Electron spin mapping of coal molecular structure by ENDOR (Electron-Nuclear Double Resonance): Quarterly technical progress report
In any paramagnetic material the unpaired electrons interact with those neighboring nuclei having non-zero moments. In electron spin echo (ESE) spectroscopy these interactions manifest themselves as modulations in the echo decay envelope, commonly called electron spin echo envelope modulation (ESEEM). Comparison of 2-pulse ESEEM spectra from the vitrinite component of Illinois number6 coal taken at X-band and S-band shows modulation is difficult to discern in the X-band spectrum but is readily apparent in the S-band spectrum. Calculations show that the modulation depth at S-band is roughly 9 times the depth at X-band as expected. Gamma-irradiated quartz was the first sample the investigators examined because it exhibits strong echoes even at room temperature. Extremely weak modulations appear in the S-band ESEEM spectrum of gamma-irradiated quartz. They have attributed this modulation to an interaction with /sup 29/Si. They believe this to be the first observation of modulation from /sup 29/Si in natural abundance. The results obtained so far support their expectations of deeper modulation from the S-band spectrometer. While the modulation depth for the samples studied is deeper at the lower field this will not always be the case. Whenever possible, spectra obtained at two or more fields are desirable to allow one to verify the uniqueness of parameters obtained at one field by simulating the spectrum at another field. Even when the modulation is deeper at the lower field, the higher field spectrum may provide more information if the echo decays very rapidly because the modulation periods increase at the lower fields. This limitation of lower field ESEEM may be overcome if the relaxation times are increased by decreasing the temperature. 4 figs.
- Research Organization:
- Illinois Univ., Urbana (USA)
- DOE Contract Number:
- FG22-84PC70782
- OSTI ID:
- 6932231
- Report Number(s):
- DOE/PC/70782-14; ON: DE88013129
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010600* -- Coal
Lignite
& Peat-- Properties & Composition
ACOUSTIC ESR
CARBONACEOUS MATERIALS
CHALCOGENIDES
COAL
DESIGN
DOCUMENT TYPES
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ENDOR
ENERGY SOURCES
FOSSIL FUELS
FUELS
GAMMA RADIATION
IONIZING RADIATIONS
MACERALS
MAGNETIC RESONANCE
MATERIALS
MEASURING INSTRUMENTS
MINERALS
MOLECULAR STRUCTURE
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PROGRESS REPORT
QUARTZ
RADIATIONS
RESONANCE
SILICON COMPOUNDS
SILICON OXIDES
SPECTROMETERS