Kinetic Energies of Fragment Ions from Pentane Isomers by Electron Impact.

Abstract

Some fragment ions from pentane isomers resulting from electron impact possess considerable kinetic energies. On the basis of the information gained about the effect of discrimination on ions, the amount of the kinetic energies of fragment ions from n-pentane, iso-pentane and neo-pentane has been determined. The results of experiments show, in general, that the kinetic energies of these fragment ions increase with a decrease in the number of hydrogen atoms, that is, as the number of scissions of the C-H bond increases. However, somexceptions were observed. The C2H4+ ions from n-, iso-and neo-pentanes possess high kinetic energies(about 0.55 eV); theC3H6+ and C3H4+ ions from neo-pentane possess higher kinetic energies(about 0.45 eV)than those from n-and isopentanes; and the C4H6+ ions from n-and iso-pentanes possess higher ones(about 0.4 eV)than that from neo-pentane. Comparing the chemical structure of these isomers and appearance potentials of the ions, the dissociation processes for the fragment ions with high kinetic energies were discussed. The hypothesis of the fragmentation of doubly charged ions could not explain all of the kinetic ions.