苯磺酰基吲哚类化合物去质子化离子的质谱裂解行为研究

为阐明苯磺酰基吲哚类化合物去质子化离子的质谱裂解机制,采用电喷雾离子源（ESI）负离子模式进行多级碎片解析。采用密度泛函理论（DFT）比较了5个3-苯磺酰基吲哚类化合物和4个2-苯磺酰基吲哚类化合物去质子化离子不同裂解过程中碎片离子的优化结构,并分析其可能的裂解机制。结果表明,两种苯磺酰基吲哚类化合物的去质子化离子可以通过不同的芳香亲核取代重排路径中性丢失SO₂生成对应的苯基吲哚负离子,或C-S键均裂中性丢失苯自由基生成对应的阴离子自由基。根据两种碎片离子的丰度比值,可以快速、简便、准确地区分上述两类位置异构体。该方法可为苯磺酰基吲哚类化合物的结构鉴定和定量分析提供理论基础。     

Development of a low-temperature photoelectron spectroscopy instrument using an electrospray ion source and a cryogenically controlled ion trap

The ability to control ion temperatures is critical for gas phase spectroscopy and has been a challenge in chemical physics. A low-temperature photoelectron spectroscopy instrument has been developed for the investigation of complex anions in the gas phase, including multiply charged anions, solvated species, and biological molecules. The new apparatus consists of an electrospray ionization source, a three dimensional (3D) Paul trap for ion accumulation and cooling, a time-of-flight mass spectrometer, and a magnetic-bottle photoelectron analyzer. A key feature of the new instrument is the capability to cool and tune ion temperatures from 10 to 350 K in the 3D Paul trap, which is attached to the cold head of a closed cycle helium refrigerator. Ion cooling is accomplished in the Paul trap via collisions with a background gas and has been demonstrated by observation of complete elimination of vibrational hot bands in photoelectron spectra of various anions ranging from small molecules to complex species. Further evidence of ion cooling is shown by the observation of H2-physisorbed anions at low temperatures. Cold anions result in better resolved photoelectron spectra due to the elimination of vibrational hot bands and yield more accurate energetic and spectroscopic information. Temperature-dependent studies are made possible for weakly bonded molecular and solvated clusters, allowing thermodynamic information to be obtained.     

Measurement of H- density in plasma by photodetachment

Techniques have been developed for measurement of the density of H- in a plasma by photodetachment. Photodetachment is detected by the increase in electron density with no change in positive ion density after a light pulse from a ruby laser. The authenticity of photodetachment signals can be assured by their comparison with known cross sections for photodetachment of H-. Interpretations of photodetachment data are less ambiguous than probe interpretations because photodetachment is not affected by the mass of positive ions and is not limited in usefulness by the Debye distance. Photodetachment measurements with time resolution and spatial resolution are straightforward.     

Beam purification by photodetachment (invited)

Ion beam purity is of crucial importance to many basic and applied studies in nuclear science. Selective photodetachment has been proposed to suppress unwanted species in negative ion beams while preserving the intensity of the species of interest. A highly efficient technique based on photodetachment in a gas-filled radio frequency quadrupole ion cooler has been demonstrated. In off-line experiments with stable ions, up to 10(4) times suppression of the isobar contaminants in a number of interesting radioactive negative ion beams has been demonstrated. For selected species, this technique promises new experimental possibilities in studies on exotic nuclei, accelerator mass spectrometry, and fundamental properties of negative atomic and molecular ions.     

Laser measurement of H- ions in a field-effect-transistor based radio frequency ion source

Hydrogen negative ion density measurements are required to clarify the characteristics of negative ion production and ion source performance. Both of laser photodetachment and cavity ring down (CRD) measurements have been implemented to a field-effect-transistor based radio-frequency ion source. The density ratio of negative hydrogen ions to electrons was successfully measured by laser photodetachment and effect of magnetic filter field on negative ion density was confirmed. The calculated CRD signal showed that CRD mirrors with >99.990% reflectivity are required and loss of reflectivity due to cesium contamination should be minimized.     

Vector potential photoelectron microscopy

A new class of electron microscope has been developed for the chemical microanalysis of a wide range of real world samples using photoelectron spectroscopy. Highly structured, three-dimensional samples, such as fiber mats and fracture surfaces can be imaged, as well as insulators and magnetic materials. The new microscope uses the vector potential field from a solenoid magnet as a spatial reference for imaging. A prototype instrument has demonstrated imaging of uncoated silk, magnetic steel wool, and micron-sized single strand tungsten wires.     

Characterizing voltage contrast in photoelectron emission microscopy

A non‐destructive technique for obtaining voltage contrast information with photoelectron emission microscopy is described. Samples consisting of electrically isolated metal lines were used to quantify voltage contrast in photoelectron emission microscopy. The voltage contrast behaviour is characterized by comparing measured voltage contrast with calculated voltage contrast from two electrostatic models. Measured voltage contrast was found to agree closely with the calculated voltage contrast, demonstrating that voltage contrast in photoelectron emission microscopy can be used to probe local voltage information in microelectronic devices in a non‐intrusive fashion.     

Wave frequency dependence of H- ion production and extraction in a transformer coupled plasma H- ion source at SNU

The effect of rf wave frequencies on the production of H(-) ion is investigated in a transformer coupled plasma H(-) ion source at Seoul National University. A Langmuir probe is installed to measure the plasma density and temperature, and these plasma parameters are correlated to the extracted H(-) beam currents at various frequencies. The Langmuir probe is also used to measure the density of H(-) ions at the ion source by generating photodetachment with an Nd:YAG laser. The extracted H(-) currents decrease to a minimum value until 13 MHz and then, increase as the driving frequency increases from 13 MHz while the relative H(-) population measured by photodetachment monotonically decreases as the driving rf frequency increases from 11 MHz to 15 MHz. A potential well formed at the extraction region at high frequencies of more than 13 MHz is considered responsible for the increased H(-) beam extraction even with a lower photodetachment signal. The variation in the driving rf frequency not only affects the density and temperature of the plasma but also modifies the plasma potential with the existence of a filtering magnetic field and consequently, influences the extracted H(-) current through the extraction as well as formation of H(-) ions.     

About an anionic-radical concept of the lubrication mechanism of alcohols

To understand the chemical behaviour of alcohols in sliding contacts, especially in the boundary lubrication of aluminium-steel surfaces, the concept of a negative-ion-radical action mechanism of these compounds has been proposed. The lubrication model is based upon the ionization mechanism of alcohols caused by the action of exoelectrons. It has been shown that alcohols may produce ions and radical anions that react with a metal surface. This fact explains well the formation of a product of waxy appearance during sliding of an aluminium—steel system in the presence of fatty alcohols. The generation of radical and biradical anions elucidates the results that alcohol groups favour the production of an adherent coating composed of many components, including alkynes, dialkynes, alkenes and dialkenes, on sliding surfaces. Furthermore, the proposed action mechanism explains the chemisorption of alcohols on a clean aluminium surface prepared by cutting under high vacuum. Finally, this mechanism makes clear other findings related to pentaerythritol partial ester. The ester, which contains both hydroxyl and ester groups, reacts with the surface aluminium atoms to form amorphous substances such as aluminium complexes.     

Scanning photoelectron microscope for nanoscale three-dimensional spatial-resolved electron spectroscopy for chemical analysis

In order to achieve nondestructive observation of the three-dimensional spatially resolved electronic structure of solids, we have developed a scanning photoelectron microscope system with the capability of depth profiling in electron spectroscopy for chemical analysis (ESCA). We call this system 3D nano-ESCA. For focusing the x-ray, a Fresnel zone plate with a diameter of 200 μm and an outermost zone width of 35 nm is used. In order to obtain the angular dependence of the photoelectron spectra for the depth-profile analysis without rotating the sample, we adopted a modified VG Scienta R3000 analyzer with an acceptance angle of 60° as a high-resolution angle-resolved electron spectrometer. The system has been installed at the University-of-Tokyo Materials Science Outstation beamline, BL07LSU, at SPring-8. From the results of the line-scan profiles of the poly-Si/high-k gate patterns, we achieved a total spatial resolution better than 70 nm. The capability of our system for pinpoint depth-profile analysis and high-resolution chemical state analysis is demonstrated.     

预浓缩技术离子色谱法测定硬盘部件表面痕量阴离子

本文建立了一种采用预浓缩技术-离子色谱法测定硬盘部件表面痕量阴离子的方法。通过纯水对硬盘部件表面进行清洗,溶于水的表面痕量阴离子采用预浓缩技术浓缩富集,离子色谱进行测定。该方法选择的色谱条件是采用IonPac AS12A离子交换柱,碳酸盐等度淋洗,抑制型电导检测。用该方法对实际硬盘部件表面的痕量阴离子进行测定,测定结果加标回收率在96%～104%,具有灵敏度高,选择性好,操作简单等特点。     

Time-of-flight photoelectron spectroscopy of gases using synchrotron radiation

A gas-phase time-of-flight (TOF) photoelectron spectrometer has been developed for use with synchrotron radiation. The excellent time structure of the synchrotron radiation at the Stanford Positron Electron Accelerator Ring (SPEAR) has been used as the time base for the TOF measurements. The TOF analyzer employs two multichannel plates (MCPs) in tandem as a fast electron multiplier with a matched 50-Omega anode to form an electron detector with a timing resolution of 相似文献   

Photoelectron imaging and photoelectron labeling

Photoelectron imaging involves the photoejection of low-energy electrons from a specimen surface exposed to UV light. The electrons are then accelerated and focused by an electron-optics system in much the same way fluorescent light is focused in an optical microscope. Thus, photoelectron imaging is the electron-optical analog of fluorescence microscopy. In combination with photoemissive labels it serves to extend the range of studies possible by fluorescence, for example in work on cell surfaces and internal structures of cells that have been exposed by detergent extraction of membranes.     

Sialolith characterization by scanning electron microscopy and X-ray photoelectron spectroscopy

The objective of this study has been to characterize sialolith, a calcium phosphate deposit that develops in the human oral cavity, by high-resolution field emission scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The morphological and chemical data obtained helped in the determination of their formation mechanism in salivary glands. Sialoliths in the submandibular salivary glands may arise secondary to sialodenitis, but not via a luminal organic nidus. We believe this is the first study that characterizes a sialolith by XPS.     

在线基体消除-毛细管离子色谱测定有机溶剂中的痕量阴离子

建立了在线基体消除-毛细管离子色谱测定有机溶剂中痕量阴离子的方法。有机溶剂样品经过阴离子浓缩柱（MAC200整体柱）,痕量目标阴离子被浓缩的同时,有机溶剂不被保留而去除,接着目标离子转入毛细管离子色谱系统进行分析。六种阴离子（氟离子、氯离子、亚硝酸根、硝酸根、硫酸根和磷酸根）在1-100μg/L线性范围内,相关系数（r2）为0.9991～0.9999,考察的阴离子检出限（以S/N=3计）为2.2-34.8ng/L。用于实际样品检测,取得了很好的效果。     

Ion optical design of a collinear laser-negative ion beam apparatus

An apparatus for photodetachment studies on atomic and molecular negative ions of medium up to heavy mass (M ? 500) has been designed and constructed. Laser and ion beams are merged in the apparatus in a collinear geometry and atoms, neutral molecules and negative ions are detected in the forward direction. The ion optical design and the components used to optimize the mass resolution and the transmission through the extended field-free interaction region are described. A 90° sector field magnet with 50 cm bending radius in combination with two slits is used for mass dispersion providing a resolution of M∕ΔM?800 for molecular ions and M∕ΔM?400 for atomic ions. The difference in mass resolution for atomic and molecular ions is attributed to different energy distributions of the sputtered ions. With 1 mm slits, transmission from the source through the interaction region to the final ion detector was determined to be about 0.14%.     

Design of a cavity ring-down spectroscopy diagnostic for negative ion rf source SPIDER

The rf source test facility SPIDER will test and optimize the source of the 1 MV neutral beam injection systems for ITER. Cavity ring-down spectroscopy (CRDS) will measure the absolute line-of-sight integrated density of negative (H(-) and D(-)) ions, produced in the extraction region of the source. CRDS takes advantage of the photodetachment process: negative ions are converted to neutral hydrogen atoms by electron stripping through absorption of a photon from a laser. The design of this diagnostic is presented with the corresponding simulation of the expected performance. A prototype operated without plasma has provided CRDS reference signals, design validation, and results concerning the signal-to-noise ratio.     

The tribo-chemistry of graphite fluoride studied using X-ray photoelectron spectroscopy

A preliminary investigation involving the application of X-ray photo-electron spectroscopy (XPS) for the study of the degradation, under sliding conditions, of thin graphite fluoride films on steel has been carried out. The results described here show that the technique can provide invaluable information in establishing the mode of failure of the lubricating film.     

A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

We describe an apparatus for attosecond photoelectron spectroscopy of solids and surfaces, which combines the generation of isolated attosecond extreme-ultraviolet (XUV) laser pulses by high harmonic generation in gases with time-resolved photoelectron detection and surface science techniques in an ultrahigh vacuum environment. This versatile setup provides isolated attosecond pulses with photon energies of up to 140 eV and few-cycle near infrared pulses for studying ultrafast electron dynamics in a large variety of surfaces and interfaces. The samples can be prepared and characterized on an atomic scale in a dedicated flexible surface science end station. The extensive possibilities offered by this apparatus are demonstrated by applying attosecond XUV pulses with a central photon energy of ～125 eV in an attosecond streaking experiment of a xenon multilayer grown on a Re(0001) substrate.     

Importance of anionic reactive intermediates for lubricant component reactions with friction surfaces

To understand the chemical behaviour of lubricant components during boundary lubrication, a general concept of negative ionradical reactive intermediates formation for these components has been proposed. The concept is based upon the ionisation mechanism of these compounds caused by the action of electrons of law energy (1–4 eV). Electrons of such energy (exoelectrons) are spontaneously emitted from most fresh surfaces formed during friction. The principal thesis of the model is that lubricant components form anions which are then chemisorbed on the positively charged areas of rubbing surfaces. The formation of negative ions and their decomposition process are simulated by electron attachment mass spectrography. This type of mass spectrography uses electrons of an energy range similar to those of exoelectrons. The proposed model encompasses the following major stages: (a) low-energy electron emission process and creation of positively charged spots, (b) action of emitted electrons with lubricant components (anion and radical formation), (c) reactions of anions with metal surfaces forming a film protecting the surface from wear, (d) cracking of chemical bonds producing other radicals. The model explains many lubrication phenomena of hydrocarbons, oxygen-containing compounds, and many types of chemicals used as antiwear and extreme-pressure additives.