Experimental evidence of thermal fluctuations on the X-ray absorption near-edge structure at the aluminum K-edge

Details Experimental evidence of thermal fluctuations on the X-ray absorption near-edge structure at the aluminum K-edge Experimental evidence of thermal fluctuations on the X-ray absorption near-edge structure at the aluminum K-edge

2012-03-21

arxiv.org/abs/1203.4755v1

Physics

Condensed Matter

Strongly Correlated Electrons

Scientific paper

After a review of temperature-dependent experimental x-ray absorption near-edge structure (XANES) and related theoretical developments, we present the Al K-edge XANES spectra of corundum and beryl for temperature ranging from 300K to 930K. These experimental results provide a first evidence of the role of thermal fluctuation in XANES at the Al K-edge especially in the pre-edge region. The study is carried out by polarized XANES measurements of single crystals. For any orientation of the sample with respect to the x-ray beam, the pre-edge peak grows and shifts to lower energy with temperature. In addition temperature induces modifications in the position and intensities of the main XANES features. First-principles DFT calculations are performed for both compounds. They show that the pre-edge peak originates from forbidden 1s to 3s transitions induced by vibrations. Three existing theoretical models are used to take vibrations into account in the absorption cross section calculations: i) an average of the XANES spectra over the thermal displacements of the absorbing atom around its equilibrium position, ii) a method based on the crude Born-Oppenheimer approximation where only the initial state is averaged over thermal displacements, iii) a convolution of the spectra obtained for the atoms at the equilibrium positions with an approximate phonon spectral function. The theoretical spectra so obtained permit to qualitatively understand the origin of the spectral modifications induced by temperature. However the correct treatment of thermal fluctuation in XANES spectroscopy requires more sophisticated theoretical tools.

Affiliated with

Also associated with

No associations

Rating

Experimental evidence of thermal fluctuations on the X-ray absorption near-edge structure at the aluminum K-edge does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Experimental evidence of thermal fluctuations on the X-ray absorption near-edge structure at the aluminum K-edge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Experimental evidence of thermal fluctuations on the X-ray absorption near-edge structure at the aluminum K-edge will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-488731