Soft X-ray absorption

Soft X-ray absorption measurements are done at low-energy synchrotron X-ray facilities such as the UV ring at NSLS or the Advanced Photon Source (APS) at Lawrence Berkeley National Laboratory (LBNL). The beam size is typically 1 mm in diameter. The electron yield data are usually obtained in the total electron yield (EY) mode, measuring the current from a channel electron multiplier (Channeltron). Sometimes a voltage bias is applied to increase surface sensitivity. This is referred to as the partial electron yield (PEY) mode. Huorescence yield (EY) data are recorded using a windowless energy dispersive Si (Li) detector. The experiments are conducted in vacuum at a pressure of 2 X 10 torr. 

The Soft X-Ray Absorption Limits of Certain Elements, Davies, Andrewes and Horton, Roy. Soc. Proc., 110, 64, 1926. 

Figure 4.3 Reprinted from Wear, Vol. 202, Z. Yin, M. Kasrai, M. Fuller, G.M. Bancroft, K. Fyfe and K.H. Tan, Application of soft X-ray absorption spectroscopy in chemical characterization of anti wear films generated by ZDDP the effect of physical parameters, Part I, pp. 172-191. Copyright 1997, with permission from Elsevier.

The reduction of transition-metal species under the intense electron irradiation of the high-resolution electron microscope used in [37] additionally represents a process that could also lead to Sc-L2>3 data deviating from those presented here, which were measured with the gentle method of soft x-ray absorption. 

The first experimental observations of the absence of core levels seem to have been made by Lukirskii et al.1 and Codling and Madden2 in soft X-ray absorption spectra for Xe. They found lines converging to what seemed to be the 4 3/2 threshold but no lines were found that could be associated with the 4p1/2 threshold. Later photoabsorption experiments on Te3), Xe4 and Cs5 confirmed these results for Xe and Cs and showed that in Te both 4p-thresholds were absent (see also Sect. 9). 

The local structure of aluminate in aqueous solution has been found by Radnai et al. to be a fourfold coordination structure, [Al(OH)4], using a solution X-ray diffraction method [5]. We have spectroscopically examined the dynamic change in the structural transition from aluminate to Al(OH)3 [6], which happens with the polymerization of aluminate due to the reduction of pH [7], using the in situ soft X-ray absorption spectroscopy we have developed [8,9]. The X-ray... 

Soft X-Ray Absorption Spectral Analysis of Amorphous Carbon and Carbon Black Using the DV-Xa Method Yasuji Muramatsu... 

Abstract The discrete variational (DV)-Xa method was used to analyze the high-resolution soft X-ray absorption spectra (XAS) in the C /Cregion of sputtered amorphous carbon films and carbon black to elucidate their local structures. The measured XAS of amorphous carbon and carbon black were compared with those of reference compounds, and the fine structure in the XAS can be assigned by the calculated density of states of the reference compounds. Such a comparative analysis in the measured XAS and the calculated density of states of these carbon materials with reference compounds, which have been known their local or molecular structures, is a valid approach for elucidating the complex local structures of carbon materials. 

Figure 16.1 Soft X-ray absorption spectra (XAS) in the C K-region of amorphous carbon (a-C) films deposited by various methods (Rl-4, 11-3, El-5) and reference compounds of HOPG, C70, 60. aRd G50H36.

Although the complex local structure of carbon materials cannot be easily or completely elucidated by conventional analysis methods, the high-resolution soft X-ray absorption spectroscopy and spectral analysis using the DV-Xa method are promising tools to analyze the local structure. In addition, comparative analysis of carbon materials with reference compounds that have been known their local and molecular structures is a valid approach for elucidating the local structure. 

Evaluation of Laboratory Ultra-Soft X-Ray Absorption Spectrometer by Li-K XANES Measurements and Their DV-Xa Calculations... 

Abstract We have built a novel laboratory ultra-soft X-ray absorption (USXA)... 

Inner shell absorption spectroscopy provides a map of unoccupied electronic states (or levels) and the electronic structures of conduction bands in the vicinity of the core-excited atom. The X-ray absorption spectroscopy (XAS) represents a fingerprint of the chemical state of the element. It provides useful means of nondestructive site-dependent chemical analysis of complex systems. Ultra-soft X-ray absorption (USXA) method is categorically interesting for chemical analysis of a variety of complex materials in battery industry, environmental science, and semiconductor industry. 

Evaluation of Laboratory Ultra-Soft X-Ray Absorption Spectrometer... 

Using Near-Edge Soft X-ray Absorption Spectroscopy To Study Organic Polymers and Metal—Polymer Interactions... 

Bianconi, A. (1979). Core excitons and inner shell resonances in surface soft x-ray absorption (SSXA) spectra. Surf. Sci. 89, 41-50. 

Bianconi, A., and R. S. Bauer (1980). Evidence of SiO at the Si-oxide interface by surface soft x-ray absorption near-edge spectroscopy. Surf. Sci. 99, 76-86. 

DIET has also been applied to the study of rare earth oxides, YBaCuO oxides as well as Si02 with significant contribution to the understanding of their structure. Loubriel, Knotek, Stulen, Koel and Parks studied the ESD and PSD of oxide films of Ce and Er and compared the results with those obtained by Soft X-ray absorption, SXA [135]. From the ESD experiments they concluded that the 5p level in the rare earth is involved in the electronic transitions for ion desorption from the surface. Schmidt-May, Sent, Voss, Kunz, Flodstrom, Nyholm and Stockbauer later studied the resonant electron and ion emission and the desorption mechanism from oxides of Sm, Eu and Yb [136]. They observed that the enhancement in photoelectron at the 4d edge is also found in the ion desorption yield. They concluded that the use of PSD as a proof of the specific desorption site is strongly limited because the initial excitation does not occur in the surface complex from which the detected ion is being desorbed. 

Numerous spectroscopic techniques, such as x-ray photoelectron spectroscopy (XPS) [2], Auger electron spectroscopy (AES) [3], ultraviolet photoelectron spectroscopy (UPS), soft x-ray absorption spectroscopy (SXA) [4], high-resolution electron energy loss spectroscopy (HREELS) [5], and Fourier transform infrared... 

Lytle, F.W., D.R. Sandstrom, E.C. Marques, J. Wong, C.L. Spiro, G.P. Huffman, and F.E. Huggins. 1984. Measurements of soft x-ray absorption spectra with fluorescence ion chamber detector. Nucl. Instr. Meth, 226 542-548. 

Cotton FA, Ballhausen CJ (1956) Soft X-ray absorption edges of metal ions in complexes I. J Chem Phys 25 617... 

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