Surface second harmonic generation (SHG) allows detailed molecular measurements on a surface previously difficult to study: the ice/vacuum interface in equilibrium with its vapor. The heterogeneous reaction ClONO₂ + H₂O yields HOCl + HNO₃, a key reaction in ozone-depletion mechanisms in the Antarctic stratosphere, was followed on the basal ice surface maintained under stratospheric conditions (185 K, 10^-4 Torr water). SHG signals characteristic of the product HOCl allow us to determine reaction kinetics at various ClONO₂ exposures and temperatures and in the presence of co-adsorbates. We find that the reaction is autocatalytic in HOCl.

Date Published: 30 April 1998
PDF: 10 pages
Proc. SPIE 3272, Laser Techniques for Surface Science III, (30 April 1998);

Published in SPIE Proceedings Vol. 3272:
Laser Techniques for Surface Science III
Hai-Lung Dai; Hans-Joachim Freund, Editor(s)