A novel technique for measurement of thermal rate constants and temperature dependences of dissociative recombination: CO2+, CF3+, N2O+, C7H8+, C7H7+, C6H6+, C6H5+, C5H6+, C4H4+, and C3H3+

Abstract

A novel technique using a flowing afterglow-Langmuir probe apparatus for measurement of temperature dependences of rate constants for dissociative recombination (DR) is presented. Low (~10(11) cm(-3)) concentrations of a neutral precursor are added to a noble gas∕electron afterglow plasma thermalized at 300-500 K. Charge exchange yields one or many cation species, each of which may undergo DR. Relative ion concentrations are monitored at a fixed reaction time while the initial plasma density is varied between 10(9) and 10(10) cm(-3). Modeling of the decrease in concentration of each cation relative to the non-recombining noble gas cation yields the rate constant for DR. The technique is applied to several species (O2(+), CO2(+), CF3(+), N2O(+)) with previously determined 300 K values, showing excellent agreement. The measurements of those species are extended to 500 K, with good agreement to literature values where they exist. Measurements are also made for a range of CnHm(+) (C7H7(+), C7H8(+), C5H6(+), C4H4(+), C6H5(+), C3H3(+), and C6H6(+)) derived from benzene and toluene neutral precursors. CnHm(+) DR rate constants vary from 8-12 × 10(-7) cm(3) s(-1) at 300 K with temperature dependences of approximately T(-0.7). Where prior measurements exist these results are in agreement, with the exception of C3H3(+) where the present results disagree with a previously reported flat temperature dependence.

The ALMA-PILS survey: First detection of nitrous acid (HONO) in the interstellar medium

“…329828.8 215.9 3.34 × 10 −4 29 trans-HONO 14 5 9 -13 5 8 329829.2 215.9 3.34 × 10 −4 29 trans-HONO 14 4 11 -13 4 10 330071.5 181.0 3.52 × 10 −4 29 trans-HONO 14 3 12 -13 3 11 330281.2 153.8 3 -0.5 -0.5 -0.5 -0.5 0 0 0 0 3 3 3 3 0 0 0 0 Rate by comparison with similar DR (Fournier et al 2013;Florescu-Mitchell & Mitchell 2006;Geppert et al 2004) and branching ratios deduced roughly from similar reactions using Plessis et al (2012). The important fact is that HONO is likely non negligible product.…”

The interstellar chemistry of H2C3O isomers

“…19.! HCCCHO + HCO + → HCCCHOH + + CO 1.0 1.2e-9 4.1 3 0 Capture rate, Ionpol1 Fournier et al 2013). Branching ratio deduced from the fact that H 2 C 3 O is not detected.…”

Kinetics of Cations with C2 Hydrofluorocarbon Radicals

“…The flowing afterglow–Langmuir probe (FALP) apparatus and VENDAMS method have been described in detail previously. , The FALP consists of a 1 m long, 7 cm diameter stainless steel-lined glass flow tube containing a microwave discharge cavity on a 2.5 cm diameter arm at the upstream end. Approximately 13 std.…”