PHYSISORPTION OF CO ON AG(111) - INVESTIGATION OF THE MONOLAYER AND THE MULTILAYER THROUGH HREELS, ARUPS, AND TDS
PHYSISORPTION OF CO ON AG(111) - INVESTIGATION OF THE MONOLAYER AND THE MULTILAYER THROUGH HREELS, ARUPS, AND TDS
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DOI：
10.1016/0039-6028(91)90576-e
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发表时间：
1991-08-01
期刊：
影响因子：
1.9
通讯作者：
JACOBI, K
中科院分区：
文献类型：
--
作者：
HANSEN, W;BERTOLO, M;JACOBI, K
通过高分辨率电子能量损失光谱 (HREELS)、角分辨紫外光电子能谱 (ARUPS) 和热解吸光谱 (TDS) 在低于 35 K 的温度下研究了 CO 与 Ag(111) 的相互作用。 根据 HREELS 中观察到的 nu-(C-O) 拉伸模式的偶极活性以及 ARUPS 中偶极选择规则的应用，我们得出结论，分子在单层中以分子轴的随机方向被吸收。 在单层中没有观察到价态的分散。 在多层中，5-sigma 能级在 GAMMA-BAR 点处呈现出相当于 0.65 eV 的分裂，并在 k-parallel-to = 0.8 angstrom-1 处消失，表明在晶胞中形成了具有多个分子的有序超结构。 4-sigma 水平根本无法解决任何分裂问题。 根据气相 HREELS 测量可知，负离子共振散射只有在超过一个单层的覆盖范围时才能观察到，这表明即使在物理吸附的情况下，金属表面也会影响未占据的 2-pi 水平的 CO。
The interaction of CO with Ag(111) has been investigated at temperatures below 35 K through high-resolution electron energy-loss spectroscopy (HREELS), angle-resolved UV photoelectron spectroscopy (ARUPS), and thermal desorption spectroscopy (TDS). From the dipole activity of the nu-(C-O) stretching mode observed in HREELS and from the application of the dipole selection rule in ARUPS we conclude that the molecules are absorbed with a random orientation of the molecular axis in the monolayer. No dispersion of the valence levels is observed in the monolayer. In the multilayer the 5-sigma level exhibits a split which amounts to 0.65 eV at the GAMMA-BAR point and vanishes at k-parallel-to = 0.8 angstrom-1 indicating the formation of an ordered overstructure with more than one molecule in the unit cell. No split at all could be resolved for the 4-sigma level. The negative ion resonance scattering, known from HREELS measurements in the gas phase, is observed only when the coverage of one monolayer is exceeded, indicating that even in the case of physisorption the metal surface influences the unoccupied 2-pi level of CO.