Spectrokinetic study of SF5 and SF5O2 radicals and the reaction of SF5O2 with NO

✍ Scribed by Jens Sehested; Thomas Ellermann; Ole John Nielsen; Timothy J. Wallington

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 930 KB
• Volume: 26
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550260604

✦ Synopsis

Abstract

UV spectra of SF~5~ and SF~5~O~2~ radicals in the gas phase at 295 K have been quantified using a pulse radiolysis UV absorption technique. The absorption spectrum of SF~5~ was quantified from 220 to 240 nm. The absorption cross section at 220 nm was (5.5 ± 1.7) × 10^−19^ cm^2^. When SF~5~ was produced in the presence of O~2~ an equilibrium between SF~5~, O~2~, and SF~5~O~2~ was established. The rate constant for the reaction of SF~5~ radicals with O~2~ was (8 ± 2) × 10^−13^ cm^3^ molecule^−1^ s^−1^. The decomposition rate constant for SF~5~O~2~ was (1.0 ± 0.5) × 10^5^ s^−1^, giving an equilibrium constant of K~eq~ = [SF~5~O~2~]/[SF~5~][O~2~] = (8.0 ± 4.5) × 10^−18^ cm^3^ molecule^−1^. The SF~5~O~2~ bond strength is (13.7 ± 2.0) kcal mol^−1^. The SF~5~O~2~ spectrum was broad with no fine structure and similar to the UV spectra of alkyl peroxy radicals. The absorption cross section at 230 nm was found to (3.7 ± 0.9) × 10^−18^ cm^2^. The rate constant of the reaction of SF~5~O~2~ with NO was measured to (1.1 ± 0.3) × 10^−11^ cm^3^ molecule^−1^ s^−1^ by monitoring the kinetics of NO~2~ formation at 400 nm. The rate constant for the reaction of F atoms with SF~4~ was measured by two relative methods to be (1.3 ± 0.3) × 10^−11^ cm^3^ molecule^−1^ s^−1^. © 1994 John Wiley & Sons, Inc.