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The photoluminescence of several natural and synthetic diamonds of type I and type II has been examined in the spectral range 1.35--1.85 eV (920--670 nm) at 300 and 79 K at ambient pressure. Two emission bands with zero-phonon lines at 1.575 and 1.770 eV are observed in all yellow type-Ia natural diamonds. These bands are attributed to aggregate nitrogen defects and coexist with other known defect emission bands N2 and N3. The implications for high-pressure research using diamond anvils are discussed.
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Vohra et al. (1989) studied this question.
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