Fun-Dow Tsay

Ti^(3+) in meteoritic and synthetic hibonite

Electron spin resonance has been used to make the first direct determination of Ti^(3+) in synthetic hibonite and hibonite from inclusion SH-7 of the Murchison C2 chondrite. Ti^(3+) concentrations range from 0.02 to 0.64 wt% in synthetic blue hibonite and 0.35–0.44 wt% in hibonite from SH-7. No Ti^(3+) could be detected in orange hibonite, supporting the earlier conclusion that the orange-to-blue transition is associated with the presence of Ti^(3+). At constant temperature and oxygen fugacity, Ti^(3+)/Ti^(4+) in synthetic hibonite increases with decreasing V but is not strongly dependent on bulk Ti. At the concentration levels encountered in meteoritic hibonite, Fe and Cr contents do not have a significant effect on the amount of Ti^(3+). In both synthetic and meteoritic hibonite, Ti^(3+) occupies a 5-coordinated crystallographic site, which is consistent with the formation of doubly ionized oxygen vacancies. At low oxygen fugacities, essentially all Ti^(4+) on the five-fold Al-site has been reduced to Ti^(3+). Hibonite from SH-7 equilibrated with a gas that could have been as reducing as a gas of solar composition. This is consistent with other estimates based on mineral equilibria of high temperature oxygen fugacities in Ca-Al-rich inclusions. With the possible exception of Mo-W depletions, indicators based on bulk trace element concentrations in CAIs are inconclusive. There is considerable evidence that as CAIs cooled to lower temperatures, they experienced conditions significantly more oxidizing than those of a solar gas, perhaps in planetary environments.

Ferromagnetic resonance of lunar samples

Abstract Evidence is presented to support that the electron spin resonance (ESR) spectra observed for a selection of Apollo 11 lunar samples (10087-10, 11; 10046-29, 30; 10062-26, 27; 10017-35, 36) arise from the ferromagnetic centers consisting of metallic Fe. A model study to simulate the polycrystalline spectra has been carried out, from which it was possible to ascertain with some degree of certainty the size and shape of the ferromagnetic centers as well as the metallic iron content. Some variations in the metallic Fe content have been noted in these samples, for example, between rocks and fine soil.

Electron Paramagnetic Resonance and Optical Spectra of Pentacyanocobaltate(II)

Electron paramagnetic resonance (EPR) and optical spectral studies have been carried out on the pentacyanocobaltate(II) ion in ethylene glycol–water solutions, and in electron‐irradiated powder samples of K3Co(CN)6. Both EPR and optical spectra observed for the ion in the powder samples are essentially similar to those obtained from the ethylene glycol–water solutions. There was no observable linewidth variation with nuclear spin states MI, no dependence on the different solvent media used, and no dependence on the concentration ratio Co2+/CN−, in both X‐band and K‐band spectra. The results indicate that the structure of Co(CN)53− in solutions and in polycrystalline media is a slightly distorted square pyramid with no solvent bound in the sixth coordination site. The two strong hyperfine components with exceptionally large spacings occurring at the low‐field end of the X‐band spectrum are identified as the so‐called angular anomalies. An effective method of simulation of the first‐derivative EPR spectra o...

Electron spin resonance of manganous ions in frozen methanol solution.

An analysis of the electron spin resonance of Mn2+ in frozen methanol is presented. The broadened, asymmetric lineshape is shown to be due to inhomogeneous broadening caused by combined second - and third-order effects of randomly distributed zero-field splittings in the range of 80-150 G.

Magnetic resonance studies of lunar samples.

Electron spin resonance searches at 9.5 gigahertz on several fines samples and portions of several rocks have yielded signals whose lineshapes and temperature dependences show that the samples are principally ferromagnetic in nature. Proton magnetic resonance searches at 60 megahertz of these samples have not revealed any signals ascribable to water or any other types of hydrogen in concentrations greater than 0.0001 percent by weight contained in narrow lines (5 oersteds wide or less) and 0.01 percent by weight in wide lines (as wide as 100 oersteds).