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Title: Dynamics of the reaction of C{sub 2} with C{sub 6}H{sub 2}: An implication for the formation of interstellar C{sub 8}H

The reaction C{sub 2} + C{sub 6}H{sub 2} → C{sub 8}H + H was investigated for the first time. Reactant C{sub 2} (C{sub 6}H{sub 2}) was synthesized from 1% C{sub 3}F{sub 6}/He (5% C{sub 2}H{sub 2}/He) by pulsed high-voltage discharge. We measured the translational-energy distribution, the angular distribution, and the photoionization spectrum of product C{sub 8}H in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. This reaction released average translational energy of 8.5 kcal mol{sup −1} corresponding to a fraction of 0.37 in translation. C{sub 8}H was identified as octatetranyl based on the maximal translational-energy release 23 ± 2 kcal mol{sup −1} and the ionization threshold 8.9 ± 0.2 eV. Kinematic constraints can qualitatively account for the nearly isotropic angular distribution. The quantum-chemical calculations indicate that the exothermic reactions C{sub 2} (X {sup 1}Σ{sub g}{sup +}/a {sup 3}Π{sub u}) + HC{sub 6}H → C{sub 8}H + H can proceed without entrance and exit barriers, implying the importance in the cold interstellar medium. This work verifies that interstellar C{sub 8}H can be formed through the C{sub 2} + C{sub 6}H{sub 2} reaction.
Authors:
; ; ;  [1]
  1. National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)
Publication Date:
OSTI Identifier:
22415379
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 19; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ANGULAR DISTRIBUTION; ENERGY SPECTRA; MOLECULAR BEAMS; PHOTOIONIZATION; PULSES