UV Radiation Source Based on the Plasma of a Glow Discharge in a Mixture of Helium with Water Vapors

The results on the optical characteristics of the glow–discharge plasma in an He/H₂O mixture are presented. It has been established that it is a source of UV radiation in the region 306–315 nm (_max = 309.6 nm). Radiation lines of the atoms of hydrogen (H 486.1 nm and H 656.3 nm) and helium (491.1, 501.1, 587.6, and 667.8 nm) were recorded in the visible region of the spectrum; they can be used as diagnostic lines in measuring the parameters of this plasma (n _e, T _e) by the method of emission spectroscopy. The intensity of the UV bands and of the spectral lines HI and HeI have been optimized depending on the partial pressure of helium and the discharge current. The results obtained are of interest for the development of an ecologically pure source of UV radiation on the basis of chemiluminescence of water vapors in a longitudinal glow discharge.     

Emission characteristics of a barrier discharge in an Ar-H2O mixture

We have experimentally studied the UV radiation of a low-temperature barrier discharge plasma in an Ar-H₂O mixture. The spectral interval 300–400 nm has been examined in detail. Addition of argon with a pressure of 24 kPa to a barrier discharge in water vapor at a pressure of ～0.1 kPa leads to a ninefold increase in the UV radiation power of excited hydroxyl molecules. An increase in the duration of the UV radiation pulse of the mixture in the longitudinal discharge decay has been achieved for the first time, which may be direct evidence of energy transfer from metastable argon atoms to water molecules. An estimate of the upper boundary of the dissociative excitation rate constant of hydroxyl molecules OH*(A ²Σ⁺) upon interaction of metastable argon atoms with water molecules has been obtained.     

Optical characteristics of a transverse discharge in neon at atmospheric pressure

We present the results of investigation into radiation of a pulsed transverse discharge in neon at a pressure of 10–200 kPa. Survey spectra of plasma radiation, time characteristics of radiation, and the effect of small impurities of water vapors and air on the optical characteristics of a neon plasma were studied. We show that at a pressure of residual gases at a level of 10 Pa intense OH*, NO*, and N _* ² bands are observed in radiation of the plasma of a nanosecond transverse discharge in Ne against the background of continuous plasma radiation, and in the spectral region with λ>400 nm radiation was observed on the H_β 486.1 nm and NeI 585.3 nm lines, and (when P≥100 kPa) on the line at the 3s–3p-transitions of a Ne atom. The radiation intensity of the third continuum of neon increases with pressure and with energy contribution to plasma, with its maximum being located in the VUV spectral region (λ _max <200 nm). To whom correspondence should be adressed. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 5–10, January–February, 1999.     

Excess thermodynamic quantities of D<Subscript>2</Subscript>O water calculated from its Raman O−D stretching spectra

Excess thermodynamic functions of D₂O water have been calculated from the vibrationally decoupled O−D stretching spectra of very dilute solutions of HOD in H₂O. Comparison of the results with reference calorimetric data for water showed a good correspondence for excess heat capacity above the melting point of ice. The excess enthalpy at the melting point also coincides well with latent heat of melting.     

Investigation of scaling laws as applied to the gas discharge in the case of a barrier-discharge-excited Kr/CCl<Subscript>4</Subscript> mixture

The electrical and luminescent characteristics of a barrier-discharge lamp filled with a Kr/CCl₄ (150: 1) mixture are experimentally studied versus the value of pd, which varies in the range (7.6–14) × 10³ Pa cm. When simulating the gas discharge using similarity parameters, the following relationships are fulfilled: for pd = const (p is the pressure, d is the interelectrode distance), the pulse duration and the mean current density are τ _j ∼ 1/p and 〈j〉 ∼ p; the surface charge density on the electrodes, σ ∼ const; the duration of the UV radiation pulse and the efficiency of UV radiation due to a KrCl* (222 nm) exciplex, τ_rad ∼ 1/p and η ∼ p ². The maximal radiation efficiency achieved in the experiments is about 13%. Deviations from the similarity laws for the gas discharge are related to the filamentary form of the observed discharge. Qualitative analysis indicates that similarity laws may be fulfilled for such a form of discharge as well but locally, within a single filament.     

Vibrational Spectra and Structure of Potassium Alum Kal(SO4)2·12[(H2O) x (D2O)1−x ]

The IR spectra and polarization Raman spectra of Kal(SO₄)₂·12(H₂O) and Kal(SO₄)₂·12[H₂O)_0.3(D₂O)_0.7] crystals at 93 K and room temperature have been obtained experimentally. The vibrational spectra of structural elements of potassium alum — the complexes [Al(H₂O)₆ ³⁺ and [Al(D₂O)₆]³⁺ — have been calculated. The vibrational spectra have been interpreted based on the calculation and factor-group analysis data. The spectral data obtained point to the fact that, in the crystals considered, the sulfate ions are partially disordered and there exist two crystallographically different types of water molecules.     

Emission from a DC glow discharge in a He/H2O mixture

The electrical and optical characteristics of a longitudinal dc glow discharge in a cylindrical discharge tube in mixtures of helium with saturated water vapor at room temperature are investigated. In the UV range, a broad band with a maximum at λ_max=309.6 nm and Δλ=9 nm prevails. The H_α 656.3-nm, H_β 486.1-nm, and HeI lines in the range 440–670 nm are the main diagnostic spectral lines. The helium partial pressure and the glow discharge current are optimized to achieve the maximum intensities of the 309.6-nm band and HeI and HI spectral lines. The results obtained are of interest for the development of an ecologically safe radiation source based on the products of the decomposition of water molecules and clusters in plasma.     

Coincidence of rotational energy of H<Subscript>2</Subscript>O ortho-para molecules and translation energy near specific temperatures in water and ice

A hypothesis of the quantum nature of the specific temperatures T _s of water and ice, whose values is not random, was formulated. It was found that the quantum energy hΩ _mn of closely located rotational transitions in the ortho and para spin isomers of H₂O molecules coincides with the translation energy kT near the well-known specific temperatures T _s in ice and water. On the basis of this fact it was suggested that ortho-para conversion occurs at temperatures close to T _s upon inelastic collisions and resonance energy exchange kT _s ↔ hΩ _mn in the rotation-translation-rotation (RTR) processes. Such conversion can induce rearrangement of the H-bond set structure and repacking of H₂O molecules. The coincidence kT _s ≈ hΩ _mn was checked for ice and water at 12 known T _s, as well as for heavy water D₂O near T _s = 11.2°C (maximum density) and −140°C (glassy transition). The previously observe strong deformation of the OH Raman band near T _s = 4, 19, 36, and 76°C (maximum density, maximum surface tension, minimum heat capacity, and maximum speed of sound, respectively) was interpreted as a manifestation of the water structure rearrangement induced by H₂O ortho-para conversion.     

Rotational motion of the water molecules in the superconductor Na0.28CoO$_{\mathsf{2}} \!\cdot \!{\sf y}$H2O

Quasielastic neutron scattering (QENS) has been used to investigate the dynamical behaviour of H₂O in the superconductor Na_0.28CoO₂ .yH₂O. The measurements were obtained at room temperature for a molar concentration of water, y = 1.3. From the analysis of the Q-dependence of the EISF and the line-width we found that the water dynamics can be well described by rotational motion that likely correspond to re-orientation of the H₂O molecule. We were also able to define a rotational correlation time of τ= 1.85 ps.     

Hydroxyl ion conduction in ytterbium-doped strontium cerate at T<580 K in H2O/air atmosphere

Open circuit voltage (OCV) measurements in H₂O/air concentration cells at T<580 K using Yb-doped SrCeO₃ electrolyte indicate that under these conditions, protons are transported through the electrolyte as -ve ions, possibly as hydroxyl (OH⁻) ions. The H⁺ ionic transport, which is generally reported, becomes the dominant mode for H₂O/air concentration cells at temperatures greater than 750 K or when H₂O/air electrodes are replaced by H₂/Ar, and the anomalous OCV sign disappears. The combination of low temperature and the presence of hydrogen and oxygen as provided by the H₂O/air system appears to be necessary for the postulated hydroxyl ion electrode reactions to take place. In addition to OCV measurements, results from impedance spectroscopy are used to provide evidence in support of the suggested hydroxyl ion mode of protonic transport under the specified conditions. These findings are directly relevant in the development of novel humidity sensors in the temperature range 450–580K and is reported in a separate paper in this conference. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Spectral characteristics of the emission from a barrier discharge plasma based on an Ar–H2O mixture in the UV spectral region

We present the results of a study of a barrier-discharge plasma in an Ar–H₂O mixture in the UV region of the spectrum (200–500 nm). The saturated water vapor pressure was varied over the range 2.0–2.5 kPa. A comparative study of the spectral characteristics of the plasma based on water vapor and the Ar–H₂O mixture showed that the intensity of the emission of the A → X band of the OH^● radical increases three-fold in the mixture of water with argon.     

RF exciplex halogen source of UV radiation on an argon-xenon-chlorine mixture

An exciplex halogen source of UV radiation that is excited by an rf transverse discharge is studied experimentally. The active medium of the source is an Ar-Xe-Cl₂ mixture kept at a low pressure (100–1000 Pa), and its working spectral range is 220–450 nm. The radiation spectrum contains 235 nm XeCl(D-X), 257 nm Cl₂(D′-A′), 306 nm XeCl(B-X), 390 nm XeCl(C-A), and 430 nm XeCl(B-A) lines. The results of optimization of the UV power as a function of the pressure, Ar-Xe-Cl₂ mixture composition, and excitation power are reported.     

Optical properties of mouse biotissues and their optical phantoms

The optical characteristics of a barrier discharge in a mixture of heavy water vapor with argon in the wavelength region 200–315 nm are presented. The dependence of the radiation intensity of the OD (A → X) band at λ = 309 nm on the partial pressure of the D₂O vapor is studied, the mechanism of hydroxyl formation in the plasma is considered, and optimal compositions of pollution-free and inexpensive mixtures based on Ar-D₂O are determined for application in UV lamps, which are promising for use in photomedicine.     

IR-Spectra of M2UO2F4.H2O Complexes

This work is devoted to the study of and Rb₂UO₂F₄.H₂O and Cs₂UO₂F₄. H₂O IR-spectra with the aim of obtaining a set of vibration frequencies characterising M₂U0₂F₄.H₂O complexe elucidating the role and nature of water bonds in the structures of the above-mentioned compounds; and receiving preliminary information on the structure of M₂UO₂F₄.H₂O. The investigated compounds were synthesized in accord with our previous paper¹. M₂UO₂D₂O and M₂UO₂F₄.HDO were obtained by recrystallizing M₂UO₂F₄.H₂O from D₂O and HDO respectively     

Investigations of multiphoton selective dissociation of (CH3)2O in the field of a pulsed CO2 laser

Experimental investigations of multiphoton selective dissociation of (CH₃)₂O induced by a pulsed CO₂ laser have been conducted. Separation of H, C, and O isotopes was performed in enriched mixtures and in samples with the natural abundance. The following coefficients of selectivity have been obtained:K _D/K_H=4.0,K ₁₃/K₁₂=1.7, andK ₁₈/K₁₆≧1.6. We studied the dependences of the selectivity coefficient on ether pressure, on the laser energy and frequency as well as the influence of secondary chemical reactions on the dissociation selectivity. Estimations made by using the RRKM theory have indicated that ether molecules that decompose have an average excitation energy above the dissociation threshold of ∼1.5 kcal/mole.     

Water in planetary and cometary atmospheres: H2O/HDO transmittance and fluorescence models

We developed a modern methodology to retrieve water (H₂O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. On the basis of a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H₂O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO₂ rich atmosphere of Mars, for which we adopted the complex Robert–Bonamy formalism for line shapes. We retrieved water and D/H in the atmospheres of Mars, comet C/2007 W1 (Boattini), and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H₂O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H₂O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.     

Glow-discharge-pumped broadband ultraviolet lamp

The optical characteristics of a UV broadband lamp that was excited by a longitudinal glow discharge and operated on Kr—Br₂—I₂, Xe—Br₂—I₂, and Kr—Xe—Br₂—I₂ mixtures are investigated. The interelectrode spacing in the lamp is 10 cm, the inner diameter of a discharge tube being 14 mm. The current-voltage characteristics, the emission spectra of the plasma, and the dependence of the intensity of spectral lines (the amplitude of radiation bands) on the power that was pumped into the plasma based on mixtures of various compositions and pressures, as well as the radiation power in the spectral range from 200 to 390 nm, are studied. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 840–842, November–December, 2005.     

Experimental and modeling study of water time histories during H2S-N2O combustion in a shock tube

With the interest in directly burning sour gas in gas turbines, and the fact that even small amounts of H₂S or its combustion products can alter combustion characteristics, many research studies have been performed to better understand the combustion chemistry of H₂S. In the present study, the water formation was followed by laser absorption with N₂O as an oxidant, instead of O₂. Nitrous Oxide being essentially consumed via N₂O (+M) ⇌ N₂ + O (+M), the water formation via the H₂S + O route can then be probed to further validate the models. Three H₂S/N₂O mixtures diluted in 98% Ar were studied to cover the following range of equivalence ratios: 0.5, 1.0, and 2.0, over a wide range of temperatures (1580–1940 K) around atmospheric pressure. A chemical kinetic model was then developed first by validating the base N₂O kinetics mechanism, then by investigating the experimental results presented herein. The N₂O kinetics mechanism was updated with recent work on the low- and high-pressure limits for N₂O decomposition (N₂O (+M) ⇌ N₂ + O (+M)) as well as a review of rate coefficients for N₂O + H ⇌ N₂ + OH from the literature. Good agreement is shown for H₂/N₂O mixtures. Updates were then made to the H₂S kinetics mechanism, specifically, an update from the literature on SO₂ + H (+M) ⇌ SO + OH (+M) and an adjustment to SO + SH ⇌ S₂ + OH. Additionally, reactions between SH and N₂O were determined using W1BD data and transition state theory which required the addition of an NNS sub-mechanism. With these updates, the mechanism provides good agreement with the H₂S/N₂O experiments.     

Electrical conductivity of BaCe0.9Nd0.1O3−α in H2+H2O+Ar gas mixture

Electroconductivity of BaCe_0.9Nd_0.1O_3−α was studied as a function of the composition of the H₂+H₂O+Ar mixture and temperature in the interval from 873 to 1173 K. It was shown that the electroconductivity was independent of P_H2 (0.97 to 0.10 atm) and P_O2 (10⁻²¹ to 10⁻²⁶ atm), but depended on P_H2O (0.08 to 0.005 atm). A mathematical processing of the P_H2O dependencies of the electroconductivity, which was performed in terms of a classical model of defect formation in high-temperature proton-conducting solid electrolytes, yielded equilibrium constants of the reaction of water dissolution in BaCe_0.9Nd_0.1O_3−α and mobilities of protons and oxygen ions. The temperature dependencies of these quantities were used to determine the mobility activation energies of protons (E_a=34±7 kJ/mole) and oxygen ions (E_a=72±8 kJ/mole), and also the enthalpy (ΔH=−150±25 kJ/mole) and the entropy (ΔS=153±26 kJ/mole·K) of the reaction of water dissolution in BaCe_0.9Nd_0.1O_3−α.     

Diode-laser absorption measurements of CO2, H2O, N2O, and NH3 near 2.0 μm

2 , H₂O, N₂O, and NH₃ concentrations in various flowfields using absorption spectroscopy and extractive sampling techniques. An external-cavity diode laser with a tuning range of 1.953–2.057 μm was used to record absorption lineshapes from measured transitions in the CO₂ 4ν₂ ⁰+ν₃, ν₁+2ν₂ ⁰+ν₃, and 2ν₁+ν₃ bands, H₂O ν₂+ν₃and ν₁+ν₂ bands, N₂O 2ν₁+4ν₂ ⁰, ν₂ ¹+2ν₃, 3ν₁+2ν₂ ⁰, and 4ν₁ bands, and NH₃ν₁+ν₄ and ν₃+ν₄ bands. Measured CO₂, H₂O, and N₂O survey spectra were compared to calculations to verify the HITRAN96 database and used to determine optimum transitions for species detection. Individual lineshape measurements were used to determine fundamental spectroscopic parameters including the line strength, line-center frequency, and self-broadening coefficient of the probed transition. The results represent the first measurements of CO₂, H₂O, N₂O, and NH₃ absorption near 2.0 μm using room-temperature near-IR diode lasers. Received: 12 March 1998/Revised version: 7 May 1998