乙酸在SmOx/Rh(100)模型表面上的吸附和分解

 用高分辨电子能量损失谱（HREELS）和热脱附谱（TDS）研究了\r\n乙酸在SmOx／Rh（100）模型表面上的吸附与分解．结果表明：低温下\r\n吸附乙酸时，SmOx的加入明显促进了乙酸分子中O－H键的断裂，从而有\r\n利于乙酸根的形成；升高表面温度，SmOx的存在促进了乙酸根中C－C键\r\n的断裂，有利于乙酸根的进一步分解．120K时，乙酸在SmOx／Rh（100\r\n）上主要以乙酸根的形式存在．225K时，乙酸根即可发生以生成CO为主\r\n的脱羧反应．在417和477K观察到受表面脱羧反应控制的CO2和H2的脱附\r\n峰．对反应的机理进行了讨论．     

乙醇在Mn薄膜／Rh（100）上吸附和分解的研究

应用高分辨电子能量损失谱（HREELS）和热脱附谱（TDS）,研究了Mn薄膜／Rh(100)上乙醇的吸附和分解,提出了表面吸附和分解的反应工,在300K时,蒸镀的Mn在清洁Rh(100)表面上以层层模式生长;在130－300K间,在25mLMn/Rh(100)表面上吸附20L乙醇的TDS结果与乙醇在Rh(100)表面上的结果一致在155K处,脱附出多层凝聚态吸附的乙醇;升温到255K,脱附出H2和CH4,继续升温,出现了与乙醇在R (100)表面上不一致的现象,在470K,同时出现了第2个H2和CH4的脱附峰,在500K,脱附极少量的CO;在950K附近,脱附出大量CO。     

Rh／SiO2催化剂上甲烷部分氧化制合成气反应

 利用程序升温脱附、程序升温还原、程序升温表面反应、程序升温反应和化学捕获反应等手段，对Rh／SiO2催化剂上甲烷部分氧化制合成气反应进行了研究．结果表明，Rh／SiO2催化剂上甲烷部分氧化制合成气机理属于热解－氧化反应机理．甲烷首先在催化剂上发生解离吸附，产生具有不同H／C比的化学吸附物种CHx（x＝1～3）．其中，具有较高H／C比的CHx可能是甲烷部分氧化反应的活性物种，而具有较低H／C比的CHx可能是催化剂上积碳并导致催化剂失活的来源．活性物种CHx在活性氧物种的作用下，生成含氧中间体物种CHxO或继续脱氢．含氧中间体物种进一步分解，即生成CO和H2；CO2也可由CHx或CHxO物种进一步氧 化生成．     

铁助剂对Rh-Mn-Li/SiO2催化剂表面上的CO脱附和CO加氢行为的影响

 采用一氧化碳程序升温脱附（CO－TPD）和吸附的一氧化碳加氢程序升温表面反应（TPSR）考察了Fe助剂对Rh基催化剂上CO的脱附行为及吸附CO的加氢行为的影响．CO－TPD实验表明，在Rh／SiO2催化剂上CO有三个脱附峰．在Rh－Mn－Li／SiO2中加入0．05％Fe后，高温脱附CO比Rh／SiO2催化剂上相应的CO量大．增加Fe的负载量，CO的脱附量减少．TPSR实验中，CO加氢反应的主要产物是甲烷．不同组分的催化剂上甲烷的生成温度有如下顺序：Rh／SiO2（482K）＜Rh－Mn－Li／SiO2（489K）＜Rh－Fe／SiO2（494K）＜Rh－Mn－Li－Fe／SiO2（501K）．甲烷峰的产生伴随着CO（s）高温脱附峰的消失，说明甲烷是由强吸附的CO加氢生成的．     

H2对Rh-Mn-Li-Ti/SiO2催化剂上CO吸附和脱附的影响

 应用红外光谱和程序升温脱附技术研究了Rh-Mn-Li-Ti/SiO2催化剂上H2对CO吸附和脱附的影响. 结果表明,预吸附的H2主要占据线式CO的吸附位. 共吸附时H2与CO在Rh位上形成了羰基氢化物,从而导致线式物种谱带红移,且高的H2浓度有利于CO的吸附. 在323 K下, H2对预吸附的CO谱带位置和强度没有影响. 但是,随着温度的升高, H2的存在促进了弱吸附CO的脱附,并使之重新吸附; 同时, H2促进了强吸附CO的解离,增强了CO的吸附强度和催化剂的吸附能力.     

CuO-ZnO-ZrO2催化甲醇水蒸汽重整反应机理和中间态

应用质谱在线技术,对CuO-ZnO-ZrO2催化甲醇水蒸汽重整（SRM）反应进行程序升温脱附（TPD）和程序升温表面反应（TPSR）研究.结果表明:在反应态催化剂表面,甲醇以分子吸附态形式存在,甲醇水蒸汽重整反应经历甲酸根中间物种.分别用CuO、CuO-ZnO、CuO-ZnO-ZrO2作催化剂,甲醇在气流中的摩尔分数分别高于5.4％、0.37％和0.17％时,甲酸根中间态的分解产物为CO2和H2;而甲醇在气流中的摩尔分数分别低于5.4％、0.37％和0.17％时,甲酸根中间态的分解产物为CO、CO2和H2.     

羧酸在Zn（0001）,Bi（0001）和多晶锰表面的吸附

本文用ESCA法研究了羧酸与清洁及预氧化的Zn(0001)、Bi(0001)和多晶Mn表面的反应.80 K时乙酸分子吸附于清洁的Zn(0001)表面,150K即完全脱附,不发生任何化学反应;乙酸与Zn (0001)-O表面80 K便发生反应,生成乙酸基和水,此表面水于136 K脱附.甲酸分子80 K吸附在清洁Bi(0001)表面,140 K便大部脱附;在Bi(0001)-O表面甲酸80 K便分解为表面甲酸根和水,表面水于170 K脱附,甲酸根则在428 K分解脱附.清洁的多晶Mn表面有强的亲氧性,室温下甲(乙)酸在其表面分解吸附,吸附物种为晶格氧O~(2-)、甲(乙)酸根、CH_x(C_2H_x)和已经形成了碳化锰的表面碳C_(α)~(δ-).650K(550 K)时甲(乙)酸根完全分解,Mn表面仅存O~(2-)和C~(δ-).甲(乙)酸室温下以甲(乙)酸根吸附于Mn-O表面,加热可使表面甲酸根分解.     

~(15)NO与Mo(100)-c(2×2)N表面相互作用的HREELS和TDS研究

利用高分辨电子能量损失谱（ Ｈ Ｒ Ｅ Ｅ Ｌ Ｓ） 和热脱附谱（ Ｔ Ｄ Ｓ）, 研究了１５ Ｎ Ｏ 在 Ｍｏ（１００）ｃ（２×２） Ｎ 表面上的吸附态及其随温度的变化． １２０ Ｋ 时, 在 Ｍ ｏ（１００）ｃ（２×２） Ｎ 表面低暴露量的１５ Ｎ Ｏ 发生解离和分子吸附, 解离生成的１５ Ｎ 在１ ２３０ Ｋ 与另一１５ Ｎ 原子或氮化钼中的１４ Ｎ 原子并合、脱附． 在升温时大部分分子吸附的１５ Ｎ Ｏ 发生解离和反应, 解离生成的１５ Ｎ 原子与另一１５ Ｎ 原子生成１５ Ｎ２ 而脱附, 或与表面残存的１５ Ｎ Ｏ 生成１５ Ｎ２ Ｏ 脱附． １５ Ｎ２ Ｏ 的脱附峰温与 Ｍｏ（１００）表面相比, 升高了约１５０ Ｋ, 可能与形成氮化钼后电子由金属钼向非金属氮转移有关． 电子能量损失谱（ Ｅ Ｌ Ｓ）表明, １５ Ｎ Ｏ 在 Ｍｏ（１００）ｃ（２×２） Ｎ 表面生成了一种新的１４ Ｎ１５ Ｎ Ｏ 物种． ３００ Ｋ 时, 低暴露量的１５ Ｎ Ｏ 在 Ｍ ｏ（１００）ｃ（２×２） Ｎ 表面解离吸附; 高暴露量时, 存在分子吸附的１５ Ｎ Ｏ．     

H2在K0-MWCNTs上储存和吸附/脱附特性研究

利用高压容积法辅以卸压升温脱附排水法，测定金属K修饰多壁碳纳米管对H2的吸附储存容量．结果表明，在室温(25℃)，7．25MPa实验条件下，x％K^0-MWCNTs （x%=30％～35％，质量百分数)对H2的吸附储存容量可达3．80wt％(质量百分数)，是相同条件下单纯MWCNTs氢吸附储量的2．5倍；室温下卸至常压的脱附氢量为3．36wt％(占总吸附氢量的～88％)，后续升温至673K的脱附氢量为0．41wt％(占总吸附氢量的～11％)．利用LRS和H2-TPD-GC／MS等谱学方法对H2/K^0-MWCNTs吸附体系的表征研究表明，H2在K^0-MWCNTs上吸附存在非解离(即分子态)和解离(即原子态)两种吸附态；在≤723K温度下，H2／K^0-MWCNTs体系的脱附产物几乎全为H2气；723K以上高温脱附产物不仅含H2，也含有CH4，C2H4和C2H2等C1／C2-烃．     

甲酸在轻微氧化的Nb(110)表面吸附的HREELS研究

用高分辨电子能量损失谱(HREELS)研究了甲酸在轻微氧化的Nb(110)表面(O/Nb原子比=0.2)上的吸附与分解,提出了相应的表面反应模式.140K时,低暴露量的甲酸在该表面解离生成甲酸根(HCOO),生成的甲酸根以单齿形式键合在Nb上,同时也有少量甲酸分解生成吸附态的CO;高暴露量时则生成多层物理吸附的固体甲酸.升温至～190K,物理吸附的甲酸脱附,此时的表面为单齿键合的HCOO和CO所覆盖.温度升至250～300K时,HCOO的吸附态由单齿式转变成桥式,同时表面吸附的CO分子消失.升温过程的HREELS表明HCOO的分解导致了Nb的氧化.暴露量较高时表面的甲酸根比较稳定以致于在540K的高温时仍不完全分解.     

Study of the thermal decomposition of a sepiolite by mid- and near-infrared spectroscopies

Near-infrared (NIR) and mid-infrared (MIR) spectroscopies were used to characterize the hydroxyl groups present in a sepiolite and its calcination products at 250, 500 and 800 °C. Calcining the sepiolite at 250 °C was found to result in its dehydration through the loss of coordination water. Raising the calcination temperature to 500 °C caused the sepiolite structure to fold and hydroxyl groups in octahedral layers to be removed. Finally, calcination at 800 °C resulted in a phase change leading to enstatite, as confirmed by XRD spectroscopy.     

Terahertz Time‐Domain Spectroscopy of Gases,Liquids, and Solids

The techniques and methods employed in the spectroscopic characterization of gases, liquids, and solids in the terahertz frequency range are reviewed. Terahertz time‐domain spectroscopy is applied to address a broadband frequency range between 100 GHz and 5 THz with a sub‐10 GHz frequency resolution. The unique spectral absorption features measured can be efficiently used in material identification and sensing. Possibilities and limitations of fundamental and industrial applications are discussed.     

Decongestion of methylene spectra in biological and non-biological systems using picosecond 2DIR spectroscopy measuring electron-vibration–vibration coupling

Methylene is found in the repeat units of many polymers including proteins. In some cases it appears to be a useful reporter of variation in local environment whilst in other contexts average behaviour seems to dominate. In this paper we apply a particular 2DIR technique to a range of systems containing methylene groups, showing that mode frequencies, linewidths and splittings can be easily extracted even when the infrared absorption bands are too congested to allow reliable analysis. 2DIR spectra of polyethylene and several liquid alkanes are compared and it is shown for the case of l-arginine that the methylene scissor modes are split and that this can be resolved by tracking the 2DIR spectrum as a function of time. Calculations from first principles reveal that for most of the methylene modes studied, electrical anharmonicity is the dominant contributor to the 2DIR cross-peak intensity, with the mechanical anharmonicity making only a small contribution.     

Synthesis and spectral characterization of dioxouranium (VI) complexes of salicylhydrazine and acetone salicylhydrazone

Dioxouranium(VI) complexes of the types UO₂LSO₄ and UO₂L₂SO₄ (where L=SH, ASH) have been prepared from reaction of uranyl sulphate with salicylhydrazine (SH) and acetone salicylhydrazone (ASH) and characterized by conventional chemical and physical measurements. Infrared and Raman spectra indicate thatmono- andbis-complexes contain six-and seven-coordinate uranium atom respectively with all the ligand atoms arranged in an equatorial plane around the linear uranyl group. The infrared spectra (4000-200 cm⁻¹) reveal that both SH and ASH act as neutral bidentate ligands coordinating through a carbonyl oxygen and primary amine/azomethine nitrogen atoms. The sulphato group coordinates to the uranyl ion as bidentate chelating ligand and terminal monodentate ligand in mono- and bis-complexes respectively.     

Synthesis and characterization of tetramethylammonium trifluorosulfate

[Me₄N]⁺[SO₂F₃]^?, the first example of a [SO₂F₃]^? salt, has been prepared from Me₄NF and SO₂F₂. The colorless, microcrystalline solid was characterized by its infrared and Raman spectra. The trigonal bipyramidal structure of C_2v symmetry of the [SO₂F₃]^? anion is predicted by ab initio calculations. Two oxygen atoms with d(SO)=143.2 pm and one fluorine atom with d(SF)=157.9 pm occupy the equatorial plane. The two fluorine atoms in the axial position with d(SF)=168.5 pm are repulsed by the two oxygen atoms forming a bent axis with ?(F_axSF_ax)=165.2°.     

Photoacoustic spectroscopy of solids and surfaces

After briefly reviewing the theory and instrumentation, results from a variety of experiments carried out by the authors on the photoacoustic spectroscopy of solids and surfaces by employing an indigenous spectrometer are discussed in the light of the recent literature. Some of the important findings discussed are, phase angle spectroscopy, anomalous behaviour of monolayers, unusual frequency dependence in small cell volumes, spectra of a variety of solids including amorphous arsenic chalcogenides, photoacoustic detection of phase transitions and determination of surface areas and surface acidities of oxides. Recent developments such as piezoelectric photoacoustic spectroscopy, depth profiling and subsurface imaging are also presented. Contribution No. 124 from the Solid State and Structural Chemistry Unit.     

The Kinetic and Mechanistic Evaluation of NMR Spectra. New analytical methods (18)

In addition to the static parameters of the chemical shifts and coupling constants, which serve as a source of knowledge for molecular structure and stereochemistry, an NMR spectrum can frequently furnish dynamic quantities characterizing relaxation and exchange phenomena. The information about nuclear switching processes has proved to be particularly useful in practice for the detection of internal molecular motions and for the estimation or determination of the corresponding energy barriers. A plethora of studies of this nature has in the past been performed on simple proton spectra. Methodological developments of recent years have led to a significant reduction of the effort required for the quantitative dynamic evaluation of NMR spectra arising from complex spin systems or involving other nuclei. In many cases it has, moreover, become possible to extract detailed mechanistic information inaccessible by other means. The practical execution of such analyses will be explained and illustrated by a selected number of applications.     

Fourier-transform Raman and infrared spectroscopic analysis of dipyrrinones and mesobilirubins

The Fourier-transform Raman (FT-Raman), infrared (FT-IR), and UV-visible absorption spectra of four dipyrrinones and two mesobilirubins have been investigated in the solid state and in CH2Cl2 solutions. A detailed spectral analysis, assignment and discussion of these spectra are presented. The bands at 1735-1738, 1691-1707 and 1359-1377 cm(-1) which were assigned to the stretching vibrations of the C-O-C and C-O-H and symmetric deformation of C-H bonds, respectively, can act as a marker to distinguish the compounds of this class. The striking differences between the spectra of the compounds suggest that mesobilirubin XIIIalpha is tending to adopt as ridge-tile conformation, rather than linear conformation.     

Isolation and Spectroscopic Characterization of New Endohedral Fullerenes in the Size Gap of C74 to C76

New alkaline earth metal endohedral fullerenes Sr@C₇₄, Sr@C₇₆‐I, II and Ca@C₇₄, prepared by means of the RF‐method, have been isolated using multistep HPLC. The purity was ascertained by anionic LDI TOF mass spectroscopy, considering the isotopic patterns of the compounds. The influence of the incorporated metal on the electronic structure has been studied by VIS‐NIR and Raman spectroscopy. Photoexcited triplet‐state EPR spectroscopy was used to investigate the structure of these otherwise EPR‐silent fullerenes. Displaying the frequency of the cage vs. encapsulated metal vibrational modes as a function of the square root of the reciprocal masses of the metals clearly separates the M³⁺@C_n^3— and the M²⁺@C_n^2— families. This seems to be a generally applicable tool for monitoring the metal to fullerene charge transfer.     

Polarization Dependent Time-Resolved Infrared Spectroscopy and Its Applications

Polarization dependent time-resolved infrared (TRIR) spectroscopy has proven to be a useful technique to study the structural dynamics in a photochemical process. The angular information of transient species is obtainable in this measurement, which makes it a valuable technique for the investigation of electron distribution, molecular structure, and conformational dynamics. In this review, we briefly introduce the principles and applications of polarization dependent TRIR spectroscopy. We mainly focused on the following topics: (i) an overview of TRIR spectroscopy, (ii) principles of TRIR spectroscopy and its advantages compared to the other ultrafast techniques, (iii) examples that use polarization dependent TRIR spectroscopy to probe a variety of chemical and dynamical phenomena including protein conformational dynamics, excited state electron localization, and photoisomerization, (iv) the limitations and prospects of TRIR spectroscopy.