Electron attachment and cesium collisional ionization studies of tetrafluorosuccinic and hexafluoroglutaric anhydrides: Molecular electron affinities

The electron affinities of tetrafluorosuccinic anhydride(I) and hexafluoroglutaric anhydride(II) were measured to be 0.5 ± 0.2 eV and 1.5 ± 0.2 eV, respectively, using a cesium collisional ionization technique. Dissociative electron attachment to I produced the negative ions: ${\mathrm{C}}_2{\mathrm{F}}_4{\mathrm{CO}}_2^{\mathrm{-*}}\text{\hspace{0.17em}(≥ 5\hspace{0.17em}}\mathrm{msec})$ , C₂F₄CO^−* (124 μsec), ${\mathrm{C}}_2{\mathrm{F}}_4^{\mathrm{-*}}\text{\hspace{0.17em}(14\hspace{0.17em}μ}\sec )$ , and F⁻; while ${\mathrm{C}}_3{\mathrm{F}}_6{\mathrm{CO}}_2^{\mathrm{-*}}\text{\hspace{0.17em} (≥ 1.2\hspace{0.17em}}\mathrm{msec})$ , C₃F₆CO^−* (80 μsec), ${\mathrm{C}}_3{\mathrm{F}}_6^{\mathrm{-*}}\text{\hspace{0.17em}(760\hspace{0.17em}μ}\sec )$ , and F⁻ were observed from II. The asterisk indicates that the ion is metastable with respect to autodetachment, and the numbers in parentheses are the measured autodetachment lifetimes for incident electrons at the maximum in the cross section. Very large cross sections (∼ 10⁻¹⁴ cm²) for production of ${\mathrm{C}}_2{\mathrm{F}}_4{\mathrm{CO}}_2^{\mathrm{-*}}$ and ${\mathrm{C}}_3{\mathrm{F}}_6{\mathrm{CO}}_2^{\mathrm{-*}}$ were observed for dissociative attachment of thermal electrons to I and II, respectively. The parent negative ions ${\mathrm{C}}_4{\mathrm{F}}_4{\mathrm{O}}_3^{-}$ and ${\mathrm{C}}_5{\mathrm{F}}_6{\mathrm{O}}_3^{-}$ , as well as all of the ions (with the exception of ${\mathrm{C}}_2{\mathrm{F}}_4^{-}$ ) which were observed for dissociative electron attachment, were observed from collisions between fast cesium atoms and I and II.