Diamonds in space

Huan-Cheng Chang

Institute of Atomic and Molecular Sciences, Taiwan

Since the discovery of nanodiamond grains in meteorites, the possibility for the presence of the carbon-based nanomaterials in space has been explored by various spectroscopic means in laboratories. So far, the most conclusive evidence comes from the assignment of the unidentified infrared (UIR) bands at 3.43 and 3.53 mm to the surface C-H stretching vibrations of hydrogenated diamonds. However, the identification of such distinct vibrational features can only be made for media (e.g. HD 97048 and Elias 1) where both the temperature and atomic H fluxes are high and unique hydrogen etching processes occur on diamond surface. Alternatives methods for the identification of nanodiamonds in space are to detect photoluminescence or cathodoluminescence derived from the defect centers in diamond lattice. In 2006, we showed that the photoluminescence of negatively charged nitrogen-vacancy (NV-) centers closely resembled the extended red emission (ERE) bands observed in reflection nebulae and planetary nebulae (e.g. NGC 7027 and NGC 2327). Here, we present further spectroscopic studies on both the photoluminescence and cathodeluminescence of neutral nitrogen-vacancy (NV⁰) centers, and compare the result to the ERE of the Red Rectangle.

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