Scattering of centimeter radiowaves in a gas ionized by radioactive radiation: Cluster plasma formation

A theoretical explanation is proposed for an anomalously high reflectivity of air masses exposed to radioactive radiation relative to electromagnetic waves from the rf range. The mechanism of formation of the reflected signal is connected with a change in the electric parameters of the ionized gas. The concentration of free charges under the typical conditions of radioactive contamination is ten orders of magnitude lower than that required for the formation of an experimentally detectable reflected signal. The discrepancy between the values of reflectivity observed under the real conditions of radar probing and predicted theoretically on the basis of the elementary theory of a weakly ionized gas amounts to 20 orders of magnitude. It is shown that the inclusion of the variation of the mass and the critical capture radius of ions due to their hydration changes the difference between the theoretical predictions and the experimental observations insignificantly. The discrepancy becomes smaller (but only by 1.5 orders of magnitude) when the scattering of radiowaves from turbulent vortices is taken into account. The mechanism of the formation of the high reflectivity is associated with slowing down the recombination and with the accumulation of a profuse population of unrecombined ionic pairs stabilized in the clusters of water molecules. The steady-state concentration of such electrically neutral clusters is several orders of magnitude higher than the concentration of free hydrated ions. A variation of the intensity of ionizing radiation is accompanied by proportional variations of both components. The recombination barrier is formed as a result of drawing dipole molecules into the gap between ions at the final stage of motion of counterions towards one another before their recombination. The accumulation of ionic pairs ensures the multiple enhancement of the sensitivity of the electric properties of cold plasma to the effect of ionizing radiation. A quantitative kinetic theory of the effect is constructed. The numerical calculations of the parameters of the pre-recombination states of ions against the background of the molecular component are made using computer simulation at the microscopic level. The steady-state recombination rate is an exponential function of the pre-recombination barrier height and decreases rapidly even upon an insignificant change in the number of molecules involved in an ion recombination act. The obtained theoretical conclusions are confirmed by the independent results of observations of the strong absorption band in the atmosphere in the middle part of the IR spectrum, which is attributed to the anomalously high concentration of electrically neutral water clusters.     

Melting of Water Molecule Clusters in a Strong Electric Field under the Conditions Modeling Arctic Stratosphere

The melting of (H₂O)₄₀ice microparticles under the conditions of subarctic stratosphere was numerically simulated using the Monte-Carlo method. The melting point of the microparticles was found to be 60 K lower than the melting temperature of bulk ice. The melting was detected by the behavior of the internal energy of microparticles, their heat capacity and electric susceptibility. The melting was accompanied by a qualitative change in the molecular orientation order in a cluster. Abrupt changes in the molecular arrangement in the cluster were not found. An electric field destroys the molecular orientation order in the cluster, and the clear-cut phase transition disappears. An electric field increases the rotational mobility of molecules.     

High Temperature Stability of Hydrated Ion Pairs Na<Superscript>+</Superscript>Cl<Superscript>–</Superscript>(H<Subscript>2</Subscript>O)<Subscript><Emphasis Type="Italic">N</Emphasis></Subscript> under Conditions of a Flat Nanopore

The high-temperature stability of hydrated ion pairs under conditions of a nanoscopic flat pore with hydrophobic structureless walls is studied by computer simulations. The limited space of the nanopore stimulates dissociation of the contact ion pair (CIP) with its transition to the state of the solvent-separated ion pair (SSIP); moreover, the ion pair demonstrates a high degree of stability on heating. The inverse temperature effect where the heating renders a moderate consolidating effect on the state of a hydrated contact ion pair is observed: when heated to the electrolyte boiling point, the free energy barrier that separates the CIP and SSIP states shifts by 2 molecules towards the larger hydration shells. On the pressure scale, the boundary between CIP and SSIP states shifts at the same rate as the saturating pressure with the increase in the temperature.     

Computer simulation of molecular complexes H3O+(H2O) n under conditions of thermal fluctuations: II. Work of formation and structure

The free energy, entropy, and work of formation of H₃O⁺(H₂O)_n clusters (n=1–27) in water vapor (300 K) were calculated by the Monte Carlo method. Binary correlation functions were calculated. The calculations are based on the nonpair interaction model presented in the previous publication. The hydration shell of the ion is thermally stable in the size range under study. Nonpair interactions exert an essential effect on the structure of the cluster. Fitting the cluster behavior to its experimental thermodynamic characteristics shows that the excess charge of the ion is spatially delocalized at room temperature, and the role of hydrogen bonds is strengthened on this background. Clusters formed on electric charges have such a fundamental characteristic as transition size. The transition size is independent of vapor pressure and demarcates two qualitatively different mechanisms of holding molecules in a cluster. A change in the holding mode is reflected on the mechanism of vapor nucleation.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1585–1592.Original Russian Text Copyright © 2004 by Shevkunov.For communication I, see [1].This revised version was published online in April 2005 with a corrected cover date.     

Molecular mechanisms of decomposition of hydrated Na+Cl– ion pairs under planar nanopore conditions

Russian Journal of Physical Chemistry A - The decomposition of Na+Cl– ion pairs under the conditions of a nanoscopic planar pore with structureless walls in a material contact with water...     

Charge separation in Na<Superscript>+</Superscript>Cl<Superscript>-</Superscript>(H<Subscript>2</Subscript>O)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> clusters in water vapors. 1. Intermolecular interactions

Charge separation in “soft” nanoparticles composed of water molecules, as well as sodium and chlorine ions, is studied by computer simulation. The detailed model of intermolecular interactions that includes, in addition to Coulomb, exchange, and dispersion forces, many-particle polarization and covalent interactions, as well as the effect due to the transfer of excess ion charges and influence of ion field on molecular interactions, is constructed. Model potentials are calibrated using experimental data on the free energy and enthalpy of the addition of vapor molecules to the hydration shells of ions, as well as the data of quantum-chemical calculations for stable cluster configurations and the vibration frequency of interionic bonds. The allowance for many-particle interactions makes it possible to improve the agreement between experimental and quantum-chemical data by more than an order of magnitude. The disregard for many-particle interactions leads to the significant overestimation of cluster stability.     

Layer-by-layer adsorption of water molecules on the surface of a silver iodide crystal

Computer simulations at the molecular level were used to analyze the mechanism of the nucleation of water condensate from the vapor phase on the surface of a silver iodide crystal at 260 K. The initial stage of the condensation process is the sequential growth of monolayers on the substrate surface without formation of a compact microdroplet. The dependence of the equilibrium work of formation of the condensate film on its thickness exhibits oscillations. The formation of layers close to the substrate surface involves the overcoming of a Gibbs energy barrier.     

Influence of Embedded Protons on the Structure of Ice Microcrystals. Computer Simulation

Ice microcrystals of 40 molecules with embedded proton and placed in the external electric field were simulated by the Monte Carlo method in connection with the problem of the destruction of the ozone layer in the stratosphere. The proton field does not disturb the cluster crystalline state, whereas the electric field of crystal defects on the ice surface can affect essentially the microcrystal melting and destroy the structural transition. The melting of microcrystals is mainly reduced to the distortion of orientational molecular order.