Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1193364 | International Journal of Mass Spectrometry | 2007 | 9 Pages |
Abstract
We present a new technique for measuring ion-ion recombination rate constants in a flowing afterglow Langmuir probe (FALP) apparatus. The technique involves measuring the fractional negative ion product distribution following electron attachment versus the initial electron density when two or more products are formed. The concentration of reactant gas is kept low enough that the plasma retains its electron-Ar+, ambipolar diffusion character along the entire length of the flow tube. If only polyatomic anions are formed, accurate relative rates are obtained. When one of the species is atomic, absolute rates are also possible by doing a detailed model of the plasma kinetics. Here we present rate constants for Ar+ recombining with Cl2â ((5.3 ± 1.6) Ã 10â8 cm3 sâ1 at 302 K), Br2â ((3.9 ± 1.2) Ã 10â8 cm3 sâ1 at 302 K), the phosgene negative ion CCl2Oâ ((8.9 ± 2.7) Ã 10â8 cm3 sâ1 at 302 K), and relative rate constants for Ar+ + SF6â and SF5â (ratio 1.2 at 550 K, with an uncertainty of +0.3 and â0.1). The diatomic negative ions are found to recombine slower than the polyatomic ones, in agreement with earlier indications.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Thomas M. Miller, Jeffrey F. Friedman, A.A. Viggiano,