S. Tobita et al., SINGLE-IONIZATION AND DOUBLE-IONIZATION POTENTIALS OF POLYCYCLIC AROMATIC-HYDROCARBONS AND FULLERENES BY PHOTON AND ELECTRON-IMPACT, Canadian journal of physics, 72(11-12), 1994, pp. 1060-1069
Single- and double-ionization appearance potentials of 21 polycyclic a
romatic hydrocarbons (PAHs) were determined by measurement of photoion
yield curves using a synchrotron radiation source. Analogous measurem
ents were made by electron impact on three PAHs. The origin of differe
nces, of up to 4 eV, between appearance potentials for double ionizati
on by photon and electron impact is discussed. The ratio of the double
- to single-ionization potentials of PAHs was found to be 2.65 +/- 0.0
6 for photon impact, significantly lower than for electron-impact and
charge-stripping measurements. An electrostatic model, which considers
that PAHs ionize like fragments of graphite, is applied to the PAHs s
tudied and to data on the fullerenes C-60 and C-70. The validity and l
imitations of the model are discussed and its analytical and predictiv
e propensities concerning multiple-ionization potentials and processes
are demonstrated.