Optical studies in gamma irradiated Mg doped CaF2 single crystals

Pure and Mg doped CaF2 single crystals grown by the Bridgman method were irradiated with gamma rays (gamma-rays) for doses ranging from 97 Gy to 9.72 KGy. The pristine samples showed minimal absorption indicating the purity of the samples. The gamma-irradiated pure CaF2 crystals showed prominent and strong absorption with a peak at similar to 374 nm besides three weak ones at similar to 456, 523 and 623 nm. However gamma-rayed Mg doped crystals showed a prominent absorption with a strong peak at similar to 370 nm and a broad one at similar to 530 nm. The absorption indicated the generation of F and F-aggregate centers in the irradiated crystals. The photoluminescence (PL) emission spectrum of both pure and Mg doped crystals showed prominent emission at similar to 390 nm when they were excited at similar to 250 nm. Also, when the samples were excited at 323 and 363 nm strong emissions were observed at similar to 430 and 422 nm respectively. The optical absorption and PL intensities were found to increase with increase in dose. (C) 2010 Elsevier B.V. All rights reserved

Spectroscopic studies of γ-rayed CaF2:Sr

Optical absorption spectra of gamma irradiated (γ-rayed) Strontium (Sr) doped Calcium fluoride (CaF2) single crystals showed a prominent absorption peak at ∼370 nm and two weak ones at ∼463 and 524 nm. At higher γ-dose the two weak peaks merged into a broad one at ∼520 nm. The Photoluminescence (PL) spectra showed a prominent emission at ∼394 nm when the crystals were excited at ∼240 nm. The excitation of samples at 370 nm showed strong emission at ∼530 nm with a shoulder at ∼465 nm. The optical absorption and PL intensities were found to increase with γ-dose. However, the optical absorption and PL intensities of CaF2:Sr are found to be less than those of undoped CaF2 single crystals

Morphology and optical properties of Mg and Sr doped CaF 2 nanocrystals

Magnesium (Mg) and Strontium (Sr) doped Calcium fluoride nanocrystals were synthesized by co-precipitation method. The cubic structure of the samples was confirmed by Powder X-ray diffraction. The average crystallite size of Mg doped samples was found to be ~ 25 nm whereas in Sr doped one it was ~ 35 nm. The morphological features revealed that the nanocrystals were agglomerated, crispy and porous. The as-prepared samples showed the presence of hydroxyl groups. The optical absorption spectrum of as-prepared Mg doped samples showed a strong absorption band peaked at ~ 233 nm whereas the Sr doped one showed a prominent absorption peak at 248 nm. A strong PL emission was observed at ~ 300 nm in Mg doped samples. However, the Sr doped samples showed two prominent emissions at ~ 345 and 615 n

Optical absorption and thermoluminescence studies in 100MeV swift heavy ion irradiated CaF 2 crystals

Pure and Ytterbium (Yb) doped Calcium fluoride (CaF2) single crystals were irradiated with 100 MeV Ni7+ ions for fluences in the range 5 × 1011–2.5 × 1013 ions cm−2. The irradiated crystals were characterized by Optical absorption (OA) and Thermoluminescence (TL) techniques. The OA spectra of ion irradiated pure CaF2 crystals showed a broad absorption with peak at ∼556 nm and a weak one at ∼220 nm, whereas the Yb doped crystals showed two strong absorption bands at ∼300 and 550 nm. From the study of OA spectra, the defect centers responsible for the absorption were identified. TL measurements of Ni7+ ion irradiated pure CaF2 samples indicated a strong TL glow with peak at ∼510 K. However, the Yb doped crystals showed two TL glows at ∼406 and 496 K. The OA and TL intensity were found to increase with increase of ion fluence upto 1 × 1013 ions cm−2 and thereafter it decreased with further increase of fluence. The results obtained are discussed in detail

Ion beam induced modifications in electron beam evaporated aluminum oxide thin films

Al2O3 thin films find wide applications in optoelectronics, sensors, tribology etc. In the present work, Al2O3 films prepared by electron beam evaporation technique are irradiated with 100 MeV swift Si7+ ions for the fluence in the range 1 × 1012 to 1 × 1013 ions cm−2 and the structural properties are studied by glancing angle X-ray diffraction. It shows a single diffraction peak at 38.2° which indicates the γ-phase of Al2O3. Further, it is observed that as the fluence increases up to 1 × 1013 ions cm−2 the diffraction peak intensity decreases indicating amorphization. Surface morphology studies by atomic force microscopy show mean surface roughness of 34.73 nm and it decreases with increase in ion fluence. A strong photoluminescence (PL) emission with peak at 442 nm along with shoulder at 420 nm is observed when the samples are excited with 326 nm light. The PL emission is found to increase with increase in ion fluence and the results are discussed in detail

Determination of nitrogen dioxide, sulfur dioxide, ozone, and ammonia in ambient air using the passive sampling method associated with ion chromatographic and potentiometric analyses

Concentrations of nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and ammonia (NH3) were determined in the ambient air of Al-Ain city over a year using the passive sampling method associated with ion chromatographic and potentiometric detections. IVL samplers were used for collecting nitrogen and sulfur dioxides whereas Ogawa samplers were used for collecting ozone and ammonia. Five sites representing the industrial, traffic, commercial, residential, and background regions of the city were monitored in the course of this investigation. Year average concentrations of ≤59.26, 15.15, 17.03, and 11.88 μg/m3 were obtained for NO2, SO2, O3, and NH3, respectively. These values are lower than the maxima recommended for ambient air quality standards by the local environmental agency and the world health organization. Results obtained were correlated with the three meteorological parameters: humidity, wind speed, and temperature recorded during the same period of time using the paired t test, probability p values, and correlation coefficients. Humidity and wind speed showed insignificant effects on NO2, SO2, O3, and NH3 concentrations at 95% confidence level. Temperature showed insignificant effects on the concentrations of NO2 and NH3 while significant effects on SO2 and O3 were observed. Nonlinear correlations (R2 ≤ 0.722) were obtained for the changes in measured concentrations with changes in the three meteorological parameters. Passive samplers were shown to be not only precise (RSD ≤ 13.57) but also of low cost, low technical demand, and expediency in monitoring different locations

Optical studies on lanthanum-doped calcium fluoride

Lanthanum-doped Calcium fluoride (CaF 2) nanoparticles were synthesized by co-precipitation method and characterized by powder X-ray diffraction, Fourier infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), BET surface area measurements, and Optical absorption techniques. The X-ray diffraction pattern showed the cubic phase of fluorite structure. The average crystallite size was found to be ~25 nm. The FTIR spectrum showed the presence of hydroxyl groups in the as prepared sample with two strong IR absorption bands at ~3400 and 1550 cm -1. The morphological features studied by SEM revealed that nanoparticles were agglomerated. Surface area measurements showed porous nature of the nanoparticles. The optical absorption spectrum of γ-irradiated samples showed a prominent absorption peak at ~385 nm and two weak ones at ~218 and 533 nm. The optical absorption was found to increase with increase in γ-dose. © 2011 Springer Science+Business Media, LLC