Ar H2O Mixture Research Articles

Discharge plasma in an argon–water vapor mixture as a gas laser medium

The possibility of obtaining the inverse population of the excited states of hydroxyl molecules generated in low-pressure discharge plasma in an Ar–H2O mixture was studied. The possibility of inversion of both the A 2Σ+ state relative to the X 2Π ground state and inside the vibrational-rotational structure of the levels of the A 2Σ+ excited state of the OH molecule was analyzed.

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*(A2Σ+) upon interaction of metastable argon atoms with water molecules has been obtained.

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

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

The Effect of Radicals on the Surface Treatment using Atmospheric Pressure Microwave Plasma

A microwave excited atmospheric pressure plasma source was set up and the surface modification of polyimide film and plasma cleaning experiment to an oil contaminated stainless steel plate was conducted, while considering the radical density in the plasma. Ar-O2 or Ar-H2O mixture gas was used as plasma gas. The high-speed treatment in about 1 second after plasma irradiation was observed in the polyimide film plasma treatment. In the plasma cleaning experiment, the sufficient removal of hydrocarbon oil contaminate was observed after 30 seconds treatment time. The results of these plasma treatments were discussed using the measured value of radical density and the numerically calculated axial distribution of various radicals.

The Effect of Gas Flow Rate on the Oxide Scale Morphology of a 10%Cr-Ferritic Steels in Ar-H<sub>2</sub>O and Ar-H<sub>2</sub>-H<sub>2</sub>O Mixtures

The oxidation behaviour of a Ferritic 10%Cr steel in Ar-H2O mixtures was investigated at 650°C. The studies aimed at elucidating the effect of water vapour content as well as the gas flow rate on the mechanisms of oxide scale formation. An important observation of the present investigation is, that H2 produced by the reaction of water vapour with the steel, can play a significant role in the oxidation process. It affects the possibility to form an external haematite layer and may alter the oxide scale growth rate. The extend by which the H2 affects the oxidation behaviour depends on the gas flow conditions, the water vapour content and the exposure time. To confirm these observations a number of specimens were oxidized in Ar-H2-H2O mixtures. This atmosphere guarantees a very low equilibrium oxygen partial pressure, in which H2 formed by reaction of the gas with the metal, does not substantially alter the thermodynamic properties of the gas.

The Effect of Water-Vapor Content and Gas Flow Rate on the Oxidation Mechanism of a 10%Cr-Ferritic Steel in Ar-H2O Mixtures

The oxidation behavior of a Ferritic 10%Cr steel in Ar-H2O mixtures was investigated at temperatures between 550 and 650°C. The studies aimed at elucidating the effect of water-vapor content as well as the gas flow rate on the mechanisms of oxide-scale formation. It was found that, the oxide types and morphologies depend on time and exposure conditions. An important observation is that H2 produced by the reaction of water vapor with the steel can play a significant role in the oxidation process. First, it affects the possibility to form an external hematite layer and if the latter is not present, it tends to decrease the growth rate of the magnetite-base oxide scale. The extend by which the H2 affects the oxidation behavior depends on the gas-flow conditions, the water-vapor content and the exposure time.

FTIR studies of CO–water complexes in argon matrices and in porous ices

Solid layers produced by the deposition at cryogenic temperatures of Ar–H2O–CO and of CO–H2O mixtures have been investigated by FTIR spectroscopy. Effects of variations in concentration ratios, in deposition temperature and of temperature cycling were studied. It is possible to assign all observed bands to single-component and to mixed (CO)m(H2O)n complexes. For the production of mixed species, higher deposition temperatures are more effective than temperature cycling. Formation is due more to H2O than to CO surface migration. Conclusions were applied to a previous study of porous ices produced by temperature cycling of noble gas–H2O solid mixtures onto which CO was deposited as a probe. They confirm that porous ices from Ar–H2O mixtures consist of small clusters with ‘surface porosity’ and a large proportion of dangling OH bonds. The CO gets attached to more than a single OH bond. Ice so formed from Ne–H2O mixtures has ‘bulk porosity’ with scattered free OH bonds. Deposited CO penetrates it and forms small solid-like clusters or bonds to single OH bonds.

Gas–gas equilibria of aqueous fluid binary mixtures

In a previous work [Chem. Phys. Lett. 100, 378 (1983)], by the application of thermodynamic perturbation theory to the polarizable hard-spheres dipole model, we found that on the P–T diagram the critical curve for the Ar–H2O mixture exhibits a negative slope. The same behavior on the critical curve has been found in a recent experimental reinvestigation of this mixture. Here it is investigated whether the theoretical approach can also predict the gas–gas equilibria of type I of the aqueous fluid binary mixtures. Good agreement with the experimental data is found for He–H2O and H2–H2O binary mixtures.

Kinetic study of high-pressure Ar–H2O mixtures excited by relativistic electrons

Dissociation of the H2O molecule by collisions with metastable argon (3P2) was shown a few years ago to lead to the excitation of the first vibrational levels of A 2Σ+ excited state of OH. The present work consists of a detailed kinetic study of an e-beam excited Ar–H2O mixture to evaluate the potential interest of that reaction scheme for laser applications. In this study, we have mainly shown that OH* (A 2Σ+) is populated by an Ar++H2O pathway too and we give an estimate for the OH* (A 2Σ+) and OH (X 2Π) formation branching ratios. We have also estimated that Ar*2+H2O is a minor OH* pathway. These results and measurements of main reaction rates permitted us to give a kinetic model where the predicted time dependence of population are in good agreement with the experimental result. The feasibility of a radical laser based on the collisional dissociation scheme of molecules is discussed.

Fluorescence and dissociative energy transfer in high pressure Ar–HCN mixtures excited by relativistic electrons

Studies of the radiation from Ar–HCN and Ar–H2O mixtures, excited by relativistic electrons from a Febetron 706 electron gun, are presented. The energy deposited by the electrons channels rapidly into the Ar* and Ar2* states; then by dissociative collisions with HCN it is transferred partly into the CN(B) state and partly into a reservoir state [most probably the CN(A) state] with near unit efficiency. Fluorescence emission from the electronic states A (2Πi) and B (2Σ+) of the CN radical, as well as the emission from the Ar2* excimer state, were measured for an Ar pressure range of 750–9000 torr [15–180 psi (absolute)], and an HCN pressure range of 0.2–13 torr. The quenching rates of Ar* metastable and the Ar2* excimer states, by collision with HCN molecules, were measured to be 6×10−10 and 1×10−9 cm3 sec−1, respectively. Our results suggest that population inversion can be achieved by collisional dissociation of simple molecules with excited rare gas atoms and excimers. Indeed the peak CN(B) population density was found to be 1.5×1015 cm−3, which corresponds to an optical gain for the B–X transition of 0.4 cm−1 if the ground state is empty. A computer kinetic model is presented that explains the time dependence and intensity of the CN(B) emission. In Ar–H2O mixtures the reaction rate for quenching of Ar2* excimer by H2O molecules is extremely high; however, the yield into the OH(A 2Σ+) is only 3%.

A potential hydroxyl ultraviolet laser

A strong emission band extending from 3060 to 3120 Å was observed following proton beam excitation of an Ar-H 2O mixture. This emission band was assigned to the transition of OH( A 2 Σ +) υ=0 → OH( X 2 Π) υ=0 . At high argon partial pressure (> 200 torr), the precursor of this emission band is believed to be the argon excimer Ar ★ 2(1 u). The fluorescence efficiency of Ar-H 2O is estimated to be a factor of 4 times that of Ar-N 2. Development of a highly efficient, tunable uv laser by e-beam pumping is promising.

Absolute intensity measurements for the 2·7 μ band of water vapor in a shock tube

The apparent spectral absorption coefficients of the H 2O infrared bands in the vicinity of 2·7 μ were measured in a shock tube behind reflected shock waves in an Ar-H 2O mixture. By interrupting an infrared beam at a 60 kc rate and projecting this beam across the shock tube to a monochromator, it was possible to measure simultaneously both emission and absorption of H 2O at 1000°K. The spectral absorption coefficients obtained from emission measurements averaged 9·8 per cent higher than absorption coefficients obtained from absorption measurements, probably due to experimental errors (smaller than usually encountered in shock tube measurements). At 1933°K experimental difficulties precluded simultaneous measurement of infrared emission and absorption, so measurements were restricted to emission. The apparent absorption coefficients were integrated to give the integrated absorption coefficients for the collection of bands near 2·7 μ. Integrated absorption coefficients were 49·8 cm -2 atm -1, 54·7 cm -2 atm -1, and 31·6 cm -2 atm -1 for absorption at 1000°K, emission at 1000°K, and emission at 1933°K, respectively. The two values at 1000°K were in good agreement with those of Goldstein, who made no measurements above this temperature.