New experimental methods for extended x-ray absorption fine structure spectroscopy

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7167805

Allen, P G

Two limitations that exist in conventional techniques for x-ray absorption fine-structure (XAFS) spectroscopy are the slow rate of data acquisition and the lack of site-selectivity. In order to address these problems in the past, dispersive XAFS was successfully developed and implemented for acquiring spectra rapidly, while x-ray excited optical luminescence (XEOL) had been tested on model systems for achieving site-selectivity. In this work, a new spectrometer for dispersive XAFS was designed, built, and tested. Its performance represents an improvement over existing devices in terms of focusing optics, versatility, and ease of use. The spectrometer was used to study time-resolved structural transformations of a platinum catalyst functioning in-situ in an electrochemical fuel cell. The results demonstrate some anomalous effects vis-a-vis bulk metal electrodes during the processes of surface oxide formation and desorption. In addition, the mechanism of the x-ray excited optical luminescence (XEOL) was investigated for a series of inorganic complexes in solution. The results show that the XEOL observed in these systems is dominated by indirect, solvent-based excitation rather than direct x-ray absorption of the optically emitting sites. This finding has significant implications for the feasibility of measuring site-specific XAFS for species in dilute solution.

• Research Organization: Michigan Univ., Ann Arbor, MI (United States)
• OSTI ID: 7167805
• Country of Publication: United States
• Language: English

Related Subjects

440103 -- Radiation Instrumentation-- Nuclear Spectroscopic Instrumentation
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
665100* -- Nuclear Techniques in Condensed Matter Physics -- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
DATA ACQUISITION
ELECTROCHEMICAL CELLS
FINE STRUCTURE
LUMINESCENCE
MEASURING INSTRUMENTS
RESOLUTION
SPECTROMETERS
SPECTROSCOPY
X-RAY SPECTROMETERS