Infrared Emission Spectra from Hydrogenated Amorphous Carbon

Abstract

Thermal emission spectra from hydrogenated amorphous carbon (HAC) over the 2.5-15 mu m range have been obtained at temperatures between 573 and 773 K. These spectra are similar, but not identical, to absorption spectra of HAC samples subjected to the same thermal cycle. A distinct 3.29 mu m aromatic CH emission is found in samples heated to temperatures in excess of 723 K. This emission is also observed at lower temperatures in samples that have been thermally cycled to higher temperature. Laboratory emission spectra from HAC are shown to provide a good simulation of 3.2-3.6 mu m emission from dust in the extended atmospheres of post-asymptotic giant branch objects. The ratio of 3.4 and 3.3 mu m emission in such objects may be a useful indicator of evolutionary status.