Rate Coefficients for Dissociative Electron Attachment by Halomethane Compounds between 300 and 800 K

Burns, Steven J.; Matthews, and Jeanne M.; McFadden, David L.

doi:10.1021/jp962529h

Cited by 48 publications

(46 citation statements)

References 61 publications

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“…A similar decrease for higher temperatures was observed in the measurements of [11], though the uncertainties in the measurements at high temperatures for CH 3 I are quite large. The activation energy of 25 meV obtained in [11] for CH 3 I is only for temperatures at or below 452 K. We are unable to obtain a good fi t to equation (8) for temperatures in the range 450 down to 300 K. We also show the measurements for CH 3 I of Burns et al [16] and of Shimamori and Nakatani [21].…”

Section: General Discussion Of Dea To Methyl Halidesmentioning

confidence: 61%

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Comparative studies of dissociative electron attachment to methyl halides

Wilde¹,

Gallup²,

Fabrikant³

2000

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. The dissociative electron attachment cross sections for the methyl halides vary in an enormous range from the virtually unmeasurable 10 −23 cm 2 for CH 3 Cl at room temperature to 10 −14 cm 2 for CH 3 I. In this paper we supplement our previous studies by calculations of dissociative electron attachment to CH 3 Br and compare results for all methyl halides studied so far. The rate as a function of temperature for CH 3 Cl and CH 3 Br exhibits an exponential dependence on 1/T (Arrhenius law) with the activation energy lower for CH 3 Br. CH 3 I does not obey the Arrhenius law since the crossing point of the neutral and anion potential curves occurs near the lowest vibrational levels. The cross section as a function of electron energy for all of the methyl halides studied here exhibits structure at the vibrational excitation thresholds that is associated with a vibrational

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Section: General Discussion Of Dea To Methyl Halidesmentioning

confidence: 61%

“…The reason for this discrepancy is not clear at this time. Arrhenius type plot of the calculated attachment rates for all methyl halides studied here, present calculations and experimental data for CH 3 I of Alge et al [11], Burns et al [16] and Shimamori and Nakatani [21].…”

Section: General Discussion Of Dea To Methyl Halidesmentioning

confidence: 79%

Comparative studies of dissociative electron attachment to methyl halides

Wilde¹,

Gallup²,

Fabrikant³

2000

J. Phys. B: At. Mol. Opt. Phys.

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“…CF 3 Br happens to be one of the most studied systems for electron attachment, with measurements of thermal rate constants by several groups and techniques up to as high as 777 K. [28][29][30][31] Additionally, owing to the wealth of experimental data, the system was used as a standard to empirically evaluate the functional forms used in the kinetic modeling to separate contributions from the electronic and nuclear motions. 14 Here we also report electron attachment rate constants for CF 3 Br, extending those measurements up to 890 K using traditional FALP techniques for this stable molecule, as opposed to the VENDAMS method used to measure attachment to radicals.…”

Section: Introductionmentioning

confidence: 99%

Electron attachment to CF3 and CF3Br at temperatures up to 890 K: Experimental test of the kinetic modeling approach

Shuman

Miller

Viggiano

et al. 2013

The Journal of Chemical Physics

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Thermal rate constants and product branching fractions for electron attachment to CF3Br and the CF3 radical have been measured over the temperature range 300-890 K, the upper limit being restricted by thermal decomposition of CF3Br. Both measurements were made in Flowing Afterglow Langmuir Probe apparatuses; the CF3Br measurement was made using standard techniques, and the CF3 measurement using the Variable Electron and Neutral Density Attachment Mass Spectrometry technique. Attachment to CF3Br proceeds exclusively by the dissociative channel yielding Br(-), with a rate constant increasing from 1.1 × 10(-8) cm(3) s(-1) at 300 K to 5.3 × 10(-8) cm(3) s(-1) at 890 K, somewhat lower than previous data at temperatures up to 777 K. CF3 attachment proceeds through competition between associative attachment yielding CF3 (-) and dissociative attachment yielding F(-). Prior data up to 600 K showed the rate constant monotonically increasing, with the partial rate constant of the dissociative channel following Arrhenius behavior; however, extrapolation of the data using a recently proposed kinetic modeling approach predicted the rate constant to turn over at higher temperatures, despite being only ~5% of the collision rate. The current data agree well with the previous kinetic modeling extrapolation, providing a demonstration of the predictive capabilities of the approach.

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“…A University of Houston group has reported electron attachment rate constants up to 600 K. 13 The Oak Ridge group has made electron attachment measurements up to 700 K in a drift tube. 14 A Boston College group extended the limit to 1022 K with a flowing-afterglow electroncyclotron-resonance apparatus that was capable of operating as high as 1200 K. [15][16][17] Yale University groups have reported ion yields [18][19][20] from electron attachment to SF 6 and cross sections 21 versus electron energy for attachment to SF 6 and a variety of halomethanes at temperatures as high as 1200 K using electron-beam techniques. Our laboratory relies on fast flow reactors to study plasma processes over extended temperature and pressure ranges.…”

Section: Introductionmentioning

confidence: 99%

A new instrument for thermal electron attachment at high temperature: NF3 and CH3Cl attachment rate constants up to 1100 K

Miller

Friedman

Williamson

et al. 2009

Review of Scientific Instruments

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A new high temperature flowing afterglow Langmuir probe (HT-FALP) apparatus is described. A movable Langmuir probe and a four-needle reactant gas inlet were fitted to an existing high temperature flowing afterglow apparatus. The instrument is suitable for study of electron attachment from 300-1200 K, the upper limit set to avoid softening of the quartz flow tube. We present results for two reactions over extended ranges: NF(3) (300-900 K) and CH(3)Cl (600-1100 K). Electron attachment rate constants for NF(3) had been measured earlier using our conventional FALP apparatus. Those measurements were repeated with the FALP and then extended to 900 K with the HT-FALP. CH(3)Cl attaches electrons too weakly to study with the low temperature FALP but reaches a value of approximately 10(-9) cm(3) s(-1) at 1100 K. F(-) is produced in NF(3) attachment at all temperatures and Cl(-) in CH(3)Cl attachment, as determined by a quadrupole mass spectrometer at the end of the flow tube. Future modifications to increase the plasma density should allow study of electron-ion recombination at high temperatures.

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Rate Coefficients for Dissociative Electron Attachment by Halomethane Compounds between 300 and 800 K

Cited by 48 publications

References 61 publications

Comparative studies of dissociative electron attachment to methyl halides

Comparative studies of dissociative electron attachment to methyl halides

Electron attachment to CF3 and CF3Br at temperatures up to 890 K: Experimental test of the kinetic modeling approach

A new instrument for thermal electron attachment at high temperature: NF3 and CH3Cl attachment rate constants up to 1100 K

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