Pure Water Vapor Research Articles

Correction to “Absorption cross sections for water vapor from 183 to 193 nm”

Figure 1. Absorbance versus water vapor column amount. The different symbols represent data acquired under various experimental conditions: olid symbols, flowing source of water vapor in nitrogen; open symbols, .pure water vapor measured by pressure transducer. For the flowing experiments, the water vapor concentration was determined by three methods: filled circles, based on the assumption of 100% saturation and flow dilution; filled squares, measurement of the dew point upon exiting the absorption cell;_ fill ed up-triangles, weight loss of water bubbler. For the static experiments, several tests were performed: open circles, de-lonized water; open squares, bottled water; open up-triangles, detector and source masked with 1/4 diameter irises; open hexagons, with 10 cm of ambient air between light source and absorption cell; open down-triangles, using a 100 cm long absorption cell; open diamonds, comparison of three different mercury lamps. The line is a least squares fit to all the data with equal weighting. -18

Direct comparison of meteosat water vapor channel data and general circulation model results

Following a model to satellite approach, this study points out the ability of the general circulation model (GCM) of the Laboratoire de Météorologie Dynamique to reproduce the observed relationship between tropical convection and subtropical moisture in the upper troposphere. Those parameters are characterized from Meteosat water vapor equivalent brightness temperatures (WVEBT) over a monthly scale. The simulated WVEBT field closely resembles to the observed distribution. The pure water vapor features and the convective areas are well located and their seasonal variations are captured by the model. A dry (moist) bias is found over convective (subsiding) areas, whereas the model globally best acts over Atlantic ocean than over Africa. The observed and simulated seasonal variations show that an extension of the ITCZ is correlated to a moistening of the upper troposphere in subtropical areas. Those results imply a positive large scale relationship between convective and subsiding areas in both observation and simulation, and suggest the relevance of our approach for further climatic studies.

Variations in microstructure and composition of indium tin oxide films with the deposition technique

Indium tin oxide (ITO) films have been deposited by reactive d.c.-sputtering and also by the reactive thermal evaporation technique onto glass substrates. The relationship between the microstructure and composition of the ITO films was found to strongly depend on the deposition technique. In addition the application of pure water vapour as the reactive sputtering atmosphere and its influence on the structural and compositional properties of the ITO films has been studied.

Absorption of electromagnetic radiation by pure water vapor at frequencies near 1.5 THz

The coefficient of absorption of pure water vapor is measured in the window of its relative transparency at wavelengths λ ≈ 196−205μm. The measurements were carried out using an echelette vacuum spectrometer with a spectral resolution of about 0.8 cm −1 at a temperature of 304 K in the pressure interval from 12.5to 28.5Torr. The data obtained in combination with the results of previous spectrometric measurements of absorption in a mixture of water vapor and dry air performed in this window (at the atmospheric pressure of the mixture) indicate that the component of the absorption coefficient of the atmospheric water vapor, which depends quadratically on its partial pressure, is 26% smaller than the corresponding component of the absorption coefficient of pure water vapor. Unlike in the long-wave submillimeter transparency windows, where the discrepancy of the above components was first found, in the short-wave window centered at λ=200μm the percentage difference in their values is approximately two times less.

On the calculation of heat transfer in a pulsating bubble

This paper investigates the thermodynamic processes inside an isolated pulsating bubble which contains either ideal gas or saturated vapor. The study includes the effect of heat transfer across the bubble's free surface. For a bubble containing ideal gas, the equations developed by Prosperetti are adopted in the computer model. For the case of a bubble containing water vapor, an energy equation is used to model the processes of vaporization and condensation of vapor in the bubble. The transient heat flow in the liquid domain is modelled by a dual reciprocity boundary element technique. The energy equation is expressed in the form of an integral equation, which consists of a volume integration of the domain and an area integration over its boundary. The kernels of the domain integrals are approximated by interpolation functions, thereby reducing these integrals into boundary integrals. The results compare the rebound of an ideal gas bubble and a pure water vapor bubble. Some aspects of the modes of heat transfer across the bubble-liquid interface and the consequence of irreversibility are presented.

Pattern formation in drying water films

A thick water film is deposited on a mica substrate, which it wets, from pure water vapour at a low temperature. The vapour pressure is reduced so that the water evaporates. Despite the fact that under equilibrium conditions the film wets the substrate, when it reaches a thickness of about 500 Å, dry patches nucleate in the film and the water recedes to the wet parts. During the recession, a thick rim of water is created, which becomes hydrodynamically unstable and produces a beautiful reproducible pattern of water drops. Experiments have been done showing both homogeneous and heterogeneous nucleation. The basic physics of the de-wetting, the nucleation and the origin of the pattern formation are discussed. The effect is not restricted to water on mica, but has been observed with other fluids on wetted substrates.

Cluster Beam Chemistry: Hydration of Nucleic Acid Bases; Ionization Potentials of Hydrated Adenine and Thymine

Gas phase hydration of adenine, cytosine, thymine, and uracil in supersonic molecular beams is examined by mass spectra and ionization potential measurements. In the beam source, designed for substances of low volatility that readily decompose on heating, a carrier gas (moist argon or pure water vapor) flows through a porous filter packed with the solid sample before exiting via a supersonic nozzle. With the electron impact energy below the ionization potential of water, progressions of cluster ions of the form Bm+(H2O)n with m = 1−3 and n as high as 15 are obtained. Cytosine, even with modest heating, loses two hydrogens and also undergoes tautomeric conversion to uracil. From appearance potential measurements and calibrations, the ionization potentials for B = adenine or thymine clusters (with m = 1, n = 0−3; m = 1 or 2, n = 0−1 or 2) were determined; relative to the neutral base monomer, hydration by three water molecules decreases the ionization potential by about 8%, or 0.7 eV.

An Experimental Study of Water and Carbon Dioxide Solubilities in Mid-Ocean Ridge Basaltic Liquids. Part II: Applications to Degassing

Degassing processes in basaltic magmas rich in both water and carbon dioxide can be modeled using the solubilities of the endmember systems and the assumption of Henry's law. Suites of vapor-saturated basaltic melts having a range of initial CO_2/H_2O ratios and erupted over a narrow depth interval will define negatively sloped arrays on an H_2O vs CO_2 plot. It is important that all of the major volatile species be considered simultaneously when interpreting trends in dissolved volatile species concentrations in magmas. Based on measured concentrations of water and carbon dioxide in basaltic glasses, the composition of the vapor phase at 1200°C that could coexist with a basaltic melt and the pressure at which it would be vapor saturated can be calculated. The range in vapor compositions in equilibrium with submarine basalts reflects the range in water contents in the melts characteristic of each environment. The ranges in the molar proportion of CO_2 in vapor phases (X^ν_(CO2)) calculated to be in equilibrium with submarine tholeiitic glasses are 0⋅93–1⋅00 for mid-ocean ridge basalts (MORB), 0⋅60–0⋅99 for glasses from Kilauea [representative of ocean island basalts (OIB)] and 0–0⋅94 for glasses from back-arc basins (BABB). MORB glasses from spreading centers ranging from slow (e.g. the Mid-Atlantic Ridge) to fast (e.g. East Pacific Rise, 9–13°N) are commonly supersaturated with respect to CO_2-rich vapor, resulting from magma ascent rates so rapid that magmas erupt on the sea-floor without having been fully degassed by bubble nucleation and growth during ascent. In contrast to the MORB glasses, volatile contents in submarine glasses from Kilauea are consistent with having been in equilibrium with a vapor phase containing 60–100 mol% CO_2 at the pressure of eruption, reflecting differences in average magma transport rates during eruptions at mid-ocean ridges and hotspot volcanoes. Degassing during decompression of tholeiitic basaltic magma is characterized by strong partitioning of CO_2 into the vapor phase. During open system degassing, CO_2 is rapidly removed from the melt with negligible loss of water, until a pressure is reached at which the melt is in equilibrium with nearly pure water vapor. From this pressure downward, the water content of the melt follows the water solubility curve. During closed system degassing, water and CO_2 contents in vapor-saturated basaltic magmas will depend strongly on the vapor composition as determined by the initial volatile concentrations. Deviation from open system behavior, toward lower dissolved H_2O and CO_2 saturation concentrations at a given pressure, will be greatest in melts having high total volatile concentrations and high CO_2:H_2O ratios. Closed system degassing of basaltic melts having the low initial H_2O and CO_2 contents typical of MORB and OIB, however, are similar to the open system case.

Growth of salt and acid aerosol particles in humid air

Aerosols of industrial significance like ammonium chloride, hydrochloric acid and sulphuric acid aerosols have been generated with particle number concentrations between 10 6 and 10 8 cm −3 and particle sizes between 0.1 and 0.5μmn (NH 4Cl), 0.8–1.5 μm (HCI) and 0.2–0.5 μm (H 2SO 4 ). The influence of the generating conditions on the size and the concentration of the aerosol particles have been investigated. After the generation, the particles were exposed to atmospheres of different relative humidity. If a certain level of relative humidity is exceeded, the solid salt particles dissolute and become droplets. The particle diameter of the salt and acid droplets increases if the relative humidity is raised. The particle diameters and concentrations were measured to show the dependence on the generating conditions and the relative humidity by a laseroptical extinction technique. The results of the measurements were compared with growth models. There was a very good agreement between the experimental data and the growth models for salt and acid aerosols. It is therefore possible to evaluate the limit of the growth by pure water vapour saturation, which is especially useful for the design of particle separators.

The adsorption of methanol on large water clusters

We have studied the adsorption of methanol monomers onto large water clusters by using the pick-up technique to deposit methanol onto water clusters formed in a supersonic expansion of pure water vapour. The clusters are ionised by electron impact and mass analysed. The major low-mass methanol-containing ion peaks (< 100u) correspond to unclustered and unprotonated methanol and have similar cracking patterns to free methanol monomers, although there are some heterocluster ions observed containing no more than one water and two methanol molecules. The measured ion appearance potentials indicate that the methanol is directly ionised. In contrast to previous results for methanol adsorbed onto large argon clusters [F. Huisken and M. Stemmler, J. Chem. Phys. 98 (1993) 7680], we do not find any evidence for the formation of dimers or higher clusters of methanol on the water clusters.

Water vapor absorption in the atmospheric window at 239 GHz

Absolute absorption rates of pure water vapor and mixtures of water vapor and nitrogen have been measured in the atmospheric window at 239 GHz. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with several theoretical or empirical models, and satisfactory agreement is obtained with the models involving a continuum; in the case of pure water vapor, the continuum contribution based upon recent theoretical developments gives good results. The temperature dependence is stronger than that proposed in a commonly used atmospheric transmission model.

How does a thin wetted film dry up?

We study the thinning by evaporation of completely wetted water films on clean mica surfaces in a pure water vapor environment. In the thickness range from 100 to approximately 1000 \AA{} the thinning is unstable to nucleation of dry patches, and the spreading of these patches invokes a ``dewetting'' of the substrate. The initial process is described by a simple nucleation theory. A number of hydrodynamic effects and instabilities are also observed at the boundary of the film.

Diode Laser Measurements of H 2O Line Intensities and Self-Broadening Coefficients in the 1.4-μM Region

Spectrally resolved measurements of pure water vapor absorption spectra have been performed with a tunable diode laser. The laser, a distributed feedback InGaAsP diode, emits in the 1.4-μm region. A total of 12 lines were studied corresponding to rovibrational transitions within the ν 1 + ν 3 and 2ν 1 vibrational bands. A Voigt profile analysis of lineshape is used to infer both intensities and self-collision-broadening coefficients of the water vapor. Good agreement is found between the observed line intensities and those recently measured by Toth. These results are apparently the first published measurements of the broadening coefficient within this spectral range.

Environmental fatigue of an Al-Li-Cu alloy: Part II. Microscopic hydrogen cracking processes

Microscopic fatigue crack propagation (FCP) paths in peak-aged unrecrystallized alloy 2090 are identified as functions of intrinsicda/dN- δK kinetics and environment. The FCP rates in longitudinal-transverse (LT)-oriented 2090 are accelerated by hydrogen-producing environments (pure water vapor, moist air, and aqueous NaCl), as defined in Part I. Subgrain boundary cracking (SGC) dominates for δK values where the cyclic plastic zone is sufficient to envelop subgrains. At low δK, when this crack tip process zone is smaller than the subgrain size, environmental FCP progresses on or near 100 or 110 planes, based on etch-pit shape. For inert environments (vacuum and He) and pure O2 with crack surface oxidation, FCP produces large facets along 111 oriented slip bands. This mode does not change with δK, and T1 decorated subgrain boundaries do not affect an expectedda/dN- δK transition for the inert environments. Rather, the complex dependence ofda/dN on δK is controlled by the environmental contribution to process zone microstructure-plastic strain interactions. A hydrogen embrittlement mechanism for FCP in 2090 is supported by similar brittle crack paths for low pressure water vapor and the electrolyte, the SGC and 100/110 crystallographic cracking modes, the influence of cyclic plastic zone volume (δK), and the benignancy of O2. The SGC may be due to hydrogen production and trapping at T1 bearing sub-boundaries after process zone dislocation transport, while crystallographic cracking may be due to lattice decohesion or hydride cracking.

Track Studies in Water Vapor Using a Low-Pressure Cloud Chamber: I. Macroscopic Measurements

Techniques have been developed to operate a low-pressure cloud chamber with pure water vapor. Photographs have been obtained of the tracks arising in this medium from the passage of ionizing radiation. The sources used were low-energy X rays, 242Cm alpha particles, and low-energy protons. Track lengths of the electrons were similar to those found previously in tissue-equivalent gas. W values of 35.6 +/- 0.4 and 32.6 +/- 0.6 eV per ion pair for carbon and aluminum X rays also compare closely with those in tissue-equivalent gas, but are somewhat higher than the predictions of Monte Carlo calculations. Differential w values were obtained: for alpha particles of energy 5.3 MeV the value was 33.0 +/- 3.0 eV per ion pair; for protons of energy 390, 230, and 85 keV the values were 30.6 +/- 1.9, 31.9 +/- 2.0, and 33.6 +/- 3.4 eV per ion pair. The energy losses of protons in water vapor were measured in a second (dummy) chamber used for energy calibration. Results support Janni's values of stopping power for protons in the energy range 40-480 keV.

Track Studies in Water Vapor Using a Low-Pressure Cloud Chamber: II. Microdosimetric Measurements

A low-pressure cloud chamber has been adapted to operate with pure water vapor. Photographs were obtained of tracks arising from the passage of ionizing radiation. The sources used were low-energy X rays, 242Cm alpha particles, and low-energy protons. Distributions of lineal energy, radial distances around an ion track, and interdroplet distances were measured and compared with the predictions of Monte Carlo calculations. After allowing for diffusion and the limitations of the geometry of the system, the measured and calculated distributions were found to be in good agreement.

Absorption by H 2O and H 2O-N 2 mixtures at 153 GHz

New experimental data on and a theoretical analysis of the absorption coefficient at 153 GHz are presented for pure water vapor and water vapor-nitrogen mixtures. This frequency is 30 GHz lower than the resonant frequency of the nearest strong water line (183 GHz) and complements our previous measurements at 213 GHz. The pressure dependence is observed to be quadratic in the case of pure water vapor, while in the case of mixtures there are both linear and quadratic density components. By fitting our experimental data taken at several temperatures we have obtained the temperature dependence of the absorption. Our experimental data are compared to several theoretical models with and without a continuum contribution, and we find that none of the models is in very good agreement with the data; in the case of pure water vapor, the continuum contribution calculated using the recent theoretical absorption gives the best results. In general, the agreement between the data and the various models is less satisfactory than found previously in the high-frequency wing. The anisotropy in the observed absorption differs from that currently used in atmospheric models.

Absorption measurements of water-vapor concentration, temperature, and line-shape parameters using a tunable InGaAsP diode laser

A tunable diode laser diagnostic based on spectrally resolved laser absorption has been developed to detect water vapor. The system uses a distributed feedback InGaAsP diode laser, emitting at ~ 1.38 µm. The diode laser is tuned in wavelength by modulation of the current, resulting in 1-cm(-1) tuning at 80-Hz repetition rate. The directly measured absorption spectra yield values for water-vapor concentration and temperature, as well as a collision-broadening line shape. To our knowledge, we accurately determined required data for H(2)O line strengths and self-broadening coefficients for several spectral lines in a static cell filled with pure water vapor. The temperature and concentration of the water vapor present in laboratory room air and in the postflame gases above a methane-air flat flame burner have also been measured. These results agree well with calculated values and independent measurements.

The infrared continuum of pure water vapor: Calculations and high-temperature measurements

We present experimental and theoretical studies of medium infrared absorption by pure water vapor. Measurements have been made in the 1900–2600 cm -1 and 3900–4600 cm -1 regions, for temperatures and pressures in the 500–900 K and 0–70 atm ranges, respectively. They are consistent with available data and enable the determination of continuum absorption parameters. It is shown that calculations with line shapes derived from the impact approximation are very inaccurate. Models accounting for the finite durations of collisions and line-mixing through wave-number dependent effective broadening parameters are introduced. The latter have been determined using two different approaches, which are (i) empirical determinations from fits of experimental data and (ii) direct predictions from first principles using a statistical approach. Effective broadening parameters obtained using these two different approaches are in satisfactory agreement for both the temperature and wavenumber dependencies. These data are tested by calculations of continua in various spectral regions and the agreement with measured values is satisfactory. The remaining discrepancies probably result from the influence of the internal structures of the absorption bands considered and thus from the influence of line-mixing. Nevertheless, accurate predictions are obtained in wide temperature and spectral ranges when the total absorption at elevated density is considered. This agreement, which is due to the relatively weak continuum absorption and large contributions of nearby lines, makes the present models suitable for most practical applications involving elevated densities.

Wind Extraction from Meteosat Water Vapor Channel Image Data

Abstract Wind extraction from successive Meteostat water vapor channel (WVC) images has been performed in an operational environment at the European Space Operation Centre for several months. Motions are computed with a cross-correlation algorithm; height assignment is deduced from the observed WVC brightness temperature. The scheme is fully automated. No distinction is made between clouds and pure water vapor structures. The accuracy of the produced winds is assessed by statistical comparisons with forecast winds and radiosonde winds. Above 400 hPa, WVC derived winds are mainly produced in cloudy areas. They are more numerous and generally as reliable as cloud-motion winds extracted from thermal Infrared channel images, showing a great potential to improve observation of high-troposphere circulations. Below 400 hPa, WVC-derived winds are sparse and usually do not fit with conventional wind observations. WVC-derived winds are very sensitive to signal-to-noise ratios in the imagery.