The absorption cross sections of cf₃o₂, chf₂o₂ and CF₂O radicals

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Abstract

An investigation of photolysis of CHF₂Br, CF₃Br and CF₂ClBr in a mixture with oxygen was carried out at T = 298 K when the mixture was irradiated with a mercury lamp with a maximum radiation at a wavelength of λ = 253.7 nm. Absorption spectra were recorded in the range of 200–900 nm on a Specord M-40 spectrophotometer. The kinetics of photolysis was investigated by the consumption of the initial refrigerant and the accumulation of molecular bromine. The kinetic curves of changes in optical density depending on the irradiation time for CHF₂Br and CF₃Br refrigerants at wavelengths of 214, 224 and 240 nm had inflection points. This effect is explained by the accumulation of RO₂radicals, which in this region of the spectrum absorb UV radiation much more strongly than the original refrigerants. The coordinates of the inflection points made it possible to calculate the absorption cross sections of CF₃O₂ and CHF₂O₂ radicals at wavelengths of 214, 224 and 240 nm. For CF₂ClBr freon, the optical density at a wavelength of 222 nm decreased linearly during the entire irradiation time in accordance with the linear accumulation of photolysis products – BrCl and CF₂O. This allowed us to estimate the upper limit of the absorption cross-section of the CF₂O photolysis product.

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About the authors

I. K. Larin

Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences

Email: eltrofimova@yandex.ru
Russian Federation, Moscow

T. I. Belyakova

Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences

Email: eltrofimova@yandex.ru
Russian Federation, Moscow

G. B. Pronchev

Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences

Email: eltrofimova@yandex.ru
Russian Federation, Moscow

E. M. Trofimova

Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences

Author for correspondence.
Email: eltrofimova@yandex.ru
Russian Federation, Moscow

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Supplementary files

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2. Fig. 1. Dependence of the partial pressure P of molecular bromine on the time t of irradiation of a mixture of CF₃Br (30 Torr) with O₂ (150 Torr). Temperature T = 298 K.

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3. Fig. 2. Dependence of the optical density D on the time t of irradiation of a mixture of CF₃Br (30 Torr) with O₂ (150 Torr) in the absorption region of CF₃Br (λ = 214 nm).

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4. Fig. 3. Dependence of the partial pressure P of molecular bromine on the time t of irradiation of a mixture of CHF₂Br (39 Torr) with O₂ (150 Torr). Temperature T = 298 K.

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5. Fig. 4. Dependence of the optical density D on the time t of irradiation of a mixture of CHF₂Br (39 Torr) with O₂ (150 Torr) in the absorption region of CHF₂Br (λ = 224 nm).

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6. Fig. 5. Dependence of the optical density D on the time t of irradiation of a mixture of CF₂ClBr (10.4 Torr) with O₂ (150 Torr) in the absorption region of CF₂ClBr (λ = 222 nm).

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7. Fig. 6. Dependence of the partial pressure P of bromine chloride on the time t of irradiation of a mixture of CF₂ClBr (10.4 Torr) with O₂ (150 Torr). Temperature T = 298 K.

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