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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Identification of defect sites in calcium tungstates after irradiation from correlation of electron spin resonance and thermoluminescence data
Oxygen vacancies caused by fast neutrons in calcium tungstate single crystals measured by electron spin resonance
Hyperfine coupling constants of positive divalent Mn ion in calcium and barium fluorides, measuring temperature dependence by analyzing electron spin resonance spectrum
Free radicals formation in gamma irradiated pyrimidine-purine co-crystal complex, using electron spin resonance spectroscopy
Perhydroxyl radical electron spin resonance spectrum in solution of hydrogen peroxide and water at 77 K, noting g factor, hyperfine splitting and molecular structure
Free radicals destruction rates by gamma irradiation at 77 K measured as first order function of dosage, using electron spin resonance spectroscopy
Lorentz invariance test using bar magnet on torsion fiber, analyzing preferred reference frame in space assuming earth velocity coupled to electron spin through specific term
Free radical destruction by gamma irradiation in organic solids at low temperature measured by electron spin resonance spectroscopy, noting dosage relationship
Apollo 11 rock and fines magnetic resonance, examining line shapes, temperature dependences and electron spin
Radiation induced free radicals in thymidine single crystals, attributing electron spin resonance spectral observations to nature of various radicals
Ferromagnetic electron spin resonance spectra of Apollo 11 lunar samples, using model for polycrystalline spectra simulation
Electron spin resonance studies of Apollo 11 and 12 lunar soil samples, determining ferromagnetism due to Fe particles
A summary of selected experimental results obtained on lithium-diffused bulk silicon is presented. Particular emphasis is placed on the radiation-induced degradation and thermal annealing of minority carriers in bulk silicon because solar cell output is related to the minority carrier lifetime. The temperature dependence of the minority carrier lifetime indicates the density and energy levels of the recombination centers and provides clues to their identity. Electron spin resonance and infrared absorption techniques are used to investigate the introduction and anneal of three specific radiation induced defects, which are thought to contribute to the recombination process.
The oxidation by ZnO holes of vehicle components in thermal control coatings has been examined to develop experimental methods to study such reactions and to identify what components to avoid because of their instability when in the presence of u.v.-produced holes. Two methods were used that show consistent results. An electrochemical technique with a single crystal ZnO anode was used for quantitative comparisons, and electron spin resonance was used to study more practical powder/vehicle systems. Alcohols and dioxane were shown to be readily oxidized by ZnO holes, whereas acetonitrile, neopentane, and ethyl acetate were oxidation resistant. Some resistance to the photooxidation was provided by recombination centers.
Electron spin resonance (ESR) has been employed in a study of the ferromagnetic constituents of a wide variety of soils from six sampled regions of the moon as well as glasses made to simulate lunar compositions. A significant result has been that magnetite-like phases (magnetic iron spinel) precipitated in and on simulated lunar glasses as a result of sub-solidus oxidation yield room-temperature ESR spectra virtually identical with the line shape predicted for spherical, single domain particles of metallic Fe. It is shown that such magnetite-like phases can nevertheless be distinguished from metallic iron on the basis of the temperature dependence of the ESR intensity.
The oxygen and hydrogen free radical (atom) concentration profiles in the premixed propane/oxygen flame at 92.5% oxygen were determined using electron spin resonance (ESR) spectroscopy techniques. The ESR instrument was specially modified so that the flame can be probed for determining the oxygen and hydrogen atom population densities during the actual combustion process of propane burning in oxygen. The technique used for propane is similar to that suggested by Fristrom and Westenberg to measure the free radical concentration profiles in C-C hydrocarbon/oxygen combustion.
Results of an electron spin resonance study of free radicals in the ultraviolet irradiation of a simulated Martian surface suggest that the ultraviolet photolysis of CO or CO2, or a mixture of both, adsorbed on silica gel at minus 170 C involves the formation of OH radicals and possibly of H atoms as the primary process, followed by the formation of CO2H radicals. It is concluded that the photochemical synthesis of organic compounds could occur on Mars if the siliceous surface dust contains enough silanol groups and/or adsorbed H2O in the form of bound water.
Various redox couple surface additives are studied which increase the photostability of coprecipitated zinc orthotitanate pigment. The electron spin resonance technique was used to examine the characteristic photodamage centers. Results indicate that cerium surface redox additive completely passivates the pigment at the surface concentrations studied. Less passivation occurs with the iridium chloride and the iron cyanide redox couples.