Modulations in the Double-to-Single Photoionization Cross Section Ratio of Benzene

In our previous experiments, we have observed the existence of modulations in the relative double-to-singlephotoionization cross section ratio of C$_{60}$. The de Broglie wavelengths of the excess(above double ionization threshold) energies of these modulations closely matched inter-atomic distances within the C$_{60}$ molecule \footnote{P. N. Jurani\'c, D. Luki\'c, K. Barger, and R. Wehlitz, Phys. Rev. Lett. {\bf 96}, 023001 (2006)}. We have conducted further experiments with benzene, which has a much simpler structure than C$_{60}$, to find out whether these modulations exist and can be similarly linked to inter-atomic distances in other molecules. The results of the experiment indicate that there seems to be such modulations in benzene.