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

Miller, Thomas M.; Friedman, Jeffrey F.; Williamson, John S.; Schaffer, Linda C.; Viggiano, A. A.
March 2009
Review of Scientific Instruments;Mar2009, Vol. 80 Issue 3, p034104
Academic Journal
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: NF3 (300–900 K) and CH3Cl (600–1100 K). Electron attachment rate constants for NF3 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. CH3Cl attaches electrons too weakly to study with the low temperature FALP but reaches a value of ∼10-9 cm3 s-1 at 1100 K. F- is produced in NF3 attachment at all temperatures and Cl- in CH3Cl 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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