title: Dynamics of the reaction of C2 with C6H2: an implication for the formation of interstellar C8H.
abstract: The reaction C2 + C6H2 → C8H + H was investigated for the first time. Reactant C2 (C6H2) was synthesized from 1% C3F6/He (5% C2H2/He) by pulsed high-voltage discharge. We measured the translational-energy distribution, the angular distribution, and the photoionization spectrum of product C8H in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. This reaction released average translational energy of 8.5 kcal mol(-1) corresponding to a fraction of 0.37 in translation. C8H was identified as octatetranyl based on the maximal translational-energy release 23 ± 2 kcal mol(-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 C2 (X (1)Σg (+)/a (3)Πu) + HC6H → C8H + H can proceed without entrance and exit barriers, implying the importance in the cold interstellar medium. This work verifies that interstellar C8H can be formed through the C2 + C6H2 reaction.
authors.affiliation: National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan.
authors.forename: Yi-Lun
authors.initials: YL
authors.lastname: Sun
authors.affiliation: National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan.
authors.forename: Wen-Jian
authors.initials: WJ
authors.lastname: Huang
authors.affiliation: National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan.
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Chin
authors.affiliation: National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan.
authors.forename: Shih-Huang
authors.initials: SH
authors.lastname: Lee