Laboratory Investigation of Hydrogenated Diamond Surfaces: Implications for the Formation and Size of Interstellar Nanodiamonds

Abstract

The formation and size of interstellar diamonds have been investigated by infrared spectroscopy in the laboratory. Employing hot-filament chemical vapor deposition (CVD) to synthesize the interstellar analogs, we successfully reproduced the infrared emission bands of nanodiamonds around HD 97048 and Elias 1. Analysis of the infrared absorption spectra of synthetic diamond crystallites (25-700 nm) from a commercial source reveals a strong size-dependent effect. The 3.53 mum feature emerges only for particles larger than 25 nm. Our experiments suggest that the carriers of the anomalous infrared emission bands at 3.43 and 3.53 mum could be nanodiamonds that are larger than 25 nm and are formed by a CVD-like process.