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CAER Seminars

Carbon Inner Shell (1s) Spectroscopy (NEXAFS) and Soft X-ray Imaging of Coals and Other Heterogeneous Organic Solids

Speaker:
Dr. George D. Cody
Geophysical Laboratory
Carnegie Institution of Washington
Washington, DC 20015

Date:
Wednesday, May 29th, 3:30 p.m.
Ben Bandy Conference Room
center for Applied Energy Research

Abstract:
Understanding the chemistry of solid phase organics is often compromised by intrinsic sample heterogeneity at fine scales. Advances in X-ray microfocusing techniques coupled with intense X-ray sources has led to the development of a scanning transmission X-ray microscope located at the X1A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory.

The microscope has a resolution of 50 nm. A soft x-ray undulator and a scanning monochromator allows for C-NEXAFS spectra to be obtained on regions containing less than 1 femptogram of carbon. X-ray imaging employs contrast based on the differential intensity of various core level to LUMO and higher state transitions in the C-NEXAFS region of the carbon 1s absorption edge.

Applications to be presented include: chemical structural analysis of compositionally discrete microdomains in coals, elucidating surface chemical reactions on organic thin-films, and X-ray linear dichroism studies nematic phase organic solids.