Kinetics of Sulfur Oxide, Sulfur Fluoride, and Sulfur Oxyfluoride Anions with Atomic Species at 298 and 500 K
Abstract
The rate constants and product-ion branching ratios for the reactions of sulfur dioxide {SO2(-)}, sulfur fluoride {SF (n)-}, and sulfur oxyfluoride anions {SO(x)F(y)-} with H, H2, N, N2, NO, and 0 have been measured in a selected-ion flow tube (SIFT). H atoms were generated through a microwave discharge on a H2/He mixture, whereas O atoms were created via N atoms titrated with NO, where the N had been created by a microwave discharge on N2. None of the ions reacted with H2, N2 or NO; thus, the rate constants are <1 x 10(exp 12) cc/s. SO(x)F(y)- ions react with H by only fluorine-atom abstraction to form HF at 298 and 500 K. Successive F-atom removal does not occur at either temperature, and the rate constants show no temperature dependence over this limited range. SO2(-) and F(-) undergo associative detachment with H to form a neutral molecule and an electron. Theoretical calculations of the structures and energetics of HSO2 isomers were performed and showed that structural differences between the ionic and neutral HSO2 species can account for at least part of the reactivity limitations in the SO2(-) + H reaction. All of the SO(x)F(y)- ions react with O; however, only SO2(-) reacts with both N and O. SO(x)F(y)- reactions with N {S02(-) excluded} have a rate constant limit of <1 x 10(exp 11) cc/s. The rate constants for the SO(x)F(y)- reactions with H and O are </=25% of the collision rate constant, as seen previously in the reactions of these ions with O3, consistent with a kinetic bottleneck limiting the reactivity. The only exceptions are the reactions of SO2(-) with N and O, which are much more efficient. Three pathways were observed with O atoms: F-atom exchange in the reactant ion, F(-) exchange in the reactant ion, and charge transfer to the O atom. No associative detachment was observed in the N- and O-atom reactions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2007
- Accession Number
- ADA470337
Entities
People
- A. A. Viggiano
- Anthony J. Midey
Organizations
- Boston College