Sticking of HCl and HBr on a type-II polar stratospheric cloud mimic

Abstract

A high-vacuum methodology has been applied to the study of physical and chemical processes which play a crucial role in determining the balance of stratospheric ozone. Using the combination of a thermal molecular beam and in situ grazing-incidence Fourier-transform IR spectroscopy the sticking of HCI and HBr on a Type-II polar stratospheric cloud (PSC) mimic has been investigated. Effusive and collimated sources of molecular HCI and HBr, when incident on a liquid-nitrogen-cooled ice sample in the temperature range 80–130 K are, initially, taken up with high efficiency: the initial sticking coefficients are, S_o= 0.95 ± 0.05, and 1.00 ± 0.05, respectively. FTIR reveals that the adsorbed HCI and HBr are exclusively ionic in nature.