UV Wavelength Range Research Articles

Dispersion of refractive properties of solvents: Chloroform, toluene, benzene, and carbon disulfide in ultraviolet, visible, and near-infrared

Refractive index dispersion formulas have been derived for chloroform, toluene, benzene, and carbon disulfide from a broad range of the experimental refractive index data at 20 °C. The data were examined with the linear least-squares method. The dispersion equations allow one to calculate the values of refractive index required for analysis of nonlinear optical measurements in the UV, visible, and near-IR wavelength range (0.3–2.5 μm) in these liquids and solutions. The indices were compared to those estimated from quantum chemical calculations. A survey of the experimental data revealed that the measurement results published recently [Opt. Mater. 20, 81 (2002); Rev. Sci. Instrum. 65, 2056 (1994); 66, 38 (1995); 69, 1243 (1998)] were significantly different from other data reported in the literature.

Determination of the hydrogen and helium ion densities in the initial and final stages of a plasma in the Large Helical Device by optical spectroscopy

Emission line intensities in the UV and visible wavelength range have been measured in the initial and final stages of a discharge in the Large Helical Device (LHD) [O. Motojima et al., Phys. Plasmas 8, 1843 (1999)]. From these results combined with Te and ne, which are determined spectroscopically, the ionization and recombination fluxes of hydrogen and helium are estimated in the region of high line emissivities. The temporal behavior of line-averaged ne which is evaluated from these fluxes is found to be consistent with the results of the interferometer measurement. This implies that in such transient stages of the plasma the temporal variation of ne is dominated by the atomic ionization-recombination processes rather than the particle transport or diffusion. On the basis of that characteristic in LHD, the line-averaged ion densities for hydrogen and helium just before the termination of the plasma heating are determined. Thus, a method of the density determination of the fueling gas and of the ash is suggested for future fusion devices.

High-Throughput Measurement of pKa Values in a Mixed-Buffer Linear pH Gradient System

A procedure is described for measuring pKa values in a short time, e.g., 4 min/assay. Samples, as 10 mM solutions, are prepared in DMSO in 96-well plates. A flowing pH gradient is produced by mixing two buffer solutions containing mixtures of weak acids and bases that do not absorb significantly in the UV above 250 nm. The sample solution is diluted with water and then injected directly into the flowing gradient, which then passes through a diode array spectrophotometer measuring in the UV wavelength range. The buffer has been formulated so that its acid-base titration curve is linear over a wide pH range, such that the pH of the gradient is a linear function of time. The solution pH in the measurement flow cell is therefore proportional to the time elapsed since the start of gradient generation. The sample's pKa values are calculated from the change in UV absorbance at multiple wavelengths as a function of pH. The pKa values of 71 drugs have been measured, and results compare well with values measured by pH-metric or traditional UV methods. Rules are suggested for the rapid inspection of data and the choice of method for the calculation of pKa from the data.

Photodegradation of VOCs and Bad Smells in a TiO2 Coated Honeycomb Monolith Reactor

AbstractPhotocatalyst has long been studied and used as a promising agent for reduction of air pollution, as it carries such useful characteristics as self-cleaning and powerful oxidation, and it leaves non-toxic by-products. Photocatalysis is a surface reaction and is initiated by absorbing light in the UV wavelength range, therefore the system efficiency is strongly dependent upon surface area and UV intensity. Until recently application of photocatalyst has been limited to low air flow rate with low concentration of pollutants since it has been very difficult for a compact system to provide the large surface area as well as the strong UV intensity. In this study, a very compact and innovative system with a honeycomb monolith substrate coated with photocatalyst and non- thermal plasma as an UV light generation source is suggested to obtain larger specific surface area and stronger UV intensity to effectively enhance the efficiency of photocatalysis. Using this system, parametric study has been made to determine the functional dependency of UV intensity and electric power consumption on such factors as supplied voltages, substrate lengths, air flow conditions and photocatalyst loading ratios.

Light, Plasma, and Microscopic Processes

Glow discharges with different gases in the Large Helical Device (LHD at the National Institute for Fusion Science (NIFS show different visual colors of the plasma and these colors are ascribed to different spectra in the UV and visible wavelength range. From the wavelengths of the observed emission lines these gases are identified as neon helium and hydrogen. The emission line intensity is given by the upper level popula‑ tion density of the corresponding transition via the spontaneous transition probability or Einstein's A coeffi‑ cient. On the assumption of corona equilibrium relative emission line intensities of neutral helium are esti‑ mated for thetotransitions. The results are in gross disagreement with the glow discharge spec‑ trum. For a single pulsed helium discharge in a Pyrex tube line emissions are intense during the beginning of the pulse and after the pulse [A. Hirabayashi et al., Phys. Rev. A 37 77 (1988]. The population distribution over the levels is determined for these two emission peaks and neither of the results agrees with the expectationsfromcoronaequilibrium.Itisalsofoundthatthecoloroftheplasmaobservedforamaindischarge withhelium inLHDisdrasticallydifferent dependingontheplasmaconditionandnevershowsasimilarcolor tothatintheglowdischarge.Alltheseresultsindicatebreakdownofcoronaequilibriumanddemandusdeeper considerations.

The influence of hydrogen loading and the fabrication process on the mechanical strength of optical fibre Bragg gratings

Abstract This paper investigates the influence of hydrogen loading and other stages of the fabrication process on the mechanical strength of fibre Bragg gratings. Following UV irradiation, tensile tests were carried out on Ge–B codoped photosensitive fibres with and without hydrogen loading. Fibre Bragg gratings (FBGs) were written using a range of UV wavelengths, namely 246, 255 and 266 nm. The tensile strength of the optical fibres was determined in their as-received status and following the various stages of FBG fabrication. The mechanical strength was assessed using Weibull statistics. The results indicate that the strength of FBGs is influenced by the UV irradiation parameters and by the hydrogen-loading process. FBGs fabricated using shorter UV wavelengths and low pulse power intensity exhibit a high mechanical strength. The FBGs written in hydrogen loaded fibres have less than 50% of the strength of FBGs that have not been hydrogen loaded. Fibre fracture morphology observed by scanning electron microscope reveals fracture mechanisms of FBGs, which are correlated with the structural change of the silica fibres induced during the FBG inscription process. Combined with surface information gathered by atomic force microscopy, fracture mechanics is applied to understand the mechanisms of strength degradation caused by the FBG inscription process.

Nitrogen and hydrogen depth profiling with MaRPel

We report on the first measurements carried out with the new accelerator facility MaRPel (Materials Research Pelletron) in Göttingen. Samples of pure tantalum were irradiated with a pulsed nanosecond excimer laser in the UV wavelength range in a nitrogen atmosphere. The laser-nitrided tantalum samples were perfectly suited for testing a low-level set-up for resonant nuclear reactions analysis. The samples also allowed for a recalibration of the mass separator magnet, which was necessary after moving the 3 MV NEC-Pelletron from the Max Planck Institut für Kernphysik in Heidelberg to the University of Göttingen. In addition, it is shown that the low-level set-up allows high resolution hydrogen depth profiling.

The effect of water vapor on the characteristics of a pulsed-periodic ultraviolet radiation source

The effect of a small admixture of water vapor on the optical characteristics of an UV radiation source using a He-air-H2O mixture as the working medium was studied. The gas mixture was excited in a short-pulse transverse volume discharge operating at a charging voltage of U ch ≤10 kV. As the partial pressure of helium was varied in the 10–45 kPa range at an air pressure of P(air)=130 Pa and the water vapor pressure within P(H2O)=50–100 Pa, the main optical emission from plasma in the UV wavelength range was concentrated in a broad band peaked at λmax=309.7 nm and was two times greater than the intensity of the base emission bands of the nitrogen molecule in this spectral range (λ=337.1 and 315.9 nm, N2(C-B)). Adding water vapor to the He-air mixture increases the spectral range of the UV source toward shortwave region, which is related to a spontaneous decay of the products of dissociation of water molecules.

IR Spectrum of C8H2: Integrated Band Intensities and Some Observational Implications

Polyynes are of astrophysical interest since they appear to be involved in organic chemistry in very different mediums. In Titan's atmosphere, the lightest polyyne, C4H2, was detected by Voyager. Recently C4H2 and C6H2 have been discovered in a protoplanetary nebula, suggesting polyynes as a possible chemical pathway to PAH (polycyclic aromatic hydrocarbons). Moreover, several experimental simulations and modeling imply their production from the photochemistry of methane and their involvement in the formation of organic aerosols. After the study of C4H2 and C6H2 spectra in the UV and IR wavelength range, we report here the first spectrum of gaseous C8H2 in the range 400–4000 cm−1 at room temperature and low resolution. The task was hardly achieved because of the high instability of this molecule with temperature and pressure. To avoid exothermic polymerization, the compound as mixed with a solvent. We have performed a separate spectroscopic study of the solvent to determine C8H2 partial pressure within the mixture. This allowed us to calculate C8H2 integrated band intensities. In the studied wavelength range, C8H2 presents three main bands similar to those of C6H2 in terms of vibrational type, position, and relative intensity. To study the possible identification of these polyynes by spatial observatories (Cassini–Huygens, ISO), we have also measured the C6H2 and C8H2 infrared spectra in the range 400–1500 cm−1 at 0.35 cm−1 resolution.

Laser nitriding of iron and aluminum

Samples of pure iron and pure aluminum have been irradiated in nitrogen atmosphere with a pulsed nanosecond excimer laser in the UV wavelength range. For iron, almost all the phases predicted by the Fe–N equilibrium phase diagram are observed, while in aluminum the wurtzite AlN phase is formed. The dimension of the laser spot (typically 5×5 mm 2 ), the number of laser pulses (1–512), the laser beam fluence (1–8 J/cm 2) and the pressure of the reactive atmosphere (0.01–10 bar) strongly affect the nitrogen depth profiles and the characteristics of the resulting compounds. Therefore, the influence of these experimental parameters has been systematically investigated. A detailed study of the nitrogen incorporation as a function of the number of pulses and the beam fluence allowed us to model the experimental results giving some important hints on the nitriding process.

Effects of solar radiation on the Patagonian macroalga Enteromorpha linza (L.) J. Agardh — Chlorophyceae

The photosynthetic performance of Enteromorpha linza (L.) J. Agardh — Chlorophyceae was determined with a portable PAM instrument in situ and under seminatural radiation conditions in Patagonia, Argentina. Solar radiation was measured in parallel with a three-channel radiometer, ELDONET (Real Time Computer, Möhrendorf, Germany), in three wavelength ranges, UV-B (280–315 nm), UV-A (315–400 nm), and PAR (400–700 nm). The effective photosynthetic quantum yield decreased after 15-min exposure to solar radiation when the thalli were kept in a fixed position but recovered in the subsequent shade conditions within several hours. A 30-min exposure of free floating thalli, however, caused less photoinhibition. The photosynthetic quantum yield of E. linza was also followed over whole days under clear sky, partly cloudy and rainy conditions in a large reservoir of water (free floating thalli) and in situ (thalli growing in rock pools). Most of the observed effect was due to visible radiation; however, the UV wavelength range, and especially UV-B, caused a significant reduction of the photosynthetic quantum yield. Fluence rate response curves indicated that the species is a typical shade plant which showed non-photochemical quenching at intermediate and higher irradiances. This is a surprising result since these algae are found in the upper eulittoral where they are exposed to high irradiances. Obviously they utilize light only during periods of low irradiances (morning, evening, high tide) while they shut down the electron transport chain during intensive exposure. Fast induction and relaxation kinetics have been measured in these algae for the first time and indicated a rapid adaptation of the photosynthetic capacity to the changing light conditions as well as a fast decrease of PS II fluorescence upon exposure to solar radiation. There was a strong bleaching of chlorophyll due to exposure to solar radiation but less drastic bleaching of carotenoids.

Photosynthetic performance of the Atlantic brown macroalgae, Cystoseira abies-marina, Dictyota dichotoma and Sargassum vulgare, measured in Gran Canaria on site

Photosynthetic performance was determined in three common Atlantic brown macroalgae, Cystoseira abies-marina, Dictyota dichotoma and Sargassum vulgare, in Gran Canaria, Canary Islands, on site. The photosynthetic quantum yield was measured with both a portable PAM instrument on site and a diving PAM under water in the habitat. In parallel, solar radiation was measured continuously above and under water by means of two three-channel dosimeters, eldonet (Real Time Computer, Möhrendorf, Germany), in three wavelength ranges, UV-A, UV-B and PAR. The effective photosynthetic quantum yield decreased in all species in response to exposure to 15 min of solar radiation but recovered in the subsequent shade conditions within several hours. A 30-min exposure caused an even more profound photoinhibition from which the algae recovered only partially. Most of the effect was due to visible radiation, however, the UV wavelength range, and especially UV-B, considerably enhanced the decrease in photosynthetic quantum yield. In all species except Sargassum a significant photoinhibition was detected at their growth sites at high solar angles in the water column, measured with the diving PAM.

Velocity dependence of single-electron capture for the 0.4–5-keV/amuAr8+−Cs(6s)collision system

The single-electron capture (SEC) process which occurs in ${\mathrm{Ar}}^{8+}$-$\mathrm{Cs}(6s)$ collisions is experimentally studied, in the 0.4--5-keV/amu energy range, by optical spectroscopy in the near UV and visible wavelength range (200--600 nm). The classical-trajectory Monte Carlo (CTMC) method is also used to determine the state-selective electron-capture cross sections. For high collision energies, strong lines corresponding to $\ensuremath{\Delta}n=1$--4 transitions from $n=7$ to 13 states with large angular momentum values of Ar VIII and $\ensuremath{\Delta}n=0$ transitions from $n=5$ states are observed. For low collision energies, together with the lines observed for high collision energies, lines corresponding to transitions from states with low-$l$ values $(10s,$ $11s,$ and $13s)$ are detected. Production cross sections for the most populated levels $(n=9,$ 10, and 11) are determined and compared with the previous experimental data of Martin et al. [Phys. Rev. A 46, 1316 (1992)] and Denis et al. [Phys. Rev. A 50, 2263 (1994)], and with the CTMC calculations. From molecular structure calculations which are performed for the ${{\mathrm{Ar}}^{7+}+\mathrm{Cs}{}}^{+}$ molecular system, our results are analyzed in terms of dynamical couplings between the relevant molecular channels involved in the electron-capture process. Polarization degrees for SEC lines corresponding to transitions between high-$l$ values states are also measured. The comparison with those calculated from the CTMC results provides information about the Zeeman sublevel distributions.

Measurements of the Reflectivity in the Ultraviolet and Visible Wavelength Range in a Mountainous Region

The reflectivity distribution of the surrounding area of Zugspitze (2964 m) was measured within the scope of the EU project CUVRA. The albedo measurements were performed in the UVA and visible range by using a CCD camera and a UVA sensor. First results of the albedo distribution in the visible wavelength range of the surrounding areas are shown. The reflectivity of snow, rocks and of vegetation and its dependence on illumination are studied. The albedo of snow surfaces ranges between 0.4 in the shade and values up to 2 when the orientation of the facet is favourable. Reflectivity of rocks and forests lies between 0.1 and 0.25. Further work on the albedo in the UV wavelength range will be carried out. First, a relationship between UV albedo and visible albedo will be established.

A new class of oxygen isotopic fractionation in photodissociation of carbon dioxide: Potential Implications for atmospheres of Mars and Earth

Photodissociation of CO2 by ultraviolet light (λ = 185 nm) generates CO and O2, which are unusually enriched (more than 100‰) in 17O. The dissociation takes place through a spin forbidden process during transition from a singlet to a triplet state, the latter lying on a repulsive potential energy surface. The 17O isotopic enrichment is a primary process associated with this transition and could be due to near resonant spin‐orbit coupling of the low energy vibrational levels of the 16O12C17O molecule in the singlet state with those of the triplet state near the zone of transition. In contrast, photodissociation at shorter wavelengths (λ < 160 nm) involves no spin violation and produces CO and O2 which are fractionated in a conventional mass dependent fashion. The proposed explanation is further supported using 13C enriched CO2; in this case the products are enriched in both heavy isotopes but about 100‰ more in 18O. The 17O enrichment in CO and O2 generated by CO2 photolysis in a range of UV wavelengths may be a useful tracer in delineating processes in the atmospheres of Earth and Mars.

Stoichiometric LiTaO3 for Dynamic Holography in Near UV Wavelength Range

LiTaO3 single crystals with near-stoichiometric composition are grown using a double crucible Czochralski method equipped with an automatic powder supply system. Their photorefractive properties are compared with those of LiTaO3 crystals grown from the congruent composition melt. Two beam coupling experiments show that nearly stoichiometric LiTaO3 crystals exhibit considerably higher photorefractive gain, speed and sensitivity than conventional congruent crystals. Due to the relatively large photoconductivity observed at near UV wavelengths, stoichiometric crystals are further characterized by small photogalvanic fields, making them very attractive for dynamic holography in this wavelength range.

Rapid and sensitive determination of paclitaxel in mouse plasma by high-performance liquid chromatography

This report describes a rapid, simple and sensitive isocratic high-performance liquid chromatography with diode array UV detection for micro-sample analysis of paclitaxel in mouse plasma. The analysis utilized a Capcell-pak octadecyl analytical column and a mobile phase consisting of acetonitrile–0.1% phosphoric acid in deionized water (55:45, v/v). Paclitaxel and n-hexyl p-hydroxybenzoic acid (internal standard) were extracted from plasma by one-step extraction with tert.-butyl methyl ether. Peak purity was determined over a UV wavelength range of 200 to 400 nm. Paclitaxel and the internal standard were eluted at 3.4 min and 5.4 min, respectively, at a mobile phase flow-rate of 1.3 ml/min. No interfering peaks were observed and the total run time was 10 min. The standard curve was linear ( r=0.9999) over the concentration range of 0.010–500 μg/ml. The extraction recovery was >90% for both paclitaxel and n-hexyl p-hydroxybenzoic acid. The intra- and inter-day assay variabilities of paclitaxel ranged from 0.4 to 2.2% and 0.6 to 7.8%, respectively. The LOD and LOQ were 5 and 10 ng/ml, respectively, for paclitaxel using a plasma sample volume of 100 μl. This highly sensitive and simple assay method was successfully applied to a pharmacokinetic study after i.v. administration of paclitaxel 20 mg/kg to mice.

Normal mode analysis of optical polarisation response in nanocomposite particles

A new technique for establishing the spectral density and resonance positions of normal optical modes in fine particle systems is outlined and applied to finite chains of closely spaced aluminium cylinders. The method uses multiple conformai frames and a new type of structure factor. Finite chain results are compared to those of the pair and infinite chain on a per particle basis. One key result is the dominance and strong red shift of the fundamental mode as chain length increases beyond a few cylinders. Another is that this fundamental mode is largely isolated in the long UV, visible and NIR wavelength range. Surprisingly long chains (typically > 100 cylinders) are needed to give results resembling the infinite chain, unless gaps are large.

Velocity Dependence of the Emitted Light Polarisation Following Single Electron Capture for the Kr8+-Li(2s) Collision System between 0.1 and 3 keV/amu.

The Kr8+-Li(2s) collision has been studied by photon spectroscopy in the near UV and visible wavelength range (200–600 nm). A particular attention has been paid to the polarisation degree of each observed line in order to determine the behaviour of m-sublevel distribution versus energy collision.

Highly absorptive coating for the vacuum ultraviolet range

We have developed new, highly absorptive coatings for the vacuum UV wavelength range. These coatings display two distinct granularity scales: large structures of a 10-100-microm scale form efficient light traps, upon which are superimposed structures of a submicrometer scale. We present results for the total hemispherical reflectivity at normal incidence for 121.6 nm and at a grazing angle incidence for 17.1, 30.4, 58.4, and 121.6 nm. These measurements were made for the new coatings as well as for various coatings in common use. Absorption of the new coatings is in some cases higher than for the best-known coatings and, in contrast to the latter, they are mechanically robust.