Multiple-pulse fourier-transform EPR of free radical reactions

Conference · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6951537

Bowman, M K

Fourier-Transform (FT) EPR spectroscopy is a natural outgrowth of Electron Spin Echo (ESE) spectroscopy. The FT-EPR spectrum collected with a single microwave pulse yields a snapshot of whatever free radicals are present in the sample during the time of the microwave pulse. Since the pulse can be as short as 2-10 ns, FT-EPR provides a convenient way of measuring the kinetics for EPR spectra of free radicals produced by laser photolysis, pulse radiolysis, etc. Although the resulting spectra have high-time and high-spectral resolution and are easily quantified, the one-pulse kinetic measurements have limitations. First, chemical reaction rates can not be measured at equilibrium. Second, the information is primarily about kinetics and not about reaction mechanisms. Third, many such systems show pronounced Chemically-Induced Dynamic Electron Polarization (CIDEP) so that the measured kinetics reflects not the chemical reaction rates; but rather, the electron spin relaxation rates. This is a particular problem for fast reactions of excited triplet states where the triplet spin-lattice relaxation rate is the major determinant of the rate of appearance of the product free radical signal.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6951537
• Report Number(s): CONF-8803116-1; ON: DE88011983
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
AROMATICS
CHEMICAL ANALYSIS
DATA
ELECTRON SPIN RESONANCE
EXPERIMENTAL DATA
FOURIER TRANSFORM SPECTROMETERS
INFORMATION
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PULSE TECHNIQUES
QUANTITATIVE CHEMICAL ANALYSIS
QUINONES
RADICALS
RESONANCE
SPECTROMETERS