ESCA X-ray photoelectron

The structure assignment problem, which offers difficulties similar to those discussed for the alkylation products, was solved by means of mass spectrometry in combination with isotope labeling at position 2 with 15N. ESCA (X-ray photoelectron) spectroscopy and IR spectra are in agreement with the assignment as a 3-oxide.23... 

Technique abbreviations AES = Auger Electron Spectroscopy EXAFS = Extended X-Ray Absorption Fine Structure ISS = Ion Scattering Spectroscopy SIMS = Secondary Ion Mass Spectroscopy UPS = Ultraviolet Photoelectron Spectroscopy XANES = X-Ray Absorption Near Edge Structure XPS (or ESCA) = X-Ray Photoelectron Spectroscopy bAnalysis type C = chemical, E = elemental... 

XPS (ESCA) X-ray photoelectron spectroscopy (electron spectroscopy for chemical analysis) Study of surface composition and oxidation states of surface atoms... 

XPS/ESCA X-ray photoelectron spectroscopy/electron spectroscopy for chemical analysis... 

X-ray photoelectron spectroscopy (XPS), also called electron spectroscopy for chemical analysis (ESCA), is described in section Bl.25,2.1. The most connnonly employed x-rays are the Mg Ka (1253.6 eV) and the A1 Ka (1486.6 eV) lines, which are produced from a standard x-ray tube. Peaks are seen in XPS spectra that correspond to the bound core-level electrons in the material. The intensity of each peak is proportional to the abundance of the emitting atoms in the near-surface region, while the precise binding energy of each peak depends on the chemical oxidation state and local enviromnent of the emitting atoms. The Perkin-Elmer XPS handbook contains sample spectra of each element and bindmg energies for certain compounds [58]. 

Barr, T. L. (1994) Modern ESCA The Principles and Practice of X-ray Photoelectron Spectroscopy, CRC Press, Boca Raton, FL. 

Other techniques in which incident photons excite the surface to produce detected electrons are also Hsted in Table 1. X-ray photoelectron Spectroscopy (xps), which is also known as electron spectroscopy for chemical analysis (esca), is based on the use of x-rays which stimulate atomic core level electron ejection for elemental composition information. Ultraviolet photoelectron spectroscopy (ups) is similar but uses ultraviolet photons instead of x-rays to probe atomic valence level electrons. Photons are used to stimulate desorption of ions in photon stimulated ion angular distribution (psd). Inverse photoemission (ip) occurs when electrons incident on a surface result in photon emission which is then detected. 

X-rays provide an important suite of methods for nondestmctive quantitative spectrochemical analysis for elements of atomic number Z > 12. Spectroscopy iavolving x-ray absorption and emission (269—273) is discussed hereia. X-ray diffraction and electron spectroscopies such as Auger and electron spectroscopy for chemical analysis (esca) or x-ray photoelectron spectroscopy are discussed elsewhere (see X-raytechnology). 

X-ray photoelectron spectroscopy (XPS) is currently the most widely used surface-analytical technique, and is therefore described here in more detail than any of the other techniques. At its inception hy Sieghahn and coworkers [2.1] it was called ESCA (electron spectroscopy for chemical analysis), hut the name ESCA is now considered too general, because many surface-electron spectroscopies exist, and the name given to each one must be precise. The name ESCA is, nevertheless, still used in many places, particularly in industrial laboratories and their publications. Briefly, the reasons for the popularity of XPS are the exceptional combination of compositional and chemical information that it provides, its ease of operation, and the ready availability of commercial equipment. 

One other technique has become central in surface research this is X-ray photoelectron spectrometry, earlier known as ESCA, electron spectroscopy for chemical analysis . Photoelectrons are emitted from a surface irradiated by X-rays. The precautions which have to be taken to ensure accurate quantitative analysis by this much-used technique are set out by Seah (1980). 

Electron Spectroscopy for Chemical Analysis (ESCA) or X-Ray Photoelectron Spectroscopy (XPS)... 

Table 8 shows results obtained from the application of various bulk and surface analysis methods to lithium metal at rest or after cyclization experiments, as well as at inert and carbon electrodes after cathodic polarization. The analytical methods include elemental analysis, X-ray photoelectron spectroscopy (XPS or ESCA), energy-dispersive analysis of X-rays (X-ray mi-... 

Other techniques utilize various types of radiation for the investigation of polymer surfaces (Fig. 2). X-ray photoelectron spectroscopy (XPS) has been known in surface analysis for approximately 23 years and is widely applied for the analysis of the chemical composition of polymer surfaces. It is more commonly referred to as electron spectroscopy for chemical analysis (ESCA) [22]. It is a very widespread technique for surface analysis since a wide range of information can be obtained. The surface is exposed to monochromatic X-rays from e.g. a rotating anode generator or a synchrotron source and the energy spectrum of electrons emitted... 

X-ray photoelectron spectroscopy (XPS), which is synonymous with ESCA (Electron Spectroscopy for Chemical Analysis), is one of the most powerful surface science techniques as it allows not only for qualitative and quantitative analysis of surfaces (more precisely of the top 3-5 monolayers at a surface) but also provides additional information on the chemical environment of species via the observed core level electron shifts. The basic principle is shown schematically in Fig. 5.34. 

Surface composition and morphology of copolymeric systems and blends are usually studied by contact angle (wettability) and surface tension measurements and more recently by x-ray photoelectron spectroscopy (XPS or ESCA). Other techniques that are also used include surface sensitive FT-IR (e.g., Attenuated Total Reflectance, ATR, and Diffuse Reflectance, DR) and EDAX. Due to the nature of each of these techniques, they provide information on varying surface thicknesses, ranging from 5 to 50 A (contact angle and ESCA) to 20,000-30,000 A (ATR-IR and EDAX). Therefore, they can be used together to complement each other in studying the depth profiles of polymer surfaces. 

The films were characterized using x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The photoelectron spectroscopy utilized a Vacuum Generators ESCA Lab II system with Mg(Ka) radiation. Binding energies (BE) were measured with respect to the surface C(ls) peak (284.5 eV) which was always present In these films. Scanning electron microscopy was done with a JEOL JSM-35C system. 

For probing the nature of the acid sites by X-ray photoelectron spectroscopy (XFS), the samples were evacuated before gaseous pyridine was adsorbed. Excess pyridine was desorbed at 1S0°C, and then samples were pressed onto a sample stub imder Nj and loaded into the SCIENTA ESCA-300 instrument without exposure to air. Sample charging was minimized by using a Qood gun while acquiring the experimental data. 

Analytical Techniques. Sessile drop contact angles were measured with a NRL C.A. Goniometer (Rame -Hart, Inc.) using triply distilled water. The contact angles reported are averages of 2-8 identically treated samples with at least three measurements taken on each sample. ESCA spectra were obtained on a Kratos ES-300 X-ray Photoelectron Spectrometer under the control of a DS-300 Data System. Peak area measurements and band resolutions were performed with a DuPont 310 Curve Resolver. 

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