Vogt Jochen
Chemisches Institut der Universität Magdeburg, Universitätsplatz 2, D-39106 Magdeburg, Germany.
J Chem Phys. 2007 Jun 28;126(24):244710. doi: 10.1063/1.2748376.
The interaction of water with the BaF2(111) single crystal surface is investigated using the helium atom scattering technique. It is found that H2O forms a long-range ordered two-dimensional (2D) phase with (1 x 1) translational symmetry already after an exposure of 3 L (1 L=10(-6) Torr s) at temperatures below 150 K. The activation energy for desorption of the saturated 2D phase, which is assigned to a bilayer, is estimated to be 46+/-2 kJ mol(-1), corresponding to a desorption temperature of 165 K. The desorption of multilayers was observed at 150 K, consistent with a binding energy of 42+/-2 kJ mol(-1). Before completion and after desorption of the saturated 2D phase, a superstructure consistent with a disordered (square root of 3 x square root of 3)R30 degrees lattice has been observed, which is attributed to the first layer of water with a coverage of one molecule per surface unit cell, in accordance with recent theoretical studies. Desorption of this phase is observed at temperatures above 200 K, consistent with an unexpectedly strong bonding of the molecules to the substrate.
利用氦原子散射技术研究了水与BaF₂(111)单晶表面的相互作用。研究发现，在低于150 K的温度下暴露3 L（1 L = 10⁻⁶托秒）后，H₂O就会形成具有(1×1)平移对称性的长程有序二维(2D)相。饱和二维相（被认为是双层）的解吸活化能估计为46±2 kJ mol⁻¹，对应解吸温度为165 K。在150 K时观察到多层的解吸，这与42±2 kJ mol⁻¹的结合能一致。在饱和二维相形成完成之前和解吸之后，观察到一种与无序的(√3×√3)R30°晶格一致的超结构，根据最近的理论研究，这归因于第一层水，其覆盖度为每个表面单位晶胞一个分子。在高于200 K的温度下观察到该相的解吸现象，这与分子与衬底之间意外强烈的键合相一致。
