A. I. Spasskii

Experimental Evidence for Acceleration of Reaction between Iodine Monoxide and Chlorine Monoxide at the Reactor Surface

The reaction of iodine monoxide with chlorine monoxide resulting in atom escape to the gas phase is studied at T = (303 ± 5) K and P = 2.5 Torr using a flow setup for measuring the resonance fluorescence signals of atomic iodine and chlorine. The heterogeneous reaction between chlorine monoxide and iodine monoxide occurring at the reactor surface covered with an F32-L Teflon-like compound and treated by the reaction products is characterized by the rate constant k = (4.9 ± 0.2) × 10–11 cm3 molecule–1 s–1. This value is substantially higher than the rate constant for the homogeneous reaction IO· + ClO· (k1 ≤ 1 × 10–12 cm3 molecule–1 s–1).

Measurements of the apparent rate constant for the reaction of iodine monoxide with chlorine monoxide to form iodine atoms

An apparatus for measuring the resonance fluorescence signals of iodine and chlorine atoms is constructed to study iodine monoxide reaction with chlorine monoxide. A technique using the reaction of chlorine atoms with C2H6 is developed to calibrate the sensitivity of the apparatus to chlorine atoms. The apparent rate constants for the reaction between 10• and CIO• radicals producing iodine atoms was measured at 295 K kapp = (2.62 ± 0.57) x 10--11 cm3 molecule-1 s-1.

Kinetics and mechanism of CH3Br, CHF2Br, and C2HF4Br photolysis in the presence of dioxygen under the action of λ = 253.7 nm light

The photolysis of CH3Br, CHF2Br, and C2HF4Br mixed with oxygen under radiation emitted by a bactericidal mercury lamp (radiation intensity maximum at λ = 253.7 nm) has been investigated. Oxygen was added in order to simulate natural conditions. A photolysis mechanism has been suggested, the corresponding model calculations have been carried out, and the calculated data have been compared with experimental data. The calculated absorption cross sections are in agreement with the literature, thus proving the validity of the mechanism suggested. The ratios between the rate constants of the reactions of the photolytically generated CH3, CHF2, and C2HF4 radicals with molecular bromine and oxygen have been determined.

Formation of iodine atoms in the heterogeneous reaction between chlorine and iodomethane

The rate constant of the reaction between iodomethane and chlorine atoms at 323 K, measured by the resonance florescence method under jet stream conditions as the iodine atom yield, is k1I = (2.9±0.6) × 10−12 cm3 molecule−1 s−1. It is demonstrated experimentally that this reaction takes place mainly on the reactor wall.

Mechanism and kinetics of the reaction between hydrogen iodide and ozone

The reaction between hydrogen iodide and ozone at 295 K has been investigated by the resonance fluorescence method applied to the detection of iodine atoms. A chain mechanism is suggested for this reaction. The chain initiation rate constant is k1 = (5.45 ± 1.80) × 10−17 cm3/s, and the chain propagation rate constant is k3 = (1.1 ± 0.4) × 10−12 cm3/s.

Measuring the rate constant of the reaction between carbon monoxide and iodine oxide at 298–363 K by the resonance fluorescence method

The rate constant of the reaction between the IO radical and carbon monoxide has been measured by the iodine atom resonance fluorescence method in the temperature range from 298 to 363 K. The reaction mainly takes place on the wall of the reactor.

Measurement of the reaction rate constants of oxygen atoms with chlorine and iodomethane using a resonance fluorescence technique

The following reaction rate constants of oxygen atoms with iodomethane and chlorine were measured using resonance fluorescence under jet conditions at 298 K: k1 = (2.4 ± 0.5) × 10–15 and k2 = (6.9 ± 0.2) × 10−14 cm3/s, respectively.

Measurement of the Rate Constant of a Reaction of Chlorine Atoms with CH3Br in a Temperature Range of 298–358 K Using the Resonance Fluorescence of Chlorine Atoms

The rate constant of the reaction of chlorine atoms with CH3Br was measured in a temperature range of 298–358 K using the resonance fluorescence of chlorine atoms. The possible role of this reaction in atmospheric chemistry and fire extinguishing was discussed. It was found that this reaction is homogeneous in contrast to the previously studied reaction of chlorine atoms with CH3I, with occurs at the reactor surface.

Kinetics and mechanism of the photolysis of CF2ClBr exposed to light with a wavelength of 253.7 nm

CF2ClBr mixed with oxygen was photolyzed using a low pressure mercury lamp, and the kinetics of photolysis was studied. The absorption spectra of the starting material and products of photolysis were recorded in the wavelength range from 200 to 900 nm on an Agilent 8453 spectrophotometer. The concentrations of the main photolysis products at different irradiation times were calculated by the mathematical processing of the absorption spectra. The scheme of CF2ClBr photolysis was suggested, the model calculations according to this scheme were performed, and the results of simulation were compared with experimental data.

Measuring the rate constant of the reaction between chlorine atoms and CHF2Br by Cl atom resonance fluorescence

The rate constant of the reaction between Cl atoms and CHF2Br has been measured by chlorine atom resonance fluorescence in a flow reactor at temperatures of 295–368 K and a pressure of ~1.5 Torr. Lining the inner surface of the reactor with F-32L fluoroplastic makes the rate of the heterogeneous loss of chlorine atoms very low (khet ≤ 5 s–1). The rate constant of the reaction is given by the formula k = (4.23 ± 0.13) × 10–12e(–15.56 ± 1.58)/RT cm3 molecule–1 s–1 (with the activation energy in kJ/mol units). The possible role of this reaction in the extinguishing of fires producing high concentrations of chlorine atoms is discussed.