Approximate scaling formula for ion–ion mutual neutralization rates

Hickman, A. P.

doi:10.1063/1.437364

Cited by 116 publications

(51 citation statements)

References 18 publications

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“…Additional losses of the high‐mass ions could come from ion‐ion recombination of negative ions with these ions. A common formulation for this rate coefficient is that developed by Hickman [] that utilizes a complex potential model of the mutual neutralization reaction given by

k = 5.34 \times 10^{- 7} E A^{- 0.4} m_{i j}^{- 0.5} {(\frac{T_{normalgas}}{300})}^{- 0.5} {cm}^{3} s^{- 1} .

Rate coefficients for this process range from about 5 × 10 −8 cm 3 s −1 to 1 × 10 −7 cm 3 s −1 . Therefore, for a negative ion density of about 1000 cm 3 [ Wellbrock et al ., ] we retrieve a loss rate of about 5 × 10 −5 s −1 to 1 × 10 −6 s −1 , which is very small compared to the electron recombination loss rate of about 10 3 s −1 for this flyby.…”

Section: High‐mass Ion Structure and Growthmentioning

confidence: 99%

The role of ion‐molecule reactions in the growth of heavy ions in Titan's ionosphere

et al. 2014

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The Ion and Neutral Mass Spectrometer (INMS) and Cassini Plasma Spectrometer (CAPS) have observed Titan's ionospheric composition and structure over several targeted flybys. In this work we study the altitude profiles of the heavy ion population observed by the Cassini Plasma Spectrometer-Ion Beam Spectrometer (CAPS-IBS) during the nightside T57 flyby. We produce altitude profiles of heavy ions from the C6-C13 group (C i indicates the number, i, of heavy atoms in the molecule) using a CAPS-IBS/INMS cross calibration. These altitude profiles reveal structure that indicates a region of initial formation and growth at altitudes below 1200 km followed by a stagnation and dropoff at the lowest altitudes (1050 km). We suggest that an ion-molecule reaction pathway could be responsible for the production of the heavy ions, namely reactions that utilize abundant building blocks such as C 2 H 2 and C 2 H 4 , which have been shown to be energetically favorable and that have already been identified as ion growth patterns for the lighter ions detected by the INMS. We contrast this growth scenario with alternative growth scenarios determining the implications for the densities of the source heavy neutrals in each scenario. We show that the high-mass ion density profiles are consistent with ion-molecule reactions as the primary mechanism for large ion growth. We derive a production rate for benzene from electron recombination of C 6 H 7 + of 2.4 × 10 À16 g cm À2 s À1and a total production rate for large molecules of 7.1 × 10 À16 g cm À2 s À1 .

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k = 5.34 \times 10^{- 7} E A^{- 0.4} m_{i j}^{- 0.5} {(\frac{T_{normalgas}}{300})}^{- 0.5} {cm}^{3} s^{- 1} .

Section: High‐mass Ion Structure and Growthmentioning

confidence: 99%

The role of ion‐molecule reactions in the growth of heavy ions in Titan's ionosphere

et al. 2014

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“…Ar [56] the trimethylsilyl anion and CH 3 . The corresponding electron collision cross sections are given in [45,46].…”

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confidence: 99%

Modeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane

Loffhagen

Becker

Czerny

et al. 2020

Plasma Chem Plasma Process

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A time-dependent, spatially one-dimensional fluid-Poisson model is applied to analyze the impact of small amounts of tetramethylsilane (TMS) as precursor on the discharge characteristics of an atmospheric-pressure dielectric barrier discharge (DBD) in argon. Based on an established reaction kinetics for argon, it includes a plasma chemistry for TMS, which is validated by measurements of the ignition voltage at the frequency $$f =86.2\, {\hbox{kHz}}$$ f = 86.2 kHz for TMS amounts of up to 200 ppm. Details of both a reduced Ar-TMS reaction kinetics scheme and an extended plasma-chemistry model involving about 60 species and 580 reactions related to TMS are given. It is found that good agreement between measured and calculated data can be obtained, when assuming that 25% of the reactions of TMS with excited argon atoms with a rate coefficient of $$3.0 \times 10^{-16}\, {\hbox{m}^3/\hbox{s}}$$ 3.0 × 10 - 16 m 3 / s lead to the production of electrons due to Penning ionization. Modeling results for an applied voltage $${U}_{{\mathrm{a}},0} = 4\, {\hbox{kV}}$$ U a , 0 = 4 kV show that TMS is depleted during the residence time of the plasma in the DBD, where the percentage consumption of TMS decreases with increasing TMS fraction because only a finite number of excited argon species is available to dissociate and/or ionize the precursor via energy transfer. Main species resulting from that TMS depletion are presented and discussed. In particular, the analysis clearly indicates that trimethylsilyl cations can be considered to be mainly responsible for the film formation.

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“…A complex potential model has been used to treat the mutual neutralization of positive and negative ions (Hickman 1979 . This is consistent with experimental results, rate constants varying from about 5 10 -8 to 10 -7 cm 3 s -1 at room temperature with power law temperature dependencies of ~0.5 for both simple and cluster ion reactions (Smith et al, 1978).…”

Section: Ion-ion Recombinationmentioning

confidence: 99%