Vl. Orkin et al., ATMOSPHERIC LIFETIMES OF HFC-143A AND HFC-245FA - FLASH-PHOTOLYSIS RESONANCE FLUORESCENCE MEASUREMENTS OF THE OH REACTION-RATE CONSTANTS, Journal of physical chemistry, 100(21), 1996, pp. 8907-8912
Rate constants for the reactions of hydroxyl radicals with CH3CF3 (HFC
-143a) and CHF2CH2CF3 (HFC-245fa) have been measured using the flash p
hotolysis resonance fluorescence technique over the temperature range
273-370 K. A data analysis procedure is presented which should minimiz
e rate constant errors introduced by the possible effects of radical d
iffusion. The following Arrhenius expressions have been derived for th
e reactions of OH with CH3CF3 and CHF2CH2CF3, respectively (in units o
f cm(3) molecule(-1) s(-1)): (0.95(-0.17)(+0.21)) x 10(-12) exp{-1979
+/- 65)/T} and (0.632(-0.078)(+0.089)) x 10(-12) exp{-1331 +/- 43)/T}.
With these values, the atmospheric lifetimes for the two HFCs have be
en estimated to be 51 and 7.4 years, respectively. An error analysis i
s presented from which the rate constant uncertainty at any temperatur
e can be calculated.