Accession Number:

ADA626685

Title:

Arrhenius Behavior of Electron Attachment to CH3Br from 303 to 1100 K

Descriptive Note:

Journal article

Corporate Author:

AIR FORCE RESEARCH LAB KIRTLAND AFB NM SPACE VEHICLES DIRECTORATE

Report Date:

2013-12-21

Pagination or Media Count:

8.0

Abstract:

Thermal electron attachment to CH3Br has been studied over the temperature range 303-1100 K using two flowing-afterglow Langmuir-probe apparatuses. The reaction yielded only Br- product over this temperature range. The rate coefficient for electron attachment to CH3Br was measured to be 8 - 4 10-12 cm3 s-1 at 303 K, and was observed to increase strongly with gas temperature. Rate coefficients for the reaction show Arrhenius behavior over the entire temperature range with an activation energy of 260 - 20 meV. The results are in substantial agreement with earlier data covering a smaller temperature range. Kinetic modeling implies that this behavior and the small rate coefficient at room temperature are due to a barrier in the crossing from the neutral to the anionic potential surfaces of approximately 280 meV that dominates other factors in the attachment reaction. There is a hint of the Arrhenius plot reaching saturation at the highest temperatures. While examining an electron-cation recombination correction, the rate coefficient 1.8 - 0.4 10-9 cm3 s-1 of the reaction Ar CH3Br was measured at 302 K, and the ion products identified 80 CH3 and 20 CH2Br. A secondary reaction forming the adduct CH3BrCH3 was seen to occur with a rate coefficient of 2.8 - 1.0 10-9 cm3 s 1.

Subject Categories:

  • Physical Chemistry
  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE