Absolute and total electron-capture cross sections in slow Arq+-C-60 collisions - art. no. 013201

We present experimental absolute and total electron-capture cross sections for Arq+-C-60 (q = 4, 6, and 8-18) collisions at 3.3q keV. The absolute sca le is based on the C-60 vapor pressure by Abrefah et al. [Appl. Phys. Lett. 60, 1313 (1992)], which together with the results of Mathews et al. [J. Ph ys. Chem. 96, 3566, (1992)] are the only possible choices among the many, w idely dispersed, vapor pressures reported in the literature. In order to su pport this statement, we calculate total electron-capture cross sections mo deling C-60 as a pointlike object and as an infinitely conducting sphere (I CS). These model results are shown to differ little, since polarization and finite-size effects are relatively unimportant for the distant collisions at which the outermost (first) electrons me transferred. We are thus able t o use the semiempirical formula for absolute ion-atom cross sections by Sel berg et nl. [Phys. Rev. A 54, 4127 (1996)], treating C-60 as a hypothetical atom with ionization potential I-1 = 7.6 eV, and the ICS model to define l ower and upper bounds for the absolute cross-section scale. We find signifi cant oscillations in the total electron-capture cross sections as functions of q.