AVS 52nd International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThM

Paper SS1-ThM10
A Comparison of H@sub 2@O and D@sub 2@O Adsorption on MgO(100) Under Ambient Conditions

Thursday, November 3, 2005, 11:20 am, Room 200

Session: Water-Surface Interactions
Presenter: M.C. Foster, University of Massachusetts - Boston
Authors: M.C. Foster, University of Massachusetts - Boston
N.J. Ward, University of Massachusetts - Boston
D. Passno, University of Massachusetts - Boston
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Transmission Fourier transform infrared spectroscopy is used to investigate both H@sub 2@O and D@sub 2@O adsorbed on the (100) face of MgO under ambient conditions. A sample cell has been constructed such that many of these infrared transparent surfaces are investigated while the volume of gas phase molecules probed is minimized. A number of crystals, obtained by cleaving with a hammer and chisel a larger single crystal boule under a nitrogen purge, are placed in this cell, which is essentially a hollow stainless steel tube with IR windows on either side. Water is introduced at the desired pressure and allowed to establish a dynamic equilibrium with the MgO(100). The adlayer formed on the crystal faces is observed by transmission Fourier transform infrared (FTIR) spectroscopy. Any IR absorption stemming from molecules in the gas phase in the resulting spectrum is easily subtracted out. From these measurements, we find that water reversibly adsorbs to MgO(100) creating liquid-like layers at room temperature with slight hysteresis seen during a complete adsorption / desorption cycle. The adsorption isotherm of water on MgO(100) resembles a typical BET plot, which coupled with by the fact that IR absorption due to either the OH or OD stretch of the adsorbed water does not change as a function of coverage, suggests that the layer grows in via three-dimensional island formation. Special attention has been paid to the issue of dissociative adsorption of water on the surface, either reversible or permanent with no evidence seen under these experimental conditions.