Absorption edge energy

The wavenumber is defined at a photon energy E above the absorption edge energy Eq, with respect to the mass of the electron m. ... 

It should be noted that the absolute energy calibrations of beamlines vary. Determining the peak position of an element within a protein relative to a known standard (such as the metallic form of that element) can save time in future structural experiments. Accurate determination of absorption edge energies for various metals has been reported by Kraft et al. (1996). 

Kraft, S., Stilmpel, J., Becker, P. and Kuetgens, U. (1996). High resolution x-ray absorption spectroscopy with absolute energy calibration for the determination of absorption edge energies. Rev. Set. Instrum. 67,681-687. 

Fio. 22. Correlation of Mo K absorption-edge energy with calculated coordination charge. From Cramer et al. (67). 

WO surface density (W nm" ) Figure 2.10 Indirect absorption edge energies ofWO,-Zr02 samples at several oxidation temperatures and W loadings. Two crystalline W oxide materials (monoclinic WO3 and ammonium metatungstate) are shown for... 

Absorption edge energy at the onset pressure of amorphization based on the optical absorption data given by Peanasky et al. [229], by Lorenz and Orgzall [214], and by Syassen [230]. Data have partly been adjusted to the indirect absorption edge of a-Ss at STP conditions reported by Abass et al. [231]... 

Figure 4. Diagram of the HDAC modified for transmission X-ray absorption (XAFS) studies of elements with low absorption-edge energies. Holes drilled using a laser to within 0.15 mm of the anvil faces reduce the attenuation of the X-ray beam by diamond for elements with absorption energies less than 10 keV.

Figure 29. Correlation between the absorption edge energies of S in different compounds and the oxidation states estimated based on the NEXAFS spectra [reprinted with permission of Elsevier Science from Vairavamurthy 1998].

The absorption edge energy or wavelength can be found in the literature... 

The value of the absorption edge energy is close to the electron binding energy, which is used in electron spectroscopy, ESCA (electron... 

A change of the absorption edge energy position is called the chemical shift when the element valence changes. 

The relationship between the empirically determined edge position to the energy of the orbitals at the metal centre is also often unclear. While the absorption edge position is sometimes considered to represent the energy of the vacuum level (the position of Eo which is the onset of the continuum), this seems by no means general. In cases where the absorption edge energy can be compared to the ionisation potential as measured by x.p.s., then... 

With the limitations of the strict and loose interpretations of Eq. (2,27) in mind, a number of important effects can be deduced from Eqs. (2.26) and (2.27). First of all, the fluoresced intensity li(Ei) is proportional to (a) the weight fraction of element I in the specimen, (b) the photoelectric mass absorption coefficient for element i, (c) the fluorescence yield for element i, and (d) the detection efficiency for the fluoresced line energy. Since the photoelectric mass absorption coefficient is largest just above the absorption edge, the most efficient excitation energies lie just above the absorption edge energy for element i. 

Figure 3.5 Sensitivity curves for an energy-dispersive system with a molybdenum anode. Arrows mark the absorption-edge energies, dashed lines represent extrapolation. (Reprinted by courtesy of EG G ORTEC.)...

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