jp7b07778_si_001.pdf (163.75 kB)
Kinetics of Cations with C2 Hydrofluorocarbon Radicals
journal contribution
posted on 2017-09-26, 00:00 authored by Justin
P. Wiens, Oscar Martinez, Shaun G. Ard, Brendan C. Sweeny, Albert A. Viggiano, Nicholas S. ShumanReactions
of the cations Ar+, O2+, CO2+, and CF3+ with
the C2 radicals C2H5, H2C2F3, C2F3, and C2F5 were investigated using the variable electron
and neutral density attachment mass spectrometry technique in a flowing
afterglow–Langmuir probe apparatus at room temperature. Rate
coefficients for observed product channels for these 16 reactions
are reported as well as rate coefficients and product branching fractions
for the 16 reactions of the same cations with each of the stable neutrals
used as radical precursors (the species RI, where R is the radical
studied). Reactions with the stable neutrals proceed by charge transfer
at or near the collisional rate coefficient where energetically allowed;
where charge transfer is endothermic, bond-breaking/bond-making chemistry
occurs. While also efficient, reactions with the radicals are more
likely to occur at a smaller fraction of the collisional rate coefficient,
and bond-breaking/bond-making chemistry occurs even in some cases
where charge transfer is exothermic. It is noted that unlike radical
reactions with neutral species, which occur with rate coefficients
that are generally elevated compared to those of stable species, ion–radical
reactivity is generally decreased relative to that of reactions with
stable species. In particular, long-range charge transfer appears
more likely to be frustrated in the ion–radical systems.