Analyzer resolution

Performance Parameters. Since the detector is often involved in the separation of isobars, normal mass analyzer resolution and mass accuracy do not really apply. The mass spectrometric resolution would be determined by the magnetic and electric sectors. Only atomic species are analyzed, so that sets the upper m/z... 

The convolution theorem plays a valuable role in both exact and approximate descriptions of functions useful for analyzing resolution distortion and in helping us understand the effects of these functions in Fourier space. Functions of interest and their transforms can be constructed from our directory in Fig. 2 by forming their sums, products, and convolutions. This technique adds immeasurably to our intuitive grasp of resolution limitations imposed by instrumentation. 

XPS spectra were recorded using unmonochromatized Mg K radiation (1253.6 eV), and an unmonochromatized He-resonance lamp was used for ultraviolet photoelectron spectroscopy (UPS). XPS spectra were taken with an analyzer resolution of 0.2 eV, and the net resolution measured as the full width at half-maximum (FWHM) of Au 4f(7/2) was 0.9 eV. The spectrometer is of our own construction and is, e.g., designed to provide optimum angle-dependent XPS or XPS(0) (12,l4). For high 5-values, the photoelectrons leave the sample surface near the grazing angel, and due to the limited escape depth of the electrons, this is a "surface sensitive" mode. In the "bulk sensitive" mode, for low 0-values, the photoelectrons exit near the surface normal, and hence more information from the "bulk" of the sample is obtained (15). 

Core-level excitation from a closed sub-shell results in the most intense and typically narrow photoelectron Unes. The width of a core level measured at half its maximum height, fuU width at half maximum (FWHM), is usually defined as the convolution of the width of the photon source, the natural line-width and the analyzer resolution. AU transitions (except from s levels) give rise to doublets due to spin-orbit coupling, in which the spin of the unpaired electron left in the orbital can couple in a paraUel or an anti-parallel manner with its orbital angular momentum. As all the relevant elements (except H) show at least one transition detectable by this technique, and the core levels of different elements are usually readily distinguishable, XPS is widely used for elemental analysis in the sampling depth of the topmost atomic layers. 

Table 1 Common polyatomic ion interferences with the mass analyzer resolution necessary to resolve them from the analyte of interest...

Total resolution of instrument is dependent on convolution of X-ray source width, natural linewidth of peak, analyzer resolution and is given by... 

II. c XPS spectra were recorded using a SSI-X probe (SSX-100-206) spectrometer of FISONS with monochromatised AIK, radiation.The spectrometer energy scale was calibrated using the Au 4f7/2 peak ( binding energy 93.98 eV). With the analyzer resolution used (50 eV) for rea>rding individual peaks the full v th at half maximum of Au 4f7/2 peak was of 1.0 eV. 

The energies of the electrons being collected are filtered by applying different potentials to the inner and outer cylinders. The potentials of the cylinders focus the electrons to a plane where a slit aperture is located. The slit aperture controls the energy resolution of the analyzer and in the case where retardation fields are not employed, resolutions follow an E/AE relationship. Beyond the analyzer resolution adjustment aperture is the electron detector. Modem Auger systems make use of multiple detectors in order to increase the electron counting efficiency of the instmment in a similar fashion to those found in XPS systems. 

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