The HCl+ClONO2 reaction rate on various water ice surfaces

The reaction ClONO2 + HCl --> Cl-2 + HNO3 on ice surfaces was investigated using a fast flow reactor coupled to a chemical ionization mass spectromete r. Rough and relatively smooth ice surfaces and single-crystal ice particle s were employed to investigate the effect of the different surface morpholo gies on the reaction mechanism. Large reaction probabilities (gamma > 0.1), independent of HCl partial pressure in the range from 2 x 10(-7) to 8 x 10 (-6) Ton, were measured on these three ice surfaces. These results are cons istent with an ionic reaction mechanism involving HCl solvation on a liquid -like surface layer. (C) 1999 Elsevier Science B.V. All rights reserved.