ANNIHILATION OF OH RADICALS ON THE SURFACES OF SUBSTANCES CHEMICALLY SIMILAR TO ATMOSPHERIC AEROSOL PARTICLES.

EPR has been used to measure the heterogeneous annihilation probabilities ( gamma ) of OH and H radicals on Teflon, quartz, steel, aluminum, ice, and sulfuric-acid surfaces. All of these substances, except for Teflon, are components of atmospheric aerosols. The gamma **H values of all the surfaces studied are small ( gamma **H less than equivalent to 10** minus **4). The smallest gamma **O**H approximately equals 10** minus **3 (300 K) is for F4-D Teflon. For ice and sulfuric acid, gamma **O**H equals 1. A marked decrease in gamma **O**H is observed for Teflon in the range 250-350 degree K. For the other materials there is practically no temperature dependence in this range.