STICKING OF HCL AND HBR ON A TYPE-II POLAR STRATOSPHERIC CLOUD MIMIC

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 HCl and HBr on a Type-II polar stratospheric cloud (PSC) mimic has been investigated. Effusive and collimated sources of molecular HCl 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-0 = 0.95 +/- 0.05 and 1.00 +/- 0.05, respectively. FTIR reveals that the adsorbed HCl and HBr are exclusively ionic in nature.