Nitrogen interstitials in diamond

Hyperfine interactions at nitrogen interstitial defects in diamond

Diamond has many extreme physical properties and it can be used in a wide range of applications. In particular it is a highly effective particle detection material, where radiation damage is an important consideration. The WAR9 and WAR10 are electron paramagnetic resonance centres seen in irradiated, nitrogen-containing diamond. These S = 1/2 defects have C(2v) and C(1h) symmetry, respectively, and the experimental spectra have been interpreted as arising from nitrogen split-interstitial centres. Based upon the experimental and theoretical understanding of interstitial nitrogen defect structures, the AIMPRO density functional code has been used to assess the assignments for the structures of WAR9 and WAR10. Although the calculated hyperfine interaction tensors are consistent with the measured values for WAR9, the thermal stability renders the assignment problematic. The model for the WAR10 centre yields principal directions of the hyperfine tensor at variance with observation. Alternative models for both centres are discussed in this paper, but no convincing structures have been found.

Transflectance spectra of faceted diamonds acquired by infrared microscopy

A novel transflectance technique using an infrared microscope was employed for spectral acquisition of loose and mounted faceted diamonds. The observed transflectance spectrum shows the same spectral features as those of the well-accepted diffuse reflectance spectrum. Unlike the diffuse reflectance spectrum, the transflectance spectrum was not affected by the diamond arrangements. The technique can be employed for direct spectra acquisition of mounted diamonds without taking the diamonds out of the jewelry bodies. Moreover, an individual diamond on a complex jewelry setting can be selectively measured. Infrared absorption bands unique to the chemical compositions, impurities, and treatment processes of the diamonds are discussed. The observed transflectance spectra can be exploited for diamond classification.