Borodin A, Höfft O, Kahnert U, Kempter V, Poddey A, Blöchl P E
Institut für Physik und Physikalische Technologien, Technische Universität Clausthal, Leibnizstrasse 4, D-38678 Clausthal-Zellerfeld, Germany.
J Chem Phys. 2004 Nov 15;121(19):9671-8. doi: 10.1063/1.1805498.
The interaction of NaCl with solid water, deposited on tungsten at 80 K, was investigated with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS) (He I). We have studied the ionization of Cl(3p) and the 1b(1), 3a(1), and 1b(2) bands of molecular water. The results are supplemented by first-principles density functional theory (DFT) calculations of the electronic structure of solvated Cl(-) ions. We have prepared NaCl/water interfaces at 80 K, NaCl layers on thin films of solid water, and H(2)O ad-layers on thin NaCl films; they were annealed between 80 and 300 K. At 80 K, closed layers of NaCl on H(2)O, and vice versa, are obtained; no interpenetration of the two components H(2)O and NaCl was observed. However, ionic dissociation of NaCl takes place when H(2)O and NaCl are in direct contact. Above 115 K solvation of the ionic species Cl(-) becomes significant. Our results are compatible with a transition of Cl(-) species from an interface site (Cl in direct contact with the NaCl lattice) to an energetically favored configuration, where Cl species are solvated. The DFT calculations show that Cl(-) species, surrounded by their solvation shell, are nevertheless by some extent accessed by MIES because the Cl(3p)-charge cloud extends through the solvation shell. Water desorption is noticeable around 145 K, but is not complete before 170 K, about 15 K higher than for pure solid water. Above 150 K the NaCl-induced modification of the water network gives rise to gas phase like structures in the water spectra. In particular, the 3a(1) emission turns into a well-defined peak. This suggests that under these conditions water molecules interact mainly with Cl(-) rather than among themselves. Above 170 K only Cl is detected on the surface and desorbs around 450 K.
利用亚稳态冲击电子能谱（MIES）和紫外光电子能谱（UPS，He I）研究了80 K下沉积在钨上的氯化钠与固态水之间的相互作用。我们研究了氯（3p）的电离以及分子水的1b(1)、3a(1)和1b(2)能带。通过对溶剂化Cl(-)离子电子结构的第一性原理密度泛函理论（DFT）计算对结果进行了补充。我们在80 K下制备了氯化钠/水界面、固态水薄膜上的氯化钠层以及氯化钠薄膜上的H₂O吸附层；它们在80至300 K之间进行了退火处理。在80 K时，获得了H₂O上的氯化钠封闭层，反之亦然；未观察到H₂O和氯化钠这两种成分的相互渗透。然而，当H₂O和氯化钠直接接触时，氯化钠会发生离子解离。在115 K以上，离子物种Cl(-)的溶剂化变得显著。我们的结果与Cl(-)物种从界面位置（与氯化钠晶格直接接触的Cl）转变为能量上更有利的构型（其中Cl物种被溶剂化）相一致。DFT计算表明，被溶剂化壳包围的Cl(-)物种在一定程度上仍可被MIES探测到，因为Cl(3p)电荷云延伸穿过溶剂化壳。水的脱附在145 K左右明显，但在170 K之前并不完全，比纯固态水的脱附温度高约15 K。在150 K以上，氯化钠对水网络的改性导致水光谱中出现类似气相的结构。特别是，3a(1)发射变成一个明确的峰。这表明在这些条件下，水分子主要与Cl(-)相互作用，而不是彼此之间相互作用。在170 K以上，表面仅检测到Cl，并在450 K左右脱附。
