Electron spectrometer electrostatic

The properties of monochromatized synchrotron radiation have been discussed in detail in the previous section and the characteristic features of electrostatic spectrometers will be discussed in detail in Chapter 4, with examples of photoionization processes in certain atoms and specific questions of interest presented in Chapter 5. Therefore, the following discussion is restricted to basic aspects of electron spectrometry with monochromatized synchrotron radiation, in particular to some of the fundamental properties of electron spectrometers and to the special polarization properties of this radiation which require appropriate experimental set-ups for angle-resolved electron spectrometry (without spin-analysis for the determination of spin-polarization see Section 5.4). 

Figure 1.13 Definition of the source volume of an electrostatic energy analyser. In the case shown, the diameter of the source volume is determined by the diameter of the photon beam, and the restricted length Azmax by diaphragms in the electron spectrometer which prevent the acceptance of electrons from regions outside of Azmax. The average length, Az, usually identified with the length is also indicated.

An experimental set-up using a lens system for the acceleration/retardation of the electrons in conjunction with an electrostatic analyser is shown in Fig. 4.32. The electron spectrometer is a spherical analyser with a mean radius R0 of 101.6 mm combined with a three-aperture zoom lens at the entrance and the exit. Only the purpose and the characteristic properties of the entrance lens will be... 

Figure 3 demonstrates the electron spectrometer part of a depth-resolved conversion electron MOssbauer spectrometer specially designed for such measurements in our laboratory (10, 11). The electron spectrometer is of the cylindrical mirror type back-scattered K conversion electrons from resonantly excited Fe nuclei are resolved by the electrostatic field between the inner and outer cylinders (cylindrical mirror analyzer) and then detected by a ceramic semiconductor detector (ceratron). The electron energy spectra taken with this spectrometer indicate that peaks of 7.3-keV K conversion electrons, 6.3-keV KLM Auger electrons, 5.6-keV KLL Auger electrons, etc., can be resolved well, with energy resolution better than 4%. 

Figure 15.6. Schematic diagram of an electron spectrometer. The electrostatic analyzer sorts or spreads out the photoelectrons. Auger electrons, and other secondary electrons of various energies so that only monoenergetic electrons reach the detector. In this, the energy analyzer serves much the same function as does a monochromator in optical spectroscopy.

The electron spectrometer could, in principle, be based on magnetic as well as on different kinds of electrostatic energy analyzers. However, owing to their early dominance in the field, only electrostatic 127° cylinder analyzers are in use nowadays. Starting from the earlier vibrational studies with instrumental resolutions of about 10-20 meV, the total energy resolution of the HREEL spectrometer improved substantially to 0.6 meV, which is close to the theoretical limit for this... 

E 1016-07 Guide for literature describing properties of electrostatic electron spectrometers... 

Figure Bl.7.4. Schematic diagram of a reverse geometry (BE) magnetic sector mass spectrometer ion source (1) focusing lens (2) magnetic sector (3) field-free region (4) beam resolving slits (5) electrostatic sector (6) electron multiplier detector (7). Second field-free region components collision cells (8) and beam deflection electrodes (9).

Modem EMs use electromagnetic lenses, shift devices and spectrometers. However, electrostatic devices have always been used as electron beam accelerators and are increasingly being used for other tasks, e.g. as the objective lens (LVSEM, [10]). 

Figure Bl.23.5. Schematic illustration of tlie TOE-SARS spectrometer system. A = ion gun, B = Wien filter, C = Einzel lens, D = pulsing plates, E = pulsing aperture, E = deflector plates, G = sample, PI = electron multiplier detector with energy prefilter grid and I = electrostatic deflector.

Figure 7 Schematic of a typieai eiectron spectrometer showing aii the necessary components. A hemisphericai electrostatic electron energy analyser is depicted.

A simple spectrometer that we have used successfully is shown in Figure 2. Electrons from an electron microscope hairpin tungsten filament are focused with an Einzel lens onto the monochromator entrance slit, pass through the monochromator and exit slit, and are focused on the sample s surface by additional electrostatic... 

In 1951Castaing8 published results to show that an electron microscope could be converted into a useful x-ray emission spectrograph for point-to-point exploration on a micron scale. The conversion consisted mainly in adding a second electrostatic lens to obtain a narrower electron beam for the excitation of an x-ray spectrum, and adding an external spectrometer for analysis of the spectrum and measurement of analytical-line intensity. Outstanding features of the technique were the small size of sample (1 g cube, or thereabouts) and the absence of pronounced absorption and enhancement effects, which, of course, is characteristic of electron excitation (7.10). Castaing8 gives remarkable quantitative results for copper alloys the results in parentheses are the quotients... 

HREELS experiments [66] were performed in a UHV chamber. The chamber was pre-evacuated by polyphenylether-oil diffusion pump the base pressure reached 2 x 10 Torr. The HREELS spectrometer consisted of a double-pass electrostatic cylindrical-deflector-type monochromator and the same type of analyzer. The energy resolution of the spectrometer is 4-6 meV (32-48 cm ). A sample was transferred from the ICP growth chamber to the HREELS chamber in the atmosphere. It was clipped by a small tantalum plate, which was suspended by tantalum wires. The sample was radia-tively heated in vacuum by a tungsten filament placed at the rear. The sample temperature was measured by an infrared (A = 2.0 yum) optical pyrometer. All HREELS measurements were taken at room temperature. The electron incident and detection angles were each 72° to the surface normal. The primary electron energy was 15 eV. 

FIG. 35. Vertical cross section of the reaction chamber equipped with the mass spectrometer system. Indicated are QMF. the quadmpole mass filter ESA. the electrostatic analyzer CD, the channeltron detector DE, the detector electronics DT, the drift tube lO, the ion optics TMP, the turbomolecular pump PR, the plasma reactor and MN. the matching network. 

Figure 5.6. Diagram of a low-energy, high-angle electron-impact spectrometer. (A) Electron gun (B) monochromator (180° spherical electrostatic energy selector) (C) electron optics (D) scattering chamber (E) analyzer (180° spherical electrostatic energy selector) (F) electron multiplier (G) amplifier and pulse discriminator (H) count-rate meter (I) multichannel scaler (J) X Y recorder (K) digital recorder. (After Kupperman et a/.<42))...

---