Laboratory investigation of hydrogenated diamond surfaces: Implications for the formation and size of interstellar nanodiamonds

Abstract

The formation & 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 & 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 mm feature emerges only for particles larger than 25 nm. Our experiments suggest that the carriers of the anomalous infrared emission bands at 3.43 & 3.53 mm could be nanodiamonds that are larger than 25 nm & are formed by a CVD-like process.