Gas-phase photodecomposition of carbon tetrachloride
1976; Elsevier BV; Volume: 6; Issue: 4 Linguagem: Inglês
10.1016/0047-2670(76)85084-8
ISSN1873-2658
Autores Tópico(s)Atmospheric and Environmental Gas Dynamics
ResumoThe gas-phase photolysis of CCl4 was investigated at 213.9, 163.3 and 147.0 nm in the presence of HCl, HBr, and C2H6. Quantum yields of the products measured in these mixtures at a temperature of 300 K led to the conclusion that at 213.9 nm over 90% of the photodecomposition can be attributed to the photodissociative process: independent of pressure (5 - 60 Torr). At 163.3 nm, CCl2 is formed via the photodecomposition process: Contrary to earlier suggestions, CCl2 is unreactive towards CCl4. Combination with other radicals and insertion into HCl are the major modes of reaction of CCl2. Experiments carried out at 313.0 nm show evidence for the occurrence of photodissociation of CCl4. On the assumption that absorption of a photon by CCl4 invariably leads to the detachment of a chlorine atom, the absorption cross-section at 313.0 nm is /s 3.7 ± 0.4 X 10−26 cm2 molecule−1 (300 K). This result indicates that photodecomposition of CCl4 in the troposphere is of minor importance as compared to other processes including diffusion up to the earth's stratosphere.
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