V. G. Artemov

Water and Ice Dielectric Spectra Scaling at 0°C

The Debye relaxation in water and ice are considered in terms of dissociation-association of H2O molecules. This process leads to the occurrence of separated charges, of concentration N±. Within the proposed approach, the charge recombination (i.e., the H2O molecules association) is controlled by the charge diffusion rate. The static permittivity, ɛ(0), is solely determined by N± and increases, due to slowing down of the diffusion rate, as temperature decreases. The transformation of the dielectric spectra at 0°C is mainly due to an abrupt (by 0.4 eV) change of the diffusion coefficient activation energy.

Analysis of electric properties of ZrO2-Y2O3 single crystals using teraherz IR and impedance spectroscopy techniques

The data obtained by impedance spectroscopy (1 Hz to 32 MHz) and broad-band dielectric spectroscopy (30 GHz-150 THz) are presented for crystals based on zirconia doped by 1.5–30 mol % Y2O3 or 10 mol % Sc2O3 and 1 mol % Y2O3. The maximum of ionic conductivity is confirmed for the latter composition in the working temperature range of solid oxide fuel cells where the doping by scandium and yttrium oxides makes it possible to obtain isotropic single crystals. Dependences of dielectric permeability and high-frequency conductivity of materials on the composition of crystals and temperature are presented.

On autoionization and pH of liquid water

The ionization constant of water Kw is currently determined on the proton conductivity sigma1 which is measured at frequencies lower than 10^7 Hz. Here, we develop the idea that the high frequency conductivity sigma2 (~10^11 Hz), rather than sigma1 represents a net proton dynamics in water, to evaluate the actual concentration c of H3O+ and OH- ions from sigma2. We find c to be not dependent on temperature to conclude that i) water electrodynamics is due to a proton exchange between H3O+ (or OH-) ions and neutral H2O molecules rather than spontaneous ionization of H2O molecules, ii) the common Kw (or pH) reflects the thermoactivation of the H3O+ and OH- ions from the potential of their interaction, iii) the lifetime of a target water molecule does not exceed parts of nanosecond.The ionization constant of water Kw (or pH) is currently determined on the proton conductivity σ0 which is measured at frequencies lower than 107 Hz. We develop the idea that the high frequency conductivity σ∞ (~1011 Hz), rather than σ0 represents a net proton dynamics in water. We count the concentration c of the H3O+ and OH– ions from σ∞ to find c to be not dependent on temperature. We conclude that spontaneous ionization of H2O molecules is not essential in water electrodynamics; the common Kw reflects the thermoactivation of the H3O+ and OH– ions from the potential of their interaction; the lifetime of a target water molecule does not exceed parts of nanosecond.

Sorption experiments with water spin isomers in glycerol

Sorption experiments with water/glycerol solution were performed by measuring the ortho/para content in saturated water vapor using the 1-THz BWO spectral method. The results were interpreted as detection (i) of preferential fugacity of ortho molecules from the glycerol surface and (ii) the ability of glycerol to keep the deviation from 3:1 normal ortho/para water ratio for unexpectedly long time (several weeks for 0.5 % water concentration).

On the possibility of sorting ortho and para water molecules during diffusion in nanopores

The possibility of spatial sorting of ortho and para water molecules at filtering water vapor in a nanoporous medium is justified. Three factors are indicated, which in combination can cause sorting: Knudsen character of motion of molecules in nanopores, inhomogeneous surface electric fields in pores, and water molecule sorting over rotational states in an inhomogeneous electric field, recently implemented in experiments with molecular beams.

Diffusion kinetics of water molecules in a nanoporous adsorbent

The diffusion of water vapor into porous polymer adsorbent MN-200 has been investigated by diode laser spectroscopy with a time resolution of 0.1 s. The cascade character of diffusion, caused presumably by the fractality of the porous matrix space, is established by decomposition analysis. The collisionless (Knudsen) mode of water motion in pores, in which water molecules can be sorted according to their spin states, is selected.

A diode-laser spectrometer for measuring ortho/para composition of water vapor

A diode laser spectrometer, which is ment for recording ortho-and paracomposition of water vapor in gas mixtures, is described. The studied mixture is probed by infrared radiation at frequencies of the resonance absorptions of ortho-and paramolecules of water (λ ≈ 1.85 μ m). The recording rate of spectral ortho-and paralines is 2 Hz, and the ortho/para composition is calculated in real time with respect to their integrated intensities. An accuracy of 1% is ensured in a 0.01- to 20-Torr partial pressure range for water vapor and in a 0- to 700-Torr partial pressure range for the buffer gas.

Deviations from the normal ortho/para ratio for water (3 : 1) in the vapor phase in dynamic sorption

Deviations of the ortho/para ratio from its normal value (3: 1) were observed by spectral selective detection of ortho and para water molecules when water vapor passed through a column with a nanoporous polymeric adsorbent. The effect was suggested to be related to the nonstationary dynamics of sorption, that is, nonequilibrium character of chromatography. In terms of this model, the factor of spin ortho/para selectivity is slow and unequal diffusion of the spin isomers of water molecules inside the adsorbent, a process spurious for ideal equilibrium chromatography.

A laser analyzer of the kinetics of interaction of water molecules with an adsorbent

A device for recording high-speed processes of water-vapor sorption at the surfaces of porous materials is described. The water-vapor pressure over a sample is measured during the sorption process by registering the integral intensity of the absorption line of H2O molecules at a wavelength of 1.85 μm. The kinetic curves of changes in the partial pressure (concentration of H2O molecules) from 1 mTorr to 20 Torr are recorded in a time range from 1 ms to 24 h with an accuracy better than 1% at buffer-gas concentrations of 0–760 Torr. The obtained data are used to determine the sorption and structural parameters of investigated materials.

Precursor effect during water vapor diffusion in a porous medium

In water vapor diffusing through a granular adsorbent layer into vacuum, water molecules overcoming an adsorption column without an appreciable delay as pulses, i.e., precursors of the main front, were detected. This effect is explained by the sluggishness of water molecule diffusion into adsorbent grains and the dependence of the adsorption capacity of molecules on their rotational states via the Stark effect in a surface electric field of an adsorbent.