Ultraviolet absorption spectrum of chlorine peroxide, ClOOCl

The photolysis of chlorine peroxide (ClOOCl) is understood to be a key step in the destruction of polar stratospheric ozone. This study generated and purified ClOOCl in a novel fashion, which resulted in spectra with low impurity levels and high peak absorbances. The ClOOCl was generated by laser photolysis of Cl2 in the presence of ozone, or by photolysis of ozone in the presence of CF2Cl2. The product ClOOCl was collected, along with small amounts of impurities, in a trap at about -125 degrees C. Gas-phase ultraviolet spectra were recorded using a long path cell and spectrograph/diode array detector as the trap was slowly warmed. The spectrum of ClOOCl could be fit with two Gaussian-like expressions, corresponding to two different electronic transitions, having similar energies but different widths. The energies and band strengths of these two transitions compare favorably with previous ab initio calculations. The cross sections of ClOOCl at wavelengths longer than 300 nm are significantly lower than all previous measurements or estimates. These low cross sections in the photolytically active region of the solar spectrum result in a rate of photolysis of ClOOCl in the stratosphere that is much lower than currently recommended. For conditions representative of the polar vortex (solar zenith angle of 86 degrees, 20 km altitude, and O3 and temperature profiles measured in March 2000) calculated photolysis rates are a factor of 6 lower than the current JPL/NASA recommendation. This large discrepancy calls into question the completeness of present atmospheric models of polar ozone depletion.     

Ultraviolet emission spectra of sunbeds

It is well known that UV radiation contributes to the development of skin cancer. Exposure to solar radiation is predominantly responsible for the high incidence rate of skin cancer, but there are also indications that sunbeds are involved. The aim of the present investigation was to determine the UV emission spectra of sunbeds. It included the most common sunbed models, which cover more than 50% of the Swiss market. The UV emission spectra of sunbeds have special characteristics and are different from the sun spectrum, which can be seen in high-resolution spectral measurements. Sunbed emission spectra are similar to the sun spectrum in the UVB (280-320 nm) range but reach values 10 to 15 times higher in the UVA (320-400 nm) range. An average erythema-effective irradiance of 0.33 W/m2 was determined for sunbeds. This corresponds to a UV index of 13, which is significantly higher than the UV index of 8.5 of the high summer sun at noon at intermediate latitudes. The measurements were spread over the whole effective area of the sunbeds, and an inhomogeneous distribution of the irradiances with variations of up to 30% from the average value was found.     

Ultraviolet absorption spectra of chloramines and chlorine in carbon tetrachloride

In order to quantify mixtures of chloramines and chlorine in carbon tetrachloride, the ultraviolet spectra of monochloramine, dichloramine, trichloramine and chlorine were measured between 250 and 410 nm. Monochloramine and chlorine absorb at 259 nm (?=484.61 mol^?1 cm^?1 ) and 331 nm (?=95.7 l mol^?1 cm^?1), respectively, while dichloramine and trichloramine exhibit two peaks. For dichloramine, the maximum absorptions are observed at 255 nm (?=126.1 l mol^?1 cm^?1) and 301 nm (?=307.8 l mol^?1 cm^?1) and for trichloramine, at 262 nm (?=635.4 l mol^?1 cm^?1) and 344 nm (?=315.0 l mol^?1 cm^?1).     

Measurement of the diffusion coefficient of atomic chlorine in molecular chlorine

A scheme for measuring the diffusion coefficients of reactive atomic species through their radiative recombination reactions is proposed. The method was employed to measure the rate of diffusion of chlorine atoms in chlorine molecules and led to an observed value for the diffusion coefficient of 0.149 ± 0.025 cm² s⁻¹ at 298 K and 1 atm.     

Temperature dependent structured absorption spectra of molecular chlorine

A dual wavelength range spectrometer system has been designed and constructed which can simultaneously perform single pass UV absorption spectroscopy and cavity enhanced absorption spectroscopy in the green region of the visible spectrum. Using the system the absorption spectrum of molecular chlorine has been measured, in the wavelength range 509-570 nm, using cavity enhanced absorption spectroscopy. Absolute absorption cross sections were obtained by simultaneous measurement of the UV spectrum to obtain the Cl(2) concentration. These are the first temperature dependent measurements of the Cl(2) absorption cross sections in this region which are vibronically resolved. Laboratory measurements were conducted at four temperatures (298, 273, 233, and 197 K). Spectral modelling of the Cl(2) B(3)Π(0(u)(+))-X(1)Σ(g)(+) electronic transition has been performed, the results of which are in good agreement with our measured spectra.     

Circular emission from molecular iodine

The resonance emission from molecular iodine excited by circularly polarised light is circularly polarised. We report the circular emission spectrum of iodine excited by the 5145 A line of Ar⁺. In zero field the prominent rotational triplet and the high energy P,R doublet are strongly circularly polarisation ratios close to theoretical.     

Low-temperature polymerization of acrylamide under the action of molecular chlorine

Acrylamide can polymerize under the action of molecular chlorine in the temperature range 180–210 K, as evidenced by the methods of calorimetry; UV, IR, and EPR spectroscopy; and elemental analysis.     

Use of a fluorous bridge for diffusion controlled uptake of molecular chlorine in chlorine addition to alkenes

Fluorous solvent was used for passive transport of molecular chlorine from one side of the U-tube to the other, where addition of chlorine to alkenes was quantitative and diffusion controlled.     

Optical emission of a molecular nanoantenna pair

The optical emission from a pair of nanoantennas is investigated within the theoretical framework of quantum electrodynamics. The analysis of fluorescent emission from a pair of molecular antenna species in close proximity is prompted by experimental work on oriented semiconductor polymer nanostructures. Each physically different possibility for separation-dependent features in photon emission by any such pair is explored in detail, leading to the identification of three distinct mechanisms: emission from a pair-delocalized exciton state, emission that engages electrodynamic coupling through quantum interference, and correlated photon emission from the two components of the pair. Although each mechanism produces a damped oscillatory dependence on the pair separation, each of the corresponding results exhibits an analytically different form. Significant differences in the associated spatial frequencies enable an apparent ambiguity in the interpretation of experiments to be resolved. Other major differences are found in the requisite conditions, the associated selection rules, and the variation with angular disposition of the emitters, together offering grounds for experimental discrimination between the coupling mechanisms. The analysis paves the way for investigations of pair-wise coupling effects in the emission from nanoantenna arrays.     

Modulated structure and molecular dissociation of solid chlorine at high pressures

Among diatomic molecular halogen solids, high pressure structures of solid chlorine (Cl(2)) remain elusive and least studied. We here report first-principles structural search on solid Cl(2) at high pressures through our developed particle-swarm optimization algorithm. We successfully reproduced the known molecular Cmca phase (phase I) at low pressure and found that it remains stable up to a high pressure 142 GPa. At 150 GPa, our structural searches identified several energetically competitive, structurally similar, and modulated structures. Analysis of the structural results and their similarity with those in solid Br(2) and I(2), it was suggested that solid Cl(2) adopts an incommensurate modulated structure with a modulation wave close to 2∕7 in a narrow pressure range 142-157 GPa. Eventually, our simulations at >157 GPa were able to predict the molecular dissociation of solid Cl(2) into monatomic phases having body centered orthorhombic (bco) and face-centered cubic (fcc) structures, respectively. One unique monatomic structural feature of solid Cl(2) is the absence of intermediate body centered tetragonal (bct) structure during the bco → fcc transition, which however has been observed or theoretically predicted in solid Br(2) and I(2). Electron-phonon coupling calculations revealed that solid Cl(2) becomes superconductors within bco and fcc phases possessing a highest superconducting temperature of 13.03 K at 380 GPa. We further probed the molecular Cmca → incommensurate phase transition mechanism and found that the softening of the A(g) vibrational (rotational) Raman mode in the Cmca phase might be the driving force to initiate the transition.     

Continuous-flow molecular emission cavity analysis for sulphide

Sulphide (1–10 μg ml^?1) is determined by mixing the sample with an excess of orthophosphoric acid in a segmented continuous-flow system. The hydrogen sulphide evolved is swept into the cavity for generation of S₂ emission. The analysis is completely automated, requires no sample pretreatment and samples can be analyzed at 24 h^?1.     

Solvation emission spectral peaks of single molecular oxygen

Distinct new emission peaks of solvated single (¹Δ_g) molecular oxygen, generated by photosensitization, are observed in a series of oxygen-sa     

分子束弛豫谱研究Ge(111)表面与氯分子热反应动态学

本文用分子束弛豫谱研究了Ge(111)表面与氯分子热反应动态学。采用种子束技术,发现增加氯分子的入射平动能, 将有效地增加Cl2与Ge表面的化学蚀刻反应, 对分子束弛豫谱的数据分析表明, 在表面温度Ts为700-900K的范围内, GeCl2为该反应体系的唯一产物, 它的脱附过程是蚀刻反应的速率控制步骤; 并且测得脱附活化能Ed为66.0±2.0kJ·mol^-^1。此外, 对该化学蚀刻的反应机理进行了讨论。     

Determination of traces of chloride in solution by microwave-induced plasma emission spectrometry using chlorine generation

The method described for the determination of traces of chloride in solution by microwave-induced argon plasma emission spectrometry is based on the evolution of chlorine from a potassium permanganate solution in sulphuric acid and measurement of the chlorine molecular emission at 257 nm. The detection limit is 10 ng of chloride and the log—log calibration plots are linear over ranges of 0.025–100 μg of chloride, depending on the orientation of the plasma. Potential interfering elements are shown not to present any major problems.     

Investigation of x-ray absorption k-spectra of chlorine in certain gases and molecular crystals

The X-ray absorption K-spectra of chlorine were investigated in gaseous and solid Cl₂, HCl, CCl₄, and CHCl₃. The first absorption peak does not undergo any changes on passing from the gaseous to the crystalline state, while the group of maxima with lower wavelength undergoes extremely substantial changes. It is proposed that in both the gas and the crystal the first maximum indicates a transition of the K-electron to an antibonding molecular orbital containing the 3p_x-orbital of chlorine, while the short-wavelength region for the solid state indicates the presence of wide energy bands in the crystal.     

Electronic absorption spectra of solutions of molecular chlorine in molten alkali metal chlorides

Electronic reflection absorption spectroscopy has been used for measuring the electronic spectra of chlorine solutions in molten alkali metal chlorides 2CsCl-NaCl, KCl-NaCl, and CsCl in the range 240–400 nm. Absorption bands of chloride melts are interpreted as electronic transitions in the molecular group Cl₂ and in the triatomic linear group Cl ₃ ^? of symmetry D _∞h and C _∞V .     

Initiation of free-radical polymerization of acetylene monomers with molecular chlorine at low temperatures

The reactions of molecular chlorine with phenylacetylene (PA) and para-diethinylbenzene (p-DEB) at low temperatures (77–210 K) were studied by electronic paramagnetic resonance (EPR), size exclusion chromatography, double bond analysis (DBA), calorimetry, and UV, visible, and IR spectroscopy. The low-temperature (100–210 K) reactions of molecular chlorine without high-energy chemical (HEC) effects formed radicals capable of oligomerizations and polymerizations. A readily soluble polymer para-diethinylbenzene having no spatial cross-linkages (but possibly having a branched structure) was obtained. Polymerization occurred in direct contact with chlorine. It accelerated near the melting point (T _m) of chlorine and proceeded vigorously along with chlorination at T _m = 172 K. The occurrence of low-temperature polymerization without HEC treatment points to the high reactivity of the reagents. From the viewpoint of applications, low-temperature oligomerization or polymerization of monomers with molecular chlorine can afford oligomers or polymers with definite properties, which cannot be obtained by other initiation procedures.     

A study of the UV—visible absorption spectrum of molecular chlorine

The UV—visible absorption spectrum of molecular chlorine at 298 K was investigated in the wavelength range 200–550 nm with a spectral resolution of 0.2 nm. Except for minor discrepancies, the absorption cross-sections are in agreement with those found in the literature. In the region 250λ-550 nm, the Cl₂ spectrum can be adequately described by a semi-empirical function of the wavelength A (in vacuum) and temperature T

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where TANH=tanh(hcx559.751 cm⁻¹/2kT). The absorption of solar radiation by the weak continuum around λ_max=406.5 nm contributes 9% or more of the photodissociation of molecular chlorine in the atmosphere, but the banded Cl₂ features (λ 479 nm) are of negligible atmospheric significance.     

Chemical speciation of chlorine in atmospheric aerosol samples by high-resolution proton induced X-ray emission spectroscopy

Chlorine is a main elemental component of atmospheric particulate matter (APM). The knowledge of the chemical form of chlorine is of primary importance for source apportionment and for estimation of health effects of APM. In this work the applicability of high-resolution wavelength dispersive proton induced X-ray emission (PIXE) spectroscopy for chemical speciation of chlorine in fine fraction atmospheric aerosols is studied. A Johansson-type crystal spectrometer with energy resolution below the natural linewidth of Cl K lines was used to record the high-resolution Kα and Kβ proton induced spectra of several reference Cl compounds and two atmospheric aerosol samples, which were collected for conventional PIXE analysis. The Kα spectra which refers to the oxidation state, showed very minor differences due to the high electronegativity of Cl. However, the Kβ spectra exhibited pronounced chemical effects which were significant enough to perform chemical speciation. The major chlorine component in two fine fraction aerosol samples collected during a 2010 winter campaign in Budapest was clearly identified as NaCl by comparing the high-resolution Cl Kβ spectra from the aerosol samples with the corresponding reference spectra. This work demonstrates the feasibility of high-resolution PIXE method for chemical speciation of Cl in aerosols.