page_title: Crystallographic defects in diamond
section_title: B-nitrogen center
hierarchical_section_title: Crystallographic defects in diamond / Extrinsic defects / Nitrogen / B-nitrogen center
caption_attribution_description: English: N3 center in diamond
context_page_description: Imperfections in the crystal lattice of diamond are common. Such crystallographic defects in diamond may be the result of lattice irregularities or extrinsic substitutional or interstitial impurities, introduced during or after the diamond growth. The defects affect the material properties of diamond and determine to which type a diamond is assigned; the most dramatic effects are on the diamond color and electrical conductivity, as explained by the electronic band structure.
  The defects can be detected by different types of spectroscopy, including electron paramagnetic resonance, luminescence induced by light or electron beam, and absorption of light in the infrared, visible and UV parts of the spectrum. The absorption spectrum is used not only to identify the defects, but also to estimate their concentration; it can also distinguish natural from synthetic or enhanced diamonds.
context_section_description: There is a general consensus that B center (sometimes called B1) consists of a carbon vacancy surrounded by four nitrogen atoms substituting for carbon atoms. This model is consistent with other experimental results, but there is no direct spectroscopic data corroborating it. Diamonds where most nitrogen forms B centers are rare and are classed as type IaB; most gem diamonds contain a mixture of A and B centers, together with N3 centers.
  Similar to the A centers, B centers do not induce color, and no UV or visible absorption can be attributed to the B centers. Early assignment of the N9 absorption system to the B center have been disproven later. The B center has a characteristic IR absorption spectrum (see the infrared absorption picture above) with a sharp peak at 1332 cm⁻¹ and a broader feature at 1280 cm⁻¹. The latter is routinely used to estimate the nitrogen concentration in the B form.
  Note that many optical peaks in diamond accidentally have similar spectral positions, which causes much confusion among gemologists. Spectroscopists use the whole spectrum rather than one peak for defect identification and consider the history of the growth and processing of individual diamond.
caption: Schematic of the N3 center
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