Difference of Lattice Radiation Damage and Spectroscopic Characterization in Natural and Artificial Radiation Green Diamonds

Based on the experimental results of artificial radiation of green diamonds, with respect to the difficulties in detecting green diamonds under artificial and natural radiation in the market in recent years, the gemmological and spectroscopic characteristics of green diamond after natural and artificial radiation were tested and analyzed by using laser Raman spectrometer, ultraviolet-visible spectrometer, photoluminescence spectrometer, infrared spectrometer, and other spectroscopic test methods. According to the results, the absorbed secondary uranium minerals attached to the diamond surface is a natural radiation source, and the α-rays emitted during the spontaneous decay process of atomic nuclei on ²³⁸U isotope chains are the main factors causing the formation of green radiation spots or green thin shells on the surface of green diamonds. As the radiation damages of lattice increase, the degree of metamictization of the green radiation spots on the surface of the green diamond samples continue to increase progressively until it tends to be amorphous state from outside inwards. Correspondingly, the intensity of the Raman peak near 1 332 cm^-1, that is caused by the lattice vibration in the surface green radiation spots, decreases sequentially from outside inwards until annihilation. Conversely, the intensity of the Raman peak near 1 625 cm^-1 and its half-height width increase sequentially from outside inwards. In view of the difference between the radioactive intensity and the radiation dose produced by natural and artificial radiation sources, the concentration of GR1 center induced in diamond and its corresponding spectroscopic properties also differ to some extent. Corresponding to the splitting degree and half-height width of the PL peak at the GR1 center (741 nm) of green diamond, the combined properties of ZPL, phonon replica(sideband) and electron-phonon coupled bands of GR1 center in the UV-Vis spectrum, and the characteristic infrared absorption peaks near 1 450, 4 936 cm^-1, and 5 165 cm^-1 caused by H1a, H1b, and H1c center vibrations, are helpful to distinguish green diamonds treated by natural or artificial radiation.