• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.435-442
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• 2008

Natural, synthetic, and treated diamonds were studied by NMR and EPR. It was demonstrated that natural and synthetic diamonds, treated and non-treated diamonds, high pressure high temperature (HPHT) treated and electron beam treated diamonds could be distinguished among each other based on the $^{13}C$ NMR spectra acquired for relatively short periods of 100 minutes. The $^{13}C$ NMR linewidths of gem quality synthetic diamonds were broader than 1.6 ppm due to the paramagentic effects of transition metals, generally used as catalysts, while the linewidths of gem quality natural diamonds were narrower than 0.5 ppm regardless of the methods of treatment. The linewidth (0.5 ppm) for a HPHT treated, gem quality natural diamond was as broad as more than twice of the linewidth (0.2 ppm) of an electron beam treated diamond. The $^{13}C$ NMR signal intensities of treated, gem quality natural diamonds were as strong as more than 10 times of the intensities of non-treated, gem quality natural diamonds. When correlated with the concentrations of the paramagnetic defects (electrons) obtained from the EPR spectra, the relative $^{13}C$ NMR signal intensities increased in proportion to the concentrations of the paramagnetic electrons contained in each sample but the electron beam treated diamond was an exception. This suggested that the lattice component, in addition to the paramagnetic defect component, should also be considered in determining the $^{13}C$ NMR signal intensity of the electron beam treated diamond.

• Journal of the Mineralogical Society of Korea
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• v.20 no.3
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• pp.175-180
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• 2007

FTIR technique was applied to delineate spectroscopic characteristics of natural, synthetic and irradiated diamonds. All of the samples studied in this work show the absorption peaks, which are generally observed in diamond as well as the specific one related to N in diamonds. Synthetic diamond is characterized with both the peaks of 1344 and $1128 cm^{-1}$ related to HPHT synthesis and specific $1050 cm^{-1}$ peak only observed in synthetic diamond, which can be used to discriminate natural from synthetic. Type (natural blue diamond: IIb, electron beam Irradiated blue diamond: Type Ia) can be used to discriminate natural from irradiated diamond. The intensity of specific $1450 cm^{-1}$ peak observed only in irradiated diamond is related with irradiation and annealing process.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.407-415
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• 2009

The change of the nitrogen-related centers and the color change of electron beam irradiated type Ia natural diamonds were studied. The irradiation of diamond with high-energy electron beam creates lattice defects which are neutral single vacancy $V^0$. It increased with increasing electron dose density. The B aggregation seems to produce vacancies more easily than the A aggregation, because diamonds with more B aggregation have more platelets, which are sufficient breakable size by electron beam. Greenish blue color of irradiated diamond is changed to darker with increasing electron dose density. GR1 centers with a zero-phonon line at 741 nm and phonon sidebands make transmit visible light at 530 nm and it moves to 500 nm with higher intensity of GR1 centers.