NASA Office of Mission to Planet Earth, Science Division, Washington, D.C., USA
Abstract
Improved laboratory data have been obtained from reactions of OH with 14 different halocarbons. The most significant changes were those in reactions with HCFC-141b (CH3CFC12), HCFC-142b (CH3CF2Ci), HFC-125 (CHF2CF3) and HFC-143a (CH3CF3). The largest change in rate constant at atmospheric temperatures is a decrease of about 30% for HCFC-141b. New evaluations of reaction rates of O(1D) with 8 different halocarbons were obtained. The branching ratios for the quenching of O(1D) to O(3p) were also obtained. In addition, reaction rates of CI (chlorine) with 18 different halocarbons were measured and the rates of reactions of NO 3 (nitrogen trioxide) with various halocarbons were found to be very slow (room temperature rates slower than 3 x 10-18 cm 3 molec _1 sec-1 ). Absorption cross sections (including temperature dependence) were re-evaluated for CFC-11, CFC-12, CFC-113, CFC-114 (CCIF2CCIF2), CFC-115 (CCIF2CF3) and the halons. Hydrolysis rates and Henry's Law constants for methyl chloroform and carbon tetrachloride have been reviewed in the context of recent data
