Pass energy

Electron lens systems between each component serve a number of fiinctions. A lens following the source focuses electrons on the entrance aperture of the premonocliromator and decelerates these electrons to the pass energy required... 

Thus, for a set K, an inverse relationship between pass energy, and sht width, w, exists. Retardation with a CFIA can either be in the CAE or CRR modes. This retardation is accomphshed by planar retarding grids placed across the entrance aperture of the CFIA. 

In XPS the photoelectrons are retarded to a constant energy, called the pass energy, as they approach the entrance slit. If this were not done, Eq. (2.5) shows that to achieve an absolute resolution of 1 eV at the maximum kinetic energy of approximately 1500 eV (using A1 Ka radiation), and with a slit width of 2 mm, would require an analyzer with an average radius of about 300 cm, which is impracticable. Pass energies are selected in the range 20-100 eV for XPS, which enables the analyzer to be built with a radius of 10-15 cm. 

The spectrometer was a Physical Electronics Model 548 modified for emplacement in a glovebox so that actinide samples could be examined. Spectra were taken using AIK radiation (1486.6 eV). The overall energy resolution of tne spectrometer was 1.2 eV using an analyzer pass energy of 25 eV. The spectrometer control was interfaced to a Nicolet 1180 minicomputer providing automatic data acquisition and analysis capability. 

The spectroscopic investigations were carried out in a modified LHS 12 MCD system. For the XPS measurements (Mg Ka 1253.6 eV, 240 W power) a fixed analyser pass energy of 108 eV... 

There are two operating modes known as Constant Retard Ratio (CRR) or Constant Analysis Energy (CAE). In CRR, the electrons are slowed down by an amount which is a constant ratio of the electron energy to be analysed. For example, if the retard ratio is 10 and 1000 eV electrons are to be detected, then the electrons will be slowed down to 100 eV and the pass energy will be set to 100 eV. In CAE, the pass energy is fixed. If the pass energy is 50 eV, then electrons of 1000 eV will have to be slowed down by 950 eV in order to be detected. 

The broadening due to the analyzer depends on the energy at which the electrons travel through the analyzer and the width of the slits between the energy filter and the actual detector. The analyzer contribution to the line width becomes irrelevant at low pass energies, however, at the cost of intensity. 

The XPS data were acquired on a Physical Electronics model 5400 XPS system using a Mg anode. For survey spectra, the pass energy was 44.75 eV with a step size of 0.5 eV. The time per step was 50 msec. High resolution spectra were acquired with a pass energy of 35.75 eV and step size of 0.1 eV, The time per step was 50 msec. Thermogravimetric data were obtained on a Perkin-Elmer, Diamond Thermogravimetric/ Differential Thermal Analyzer (TG/DTA) with Pyris software, version 7.0-0.0110. 

Figure 5. Heaviside and Poynting energy flow components. The Heaviside component is often 10 trillion times the Poynting component, but is simply wasted in ordinary single-pass energy flow circuits.

The excited antenna molecule passes energy to a neighboring hlorophyll molecule (resonance energy transfer), exciting it. 

The preparation of the used Fe-loading molecular sieves materials and the catalytic synthesis of carbon nanotubes have been described in detail in our previous report [22]. The textural properties and compositions of catalysts are shown in Table 1. XPS spectra for samples were recorded on a PHI-5300 ESCA system. The pass energy was 71.550 eV. Before the XPS measurement, all the samples were ground and then dried at 393 K for 2 h. For these samples, the C(ls) level (284.4 eV) was taken as the reference binding energy (B.E.). 

XPS analysis of y-APS applied to nickel and silicon substrates was also carried out using a Surface Science Instruments SSX-100-03 instrument equipped with a monochromatic A1 Ka source. The X-ray source had an energy of 1487 eV and the instrument operated at a spot size of 600 //m. Pass energies for survey and high resolution spectra were 150 and 52 eV, respectively. Atomic concentrations were once again obtained from the high resolution spectra using sensitivity factors provided with the software. 

Note that such convolutions are commutative, associative, and distributive.) If these photoelectrons, created with the distribution function Fs( kin, kin) in the source region, are detected with an energy analyser, a further convolution is necessary to account for the instrumental resolution as described by the spectrometer functions Gsp( kin, pass), equ. (1.48). The convolution yields the distribution function fexp( pass, kin), or equivalently Fexp(Usp, l/°p), of photoelectrons observed at a preselected pass-energy pass or, equivalently, at a given spectrometer voltage Gsp. One has (see equ. (10.54b))... 

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