White Lines in EELS  Practical Electron Microscopy and Database   An Online Book  

Microanalysis  EM Book http://www.globalsino.com/EM/  
White lines are the outstanding features observed in the electronenergyloss spectra (EELS) and xrayabsorption spectra (XAS) of transition metals, presented at the onsets of the L_{2} and L_{3} absorption edges. These white lines arising from transitions from the 2p core level are induced by the excitations of 2p_{1/2} and 2p_{3/2} core electrons to unoccupied dlike states near the Fermi level (dipole transitions). The whiteline intensities represent the unoccupied 3d density of states (DOS). These peaks are normally quite intense for the transition metals and their alloys of each transition series. The peaks have been called white lines because they were originally observed in overexposed regions on the photographic film used to record xrayabsorption spectra [1]. Based on an atomic, oneelectron model Mattheiss and Dietz [2] had shown that the total area (A_{total}) of A_{2} and A_{3} under the L_{2} and L_{3} white lines is given by,  [3436] where, R_{2p} represent R_{2p3/2} and R_{2p1/2} (assuming R_{2p3/2} and R_{2p1/2} are approximately equal). Here, R_{2p3/2} and R_{2p1/2} are the radial matrix elements for the excitations of the 2p_{3/2} and 2p_{1/2} core electrons. h_{total} is the total number of d holes (or alternatively, d occupancy). Pearson et al. [1] experimentally and theoretically (based on oneelectron HartreeSlater calculations) found that the intensities of L_{2,3} white lines for most of the 3d and 4d transition metals decreased nearly linearly with increasing atomic number, reflecting the filling of the d states. Figure 3436 shows the deconvoluted and backgroundsubtracted L_{2,3} energyloss spectra for the 3d transition metals. The edge energies are not shown in order to present all the spectra in the same figure, while the intensities of the white lines are scaled simultaneously for all elements. Metallic Cu does not have these two L_{3} and L_{2} lines since its dband is fully occupied, while all the other transition elements from Ti (22) to Ni (28) have clearly.
[1] J. Veldkamp, Physica 2, 25 (1935). 

