Penning ionization of C60 molecules

A mass-spectrometric study of Penning ionization of C-60 with metastable rare-gas atoms (Rg = He, Ne, Ar, Kr and Xe) shows that the sole channel is C-60(+) formation. The ionization cross-sections, at an average collision energy of 0.05 eV, strongly decrease from helium to xenon. The interaction potentials for C-60-Rg*, C-60(+)-Rg, C-60-Rg and C-60(-)-Rg(+), and matrix elements for the coupling of the C-60-Rg* and C-60(-)-Rg(+) interactions at the crossing point, have been estimated using recently proposed correlation formulas. The trend of the ionization cross-sections can be explained by the low-energy collisions between Rg* and C-60, characterized by the formation of an ion-pair C-60(-)-Rg(+) intermediate with a decreasing probability on going from lighter to heavier rare gases. (C) 1998 Published by Elsevier Science B.V. All rights reserved.