Constant analyzer energy

Fig. 8. Xps spectmm of Ag acquired with Mg excitation recorded with constant analyzer energy of 100 eV. ( = Ag 3<7peak excited with MgfC ...

In most electron spectroscopic analyses, the kinetic energies of the electrons entering the analyzer are retarded to either a constant energy or by a constant factor. These approaches lead to two modes of operation the constant analyzer energy (CAE) mode and the constant retard ratio (CRR) mode. 

CONSOL pyrolysis process, 6 854 Constant analyzer energy (CAE) mode, 24 103... 

The workfunction w is a spectrometer constant and represents mainly the work necessary to excite the electron from the Fermi-level to the free electron level. Bearing in mind the experimental set-up, where EK = EK> is the constant analyzer energy, the complete equation reads... 

The XPS (X-ray Photoelectron Spectroscopy) and IR analyses have been described in detail elsewhere [14], Here, only some important facts are summarized. The XPS data acquisition was performed with a SAGE 150 Spectrometer (Specs, Berlin, Germany) using a non-monochromatized MgK or AIKq, radiation with 12.5 kV and 250 W settings at a pressure 10-7 Pa in the analysis chamber. XPS spectra were acquired in the constant analyzer energy (CAE) mode at 90° take-off angle. Peak analysis was performed using the peak fit routine from Specs. 

Small-area XPS spectra were collected with a beam size of 100 pm diameter with a power of 24.5 W in the constant analyzer energy mode using a pass energy of 26 eV and a step size of 0.05 eV. Under these conditions, the full-width-at-half-maximum (fwhm) for Ag3ds/2 is 0.55 eV. Survey spectra were acquired with 280 eV pass energy and a step size of 1 eV. The whole set of spectra (detailed and survey spectra) was acquired within 30 min/area. 

XPS Measurements. X-ray photoelectron spectra were acquired with a VG Thetaprobe spectrophotometer (Thermo Electron Corporation, West Sussex, U.K.) equipped with a radian lens, a concentric hemispherical analyzer, and a 2D channel-plate detector with 112 energy and 96 angle chatmels. A monochromatic Al Ka source with a spot size of400pm was used. Electrons were emitted at 53 with respect to the surface normak and the acceptance angle was 30. The instrument was operated in standard lens mode, and the analyzer in constant-analyzer-energy mode. Pass energies used for survey scans and detailed scans were 200 and 100 eV, respectively, for Au 4f, C Is, F Is, O Is, and... 

In common practice, it is assumed that the influence of roughness is the same on both intensities, in other words that/ Aa/f Bb = L When the kinetic energy analyzer is used in the constant-analyzer energy mode (CAE) (cf. the section on Lens System and Energy Analyzer), which is required for quantitative analysis, the residual kinetic energy of the electron reaching the detector is the same whatever its initial kinetic energy therefore, T>Aa/T>Bb = 1- The above equation may then be rewritten... 

The combination of retardation and deflection allows two different modes of operation. In the constant analyzer energy (CAE) mode the pass energy is kept constant and the spectrum is scanned by a variation of the retarding field. In this mode the resolution AEa is kept constant over the whole spectrum. In the constant retard ratio mode (CRR) the voltage difference between the hemispheres is proportional to the retarding field. In this mode the relative resolution AEjE is kept constant. The CAE mode is normally used for PES, the CRR mode for Auger spectroscopy. 

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