Nano-diamonds in proto-planetary discs

Context. Nano-diamonds remain an intriguing component of the dust in few sources where they have been observed emission. Aims. This work focusses on nano-diamonds circumstellar discs and is attempt to derive critical information about their possible sizes, compositions, evolution using a recently derived set optical constants. Methods. The complex indices refraction properties (the efficiency factors Q ext , sca abs pr ) were used determine temperatures, lifetimes, drift velocities as function radii (0.5–100 nm), composition (surface hydrogenation irradiated states), distance from central stars regions. Results. nano-diamond temperature profiles determined for HR 4049, Elias 1, HD 97048 optically thin limit. results indicate that large ( = 30–100 nm) are hottest therefore least resistant inner disc regions (~10–50 AU), while small < 10 fully hydrogenated significantly cooler these same We discuss within context formation discs. Conclusions. Large nano-diamonds, being hottest, most affected by stellar radiation field; however, effects pressure appear be insufficient move them out harm’s way. best survive shine proto-planetary then seemingly hydrogenated, close size pre-solar (〈 〉 ≃ 1.4 nm). Nevertheless, it does not yet reconcile existence with short lifetimes such