Kinetics and mechanism of the photolysis of CF<Subscript>2</Subscript>ClBr 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.     

Heterogeneous Reaction of Dimethyl Sulfide with Iodine Oxide in a Temperature Range of 291–365 K

Kinetics and Catalysis - A reaction of the iodine oxide (IO) radical with dimethyl sulfide (DMS) in a temperature range of 291–365 K was studied using atomic iodine resonance fluorescence. It...     

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 k_app = (2.62 ± 0.57) x 10-^-11 cm³ molecule^-1 s^-1.     

Measurement of the rate constants for the reactions of the IO• radical with sulfur-containing compounds H2S, (CH3)2S, and SO2

The reactions of iodine monoxide (IO^•) with sulfur-containing compounds, which are important for the atmospheric chemistry, are studied. An attempt is made to distinguish between the heterogeneous and homogeneous reaction pathways. It is shown that, under the experimental conditions, the reactions proceed on the wall and generate iodine atoms into the gas phase. It is found that, at room temperature, the rate constants for the gas-phase reactions of IO^• with (CH₃)₂S and H₂S are lower than 2.5 × 10⁻¹⁴ and 8.0 × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, respectively; the rate constant for the gas-phase reaction of iodine monoxide with SO₂ ≤ 5.6 × 10⁻¹⁵ 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.     

Kinetics and mechanism of the photodecomposition of trifluorobromomethane and tetrafluorodibromoethane under the action of light with a wavelength of 253.7 nm

The kinetics of photodecomposition of Halons CF₃Br and C₂F₄Br₂ was studied at different times of the irradiation of a mixture of these substances with oxygen at the wavelength λ = 253.7 nm. Kinetic data were obtained from changes in the absorption spectra in the region of Halon absorption and at a wavelength of 416 nm, which corresponds to the absorption maximum of molecular bromine. Kinetic schemes were proposed for the photodecomposition of CF₃Br and C₂F₄Br₂ at λ = 253.7 nm, and the quantum yields of their photodecomposition at this wavelength were determined.