Hartree-Slater Calculations of the L23 Edges of 3d Transition Metal Electron Energy Loss Spectra

1990 ◽  
Vol 48 (2) ◽  
pp. 58-59
Author(s):  
D. H. Pearson ◽  
C. C. Ahn ◽  
B. Fultz ◽  
P. Rez
Keyword(s):  
Transition Metal ◽  
Energy Loss ◽  
Electron Energy ◽  
White Line ◽  
Line Intensities ◽  
3D Metals ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra ◽  
Metal Electron ◽  
The Continuum

A straightforward method for measuring the white line intensities of the L23 absorption edges of 3d transition metal electron energy loss spectra was recently reported by Pearson et al. [1]. In that analysis, the white line intensities were isolated by assuming that the continuum contribution for the 3d metals could be approximated by an edge shape similiar to that of copper, which has a full 3d band. When normalized to the continuum, the white line intensities were found to decrease linearly with atomic number (or 3d state occupancy). A similar analysis for the 4d metals showed that the white line intensities initially increased, peaked at Nb, and then decreased nearly linearly with atomic number [2]. The white line calculations of Ahn et al. were in qualitative agreement with these results for the 4d metals, but deviated from experimental results for the early 3d metals [3]. In an effort to determine if the continuum L23 edge is indeed copper-like for the early 3d metals we have calculated the continuum edge shapes based on an atomic, one electron model.

Measurements of white line intensities in 4d transition metals using Electron Energy Loss Spectrometry (EELS)

1989 ◽  
Vol 47 ◽  
pp. 386-387
Author(s):  
Douglas H. Pearson
Keyword(s):  
Transition Metals ◽  
Energy Loss ◽  
Electron Energy ◽  
Background Intensity ◽  
White Line ◽  
Line Intensities ◽  
Electron Energy Loss Spectrometry ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra ◽  
The Continuum

A feature of considerable interest in the electron energy loss spectra of transition metals is the L23 edge which is composed of two sharp “white lines” superimposed on a broad edge that makes up the trailing background. The white lines are due to the excitations of electrons from filled 2p1/2 and 2p3/2 states to unoccupied 3d or 4d states, and the background intensity is due to continuum excitations. Recent work on the white lines of the 3d transition metals has shown that when normalized to the continuum excitations, the total white line intensity decreases nearly linearly with atomic number (or d band occupancy) across the 3d series. Furthermore, this linear relationship may be used to measure the changes in 3d state occupancy local to specific atoms during alloying and during solid state phase transformations. In the present paper the experimental analysis of the white lines is extended to the 4d transition metals and is then compared to experimental results from the 3d metals.Electron-transparent specimens of the pure 4d metals were prepared by standard electropolishing and evaporation techniques. To prevent oxidation of the Yttrium specimen, however, a 40 nm film of Yttrium was deposited between 15 nm films of Vanadium by direct current ion sputtering in a chamber with a base pressure of < 1.0 × 10−7 Torr. Energy loss spectra were obtained using a Gatan 607 electron energy loss spectrometer attached to a Philips EM 430 electron microscope operating in image mode at 200 kV.

Can the Number of D Electrons in Transition Metals be Measured from White Lines?

1997 ◽  
Vol 3 (S2) ◽  
pp. 957-958 ◽  
Author(s):  
P. Rez
Keyword(s):  
Transition Metals ◽  
Energy Loss ◽  
Electron Energy ◽  
Transition Elements ◽  
White Line ◽  
Line Intensities ◽  
Continuum Region ◽  
The Matrix ◽  
Image Position ◽  
Electron Energy Loss

Sharp peaks at threshold are a prominent feature of the L23 electron energy loss edges of both first and second row transition elements. Their intensity decreases monotonically as the atomic number increases across the period. It would therefore seem likely that the number of d electrons at a transition metal atom site and any variation with alloying could be measured from the L23 electron energy loss spectrum. Pearson measured the white line intensities for a series of both 3d and 4d transition metals. He normalised the white line intensity to the intensity in a continuum region 50eV wide starting 50eV above threshold. When this normalised intensity was plotted against the number of d electrons assumed for each elements he obtained a monotonie but non linear variation. The energy loss spectrum is given bywhich is a product of p<,the density of d states, and the matrix elements for transitions between 2p and d states.

Parallel Detection of Electron Energy Loss Spectra in Direct Mode

1990 ◽  
Vol 48 (2) ◽  
pp. 82-83
Author(s):  
Eckhard Quandt ◽  
Stephan laBarré ◽  
Andreas Hartmann ◽  
Heinz Niedrig
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Large Angle ◽  
Maximum Energy ◽  
Semiconductor Detectors ◽  
Parallel Detection ◽  
Photodiode Arrays ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Due to the development of semiconductor detectors with high spatial resolution -- e.g. charge coupled devices (CCDs) or photodiode arrays (PDAs) -- the parallel detection of electron energy loss spectra (EELS) has become an important alternative to serial registration. Using parallel detection for recording of energy spectroscopic large angle convergent beam patterns (LACBPs) special selected scattering vectors and small detection apertures lead to very low intensities. Therefore the very sensitive direct irradiation of a cooled linear PDA instead of the common combination of scintillator, fibre optic, and semiconductor has been investigated. In order to obtain a sufficient energy resolution the spectra are optionally magnified by a quadrupole-lens system.The detector used is a Hamamatsu S2304-512Q linear PDA with 512 diodes and removed quartz-glas window. The sensor size is 13 μm ∗ 2.5 mm with an element spacing of 25 μm. Along with the dispersion of 3.5 μm/eV at 40 keV the maximum energy resolution is limited to about 7 eV, so that a magnification system should be attached for experiments requiring a better resolution.

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