Interaction of Water with the Surface of SrF₂. 2. Physisorption of Water on Water Strongly Adsorbed onto SrF₂

When physisorption of H₂O occurs on the strongly adsorbed H₂O on SrF₂, the IR peaks at 3684, 2561, 1947,1656, and 1000 cm^-1, which originate from the strongly adsorbed H₂O being hydrogen-bonded to the surface F^- ion in the form of OH-F^-, are widely varied: the consolidation of the peak at 3684 cm^-1 into a broad band centered at 3400 cm^-1, the shift of the peak at 2561 cm^-1 to 2980 cm^-1, the disappearance of the peak at 1947 cm^-1, the appearance of the peak at 2280 cm^-1, an increase in the intensity of the peak at 1656 cm^-1, and a gradual shift of the peak at 1000 cm^-1 to 880 cm^-1. Most of these phenomena were interpreted in terms of the physisorption of H₂O on top of the surface F^- ion, which results in a weakening of the hydrogen bonding of the preadsorbed H₂O. An additional effect comes from the physisorbed H₂O itself.