Current–voltage and low-frequency noise characteristics of structures with porous silicon layers exposed to different gases

Current–voltage and noise characteristics of porous silicon (PS)/single crystalline silicon (SCS) samples were measured under exposure to dry air, air +0.4% CO, dry air +1.7% CO, and dry air+ethyl alcohol vapor. The samples have a sandwich structure comprising Al/PS/SCS/Al. For the dry air +CO mixtures, the noise level was sensitive not only to the presence of CO but also to its percentage, and an increase of the CO concentration led to a change in the spectral density function of the low-frequency noise.     

50 keV/u Ne8+与CO转移电离反应中分子轴取向效应测量

利用反应显微成像谱仪,研究了50 keV/u Ne8+碰撞CO转移电离反应中生成的CO2+碎裂过程。通过重构分子离子爆炸碎片C+和O+的三维动量,获得了质心系中CO2+碎裂过程中释放的动能（KER）。在KER谱中发现了来自亚稳态1Σ+,1Π,3Π解离的峰、3Σ+态解离的峰和1Σ_（II）+态解离的峰,同时发现了排斥态3Σ-的贡献。在3Σ-态解离的分子轴取向分布中,首次观测到CO2+解离的分子轴取向效应。The fragmentations of CO2+ are studied in transfer ionization processes of 50 keV/u Ne8+ impact on CO with reaction microscopes. The 3D momenta of C+ and O+ were measured, and the kinetic energy release (KER) of dissociative(CO2+) was obtained accordingly. The peaks resulted from the metastable states of 1Σ+, 1Π and 3Π, of 3Σ+, and of 1Σ(II)+ are identified in KER spectrum. Meanwhile, the repulsive state of 3Σ- was also observed, which forms a broad peak lying between the peaks of 3Σ+ and 1Σ(II)+. In the CO2+ dissociations from 3Σ- state, the orientation effect of CO molecular axis was observed for the first time.     

固体和熔融碱金属碳酸盐的Raman光谱研究

用高温共焦显微激光 Raman光谱仪测定了不同温度下固体和熔融态的碳酸钠、碳酸锂以及不同成份的固态和液态 Li2 CO3- Na2 CO3混合物的 Raman光谱图 ,分析了 Na+和 Li+对碳酸根离子作用力的变化。根据 CO32 -对称伸缩振动模的波数移动情况 ,在固态混合物中也发现了混合效应     

The electron beam technique in carbon monoxide: Density and quenching rates

Electron-induced emissions of the First Negative System of CO⁺ were studied in CO and Ar+CO(10%) free jets. The mechanisms of the excitation–emission process were analysed to make use of the electron beam technique in CO as well as in a CO+Ar mixture. It was shown that more than 85% of the (0,0) band emission was excited by primary electrons. Rate constants of collisional quenching of the CO⁺(B) state by CO and Ar were measured at low (<200 K) temperatures. The negative temperature dependence of the quenching rates is in qualitative agreement with the results obtained for other molecular ions.     

Stimulated desorption from CO chemisorbed on Cr(110)

Electron stimulated desorption (ESD) experiments using a time-of-flight pulse counting method are reported for molecular CO chemisorbed on the Cr(110) surface at 90 K. Consistent with previous qualitative observations, negligible CO⁺ and O⁺ desorption signals were measured from the ₁CO overlayer which saturates at 1/4 monolayer. For θ_CO > 0.25, a terminally-bonded (₂CO) binding mode is populated in addition to the existing ∝₁CO binding mode and the ion yield increases sharply. For ₂CO, both O⁺ and CO⁺ ions are observed; the CO⁺ ions desorb with characteristically lower kinetic energies than O⁺ ions. Near saturation coverages of CO(ads), an observed decrease in the O⁺ yield is attributed to adsorbate-adsorbate interactions which reduce the ion desorption probability, as seen in ESD studies of terminally-bonded CO on other metals. These results are considered in the context of two possible models proposed for the ₁CO binding state and related ESD observations for CO chemisorbed on Fe(001) and potassium-promoted Ru(001).     

Rotational relaxation rates in CO-He mixtures

The rotational level populations of CO molecules were measured in CO(<10%) + He free jets by electron beam fluorescence (in a stationary jet) and resonantly enhanced multiphoton ionization (in a pulsed jet). The measured evolution of the non-equilibrium rotational energy was used to derive the rotational relaxation cross-sections in the temperature range from 6 K to 140 K. To compare and analyse on a common basis all available experimental data (ours and others) on rotational relaxation of CO in He, the infinite order sudden approximation was explored. The following quantities were investigated: integral rotationally inelastic cross-sections, state-to-state rate coefficients, rotational relaxation times, line broadening coefficients, and non-equilibrium rotational energy distributions in a free jet.     

溶液中CO…CO+体系相互作用的理论研究

在B3LYP/6-311+G水平上利用SCRF方法中的Onsager model模型考察了CO…CO+体系在两种介质(水和苯)中可能存在的相互作用复合物,发现由于H2O与CO+之间存在较强的相互作用,在水中仅能存在一种稳定结构,而在苯溶液中存在三种稳定的复合物.通过消除基函数引起的叠加误差(BSSE)和零点振动能(ZPVE)的校正,精确求算出三种复合物在两种介质中的相互作用能,表明溶剂的性质对复合物的稳定性有着重要的影响.     

Velocity map imaging study of OCS photodissociation followed by S(1S) autoionization at 157 nm

Atomic sulphur ions (S+) were observed directly by crossing a carbonyl sulphide (OCS) molecular beam with a F2 laser. In this study both S+ ion and electron images were measured using the velocity map imaging technique. The results imply that S+ is produced from the well-known photodissociation of OCS at 157 nm leading to the dominant S(1S) + CO(1Σ+) channel, and then the excited S(1S) atom is directly ionized by another 157 nm photon. Correlated vibrationally resolved angular distributions and internal energy distribution of the CO coproducts are reported here and compared with previous studies. This experiment yields strong and sharp S+ images which may be useful for calibrating any imaging or laser ionization apparatus when using a 157 nm laser. A number of technical aspects such as corrections for partial slicing and imperfect laser polarization are described. Abstraction of product angular distributions using both polarized and unpolarized photolysis lasers is also demonstrated using velocity map imaging.     

LiM(M=Ca,Sr,Ba)BO_3∶Tb~(3+)材料光谱特性研究

采用固相法制备了绿色LiM(M=Ca,Sr,Ba)BO3:Tb3+发光材料.测量结果显示材料均可被紫外(350～410 nm)光激发,发射绿光.研究了Tb3+浓度对材料发射光谱的影响,结果显示,随Tb3+浓度的增大,发射光谱峰位未发生变化,但其强度呈现出先增大后减小的趋势,即:存在浓度猝灭效应.加入电荷补偿剂Li+,Na+和K+提高了LiM(M=Ca,Sr,Ba)BO3:Tb抖材料的发射强度.     

CH2Cl与OH自由基反应机理的理论研究

用量子化学从头算方法对CH2 Cl与OH自由基反应生成HCCl+H2 O、HCOCl+H2 和H2 CO +HCl的机理进行了研究 .在UMP2 (FC) / 6 311++G 水平上计算出了各物种的优化构型、振动频率 ;并在Gaussian 3(G3)水平上计算了他们的零点能 (ZPE)、相对能量及总能量 .结果表明 ,CH2 Cl和OH自由基反应首先经无垒过程生成一个富能中间体CH2 ClOH ,中间体再经过一系列原子转移、基团旋转和键断裂分别生成产物HCCl+H2 O、HCOCl+H2 和H2 CO +HCl;三者均为放热反应 ,放热量分别为 72 .81、338.5 4和 35 4 .0 8kJ/mol;生成H2 CO +HCl放出的热量比生成HCCl+H2 O放出的热量多 2 81.2 7kJ/mol,与实验结果吻合 .     

Auger electron emission from fixed-in-space CO

We have measured the angular distribution of carbon K-Auger electrons from fixed in space, core-ionized, CO molecules in coincidence with the kinetic energy release of the C+ and O+ fragments. We find a very narrow ejection of Auger electrons in the direction of the oxygen and an oscillatory diffraction pattern. Even for similar electron energies, the angular distribution strongly depends on the symmetry of the final state.     

Ni(111)表面一氧化碳和氢共吸附的密度泛函理论研究

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 关键词： Fisher-Tropsch反应 催化作用 Ni(111) p(2×2)/(CO+H) 共吸附     

铁铜双核羰基簇合物结构的理论研究

采用密度泛函理论BPW91方法在6-311+G(d)基组水平上, 对FeCu团簇吸附CO过程中可能的几何结构和电子态进行了系统研究. 计算结果表明: FeCu双原子团簇饱和吸附CO分子数是7, 配位过程均为放热反应, 吸附能最大的结构是FeCu(CO)1. 金属原子满足18电子规则,对CO的吸附位置起主要决定作用, 即CO配位由于遵循18电子规律, 即Fe原子上形成Fe(CO)4Cu 之后CO与Cu原子发生配位形成Fe(CO)4Cu(CO)3. 各配合物中 Fe电荷密度最大的结构是Fe(CO)4Cu(CO)1, Cu电荷密度最大的结构Fe(CO)4Cu(CO)3.     

Tracer studies on the reaction path and kinetics of the Co oxidation over iridium

The reaction path and kinetics of the CO oxidation over polycrystalline indium were studied under low pressures by a transient isotope tracer method. Carbon monoxide is oxidized entirely through a Langmuir-Hinshelwood (LH) process, namely CO(a) + O(a) → CO₂. No evidence of an Eley-Rideal process, namely CO(g) + O(a) → CO₂, was observed. At constant temperatures the apparent rate constant of the LH process, i.e., the CO₂ formation rate divided by the product of the coverages of CO and oxygen, decreased rapidly with an increase in the total coverage. The kinetics was explained in terms of the boundary reaction model in which the oxidation took place predominantly outside or near the boundary of the CO(a) island.     

CaO表面CO对NO还原作用的实验与模型研究

循环流化床炉内石灰石脱硫对NOx排放产生影响,包括对挥发分氮氧化的催化作用以及对CO-NO还原的催化作用。利用固定床反应器对不同条件下CaO颗粒表面NO+CO的催化反应特性进行了探究。实验表明,无氧条件下,CaO能够显著催化CO还原NO,NO转化率与反应温度和CO浓度正相关,与NO浓度负相关.基于Langmuir-Hinshelwood机理建立了CaO催化NO+CO反应动力学模型,模型考虑了颗粒内、外扩散的影响.该模型适用于氧气浓度很低、CO浓度较高条件下。而在有氧气氛中,该反应受到明显抑制,且O2浓度越高,抑制作用越明显;当CaO周围氧气浓度远大于CO时,可忽略CaO对NO的催化还原作用。     

FeO+催化N2O与CO反应的密度泛函理论研究

本文采用密度泛函理论DFT-B3LYP方法6-311+G(2d) 的基组, 计算研究了气相中六重态和四重态FeO+离子催化N2O和CO生成N2和 CO2反应的微观机理, 通过计算两种重态金属离子亲氧性（OA）, 从热力学方面说明了主题反应的可行性。分析反应过程的热力学性质和动力学因素得到FeO+与N2O复合生成反应复合物, 之后继续与CO复合成中间体是能量有利反应路径,所得结果与实验观测相符.     

FeO~+催化N_2O与CO反应的密度泛函理论研究

本文采用密度泛函理论DFT-B3LYP方法6-311+G(2d)的基组,计算研究了气相中六重态和四重态FeO+离子催化N2O和CO生成N2和CO2反应的微观机理,通过计算两种重态金属离子亲氧性(OA),从热力学方面说明了主题反应的可行性.分析反应过程的热力学性质和动力学因素得到FeO+与N2O复合生成反应复合物,之后继续与CO复合成中间体是能量有利反应路径,所得结果与实验观测相符.     

TP-LIF技术测量甲烷-空气火焰中CO的相对浓度分布

 阐述了双光子激光诱导荧光(TP-LIF)技术的原理及线性模型，利用双光子过程激励CO分子B¹∑+←←X¹∑＋(0,0)带Q支的跃迁(约230 nm)，分析了B¹∑+→A¹Π荧光带的荧光光谱特性，探讨了激光功率密度、激光波长及火焰温度等因素对测量的影响，并给出甲烷-空气火焰在一定燃烧条件下CO分子浓度随火焰位置及高度的变化关系。实验结果表明，利用TP-LIF技术测量CO的浓度分布，其时空分辨率及探测灵敏度都很高。当激光功率密度较强时，TP-LIF信号和激光能量成线性关系，而且由于光电离速率的增强，大大降低了碰撞猝灭速率等环境因素对信号测量造成的影响，该特性对实验标定及定量测量都非常有帮助。     

Nitric oxide reduction by CO ON Rh(111): Temperature programmed reaction

The reaction of NO with CO on Rh(111) has been studied with temperature programmed reaction (TPR). Comparisons are made with the reaction of O₂ with CO and the reaction of NO with H₂. The rate-determining step for both CO oxidation reactions is CO(a) + O(a) → CO₂(g). Repulsive interactions between adsorbed CO and adsorbed nitrogen atoms lead to desorption of CO in a peak at 415 K which is in the temperature range where the reaction between CO(a) and O(a) produces CO₂(g). Thus the extent of reaction of CO(a) with NO(a) is less than that between CO(a) and O(a) due to the lower coverage of CO caused by adsorbed N atoms and NO. A similar repulsive interaction between NO(a) and H(a) suppresses the NO + H₂ reaction. CO + NO reaction behavior on Rh(111) is compared to that observed on Pt(111).