ISSN:
1572-8986
Keywords:
Microwave discharge
;
reaction rates
;
mass spectrometer sampling
;
discharge chemistry of SF6
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Technology
Notes:
Abstract Reactions of both SF4 and SF5 with F have been studied at 295 K in a gas-flow reactor sampled by a mass spectrometer. The rate coefficient for the combination reaction of F with SF4 to produce SF5 was found to increase from (0.9 to 3.0)×10−12 cm3 s−1 when the helium bath gas number density was increased from (2 to 26)×1016 cm−3. The values obtained here are three orders of magnitude higher than a recent estimate of the high-pressure value based on the modelling of photochemical studies. The experimental results have been compared with RRKM and master equation calculations in which a simplified Gorin model has been used to determine the structure of the transition state. These calculations show that reasonable agreement can be obtained between the experimental data and the calculation if a small (∼2 KJ/mol) activation energy is assumed. The rate coefficient for the reaction between SF5 and F to produce SF6 was found to be independent of helium bath gas number density within the range given above. The value obtained for the rate coefficient was 9×10−12 cm3 s−1 with an uncertainty of a factor of 2. This value is close to that of 1×10−11 cm3 s−1 computed from the simplified Gorin model and to the value of 1.7×10−11 cm3 s−1 deduced from modelling of photochemical experiments.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01020407
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