Cross-Section Ratios of Multiple-Photoionized C60 Clusters

Relative C$_{60}^{2+}$/ C$_{60}^{+}$, C$_{60}^{3+}$/ C$_{60}^{+}$, and C$_{60}^{4+}$/ C$_{60}^{+}$ photoionization cross-sections have been obtained by using synchrotron radiation between 19 and 180 eV. The measurements were carried out at the Synchrotron Radiation Center (SRC) in Stoughton, WI, using an oven to vaporize C$_{60}$ powder and synchrotron light to photoionize the gas. In addition to procuring the above-mentioned curves, we have also observed the photoionization-induced fragmentation of C$_{60}$ at higher ($>50$ eV) photon energies. The measurements are an improvement to existing data \footnote{T.\ Drewello {\it et al.}, Int. Journal of Mass Spectrom. and Ion Processes {\bf 124}, R1 (1993).} \footnote{A.\ Reink\"oster {\it et al.}, J.\ Phys.\ B {\bf 37}, 2135 (2004).}. The C$_{60}^{2+}$/ C$_{60}^{+}$ relative cross-section curve seems to exhibit an oscillatory behavior, and the possible causes of this behavior will be discussed.