Electron analyzing

The hybridization of carbon atoms is the major structural parameter controlling DLC film properties. Electron energy loss spectroscopy (EELS) has been extensively used to probe this structural feature [5. 6]. In a transmission electron microscope, a monoenergetic electron beam is impinged in a very thin sample, being the transmitted electrons analyzed in energy. Figure 27 shows a typical... 

Fig. 3. Schematic drawing of the high pressure electron spectrometer. A, Argon ion gun D, differentially pumped region EL, electron lens G, gas cell HSEA, hemispherical electron analyzer LO, two-grid LEED optics LV, leak valve M, long travel rotatable manipulator P, pirani gauge S, sample TSP titanium sublimation pump W, window X, twin anode x-ray source.

IV. EXPERIMENTAL CONSIDERATIONS A. Electron Analyzers and Transmission Efficiency... 

In the case of lower impact energies in forward scattering and for ejected electron analyzers used in photoelectron as well as electron-impact spectroscopy, the larger changes in voltage ratios at the analyzer input result in transmission variations (with electron energy) that may not be readily corrected with zoom lenses (this is particularly true where slits are... 

Ejected electron analyzers can be calibrated at lower energies (<25 eV) using UV photoelectron spectroscopy and comparison with quantitative photoelectron spectra. The intensity ratios provide a relative transmission function (7 ) directly. Quantitative (relative) photoelectron spectra have been reported by Hotop and Niehaus79 at an ejection angle of 90°, and these results have been used by Yee et al.66 to calibrate a 127° analyzer for which the correction curve has already been shown in Fig. 3. More recently Gardner and Samson80 reported quantitative (relative) photoelectron spectra that can be used as a standard for analyzer... 

Figure 40. Spectra of electron ejected from CH4 at 54.7°, recorded in coincidence with scattered (3.5 keV) electrons at energy losses of 35 and 40 eV. Correction has been made for transmission of ejected electron analyzer. The 40-eV spectrum is a composite of two overlapping runs (10 to 26 eV and 20 to 34 eV).194...

The XPS mechanism, which can be used for quantitative and qualitative chemical analysis of surfaces, is based on the photoelectric effect. A monochromatic soft Mg or Al anode X-ray source is used to irradiate the surface. The absorbed X-rays ionize die core shell, and in response, the atom creates a photoelectron that is transported to the surface and escapes. The ionization potential of a photoelectron that must be overcome to escape into vacuum is the binding energy (BE) plus the work function of the material. The emitted photoelectrons have a remaining kinetic energy (KE), which is measured by using an electron analyzer. Individual elements can be identified on the basis of their BE. The resulting XP spectrum is a characteristic set of peaks for a specific element, with BE as the abscissa and counts per unit time as... 

II-2 Gas-solid Interface Experiments. Low pressure photo-reactivity experiments were carried out in a UHV chamber previously described (15) equipped with an electron analyzer for Auger, photoelectron, and low resolution energy loss spectroscopies. 

Figure 2. Diagram of an ESCA spectrometer. Key X, X-rays A, sample B, electron analyzer C, detector D, amplifier E, computer F, recorder.

Exchanged zeolites were characterized by N2 adsorption at 77K, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), immersion calorimetry and NHs-temperature programmed desorption (NH3-TPD). X-ray diffraction patterns (XRD) were obtained with a JSO Debye-Flex 2002 system, from Seifert, fitted with a Cu cathode and a Ni filter, using CuXa radiation (A,=1.5419) and 2°min of scanning rate. X-ray photoelectron spectroscopy (XPS) spectra were acquired with a VG-Microtech Multilab 3000 spectrometer equipped with a hemispherical electron analyzer and Mg Ka (1253.6 eV) 300W X-ray source. 

Pt substrates. All the results reported here for the Pt/Sn system were obtained using a multichannel hemispherical electron analyzer and a conventional, non monochromatized. Mg Ka or A1 Ka photon source. Unless otherwise specified, the experimental data were analyzed by means of the single scattering cluster -spherical wave (SSC-SW) model. 

X-ray photoelectron spectra were recorded on a Leybold LHS 10 spectrometer equipped with a hemispherical electron analyzer and a MgKa (1253.6 eV) X-ray radiation source. The samples were mounted on a sample rod, placed in an introduction chamber and turbo-pumped at ca. lO torr... 

Fig. 4. Experimental setup for surface XANES detection. In the soft X-ray region a grasshopper monochromator is often used. The absorption is measured by detecting the flux of emitted electrons of energy selected by the electron analyzer...

X-ray photoelectron spectra were recorded with a VG Escalab 200R electron spectrometer equipped with a Mg Ka X-ray source (hv = 1253.6 eV) and a hemispherical electron analyzer operating at constant transmission energy (50 eV). No reduction treatment of ICP catalysts was carried out before XPS measurements. The C Is peak at 284.6 eV was used as an internal standard for peak position measurement. 

Figure 3. Representation of an ESC A instrument using a hemispherical electron analyzer (Ephotoe ectron = hv — binding energy).

---