Charge-exchange reactions. Part 1.—Charge-exchange mass spectra of the polyfluorobenzenes

Abstract

The charge-exchange spectra formed by the interaction of C₂H⁺₄, N₂O⁺, CO⁺₂, Ar⁺ and Ne⁺ with hexafluoro-, pentafluoro, 1,2,3,4-tetrafluoro-, 1,2,3,5-tetrafluoro-, 1,2,4,5-tetrafluoro, 1,3,4-trifluoro-, 1,3,5-trifluoro-, 1,2-difluoro, 1,3-difluoro-, 1,4-difluoro- and fluoro-benzene have been observed. The ions with the lowest recombination energy gave predominately the parent ions of the fluoro-benzenes. As the recombination energy of the ions increases so the fragmentation increases, but even with carbon dioxide (r.e. = 13.8 eV) the parent ions predominate. When argon ions are the primary species there is a marked change, greater fragmentation occurs and for pentafluoro- the three tetrafluoro- and the 1,3,5-trifluorobenzene studied the principle ion is in every case (P-69)⁺, i.e. the polyfluorobenzene parent ion less the CF₃ radical. The difluorobenzenes similarly yield an ion m/e= 45 (i.e., the parent less the CF₂H radical). Ar + C₆F_xH_y→ Ar +[C₆F_xH_y]^+*, [C₆F_xH_y]^+*→ CF₃·+[C₅F_x–3 H_y]⁺, (M= 6 –x) When neon is the primary ion the extent of fragmentation increases still further but the parent ion less CF₃ remains a major ion in the spectra of the polyfluorobenzenes. The translational energy of the primary ion has very little effect on the charge-exchange spectra observed within the ranges studied (i.e., 10 eV down to 1.0 eV). Absolute cross sections are reported for some of the fragmentation products.