Absolute and total electron-capture cross sections in slow Arq+-C60 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 scale 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. Phys. Chem. 96, 3566, (1992)] are the only possible choices among the many, widely dispersed, vapor pressures reported in the literature. In order to support this statement, we calculate total electron-capture cross sections modeling C-60 as a pointlike object and as an infinitely conducting sphere (ICS). 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 to use the semiempirical formula for absolute ion-atom cross sections by Selberg 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 lower and upper bounds for the absolute cross-section scale. We find significant oscillations in the total electron-capture cross sections as functions of q.