Ultrahigh vacuum studies of the surfaces of ice and sulfuric acid

Jeffrey T. Roberts

doi:10.1117/12.221469

25 September 1995 Ultrahigh vacuum studies of the surfaces of ice and sulfuric acid

Jeffrey T. Roberts

Proceedings Volume 2547, Laser Techniques for Surface Science II; (1995) https://doi.org/10.1117/12.221469
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

The surface chemical properties of ice and sulfuric acid in ultrahigh vacuum have been studied using temperature programmed desorption and Fourier transform infrared reflection absorption spectroscopy (FTIRAS). Ice and sulfuric acid were deposited on Pt(111) and W(100) as films between 10 and 100 monolayers thick. FTIRAS measurements imply that amorphous ice has a greater density of `dangling,' surface OH groups than crystalline ice. The crystalline and amorphous surfaces are also chemically different: adsorbate capable of forming hydrogen bonds of the type X(DOT)(DOT)(DOT)H-O exhibit a desorption state that is unique to amorphous ice. The adsorption of OCIO on ice was investigated in order to estimate the coverage of adsorbed OCIO on stratospheric ice particles. The sticking coefficient at 100 K is nearly unity. At low coverages, desorption is first order, with an activation energy of 23 +/- 1 kJ(DOT)mol^-1 and a frequency factor of 1.5 X 10^{9+/- 1} s^-1. The coverage of OCIO on stratospheric ice particles is probably so low that thermal- and photochemistry are unimportant in the atmosphere. For H₂SO₄, the dangling OH group cannot be spectroscopically observed, nor does HCl adsorb or absorb at 100 K.

Citation Download Citation

Jeffrey T. Roberts "Ultrahigh vacuum studies of the surfaces of ice and sulfuric acid", Proc. SPIE 2547, Laser Techniques for Surface Science II, (25 September 1995); https://doi.org/10.1117/12.221469

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