Nitrogenated Amorphous Carbons: A Potential Source of Diffuse Interstellar Infrared Emission

Recent measurements of plasma-generated amorphous carbon films (a:C-H and a:C) show that nitrogen doping of the carbon imparts IR activity to the films. In particular, the Raman G and D bands which are IR inactive in typical amorphous carbons become active when nitrogen is substituted for carbon. When the nitrogen dopant level is in the range of 15-20 pct of the carbon, the G and D bands are more than 3-4 times the size of any other IR feature. It is suggested that the IR emission observed from carbon dust may have a significant component which arises from nitrogen substitution in the aromatic framework of the interstellar particles.