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Title: LABORATORY PHOTO-CHEMISTRY OF PAHs: IONIZATION VERSUS FRAGMENTATION

Interstellar polycyclic aromatic hydrocarbons (PAHs) are expected to be strongly processed by vacuum ultraviolet photons. Here, we report experimental studies on the ionization and fragmentation of coronene (C{sub 24}H{sub 12}), ovalene (C{sub 32}H{sub 14}) and hexa-peri-hexabenzocoronene (HBC; C{sub 42}H{sub 18}) cations by exposure to synchrotron radiation in the range of 8–40 eV. The results show that for small PAH cations such as coronene, fragmentation (H-loss) is more important than ionization. However, as the size increases, ionization becomes more and more important and for the HBC cation, ionization dominates. These results are discussed and it is concluded that, for large PAHs, fragmentation only becomes important when the photon energy has reached the highest ionization potential accessible. This implies that PAHs are even more photo-stable than previously thought. The implications of this experimental study for the photo-chemical evolution of PAHs in the interstellar medium are briefly discussed.
Authors:
; ; ;  [1] ; ;  [2] ;  [3] ;  [4]
  1. Leiden Observatory, University of Leiden, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
  2. Sackler Laboratory for Astrophysics, Leiden Observatory, University of Leiden, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
  3. Synchrotron SOLEIL, L’Orme des Merisiers, F-91192 Gif sur Yvette Cedex (France)
  4. Universitè de Toulouse, UPS-OMP, IRAP, Toulouse (France)
Publication Date:
OSTI Identifier:
22518994
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 804; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CATIONS; COSMIC PHOTONS; EV RANGE; FRAGMENTATION; INTERSTELLAR SPACE; IONIZATION; MOLECULES; PHOTOCHEMISTRY; POLYCYCLIC AROMATIC HYDROCARBONS; SYNCHROTRON RADIATION; ULTRAVIOLET RADIATION