Photodegradation of nitrobenzene using 172 nm excimer UV lamp

Photodegradation of nitrobenzene (NB) using an excimer UV lamp at a wavelength of 172 nm is investigated. Experimental results show that high concentration nitrobenzene can be efficiently degraded with irradiation by excimer UV lamp, and confirm that degradation of nitrobenzene is more efficient by UV/H(2)O(2) combination than UV only. In the case of using UV only, 60 min of treatment was found to be sufficient to degrade the major part of NB solution with a concentration of less than 4mM. In the case of using the combination of UV/H(2)O(2) with a H(2)O(2) concentration of 7:1 molar ratio to NB, 4.07 mM NB solution drastically decreased to 0.41 mM after treatment for only 20 min. Degradation intermediate products are identified by analyzing the degradation products with GC/HRMS and possible degradation pathways of nitrobenzene are suggested.     

Shortwave krypton-bromine excimer low-pressure lamp

The emission characteristics are reported for a small short-wavelength (UV) lamp filled with a krypton-bromine mixture and pumped by longitudinal glow discharge at a 100-mm distance between electrodes in a quartz tube with an internal diameter of 14 mm. The emission spectrum is formed by the resonance atomic lines of bromine (163.3 and 157.6 nm) and the molecular lines of bromine (Br₂) and krypton bromide (KrBr). An increase in the partial pressure of bromine in the working mixture from 50 to 270 Pa is accompanied by a decrease in the intensity of emission lines due to atomic bromine and leads to the formation of VUV-UV continuum based on the molecular bands due to Br₂ and KrBr. The operation regime was optimized with respect to the glow discharge current and the gas mixture pressure and composition. The optimum partial pressure of krypton is within 500–800 Pa, and that of bromine vapor is within 100–250 Pa. The average total VUV-UV output radiation power reached 5 W at an efficiency of 8–10%.     

An effective high-power KrCl excimer barrier-discharge lamp

The effect of the pumping pulse power and shape on the discharge character and the efficiency of emission from KrCl* molecules (λ∼222 nm) is studied. In the coaxial quartz tube KrCl excimer lamps excited by a barrier discharge, the maximum emission efficiencies are observed for a discharge in the form of diffuse cones. Based on these results, an excimer lamp with an average output power of up to 100 W is created.     

PTTL method applied to UV radiation detection during refractive surgery using excimer laser

The method of phototransferred thermoluminescence (PTTL), using CaSO(4):Dy pellets produced at IPEN as sensitive material, was used to detect the spread laser radiation inside the surgery room during refractive surgical procedures using ArF excimer lasers. The purpose of this work was to study the viability of performing the ultraviolet radiation (UVR) exposure detection of patients and the hospital's surgical staff during a refractive surgery. The CaSO(4):Dy pellets were positioned at different distances from the laser source inside the surgery room: patient's ( congruent with 0.15 m), surgeon's ( congruent with 0.5 m) and nurse's ( congruent with 1.0 m) foreheads, lateral ( congruent with 1.5 m) and back ( congruent with 4.0 m) walls. The measurements of PTTL were carried out at two different conditions: five surgeries, each one taking approximately 10 min, and during a period of 4 h (cumulative), when several operations were performed. The detectors positioned as far as 4.0 m from the UV laser source were sensitised, making the UVR detection feasible at large source-detector distances. The absorbed energy was detected in the range from 40 microJ to 30 mJ during a surgery. This result indicates that the method studied can be used to detect the spread UVR.     

Excited nitrogen molecule formation in a DC-glow-discharge-pumped excimer lamp

The plasma in an excimer lamp operating in the λ=258 nm [Cl₂(D′-A′)] and 175 nm [ArCl(B-X)] modes using an Ar-Cl₂ gas mixture excited with a longitudinal dc glow discharge was studied by the method of spectroscopic diagnostics. In the presence of small air admixtures (P≤30 Pa) in the working medium, the plasma exhibits the formation of excited nitrogen molecules decaying with the emission of molecular bands in the 193–271 nm wavelength range. The emission intensities of both molecular and excimer bands were measured and the conditions were determined under which the excited nitrogen molecules most significantly affect the optical characteristics of the discharge.     

The dynamics of annealing of ion-amorphized silicon by nanosecond pulses of excimer laser UV radiation

Phase transitions in ion-amorphized silicon annealed by nanosecond UV radiation pulses of an ArF excimer laser were studied by time-resolved reflectivity measurements at λ=633 nm. It was established that epitaxial crystallization of a melted layer of silicon takes place at a laser energy density of W < 0.8 J/cm². At 0.2 J/cm² < W < 0.7 J/cm², silicon exhibits amorphization in the course of solidification, the initial and final amorphous phases being different. This amorphization of solidifying silicon is accompanied by the nucleation of separate crystallization centers. The presence of such centers changes the kinetics of phase transformations in the course of repeated laser action, leading to the formation of a polycrystalline structure, and provides for the possibility of obtaining intermediate crystallization states of Si in a sequence of laser-induced phase transitions.     

Analysis and fabrication of minifeature lamp lens by excimer laser micromachining

A variety of shapes of lamp lenses at the feature millimeter scale have been extensively used in lamp design. To further improve the light efficiency and to reduce the overall dimension of lamps, the lamp lens at the micrometer scale is fabricated by excimer laser cross scanning on a polycarbonate sheet. To verify the proposed method, the influence of an optical system with various shapes and sizes of lamp lenses on the light efficiency is explored in advance by ASAP optical software. The lens with a miniature feature can produce a smaller divergence angle than that with a large-size lens feature. The experiment is carried out at varying laser operating parameters, mask shape, and dimensions. The simulation shows that the desired lamp lens profile can be effectively produced by excimer laser micromachining.     

Comparison of TLD algorithms for monochromatic fluorescent radiation and continuous spectrum X rays

A personal dosimetry system is required to measure the personal dose equivalent accurately in a wide range of radiation fields. However, the dose evaluation algorithm at the Korea Atomic Energy Research Institute (KAERI) has been developed with the spectral X ray fields described in the American National Standards Institute (ANSI) Standard N13.11 and the actual fields to be monitored may be significantly different from these. To evaluate the dose more accurately when workers are exposed to non-ANSI N13.11 radiation fields, a dose evaluation algorithm using monochromatic radiation (monochromatic algorithm) was developed using the experimental data of the energy responses of CaSO4:Dy thermoluminescent materials irradiated by monochromatic fluorescent X ray fields recently established at KAERI; this was compared with another algorithm developed on the basis of the ANSI N13.11 continuous spectrum X ray fields (spectrum algorithm). The paper concludes with discussions about some results of the algorithm test, including mixed field irradiation and angular response, conducted in an International Atomic Energy Authority/Regional Cooperation of Asia (IAEA/RCA) intercomparison study.     

Effect of argon buffer and the UV preionization regime on the electric-discharge XeCl laser parameters

The gas discharge and output radiation parameters were studied in XeCl lasers with various buffer gas compositions (argon vs. neon) and different types of excitation regimes (fast vs. quasi-stationary) in the preionization source. The intervals of specific energy for the neon-and argon-based buffer gas mixtures are 10–125 and 45–360 J/(l atm), respectively. The specific parameters of radiation in the neon-and argon-based buffer gas mixtures depend on the energy required for the UV preionization. For high-power UV preionization sources, the output parameters of lasers using argon-based gas mixtures may exceed those obtained with neonbased mixtures.     

Compact fluorescent lamp phosphors in accidental radiation monitoring

The application of lamp phosphors for accidental dosimetry is a new concept. Since the materials used in fluorescent lamps are good photo luminescent materials, if one can either use the inherent defects present in the phosphor or add suitable modifiers to induce thermoluminescence (TL) in these phosphors, then the device (fluorescent lamp) can be used as an accidental dosemeter. In continuation of our search for a suitable phosphor material, which can serve both as an efficient lamp phosphor and as a good radiation monitoring device, detailed examination has been carried out on cerium and terbium-doped lanthanum phosphate material. A (90)Sr beta source with 50 mCi strength (1.85 GBq) was used as the irradiation source for TL studies. The TL response as a function of dose received was examined for all phosphors used and it was observed that the intensity of the TL peak vs. dose received was a linear function in the dose range 0.1-200 Gy in each case. Incidentally LaPO(4): Ce,Tb is a component of the compact fluorescent lamp marketed recently as an energy bright light source. Besides having very good luminescence efficiency, good dosimetric properties of these phosphors render them useful for their use in accidental dosimetry also.     

Photoresonant ionization of gaseous media by excimer laser radiation

An identification is made of twenty five elements whose resonance lines overlap the emission lines of high-power pulsed ultraviolet gas lasers or lie in the immediate vicinity of them, so that the mechanism laser ionization based on resonance saturation (LIBORS) can be used to ionize the vapor of these elements. Resonance transitions of atoms and ions excited by the same laser (by krypton fluoride and xenon fluoride lasers, respectively) are observed for tantalum and uranium. It ishas been suggested that these elements may be used as “catalysts” for “ catalytic” resonance ionization (CATRION) of dense multicomponent gas mixtures. Experiments have been carried out to study the krypton fluoride laser irradiation of expanding vapor clouds of different elemental composition, created by the evaporation of targets with a ruby laser. Photographs obtained with an image converter, measurements of the refractive index gradient from the deflection of the laser beam, as well as probe and spectroscopic measurements indicate that the clouds undergo photoresonant ionization if they contain tantalum vapor but that the laser radiation has no influence otherwise. Pis’ma Zh. Tekh. Fiz. 23, 24–32 (May 12, 1997)     

准分子真空紫外辐射在材料加工中的研究与应用

真空紫外辐射有高于共价键键能的光子能量,可在室温下激起化学反应。自上世纪80年代,基于稀有气体介质阻挡放电的准分子真空紫外光灯面世以来,真空紫外光源有了很大的发展,商业化的准分子真空紫外光灯已有上百mW/cm2的光能输出,品种也不断增加。准分子真空紫外光灯强大的激发化学反应的能力已在材料科学、化学反应工程、生物医学等方面开拓了许多新的研究课题,并得到日益增多的实际应用。近20年,每年关于准分子真空紫外辐射材料加工的研究报道急剧增加,本文将简要介绍DBD准分子紫外光源的特点及其在材料加工中的研究和应用,包括无机薄膜制备、半导体材料氧化、材料表面清洗、过渡金属化合物还原、高分子合成和聚合物表面改性。     

Holographic spectrum dividers for the UV spectral range

We have theoretically and experimentally studied the possibility of using nonlinear recording of holographic mirrors for creating a spectrum divider capable of spatially separating wavelengths in the spectral region of 290–330 nm.     

Decomposition of 2-naphthalenesulfonate in electroplating solution by ozonation with UV radiation

This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined with UV radiation in the electroplating solution. 2-NS is commonly used as a brightening and stabilization agent in the electroplating solution. Semibatch ozonation experiments were conducted under various reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS were analyzed at specified time intervals to elucidate the decomposition of 2-NS. Total organic carbon (TOC) is chosen as a mineralization index of the ozonation of 2-NS. In addition, values of pH and oxidation reduction potential were continuously measured in the course of experiments. As a result, the nearly complete mineralization of 2-NS via the ozonation treatment can be achieved. The mineralization of 2-NS is found accelerated by the introduction of UV radiation and has a distinct relationship with the consumption of applied ozone. These results can provide useful information for the proper removal of 2-NS in the electroplating solution by the ozonation with UV radiation.     

Diurnal discrepancies in spectral solar UV radiation measurements

Unexpected diurnal discrepancies between high-quality spectroradiometers were observed during the 2000 Nordic Ozone Group Intercomparison campaign. The spectral ratios of the irradiances showed a diurnal variation of approximately 2-9%. This cannot be explained by the nonideal angular response of the instruments' input optics in one plane (cosine effect). Instead, by using a radiative transfer model, we show that differences in the angular response in four azimuth planes have the potential to bias the measured data by up to 4.4% (azimuth effect). Other relevant factors are also discussed and quantified and are shown to be significant when diurnal changes in radiation are explained by environmental factors, or when measured data are compared with model or satellite data. Again, intercomparison campaigns have the potential to reveal errors that would otherwise remain undetected.     

Oxidation of p-hydroxybenzoic acid by UV radiation and by TiO2/UV radiation: comparison and modelling of reaction kinetic

The phenolic compound p-hydroxybenzoic acid is very common in a great variety of agroindustrial wastewaters (olive oil and table olive industries, distilleries). The objective of this work was to study the photocatalytic activity of TiO2 towards the decomposition of p-hydroxybenzoic acid. In order to demonstrate the greater oxidizing power of the photocatalytic system and to quantify the additional levels of degradation attained, we performed experiments on the oxidation of p-hydroxybenzoic acid by UV radiation alone and by the TiO2/UV radiation combination. A kinetic model is applied for the photooxidation by UV radiation and by the TiO(2)/UV system. Experimental results indicated that the kinetics for both oxidation processes can be fitted well by a pseudo-first-order kinetic model. The second oxidation process can be explained in terms of the Langmuir-Hinshelwood kinetic model. The values of the adsorption equilibrium constant, K(pHB), and the second order kinetic rate constant, k(c), were 0.37 ppm(-1) and 6.99 ppm min(-1), respectively. Finally, a comparison between the kinetic rate constants for two oxidation systems reveals that the constants for the TiO2/UV system are clearly greater (between 220-435%) than those obtained in the direct UV photooxidation.