Even-odd effects in the ionization cross sections of[C60]2and[C60C70]dimers

We report strong even-odd effects in multiple ionization yields of van der Waals dimers in slow ${\mathrm{Xe}}^{30+}+\left[{\mathrm{C}}_{60}{]}_2\right(\left[{\mathrm{C}}_{60}{\mathrm{C}}_{70}\right])\to \cdots +{[{\mathrm{C}}_{60}{]}_2}^{r+}({\left[{\mathrm{C}}_{60}{\mathrm{C}}_{70}\right]}^{r+})$ electron-transfer collisions as functions of $r\le 7$. This behavior may be due to even-odd variations in the sequences of dimer ionization energies as calculated with an electrostatic model including an electrical fullerene-fullerene contact at the $19a_0$ center-center separation in ${[{\mathrm{C}}_{60}{]}_2}^{+}$. Prompt dissociations predominantly yield intact fullerenes ${[{\mathrm{C}}_{60}{]}_2}^{r+}\to {{\mathrm{C}}_{60}}^{r_1+}+{{\mathrm{C}}_{60}}^{r_2+}$ in the same ($r_1=r_2$, even $r$) or nearby ($r_1=r_2\pm 1$, odd $r>1$) charge states.