrinsic and extrinsic defects on the electronic structure and thermodynamics of LiF: Mg has been investigated by DFT. The calculations show that the defect complex formed by an Mg impurity with an adjacent F vacancy capturing two electrons, which forms a Z 2 center, cannot contribute to thermoluminescence or to luminescence in general. The reason is an induced Stark effect that shifts the defect states into either valence or conduction bands. These findings suggest that to maximize the thermoluminescence response, it would be important to maximize the number of Mg atoms isolated from F vacancies. Graphical Abstract. [Display omitted]. [ABSTRACT FROM AUTHOR]

- Electron irradiation of silver containing zinc phosphate glass - Electron irradiation of silver containing sodium gallo-phosphate glass - Cathodoluminescence of silver containing phosphate glasses - Electron Spin Resonance (ESR) of silver containing phosphate glasses - Luminescence spectroscopy of color center in irradiated silver containing phosphate glasses. - Effect of glass matrix structure on the glass photosensitivity In the present work, the effect of electron irradiations on silver-containing phosphate glasses using a 2.5 MeV electron beam has been explored by Electron Spin Resonance (ESR) and luminescence spectroscopy. The process involved in the interaction of electron beam with both the silver-containing and silver-free phosphate glass matrix and the formation of colored centers is discussed. This allowed an understanding of the initial phenomena of electron deposition and charge trapping that supports the photosensitivity of these glasses by identifying the point defects and the Ag species. The effect of the silver concentration and the structure of the glass depending on the integrated dose have been investigated. The in-situ cathodoluminescence measurements give additional valuable information about the cascade of chemical reactions in the formation of new silver species, namely from the initial silver ions to the molecular silver clusters. [ABSTRACT FROM AUTHOR]

Color center creation in LiF crystals irradiated with 12 C, 14 N, 40 Ar, 84 Kr, and 130 Xe MeV ions were studied as a function of the absorbed energy (fluence). For light ions ( 12 C, 14 N) the saturation of single F centers takes place at higher absorbed energy (5 × 10 23 eV/cm 3 ) than that for 40 Ar, 84 Kr and 130 Xe ions (∼10 23 eV/cm 3 ). The saturation concentration of F centers for 12 C and 14 N (2 × 10 19 cm −3 ) is twice of that for the heavier ions. Further irradiation with light ions decreases concentration of F centers, presumably due to aggregation, whereas for heavy ions the saturation concentration remains approximately the same that can be explained by much stronger recombination losses within single tracks. [ABSTRACT FROM AUTHOR]

Nanostructure formation by single slow highly charged ion impacts can be associated with high density of electronic excitations at the impact points of the ions. Experimental results show that depending on the target material these electronic excitations may lead to very large desorption yields in the order of a few 1000 atoms per ion or the formation of nanohillocks at the impact site. Even in ultra-thin insulating membranes the formation of nanometer sized pores is observed after ion impact. In this paper, we show recent results on nanostructure formation by highly charged ions and compare them to structures and defects observed after intense electron and light ion irradiation of ionic crystals and graphene. Additional data on energy loss, charge exchange and secondary electron emission of highly charged ions clearly show that the ion charge dominates the defect formation at the surface. [ABSTRACT FROM AUTHOR]

Mg 2 BO 3 F:Dy phosphor is a low Z material with an effective atomic number 9.92. This phosphor was synthesized by two different methods, because the solid state method failed to produce single phase Mg 2 BO 3 F:Dy phosphor. This study reports a comparative investigation of γ-ray and C 5+ ion beam impact on thermoluminescence (TL) properties of Mg 2 BO 3 F:Dy phosphor. TRIM/SRIM calculations were performed to correlate the changes in TL properties of Mg 2 BO 3 F:Dy phosphor. Phosphor possesses good TL response towards γ-rays as well as C 5+ ion beam irradiation. TL glow curves of the C 5+ ion irradiated phosphor show a small shift in the position of the glow peaks towards the lower temperature side. With an increase in energy of the ion beam increase in TL intensity was observed. This increase in the TL efficiency with a decrease in linear energy transfer (LET) agrees well with the results reported in literature. Trapping parameters of the γ-ray and C 5+ ion beam irradiated phosphor were calculated from the TL data using computerized glow curve deconvolution method. The trapping analysis suggests that ion beam irradiation causes only minor changes in the activation energy. The different types of defects responsible for TL glow curves were identified using the EPR technique. [ABSTRACT FROM AUTHOR]

We present a theoretical study of the impact of oxygen diffusion in oxide crystals on the dynamic changes of metal dopants in the ionic state, and on the crystal conduction type. The analysis invokes ambipolar diffusion for all participating species: oxygen vacancies, metal dopant, holes and electrons. The species dynamics are demonstrated for an oxide of 8 eV energy gap, electron and hole diffusivities being 10 5 times larger than the oxygen vacancy one, and the dopant energy level being 1.0 eV above or 1.0 eV below the mid-gap. We obtain linkage between the oxygen chemical diffusivity and the occurrence of a reaction front. The necessary condition is the existence of a sufficiently long interval, where a power dependence of the oxygen chemical diffusivity on the ambient oxygen pressure exists. In our demonstrated system, prominent reaction fronts occur at very low and at very high ambient oxygen pressures. The fronts relate to the reversible M Me × + e ′ → ← M Me ′ reaction at the low pressures, and to the reversible M Me ′ + h • → ← M Me × reaction at high pressures, where M marks the dopant metal, and Me marks an oxide lattice constituent metal. In the mid-pressure interval, the oxygen chemical diffusivity is approximately constant, being several orders of magnitude smaller than the oxygen vacancy diffusivity. [ABSTRACT FROM AUTHOR]

The periodic filamentation patterns across and along laser channel tracks, induced by high-intensity femtosecond laser pulses in magnesium and sodium fluoride crystals, have been disclosed. The patterns are rationalized by deterministic vectorial effect, difference in propagations of linearly- and circularly-polarized laser pulses, and appearances of the orbital angular momentum of the light beams due to optical astigmatism. [ABSTRACT FROM AUTHOR]

The dependence of Ca 2 V 2 O 7 :Eu 3+ photoluminescence on the crystal structure was discussed experimentally and theoretically. The important chemical parameters, especially, standard deviation of the bond environmental factor were calculated firstly. Two broad excitation bands with the peaks at 311 and 400 nm covering from 250 to 475 nm and two different types of f–f transition–emission of Eu 3+ can be found. Detailed discussion demonstrated that two different emission mechanisms exist in Ca 2 V 2 O 7 :Eu 3+ : (1) was from the Eu1 3+ ions occupying the Ca1 sites and (2) was from the Eu2 3+ ions in the Ca2 sites. The energy transfer was in two ways: one was from O–V1 charge transfer (CT) to Eu2 and another was from O–V2 CT to Eu1. [ABSTRACT FROM AUTHOR]

The kinetics of color-center formation and decay in electron-irradiated cubic yttria-stabilized zirconia (ZrO 2 : Y3+) has been followed by on-line UV/Vis absorption spectroscopy. The growth and decay with time of absorption spectra have been measured upon electron irradiation and subsequent beam shut-off for energies of 0.8, 1.0, 1.75, and 2.5 MeV. Spectra have been fitted with two broad absorption bands centered at about 3.0 eV and 3.8 eV for high beam current intensity. These bands are assigned to so-called T-centers, i.e. Zr3+ ions in trigonal point symmetry, which are produced by ionization processes induced by either photon irradiation or charged particle irradiation. A red-shift of the absorption spectra is observed for lower current intensities irrespective of electron energy: these spectra have been fitted with two broad absorption bands centered at about 3.0 eV and 3.3 eV. This modification is attributed to a change in the local environment of Zr3+ ions due to the formation of neighboring oxygen vacancies by elastic collisions, which depends on the electron energy and flux. A common behavior of an increase in differential absorbance to similar saturation values after accumulation of the irradiation dose and decays with time to similar non-zero asymptotic values has been observed, irrespective of the electron energy and flux. However, the rise time and lifetime deduced from the growth and decay curves of the absorbance are dependent on the electron energy. The increase and saturation of the T-center growth rate with electron energy can be attributed to competitive channels of hole trapping at the oxygen and zirconium vacancies induced by elastic collisions. The present on-line experiments reveal the complex process of point-defect generation resulting from the interplay of displacement damage and electronic excitation. • Color centers induced by electron irradiation in yttria-stabilized zirconia (ZrO 2 : Y) single crystals is studied by on-line optical absorption spectroscopy in the UV–visible range. • Point-defect growth and decay is followed for electron energies ranging between 0.8 and 2.5 MeV. • Absorption bands near 3.3 eV are assigned to the so-called T-center, i.e. Zr3+ ions in a trigonal point symmetry induced by electronic excitations. • The increase of the T-center growth rate versus electron energy is correlated with the free hole trapping on the Zr and O vacancies induced by elastic collisions. [ABSTRACT FROM AUTHOR]

The photostimulated luminescence (PSL) properties of the phosphor BaFBr:Eu after ion beam irradiation was analyzed; in particular, the PSL intensity dependent on ion fluence. The PSL intensity increased linearly with the ion fluence up to 10 12 ions/cm 2 , and subsequently decreased gradually. The ion fluence dependence was observed to be similar among samples containing different F centers or different Eu concentrations. The fluence dependence was quantitatively analyzed based on a trapping model, in which competition between the trapping processes to storage centers and radiation defects is assumed; the model explained the experimental data quantitatively. The results indicate that radiation defects influence the PSL properties via the trapping of photostimulated electrons. [ABSTRACT FROM AUTHOR]

Abstract: The photoluminescence technology previously employed to investigate the boron distribution of type IIb diamond has now been applied to study the nitrogen distribution of type Ib diamond. All growth sectors were clearly distinguished by the characteristic colors and the brightness of the synthetic Ib diamond's cathodoluminescence topography. As a measure of the concentration of nitrogen impurity, the nitrogen-vacancy luminescence gave relative concentrations in different growth sectors as: the {111} sector was the highest, followed by the {311}, {100} and {511} sectors. The results were reconfirmed by the evidence of the broadened and strengthened zero phonon lines of nitrogen-vacancy center with the increase of nitrogen concentration of type Ib diamond. [Copyright &y& Elsevier]