@PhdThesis{dbt_mods_00032894,
  author = 	{Walter, Hagen},
  title = 	{Irradiation processing of major dust components},
  year = 	{2017},
  month = 	{Aug},
  day = 	{28},
  address = 	{Jena},
  keywords = 	{Ru{\ss}; Amorpher Zustand; Fullerenderivate; Ultraviolett-Bestrahlung; Eisen; Nanopartikel; Laserablation; Graphen; Optische Spektroskopie},
  abstract = 	{In this thesis the behaviour of iron-containing and -free amorphous soot under UV- and X-ray irradiation in the range from 6 eV to 500 eV was investigated. The interstellar extinction bump at 217nm has been known for more than fifty years, but its carrier is still unknown. Current research supports the idea that this band can be attributed to UV-processed carbon. In order to produce soot samples, graphite was vaporised under both a hydrogen-free and -- containing helium atmosphere by means of laser-ablation, whereupon it condensed to nanoparticles. Amorphous soot forms a band around 208nm to 200nm upon UV-irradiation. This band is most probably borne by curved graphene-layers that are visible under the electron miscroscope. The curved layers arise from a process consisting of graphitisation allowing the growth of the layers, and the formation of Stone-Wales defects. Photons with energies below 8eV mainly cause graphitisation, those above 8eV mainly cause the formation of Stone-Wales defects. The thus-formed structures resemble onion-like fullerene-fragments. Compared to planar graphene layers, their orbitals are deformed and behave more diamond-like. That ultimately causes a blue-shift of the pi-electrons compared to planar graphene. Since iron is known to be catalyst for the formation of graphene layers, iron powder was added to pressed graphite powder. Upon laser-ablation, the mixture produced graphene-covered iron nano-particles with even more than one layer. The incorporation of iron resulted in an increased mass absorption coefficient and did not impede the formation of the band. This gives a hint about the depletion of iron in the interstellar medium},
  note = 	{Dissertation, Friedrich-Schiller-Universit{\"a}t Jena, 2017},
  url = 	{https://www.db-thueringen.de/receive/dbt_mods_00032894},
  url = 	{http://uri.gbv.de/document/gvk:ppn:896541886},
  file = 	{:https://www.db-thueringen.de/servlets/MCRFileNodeServlet/dbt_derivate_00039058/Dissertation_HWalter.pdf:PDF},
  language = 	{en}
}