C2H2,C2H4与K在Ru(1010)表面上共吸附的UPS研究

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,σ_CH和σ_CC能级均向高结合能方向移动.在室温下,σ_CH和σ_CC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 关键词： 乙烯 乙炔 钾 Ru(1010)表面     

C2H4在清洁和有Cs覆盖的Ru(0001)表面吸附的TDS研究

用热脱附谱(TDS)方法研究了乙烯(C₂H₄)在Ru(0001)表面上的吸附.在低温下(200K以下)乙烯可以在清洁及有Cs的Ru(0001)表面上以分子状态稳定吸附,在衬底温度升高至200K以上时,乙烯发生了脱氢分解反应,乙烯分解后的主要产物为乙炔(C₂H₂).在清洁的Ru(0001)表面,乙烯有两种吸附状态,脱附温度分别为275K和360K.而乙炔的脱附温度为350K.在Ru(0001)表面有Cs的存在时,乙烯分解 关键词： 乙烯 钌(0001)表面 铯钌(0001)表面乙烯 钌(0001)表面 铯钌(0001)表面     

C2H4在Ru(10(1-)0)表面吸附与分解的研究

用X射线电子能谱(XPS)、热脱附谱(TDS)和紫外光电子能谱(UPS)方法研究了乙烯(C2H4)在Ru(10(1-)0)表面的吸附,在低温下(200K以下)乙稀(C2H4)可以在Ru(10(1-)0)表面上以分子状态稳定吸附,在200K以上乙烯(C2H4)则发生了脱氢分解反应.TDS结果表明乙烯(C2H4)分解后的主要产物为乙炔(C2H2).乙烯(C2H4)分解后C的1s能级向低结合能方向移动了0.3eV,而价态σCC和σCH轨道能级向高结合能方向分别移动了0.5和1.1eV.     

C2H2,C2H4与K在Ru（1010）表面上共吸附的UPS研究

利用紫外光电子谱(UPS)对乙烯(C2H4)和乙烯(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能级均高结合方向移动．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物为乙炔。衬底温度从120K升到室温,Ru(1010)表面上乙炔的σCH和σCC能级均未发现变化．室温下乙炔仍然可以在Ru(1010)表面以分子状态稳定吸附．在有K的Ru(1010）表面上．室温时σCH谱峰几乎消失．碱金属K的存在促进了乙炔的分解．     

C2H4/Ni(100)近边X射线吸收谱的多重散射理论研究

本文用多重散射原子集团方法计算并分析了C₂H₄/Ni(100)系统的碳K边近边X射线吸收精细结构(NEXAFS)谱,确定了乙烯吸附在Ni(100)表面上的几何结构。结果表明,乙烯是吸附在垂直桥位上的,其中碳原子与表面最近的镍原子距离是1.70?,而乙烯分子平面倾斜于表面50°,同时发现,氢和镍之间的相互作用对结构的形成有很大的作用,这些结果得到了不同途径的验证。 关键词：     

C2H2在金刚石（001）-（2×1）重构面上吸附的分子动力学模拟

利用Brenner半经验多体相互作用势和分子动力学模拟方法，研究了乙块（C₂H₂）分子在金刚石（001）-（2×1）重构表面上的碰撞动力学过程与化学吸附构型的关系.观察到C₂H₂在金刚石表面的6种吸附结构.约95％的吸附呈C₂H₂与表面形成两个σ单键的形式.讨论了轰击能量、入射位置及金刚石表面原子的空间位形对各种吸附构型形成的影响.还给出了化学吸附过程的分子快照，并讨论了C₂H₂分子与表面的能量交换关系. 关键词：     

50—5000 eV电子被C4H8O,C5H10O2, C6H5CH3和C4H8O2散射的总截面

使用电子被C, H和O原子散射总截面的实验数据, 利用修正后的可加性规则计算了能量为50—5000eV的电子被4个复杂大分子C₄H₈O, C₅H₁₀O₂, C₆H₅CH₃和C₄H₈O₂散射的总截面, 并将计算结果与实验结果及其他理论计算结果进行了比较. 结果表明, 即 关键词： 电子散射 可加性规则 总截面 几何屏蔽效应     

乙烯在Ru（1010）表面价带电子特性研究

在200K以下乙烯(C2H4)可以在Ru（1010）表面上以分子状态稳定吸附,200K以上乙烯发生了脱氢分解反应生成乙炔(C2H2)。乙烯分解生成乙炔后,σCC和σCH分子轨道能级向高结合能方向分别移动了0．5和1.1eV。偏振角分辨紫光电子谱（ARUPS)结果表明：在RM（1010）表面上,乙烯和脱氨反应后生成的乙炔分子的C—C键轴都不平行于表面,而是沿表面(0001)晶向倾斜。     

Si衬底上异质外延金刚石的初始阶段原子H的作用及其界面结构

用高分辨率电子能量损失谱方法研究了原子H与被C₂H₂吸附的Si(100)界面的相互作用.结果显示,在Si(100)界面上,Si—Si二聚化键和C₂H₂中的C—C键被H原子打开,它们分别形成Si—H,C—H键.用AM1量子化学方法,计算了C₂H₂和C₂H₄在Si(100)上的吸附结构,指出了C₂H_{2关键词：}     

乙烯在Ru( )表面价带电子特性研究

在200K以下乙烯（C2H4）可以在Ru（1010^-）表面上以分子状态稳定吸附,200K以上乙烯发生了脱氢分解反应生成乙炔（C2H2）。乙烯分解生成乙炔后,σCC和σCH 分子轨道能级向高结合 能方向分别移动了0.5和1.1eV。偏振角分辨紫外光电子谱（ARUPS）结果表明：在Ru(10106-)表面上,乙烯和脱氢反应后生成的乙炔分子在C－C键轴都不平行 于表面,而是沿表面<0001>晶向倾斜。     

An XPS and UPS investigation of the adsorption of ethylene on the (111) surface of silver

Monolayer adsorption of pure ethylene on the (111) surface of saver at 80 K has been studied by X-ray (hv = 1486.6 eV) and ultraviolet (hv = 21.2 and 40.8 eV) photoelectron spectroscopy. The density of the adlayer is approximately 5 × 10¹⁴ molecules/cm² at saturation, multilayer formation being prohibited by the ultrahigh vacuum of the spectrometer. The molecular orbitals designated σ¹_CH, σ_CC, σ_CH and 2ss¹ by Demuth are observed at 7.0, 9.0, 10.3 and 13.6 eV below the Fermi level, respectively, but the higher lying π level is obscured by the silver d-band emission. The data are consistent with an undistorted molecule, adsorbed with the molecular axis parallel to the surface. Desorption occurs below 200 K without significant decomposition products remaining on the surface in agreement with the conventional notion that clean silver is relatively inert with respect to olefin adsorption.     

Photoemission studies of H2S,H2 and S adsorbed on Ru(110): Evidence for an adsorbed SH species

H₂S, H₂ and S adsorbed on Ru(110) have been studied by angle-integrated ultraviolet photoemission (UPS) as part of a study of the effect of adsorbed sulfur, a common catalytic poison, on this Ru surface. For low exposures of H₂S at 80 K, the work function rises to a value 0.16 eV above that of clean Ru(110) while the associated UPS spectra (hν = 21.2 eV) exhibit features similar to those of H(ads) and S(ads) and different from those of molecular H₂S. We conclude that H₂S dissociates completely at low coverages on Ru(110) at 80 K. At intermediate exposures the work function drops and the UPS spectra show new features which are attributed to the presence of an adsorbed SH species. This appears to be the first direct observation of this surface complex. At higher exposures the work function saturates at a value 0.36 eV below the clean value; the UPS spectra change markedly and indicate the adsorption of molecular H₂S. Heating adsorbed H₂S leaves a stable layer of S(ads) on Ru(110). The surface with adsorbed sulfur strongly modifies the adsorption at 80 K of a number of molecules relative to the clean Ru(110) surface.     

ELECTRONIC STRUCTURE STUDIES OF THE C60 FILM CONDENSED ON 2H-MoS2(0001) SURFACE

The electronic structure and vibrational spectrum of the C₆₀ film condensed on a 2H- MoS₂(0001) surface have been investigated by X-ray photoelectron spectroscopy (XPS), ul-traviolet photoelectron spectroscopy (UPS), Auger electron spectroscopy (AES) and infrared high-resolution electron-energy-loss spectroscopy (HREELS). AES analysis showed that at low energy side of the main transition, C₆₀ contains a total of three peaks just like that of graphite. However, the energy position of the KLL main Auger transition of C₆₀ looks like that of diamond, indicating that the hybridization of the carbon atoms in C₆₀ is not strictly in sp²- bonded state but that the curvature of the molecular surface introduces some sp²pz- bonded character into the molecular orbitals. XPS showed that the C 1s binding energy in C₆₀ was 285.0eV, and its main line was very symmetric and offered no indication of more than a single carbon species. In UPS measurement the valence band spectrum of C₆₀ within 10eV below the Fermi level (E_F) shows a very distinct five-band structure that character-izes the electronic structure of the C₆₀ molecule. HREEL results showed that the spectrum obtained from the C₆₀ film has very rich vibrational structure. At least, four distinct main loss peaks can be identified below 200 meV. The most intense loss was recorded at 66 meV, and relatively less intense losses were recorded at 95, 164 and 197meV at a primary energy of electron beam E_P = 2.0eV. The other energy-loss peaks at 46, 136, 157 and 186meV in HREEL spectrum are rather weak. These results have been compared to infrared spectrum data of the crystalline solid C₆₀ taken from recent literatures.     

Thermal evolution of acetylene and ethylene on Pd(111)

The thermal evolution of acetylene and ethylene and their deuterated counterparts on a palladium (111) surface has been studied by high-resolution electron energy loss spectroscopy in the temperature range 150–500 K. Analysis of the vibrational spectra indicates that chemisorbed acetylene evolves at 300 K in the presence of surface hydrogen to mainly ethylidyne, CCH₃, and a small amount of residual acetylene. Spectra obtained with and without preadsorbed hydrogen provide evidence for a 〉C CH₂ intermediate in the reaction. Chemisorbed ethylene also evolves to ethylidyne after heating from 150 to 300 K but much of the ethylene desorbs. The high temperature (400–500 K) behavior of C₂H₂ and C₂H₄ involves formation of a CH species. Although a small amount of the CH species may be formed from the dehydrogenation of ethylidyne, it is found that carbon-carbon bond scission of acetylene near 400 K is the dominant mechanism in CH formation.     

Adsorption and reactions of CH2I2 on Ru(001) surface

The adsorption and dissociation of CH₂I₂ were studied at 110 K with the aim of generating CH₂ species on the Ru(001) surface. The methods used included X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and work function measurements. Adsorption of CH₂I₂ is characterized by a work function decrease (0.96 eV at monolayer), indicating that adsorbed CH₂I₂ has a positive outward dipole moment. Three adsorption states were distinguished: a multilayer (T_p=200 K), a weakly bonded state (T_p=220 K) and an irreversibly adsorbed state. A new feature is the formation of CH₃I, which desorbs with T_p=160 K. The adsorption of CH₂I₂ at 110 K is dissociative at submonolayer, but molecular at higher coverages. Dissociation of the monolayer to CH₂ and I proceeded at 198–230 K, as indicated by a shift in the I(3d_5/2) binding energy from 620.6 eV to 619.9 eV. A fraction of adsorbed CH₂ is self-hydrogenated into CH₄ (T_p=220 K), and another one is coupled to di-σ-bonded ethylene, which — instead of desorption — is converted to ethylidyne at 220–300 K. Illumination of the adsorbed CH₂I₂ initiated the dissociation of CH₂I₂ monolayer even at 110 K, and affected the reaction pathways of CH₂.     

Bond polarization and image-potential screening in adsorbed C6F6 on Cu(1 1 1)

The orientation of hexafluorobenzene (C₆F₆) on the Cu(1 1 1) surface has been determined for different coverages with the help of near edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption geometry and the bonding mode of C₆F₆ differ significantly in comparison to its hydrocarbon analog C₆H₆. C₆F₆ is found to adsorb on Cu(1 1 1) with the ring plane parallel to the surface for coverages below 10 ML. Next to the distinct multilayer, bilayer and monolayer phases we also present evidence of sub-monolayer (i.e., 1/2 ML) coverage with different electronic structure. These findings are explained in a phenomenological model based on fluorine’s property as a σ-acceptor and a π-donor and the resulting bond polarization within the molecule, which is stabilized by image-potential screening within the substrate.     

Characterization of methylidyne on Pt(1 1 1) with infrared spectroscopy

Methylidyne (CH) was prepared on Pt(1 1 1) by three methods: thermal decomposition of diiodomethane (CH₂I₂), ethylene decomposition at temperatures above 450 K, and surface carbon hydrogenation. Methylidyne and its precursors are characterized by reflection absorption infrared spectroscopy (RAIRS). The C-I bond of diiodomethane breaks upon adsorption to produce methylene (CH₂), which decomposes to methylidyne at temperatures above 130 K. Above 200 K, methylidyne is the only hydrocarbon species observed with RAIRS, although reaction channels for the formation of methane (CH₄) and ethylene (C₂H₄) are indicated by temperature programmed desorption (TPD). As is well known from numerous previous studies, ethylene decomposes to ethylidyne (CCH₃) upon exposure to Pt(1 1 1) at 410 K. Upon annealing to 450 K, ethylidyne dissociates through two reaction pathways, dehydrogenation to ethynyl (CCH) and C-C bond scission to methylidyne. Ethylene dehydrogenation on the surface at 750 K and under low ethylene exposures produces surface carbon that can be hydrogenated to methylidyne with C-H and C-D stretch frequencies of 2956 and 2206 cm⁻¹, respectively. Hydrogen co-adsorption on the surface causes these frequencies to shift to higher values. Methylidyne is stable on Pt(1 1 1) to temperatures up to 500 K.     

FePc与TiO2(110)及C60界面电子结构研究

基于C₆₀受体和有机分子给体的太阳能电池是目前非常重要的一个研究热点, 利用同步辐射真空紫外光电子能谱(SRUPS) 技术研究了酞菁铁(FePc)与TiO₂(110)及C₆₀的界面电子结构, 以及FePc与C₆₀分子混合薄膜的电子结构. SRUPS价带谱显示, FePc沉积在化学计量比与还原态两种不同的TiO₂(110)表面时, FePc分子的HOMO能级均随FePc厚度的变化发生了移动, 而在化学计量比的TiO₂(110)表面位移较大, 同时发生界面能带弯曲, 说明存在从有机层向衬底的电子转移. 在FePc/C₆₀和C₆₀/FePc界面形成过程中, FePc与C₆₀分子的最高占据分子轨道(HOMO)位移大小基本相同. 由界面能级排列发现, 在FePc与C₆₀的混合薄膜中, FePc分子的HOMO与C₆₀分子的最高占据分子轨道能级差较大, 这有利于提高器件开路电压, 改善器件性能.