Ultraviolet photoproduction of ISM dust - Laboratory characterisation and astrophysical relevance

The production of a hydrogenated amorphous carbon polymer (a-C: H) via the photolysis of a series of organic molecule precursors at low temperature is described. Such amorphous material is synthesised under interstellar conditions (10 K and Lyman-alpha photons) and represents the best candidate to explain the Diffuse Interstellar Medium absorption observed in our Galaxy and in other galaxies. We perform a series of laboratory analyses ( Infrared spectroscopy, muspectroscopy, Raman, Photoluminescence and UV-visible spectroscopy) which allow a full characterisation of such polymers. This allows us to assess the importance of the polymer and possible scenarios for its role in crucial aspects of the lifecycle of dust. Such material has implications for the carbon budget at galactic scales, hydrogen formation, extended red emission, as a PAH precursor, and in explaining the 2175 Angstrom extinction bump.