A kinetic study of the interaction between atomic oxygen and aerosols

Abstract

This study was concerned with the effects of aerosols on the kinetics of disappearance of atomic oxygen. Atomic oxygen was generated by a 2450 MHz microwave discharge, and the kinetics of disappearance measured in a fast flow system using N02 titration. The recombination coefficient, for heterogeneous wall recombination was determined for clean Pyrex, H2SO4 coated wall, and (NH4)2SO4 coated wall. The values of γ were 4.97 x 10-5, 2.05 x 10-5, and 1.90 x 10-5 respectively. A rapid exothermic chemical reaction was found to occur between atomic oxygen and NH4C1; the products, as determined by mass spectrometry, were NH3, NO, H2O, HC1. An NH4Cl aerosol was generated by gas phase reaction of NH3(g) with HCl(g), The aerosol particles were approximately spherical and nearly monodisperse with a mean diameter of 1.6 ± .2 μm. The rate constant {kAERO) for the disappearance of atomic oxygen in the presence of an NH4Cl aerosol was measured. For an aerosol concentration of 4.75 x 103 µg/m3. a value of kAERO = 2.75 ± .5 sec-1 was found,