RESONANT AND NONRESONANT CHARGE-TRANSFER IN C-60(-60 AND C-70(+)+C-60COLLISIONS()+C)

Charge transfer cross sections sigma(CT) were measured for the single- electron charge transfer reactions C-60/70(+) + C-60 + C-60/70 + C-60( +) + Delta E as a function of the collision energy E in the range 200- 2100 eV. For both processes the absolute values of the cross sections are similar to the geometrical cross sections and decrease with increa sing collision energy below E = 400 eV. In the case of C-60(+) project iles, the charge transfer cross section remains almost constant for la rger collision energies while sigma(CT) increases in the case of captu re by C-70(+) beyond 400 eV and saturates around 1350 eV. From an inte rpretation of the measured cross sections using very simple models it can be concluded that the electron transfer is resonant in collisions between C-60(+) and C-60, as would be expected, and has both resonant and non-resonant contributions for C-70(+) projectiles. The qualitativ e agreement of the experimental results with very simple one-electron models developed to describe the general trends of the charge transfer cross sections determined in ion-atom collisions in the intermediate energy range (where the semiclassical impact parameter method can be a pplied) is quite surprising.