共查询到18条相似文献,搜索用时 62 毫秒
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本文介绍了CO分子分别与K原子或Na原子在Fe(110)表面上共吸附的研究。角分辨率紫外光电子能谱(ARUPS)的结果表明,碱金属原子在Fe(110)表面上的存在,紫外光电子能谱中出现了结合能低于通常CO分子1π能级的新峰。该峰位于费密能级以下6.3eV处,是C0在碱金属影响下电子结构改变的结果。该峰的出现对应着CO分子处于C—O键明显减弱的状态。偏振紫外光电子能谱的研究表明:6.3eV处的谱峰联系的电子轨道有一个对称平面和一个反对称平面,分别平行于<001>晶向和<110>晶向。CO分子轨道的对称性不因
关键词: 相似文献
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应用XPS,UPS,LEED和TD研究了CO和H2在Pd(110)上在室温下的吸附与并吸附。CO在Pd(110)上随暴露量增加至饱和,吸附位由β1态向β2态变化,相应的XPSC(1s)峰由285.3eV向高结合能方向位移至285.7eV。 相似文献
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在不同K覆盖度的W(100)面上吸附CO的Hel紫外光电子能谱研究表明:α和β态的CO由于K的影响,吸附状态发生改变,与CO分子态(α态)有关的5σ/1π分子轨道能级随K覆盖度的增加,结合能位置从8.6eV移到9.3eV,反映K出现后,衬底对α-CO分子反施的增强。在与CO分解态(β态)有关的谱峰位置上(结合能为5.5eV)出现两个离散的谱峰,一个在6.0eV左右,另一个在5.2eV左右。其中结合能在5.2eV左右的谱峰强度随K的覆盖度增加而增大,它的能量位置与O在K覆盖的W(100)面上吸附时的能级位置
关键词: 相似文献
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本文用密度泛函理论(DFT)的总能计算研究了一氧化碳和氢原子在Ni(111)表面上p(2×2)共吸附系统的原子结构和电子态,结果表明CO和H原子分别被吸附于两个对角p(1×1)元胞的hcp和fcc位置.以氢分子和CO分子作为能量参考点,总吸附能为2.81 eV,相应的共吸附表面功函数φ为6.28 eV.计算得到的C—O,C—Ni和H—Ni的键长分别是1.19?, 1.96?和 1.71?,并且CO分子以C原子处于hcp的谷位与金属衬底原子结合.衬底Ni(111)的最外两层的晶面间距在吸附后的相对变化分别是
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Fisher-Tropsch反应
催化作用
Ni(111) p(2×2)/(CO+H)
共吸附 相似文献
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The coadsorption of CO and K on Fe(110) has been studied using HREELS. Three adsorption states of CO with distinct C-O stretch frequencies have been found. These states, which are occupied sequentially during the exposure to CO and named as 1,2 and 3, have strong (1), intermediate (2) and weak (3) interaction respectively between the adsorbed CO molecule and the coadsorbed K. The distance between the CO molecule and the nearest K neighbor is the shortest for the 1 state and the longest for 3. The distance for the latter is estimated to be larger than 6 Å. 相似文献
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本文用X射线光电子能谱(XPS),紫外光电子能谱(UPS),电子能量损失谱(EELS)和低能电子衍射(LEED)研究了O与预覆盖K的Ag(110)表面相互作用及其性质。在低覆盖度K下,发现有两种O的吸附态,经鉴别为溶解到表面下的O2-和表面上吸附的Ox-增加K的覆盖度,出现分子状态的吸附物O2δ-,它与表面下存在的K相联系。XPS和UPS均清楚地显示出对应于三种不同吸附态的光电子发射峰。Ag(110)表面预覆盖K后的粘滞系数大大增加。K和O的共吸附引起它们彼此向Ag(110)表面下的溶解。LEED实验结果表明,清洁Ag(110)表面覆盖单层K原子后衍射图形从(1×1)变到(1×2),再吸附O后表面吸附层结构变为(2×1)。另外,结合UPS和EELS测量初步考察了O/K/Ag(110)共吸附系统的电子结构。本文还提出了一个共吸附模型来解释这些现象。
关键词: 相似文献
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We report normal emission, angle-resolved photoemission measurements of the system p (1×2)Co-Fe(110) at several photon energies. The lower bind-energy feature, commonly attributed to emission from both the 1π and 5σ molecular orbitals of CO, shifts from 6.9 to 8.1 eV (relative to the Fermi energy) as the photon energy is increased from 21 to 30 eV. We attribute this dispersion to a large variation in cross section for photoionization of the 1π- and 5σ-derived orbitals and use symmetry selection rules to Identify the 6.9 eV component as the 1π and the 8.1 eV component as the 5σ. This ordering is reversed from the gas phase ordering. 相似文献
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利用紫外光电子谱(UPS)对乙烯(C2H4)和乙炔(C2H2)气体在Ru(1010)表面的吸附及与K的共吸附进行了研究,实验结果表明:当衬底温度超过200K,乙烯即发生脱氢反应后,σCH和σCC能级均向高结合能方向移动.在室温下,σCH和σCC能级位置与乙炔在Ru(1010)表面的吸附时的分子能级完全一致.乙烯发生脱氢反应后的主要产
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乙烯
乙炔
钾
Ru(1010)表面 相似文献
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本文利用光学多道分析仪,着重研究了吖啶橙—银胶—吡啶体系;观察了吖啶橙荧光的两次瞬间增强的时间效应荧光谱;分析了吖啶橙与吡啶在银表面上共吸附竞争以及氯化钾在这一竞争中所起的作用。对于表面与分子间相互作用的这一规律作了初步探讨。 相似文献
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The adsorption behavior of CO on a potassium promoted Fe(111) surface was investigated in the range from zero to several monolayers of preadsorbed potassium. TD spectra show that the presence of potassium decreases the amount of CO which is desorbed in the α (molecular) desorption state and increases the desorption temperature of this state. In addition, it gives rise to second, β (recombination) desorption state which is correlated to K desorption. The total CO uptake is comparable to that for the clean surface for precoverages of up to one monolayer, beyond this, however, it increases and at three potassium monolayers it is about twice the clean surface value. At K precoverages above 0.5 monolayer the initial sticking coefficient for CO is greatly reduced so that CO exposures of up to several thousand Langmuirs are required in order to saturate the surface. The three stretch frequencies which are observed in HREELS for CO adsorbed on clean Fe(111) are all affected by the presence of potassium. At potassium precoverages between zero and 0.5 monolayers these frequencies shift both in energy and relative intensity; however, between 0.5 and 1 preadsorbed potassium monolayers the spectra are greatly modified and now show only two losses in the CO stretch region. The lower-frequency one of these gives evidence for a close interaction of CO with the coadsorbed potassium. 相似文献