Ilko M. Rusinov

Investigation of Ozone Loss Rate Influenced by the Surface Material of a Discharge Chamber

ABSTRACT Decay characteristics of ozone concentration in oxygen in a chamber with three types of wall material (stainless steel, copper, and aluminum) are measured using the 254 nm photoabsorption method. Effective lifetimes of ozone are estimated from decay curves of ozone concentration. These values depend on the wall material: They are largest for stainless steel and smallest for aluminum. The relationship between effective lifetime and gas pressure is investigated precisely to determine three values. The equivalent diffusion coefficient of ozone in oxygen and the reflection coefficient of ozone at the wall correspond to the loss rate of ozone at the wall. The collisional loss (quenching) rate coefficient of ozone in oxygen is also determined.

A method for simultaneous determination of the diffusion coefficient of particles in gas media and their reflection coefficient at the wall

A method for simultaneous investigation of the diffusion of atoms and molecules in gas buffers and their reflection at the vessel walls is proposed. It is experimentally tested to obtain the diffusion coefficient of Mg atoms in neon and the coefficient of the reflection of these atoms from the metallic wall in the afterglow plasma of a pulsed hollow cathode at 320 K temperature. The diffusion coefficient value is compared with the theoretical calculation previously reported by Redko et al.

Surface Loss Rate of Ozone in a Cylindrical Tube

In this paper, we describe the loss rate of ozone at the surface of a cylindrical tube. The loss rate of ozone at the surface is varied with the material of the tube. Therefore, tubes made of 6 different materials, borosilicate (Pyrex) glass, quartz, acrylic resin (poly methyl methacrylate, PMMA), copper, aluminum and stainless steel are prepared as specimen. The investigations are carried out on the loss rate of ozone in the tube. The temporal decay of ozone density in the tube is observed by the HgI (254 nm) photoabsorption method. Since the density decreased exponentially with time, we determined the time constant for ozone density decay whose inverse represents the effective lifetime of ozone in the tube. The experiments are performed over a wide range of gas pressures from 6.7 to 1333 hPa (5 to 1000 Torr) to investigate the gas pressure dependence of the ozone effective lifetime in the tube. From these results, we determined the loss rate of ozone in the cylindrical tube made of each material. It was found that the loss rate of ozone depends on the wall material and the surface condition of them. The loss rate of ozone in the tube is mainly determined by the loss rate at the surface of the tube. Therefore, we introduce a new parameter named the equivalent diffusion coefficient. It is useful for selecting a suitable material, which utilizes ozone for various purposes, such as the production, preservation and transportation of ozone.

Improvement of a Measurement System for Surface Loss Rate of Ozone

Ozone molecules present in high-purity oxygen as a feed gas interact with surfaces and oxygen molecules in an enclosed container. Therefore, some of the ozone molecules are destroyed and the density of ozone decreases with time. An experimental system has been constructed to monitor the temporal decrease in ozone density in a container based on the HgI 254 nm photoabsorption method. Our investigation is focused on the dependence of the effective lifetime of ozone on the wall material at various gas pressures. During the experiments, distortion of the measured decay curves often caused by instabilities in the mercury lamp intensity. We thus attempted to build a simple setup that eliminates the effect of long-term intensity drift. This setup is based on light source intensity monitoring by a separate photodetector and data correction software. This article describes the setup of the experimental apparatus, the results including some preliminary experiments and the temporal variation of the surface loss rate of ozone by repeated measurement along with inspections of the wall surface by Auger electron spectroscopy.

Investigation of the interactions of long-lived excited atoms in the afterglow of gas discharge plasma

When an electric discharge is fired in a gas consisting of atoms or molecules with long-lived excited states there are several inelastic processes releasing fast electrons in the afterglow plasma after the end of the current pulse. Most common among them are the chemiionization and de-excitation electron-atom collisions. Here these processes are investigated by measurements of the reactant particle densities at the entrance and at the exit channels of the reactions. In this way the rate coefficients of the ionising collisions of the couples Ne3P2-Ne3P2, Ar3P2-Ar3P2, Kr3P2-Kr3P2, Xe3P2-Xe3P2 as well as the rate coefficients for chemi-ionization of the ground state mercury atoms by collision with Ne 33P2 and Ar 43P2, 1, 0 atoms were obtained. By similar measurements the rate coefficients for super elastic collisions between electrons and excited heavy rare gases atoms as well as mercury atoms in the electron temperature range 500 - 2000 K were obtained. By monitoring the decay of the excited atoms density and electrons density and temperature the rate coefficients of electron impact induced transfer of excitation between the levels of configuration np5(n + 1) s in Ne, Kr and Xe were determined. In the same way were derived the rate coefficients of the transfer of excitation between Cd 63P2, 1, 0 levels induced by collisions with ground state cadmium and neon atoms. The diffusion coefficients of magnesium atoms in rare gases and their reflection coefficients from the vessel metallic wall are determined. Besides, the diffusion coefficients of metastable Cd 63P2, 0 atoms in neon are also determined.

Studies of Diffusion Losses in Gaseous Media Using a Boundary Condition of the Third Kind

The application of two approaches for the simultaneous measurement of diffusion and reflection coefficients of particles in gaseous media is carried out using one and the same data set. Both approaches are based on the analysis of the effective lifetimes of particles measured under different experimental conditions and implement a boundary condition of the third kind. The experimental data used are those of Mg atoms diffusing in neon and argon. These were obtained by a pulsed afterglow technique using a hollow cathode gas discharge. The results obtained after processing the data by the two methods are found to show good agreement.

Diffusion and depopulation of the metastable Cd 3P0,2 states in collisions with Ne and Cd atoms

The temperature dependences of the diffusion coefficients of metastable Cd(5 3P2,0) atoms in Ne are determined using the afterglow technique. In the temperature range 515-568 K they are D(3P0) = (2.2±0.7) × (T/780)1.75 cm2 s-1 and D(3P2) = (2.1±0.6) × (T/780)1.75 cm2 s-1 at 1 atm Ne pressure. The coefficients of the excitation transfer in the fine structure of a Cd triplet by collisions with a ground states Ne and Cd atoms are also determined. In the same temperature range the averaged rate coefficients for the processes Cd(5 3P2)+Ne(1S0) Cd(5 3P1,0)+Ne(1S0) and Cd(5 3P0)+Ne(1S0) Cd(5 3P1)+Ne(1S0) are K2 = (4.3±1.3) × 1014 cm3 s-1 and K01 = (3.2±1.0) × 10-14 cm2 respectively, while the rate coefficients of the reactions Cd(5 3P2)+Cd(1S0) Cd(5 3P1,0)+Cd(1S0) and Cd(5 3P0)+Cd(1S0) Cd(5 3P1)+Cd(1S0) are