Experimental S F6− /S F6 and Cl− /CF Cl3 Electron-Attachment Cross Sections in the Energy Range 0-200 meV

Experimental cross sections for the electron-attachment processes for S${\mathrm{F}}_{6}^{\ensuremath{-}}$/S${\mathrm{F}}_{6}$ and ${\mathrm{Cl}}^{\ensuremath{-}}$/CF${\mathrm{Cl}}_{3}$ are reported in the energy range 0-200 meV by normalizing each attachment line shape to measurement of a thermal rate coefficient. When the same ion states are detected, good agreement is found between present values, for which a monoenergetic electron source is used, and swarm-unfolded results. The present data constitute a new limit for cross sections reported at high resolution at the lowest electron energy.