Radiation Electron-Hole Centers (Free Radicals) in Minerals

Marfunin, A. S.

doi:10.1007/978-3-642-67112-8_7

Cited by 3 publications

(1 citation statement)

References 88 publications

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“…The most widely distributed centers in feldspars are O − and Ti 3+ , as well as Fe 3+ impurity [30]. The O − center developed in all feldspars when the samples were irradiated.…”

Section: Bleaching Of Feldspar In Sunlightmentioning

confidence: 97%

The ESR Signals in Different Minerals and the Bleaching of Feldspar

Bi,

Yi,

Yang

et al. 2023

Minerals

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The use of quartz is critical to the electron spin resonance (ESR) dating of sediments and fault gouges. The germanium center (Ge center) in quartz is a commonly used color center employed in ESR signal measurement. Although Ge center signals in quartz can be detected using an ESR spectrometer, they are weak and sometimes undetectable. Impurities in quartz grains can further aggravate these deficiencies and may even invalidate any attempt to repeat ESR ages due to the deficiencies evident in the processes used in sample preparation. Using sieving, carbonate-organic matter removal, water flotation, magnetic separation, heavy liquid separation, and HF solution etching, we separated quartz, feldspar (plagioclase), mica, and the heavy minerals and measured the ESR signal in each of them to examine the impact of impurities within mineral grains on the ESR signals. From the ESR spectra, we observed intense ESR signals in feldspar and the heavy minerals and weak signals in mica at the same positions as the Ge center in the quartz. The ESR signals in the feldspar proved to be the most intense and overrode the peaks exhibited by the Ge center in the quartz. Feldspar is commonly associated with quartz in sediments, but it is difficult to separate it from quartz as their colors, specific gravities, and magnetic properties are similar. Any ESR signal in quartz containing foreign minerals would therefore be likely to be heavily disturbed by the signals from these foreign minerals, particularly from the feldspar and heavy minerals. ESR signals in the feldspar decreased similarly to those in the quartz when exposed to sunlight, declining by 70%–80% after being exposed for 50 h. Such declination was more obvious in high-altitude areas than in low-altitude areas. Our results indicate that highly pure quartz is required when dating; we would therefore strongly suggest that the procedures for the purification of quartz grains should include floating, heavy liquid separation, and HF solution etching to remove the feldspar, heavy minerals, and any remnant magnetite. Such a procedure would guarantee that the signal that is measured comes from the quartz alone, allowing repeatable measurements using the same spectrometer as well as valid comparisons between the spectrometries derived from different spectrometers.

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“…The most widely distributed centers in feldspars are O − and Ti 3+ , as well as Fe 3+ impurity [30]. The O − center developed in all feldspars when the samples were irradiated.…”

Section: Bleaching Of Feldspar In Sunlightmentioning

confidence: 97%

The ESR Signals in Different Minerals and the Bleaching of Feldspar

Bi,

Yi,

Yang

et al. 2023

Minerals

View full text Add to dashboard Cite

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Studies on intramolecular nh‐bridging in aromatic compounds. Part 3 [1–3]

Horaguchi

Klemm

Norris

1995

Journal of Heterocyclic Chem

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A study was made of the use of calcium oxide as a catalyst at a temperature of 400–700° for the dehy‐drocyclization of four primary arylamines: 2‐aminobiphenyl, 1‐aminotriphenylene (5c), 2‐phenoxyaniline, and N‐(2‐aminophenyl)pyrrole. Maximal yields of cyclized products isolated were 53% (carbazole), 52% (4H‐naphtho[1,4‐def]carbazole), 18% (phenoxazine), and 0%, respectively. Comparison is made with reported cyclizations of the corresponding nitro and azido starting materials. In one case, treatment of I‐nitrotriphenylene with triethyl phosphite produced mainly diethyl N‐(1‐triphenylenyl)phosphoramidate (51%). Mono‐ and hemihydrochlorides of 5c are described. A mechanism for the catalyzed dehydrocy‐clization is proposed.

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Electron spin resonance of sulfite radicals in irradiated calcite and aragonite

Kai

Miki

1992

International Journal of Radiation Applications and Instrumenta

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Radiation Electron-Hole Centers (Free Radicals) in Minerals

Cited by 3 publications

References 88 publications

The ESR Signals in Different Minerals and the Bleaching of Feldspar

The ESR Signals in Different Minerals and the Bleaching of Feldspar

Studies on intramolecular nh‐bridging in aromatic compounds. Part 3 [1–3]

Electron spin resonance of sulfite radicals in irradiated calcite and aragonite

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