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Title: PHOTODETACHMENT AS A DESTRUCTION MECHANISM FOR CN{sup –} AND C{sub 3}N{sup –} ANIONS IN CIRCUMSTELLAR ENVELOPES

Absolute photodetachment cross sections of two anions of astrophysical importance CN{sup –} and C{sub 3}N{sup –} were measured to be (1.18 ± (0.03){sub stat}(0.17){sub sys}) × 10{sup –17} cm{sup 2} and (1.43 ± (0.14){sub stat}(0.37){sub sys}) × 10{sup –17} cm{sup 2}, respectively, at the ultraviolet (UV) wavelength of 266 nm (4.66 eV). These relatively large values of the cross sections imply that photodetachment can play a major role in the destruction mechanisms of these anions particularly in photon-dominated regions. We have therefore carried out model calculations using the newly measured cross sections to investigate the abundance of these molecular anions in the cirumstellar envelope of the carbon-rich star IRC+10216. The model predicts the relative importance of the various mechanisms of formation and destruction of these species in different regions of the envelope. UV photodetachment was found to be the major destruction mechanism for both CN{sup –} and C{sub 3}N{sup –} anions in those regions of the envelope, where they occur in peak abundance. It was also found that photodetachment plays a crucial role in the degradation of these anions throughout the circumstellar envelope.
Authors:
; ; ; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, A-6020 Innsbruck (Austria)
  2. Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, 18000 Prague (Czech Republic)
  3. Department of Physics, AlbaNova, Stockholm University, SE-10691 Stockholm (Sweden)
  4. Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom)
Publication Date:
OSTI Identifier:
22270903
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 776; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANIONS; ASTROPHYSICS; CARBON; CROSS SECTIONS; EV RANGE; MOLECULAR IONS; PHOTONS; STARS; ULTRAVIOLET RADIATION