ESCA photoelectron spectrometer

Fig. 9.2. Block diagram of McPherson ESCA photoelectron spectrometer.

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. 

Main group element analysis was carried out with a Perkin-Elmer CHN elemental analyzer, while molybdenum analysis was performed using atomic absorption spectroscopy. The content of Mo and O on the surface of the catalysts was obtained by X-ray photoelectron spectroscopy (XPS) using a Shimazu ESCA-850 spectrometer with monochromatic MgKa. Since Mo 3p3/2 spectra overlapped with the N Is spectra for the nitrided catalysts, the degree of nitriding (N IsfMo 3d ratio) had to be obtained from a combination of elemental analysis and XPS. 

Subsequently, Grunthaner reexamined the ESCA spectrum of the 2-norbornyl cation on a higher-resolution X-ray photoelectron spectrometer using highly efficient vacuum techniques.884 The spectrum closely matches the previously published spectra. Furthermore, the reported ESCA spectral results are consistent with the theoretical studies of Allen and co-workers885 on the classical and nonclassical norbomyl cation at the STO-3G and STO-4.31G levels. Using the parameters obtained by Allen and co-workers, Clark and co-workers were able to carry out a detailed... 

The compositions of the products were determined by inductively coupled plasma (ICP) with a Perkin-Elmer plasma 40 emission spectrometer. Simultaneous differential thermal analysis and thermogravimetric (DTA-TG) curves were carried out by using Perkin-Elmer DTA-7000, TGA-7 PC series thermal analysis instrument in air with a heating rate of 10 °C /min. The infrared (IR) spectra were recorded on an Impact 410 IR spectrometer on samples pelletized with KBr powder. Valence states were determined by X-ray photoelectron spectroscopy (XPS). The XPS for powder samples fixed on double sided tapes was measured on an ESCA-LAB MKII X-ray photoelectron spectrometer. The Cis signal was used to correct the charge effects. 

The PHI ESCA/Auger spectrometer 549 was used for determining the composition of these films. This spectrometer was operated at pressures below 5 X 10-t> pm Hg. X-ray photoelectron spectra (XPS) were recorded using a pass energy of 50 or 100 eV and a Mg Ka X-ray source. XPS were calibrated with solidified TMT vapors and Sn02 as described by Kny et al.(8) The Sn 3 C Is... 

An exciting development during this period was the ultraviolet photoelectron spectrometer invented by David W. Turner (1927- ) at Oxford in 1962. While X-ray photoelectron spectroscopy (ESCA) (see chapter 6) provides energies of core (e.g., Is) orbitals, UV photoelectron spectroscopy (UV PES) yields energies of valence-level MOs from the HOMO downward. The shapes of the UV PES bands also provide information about the nature of the orbitals. UV PES helped to improve computational theory and as computations improved they helped chemists pull more detail from UV PES data. 

A VG ESCA LAB MK II X-ray photoelectron spectrometer was employed. MgKa X-ray source (BE s 1253.6 eV) was adopted. All the obtained binding energies of the corresponding photoelectrons of the samples were calibrated by using [Pg.692]

The ESCA studies of the fractured samples from Sets I and II were done with an AEI ES 100 photoelectron spectrometer using A1 Ka radiation (1486.6 ev.). Data acquisition was accomplished using a AEI DS 100 Data System and a Digital PDP-8/e computer. Specific spectrometer conditions are noted on the spectra which follow. 

Plate 45 A researcher at the BOC Group Technical Centre, Murray Hill, New Jersey, USA, using an advanced Electron Spectroscopy For Chemical Analysis (ESCA) unit. ESCA provides qualitative and quantitative analysis of the chemistry of elements present in the outermost layers of solid materials. The unit is used in the development of thin-film coatings, medical sensors, molecular sieves and catalysts. See Photoelectron Spectrometers Photoelectron Spectroscopy. Reproduced with permission from Science Photo Library. 

The actual Fe content of doped Ti02 was determined by atomic absorption flame emission spectroscopy (Shimadzu AA-6400F). X-ray diffraction patterns of materials were measttred with a Shimadzu XRD-6100 analyzer with Cu K radiation (1=1.5417A). The X-ray photoelectron spectroscopic (XPS) investigations were carried out with a Shimadzu ESCA-3200 spectrometer in order to analyze the sttrface elemerrtal composition and valence state of elements of the photo catalysts. Diffuse reflectance UV-vis spectra of the catalysts were measured using a Shimadzu UV-2200A and a Shimadzu UV-vis spectrophotometer. The FT-IR spectra of the samples were measttred using KBr pellets (BIO-RAD FTS-3000). 

The work of Siegbahn s group who, in the 1950s, improved the energy resolution of electron spectrometers and combined it with X-ray sources. This led to a technique called electron spectroscopy for chemical analysis (ESCA), nowadays more commonly referred to as X-ray photoelectron spectroscopy (XPS) [6]. Siegbahn received the Nobel Prize for his work in 1981. Commercial instruments have been available since the early seventies. 

The 5950A ESCA spectrometer is interfaced to a desktop computer for data collection and analysis. Six hundred watt monochromatic A1 Ka X-rays are used to excite the photoelectrons and an electron gun set at 2 eV and 0.3 mAmp is used to reduce sample charging. Peak areas are numerically integrated and then divided by the theoretical photoionization cross-sections (11) to obtain relative atomic compositions. For the supported catalyst samples, all binding energies (BE) are referenced to the A1 2p peak at 75.0 eV, the Si 2p peak at 103.0 eV, or the Ti 2p3/2 peak at 458.5 eV. 

All XPS or ESCA measurements were performed using a Perkin Elmer 5300 ESCA spectrometer equipped with a dual anode (Mg, Al) X-ray source, differentially pumped Ar+ sputter gun, and the variable angle measurement set-up for angle-resolved photoelectron spectroscopic measurements. The data collection and treatment, e.g. smoothing, curve-fitting, intensity measurements, were accomplished by a Perkin Elmer 7500 dedicated computer system using PHI software package. 

The ESCA method (2) and its application to aerosol particles (3) have been extensively discussed in the literature and will not be described here. The instrument used in these experiments is a modified AEI ES-200 electron spectrometer which has been updated by the installation of a Surface Science Laboratories Model 239G position-sensitive photoelectron detector. The modifications also included replacement of all lens and analyzer power supplies, as well as changing to a modern microprocessor-based data system. Data collection with the modified spectrometer is approximately 10 times as rapid as with the original, thus substantially decreasing sample degradation during analysis. 

ESCA studies on these hexadentate complexes by Lazarus, Hoselton, and Chou191) were not successful. It has been found that the broad satellite structure in the observed 2 p X-ray photoelectron spectra were due to a radiation-induced decomposition of the HS isomer in the spectrometer rather than the result of the multiplet splitting. 

In the mid-50 s it was observed that the energy of a photoelectron, ejected from the core of an atom by an X-ray photon, is a rather sensitive probe of the chemical environment of the atom. From this observation has evolved a major research technique named electron spectroscopy for chemical analysis (ESCA) by the Uppsala group 1,2) which pioneered the subject and called X-ray photoemission spectroscopy (XPS) by many others. The field has developed rapidly a third generation of spectrometers is in use at many laboratories and the understanding of the spectra observed is improving apace. A view of the current status of X-ray photoelectron spectroscopy in application to metals and alloys is presented in this article. We have not been encyclopedic in describing what has been done we have instead attempted to cover the classes of results obtained and the kinds of problems encountered in interpretation of these results. 

Spectroscopy. Transmission and ATR IR spectra were obtained with a Perkin-Elmer Model 180 or 621 spectrometer. Absorption spectra were obtained on a Cary 14 spectrophotometer, while ESR spectra were obtained with a Varlan V-4502 spectrometer in the manner described elsewhere ( ). X-ray photoelectron spectra of the etched and unetched films were provided by Surface Science Laboratories, Palo Alto, Calif., using a Hewlett-Packard Model 5950 ESCA spectrometer. Some films were also examined with an International Scientific Instruments Model MSM-2 "Minl-Sem" scanning electron microscope. 

In x-ray photoelectron spectra (XPS or ESCA) were col 1 ecteT on" a modified Leybold Heraeus LHS-10 electron spectrometer. A moveable stainless steel block allowed sample transfer in vacuum from a reactor chamber to the ESCA chamber. 

XPS A Shimadzu ESCA-750 electron spectrometer with an aluminum anode (1486.6eV) was used to obtained X-ray photoelectron spectra. All binding energies were referenced to gold (Au 4f7/2 line 83.8eV) which was deposited on samples in vacuum. The activated sample in the flow system was outgassed in the preparation chamber of the spectrometer... 

Knowledge of the work function and Fermi (reference) level of the spectrometer is important if one wishes to obtain meaningful absolute E, values. The ESCA spectrometer should be periodically checked by measuring the energy of photoelectrons emitted from a sample with a well-established E > (e.g. the Au4f7/2 level at 83.96 eV). 

X-ray photoelectron spectroscopy (XPS). These studies were performed at the Amoco research center at Naperville, Illinois, by Dr. Theo Fleisch. A Hewlett Packard 5950B ESCA spectrometer was employed using a monochromated A1 source. Sample wafers were pressed from approximately 50 mg of catalyst powder, and placed in a pretreatment chamber attached to the spectrometer. 

XPS measurements were performed in a MARK-II ESCA spectrometer with a pretreatment cell without exposure to the air. Hydrogen reduction of the sample was carried out at 723 K in the pretreatment cell. Binding energy measuremensts were related to the C[ls) photoelectron line at 285.0 eV as a reference. Structural analysis of the zeolite samples was completed In a Shlmadzu XD-3A diffractometer. 

The ESCA spectrum of an inorganic compound is taken using A1 K radiation. The photoelectron energy (Ep) of the 4/7,2 level for gold, a thin layer of which has been deposited on the sample, is measured at 1353 eV. (a) At what photoelectron energy should you look for the carbon li photoelectron peak to determine whether the surface of the sample has been contaminated with vacuum-pump oil (b) With the same spectrometer, at what photoelectron energy should the carbon Is peak be if Mg K radiation were used ... 

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