Reaction of C{sub 2}H{sub 2}{sup +} (n{center_dot}{nu}{sub 2}, m{center_dot}{nu}{sub 5}) with NO{sub 2}: Reaction on the singlet and triplet surfaces

Journal Article · Fri Jan 21 00:00:00 EST 2011 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3517499· OSTI ID:21559982

Boyle, Jason M; Bell, David M; Anderson, Scott L ^[1]

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1. Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850 (United States)

Integral cross sections and product recoil velocity distributions were measured for reaction of C{sub 2}H{sub 2}{sup +} with NO{sub 2}, in which the C{sub 2}H{sub 2}{sup +} reactant was prepared in its ground state, and with mode-selective excitation in the cis-bend (2{nu}{sub 5}) and CC stretch (n{center_dot}{nu}{sub 2}, n = 1, 2). Because both reactants have one unpaired electron, collisions can occur with either singlet or triplet coupling of these unpaired electrons, and the contributions are separated based on distinct recoil dynamics. For singlet coupling, reaction efficiency is near unity, with significant branching to charge transfer (NO{sub 2}{sup +}), O{sup -} transfer (NO{sup +}), and O transfer (C{sub 2}H{sub 2}O{sup +}) products. For triplet coupling, reaction efficiency varies between 13% and 19%, depending on collision energy. The only significant triplet channel is NO{sup +}+ triplet ketene, generated predominantly by O{sup -} transfer, with a possible contribution from dissociative charge transfer at high collision energies. NO{sub 2}{sup +} formation (charge transfer) can only occur on the singlet surface, and appears to be mediated by a weakly bound complex at low energies. O transfer (C{sub 2}H{sub 2}O{sup +}) also appears to be dominated by reaction on the singlet surface, but is quite inefficient, suggesting a bottleneck limiting coupling to this product from the singlet reaction coordinate. The dominant channel is O{sup -} transfer, producing NO{sup +}, with roughly equal contributions from reaction on singlet and triplet surfaces. The effects of C{sub 2}H{sub 2}{sup +} vibration are modest, but mode specific. For all three product channels (i.e., charge, O{sup -}, and O transfer), excitation of the CC stretch fundamental ({nu}{sub 2}) has little effect, 2{center_dot}{nu}{sub 2} excitation results in {approx}50% reduction in reactivity, and excitation of the cis-bend overtone (2{center_dot}{nu}{sub 5}) results in {approx}50% enhancement. The fact that all channels have similar mode dependence suggests that the rate-limiting step, where vibrational excitation has its effect, is early on the reaction coordinate, and branching to the individual product channels occurs later.

• OSTI ID: 21559982
• Journal Information: Journal of Chemical Physics, Vol. 134, Issue 3; Other Information: DOI: 10.1063/1.3517499; (c) 2011 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BRANCHING RATIO
CHARGE EXCHANGE
COMPLEXES
DISSOCIATION
EFFICIENCY
ELECTRON COLLISIONS
ELECTRONS
EXCITATION
GROUND STATES
INTEGRAL CROSS SECTIONS
ION-MOLECULE COLLISIONS
KETENES
NITRITES
NITROGEN DIOXIDE
REACTIVITY
SURFACES
TRIPLETS
VIBRATIONAL STATES
CHALCOGENIDES
COLLISIONS
CROSS SECTIONS
DIMENSIONLESS NUMBERS
ELEMENTARY PARTICLES
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
FERMIONS
ION COLLISIONS
LEPTONS
MOLECULE COLLISIONS
MULTIPLETS
NITROGEN COMPOUNDS
NITROGEN OXIDES
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS