Electron impact ionization and dissociation of neutral and charged fullerenes

Abstract

Three different types of electron impact ionization experiments have been performed, involving neutral and charged C 60 and C 70 . 1) We have determined absolute partial ionization cross sections for formation of parent ions C z+ 60 and C z+ 70 in charge states up to z = 4, and of singly and multiply charged fragments of size n ≥ 44 and n ≥ 50 from C 60 and C 70 neutral precursors, respectively. 2) Previous appearance energy measurements of C 70 have been improved and extended to z = 5; ionization energies are found to depend linearly on the charge state of the precursor, in agreement with theoretical predictions. 3) A beam of mass selected C 2+ 60 has been crossed with an intense electron beam; the induced reactions (fragmentation, post-ionization, and dissociative post-ionization) have been analyzed.

Kinetic energy releases and electron-induced decay of C60z+

“…The gun is approximately one order of magnitude more powerful than the electron gun which we had used previously 12 for post-ionization of fullerene cations and anions. 12,23 In this work we chose an electron energy of 300 eV and an electron beam current of 15 mA. Figure 2 shows an example of a MIKE spectrum for electron-induced ionization and dissociative ionization of mass-selected C 60 + to C 60 2+ and fragments thereof.…”

Electron impact ionization of neutral and ionized fullerenes: ionization cross–sections and kinetic energy release

“…Similar studies concerning ionization and dissociation of mass-selected fullerene ions, however, with a specific emphasis on the kinetic energy release in the dissociation reaction, have been recently performed by our group in Innsbruck (Rauth et al . 1995;Matt et al . 1997c).…”

“…of the order of ca. 10 pA) than in the case of an ECR ion source and thus, it was necessary to develop a high-performance electron gun, yielding electron currents beyond 10 mA (Matt et al . 1997c).…”

Electron Ionization of Size-Selected Positively and Negatively Charged Helium Droplets

“…Dolder and Peart obtained the overlap by moving an aperture through the region where the ion and electron beam overlap [11]. The electron impact on large molecular target ions was investigated for fullerene cations by Matt et al [12], who reported an increase in the charge state with and without fragmentation. The group of Salzborn extended these studies and determined the absolute cross sections for positively and negatively charged fullerene ions [13,14].…”