Description
The properties of hydrogenated amorphous carbon (a-C:H) dust evolve in response to the local radiation field in the inter- stellar medium and the evolution of these properties is particularly dependent upon the particle size. A model for finite-sized, low-temperature amorphous hydrocarbon particles, based on the microphysical properties of random and defected networks of carbon and hydrogen atoms, with surfaces passivated by hydrogen atoms, has been developed. The eRCN/DG and the optEC(s) models have been combined, adapted and extended into a new optEC(s) (a) model that is used to calculate the optical properties of hydrocarbon grain materials down into the sub-nanometre size regime, where the particles contain only a few tens of carbon atoms.
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