Title

Fourier Transform-InfraredStudies of the Interaction of HCl with Model Polar Stratospheric Cloud Films

Document Type

Article

Journal/Book Title/Conference

Journal of Geophysical Research

Volume

98

Issue

6

Publisher

American Geophysical Union

Publication Date

1993

First Page

10563

Last Page

10571

Abstract

Heterogeneous reactions involving hydrochloric acid adsorbed on the surfaces of polar stratospheric clouds (PSCs) are postulated to contribute to polar ozone loss. Using Fourier transform infrared (FTIR) spectroscopy to probe the condensed phase, we have examined the interaction of HCl with ice and nitric acid trihydrate (NAT) films representative of types II and I PSCs, respectively. For HCl pressures in the range of 10−7 to 10−5 Torr our FTIR studies show that a small amount of crystalline HCl·6H2O formed on or in ice at 155 K. However, for higher HCl pressures we observed that the entire film of ice rapidly converted into an amorphous 4:1 H2O:HCl mixture. From HCl‐uptake experiments with P HCl = 8 × 10−7 Torr, we estimate roughly that the diffusion coefficient of HCl in ice is around 2 × 10−12 cm2/s at 158 K. For higher temperatures more closely approximating those found in the stratosphere, we were unable to detect bulk HCl uptake by ice. Our experiments also detected no bulk uptake of HCl by α‐NAT or β‐NAT under various temperature and pressure conditions. Indirect evidence suggests that HCl adsorption onto the surface of model PSC films inhibited the evaporation of both ice and NAT by 3–5 K.

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