The $2s_{1/2}\mathrm{\text{−}}2p_{1/2}$ energy splittings $\Delta E_L$ of the lithiumlike ions ${}_{79}{}^{197}\mathrm{A}\mathrm{u}^{76+}$, ${}_{82}{}^{208}\mathrm{P}\mathrm{b}^{79+}$, and ${}_{92}{}^{238}\mathrm{U}^{89+}$ have been measured at the Experimental Storage Ring, utilizing low energy dielectronic recombination. The resonance energies in total 41 different $1s^{2}2p_{1/2}n{l}_{j^{\prime }}$ ($n\ge 20$) autoionizing Rydberg states populated in the dielectronic capture process have been determined. The $2s_{1/2}\to 2p_{1/2}$ excitation energies have been obtained by extrapolation of these resonance energies to the associated series limits $n\to \infty$. The combined analysis of the experimental data for all three ions yields $\Delta E_L=216.134(96)\mathrm{e}\mathrm{V}$ for ${\mathrm{A}\mathrm{u}}^{76+}$, 230.650(81) eV for ${\mathrm{P}\mathrm{b}}^{79+}$, and 280.516(99) eV for ${\mathrm{U}}^{89+}$.

Neutral ${\mathrm{C}}_{60}$ is well known to exhibit a giant resonance in its photon absorption spectrum near 20 eV. This is associated with a surface plasmon, where delocalized electrons oscillate as a whole relative to the ionic cage. Absolute photoionization cross-section measurements for ${\mathrm{C}}_{60}^{+}$, ${\mathrm{C}}_{60}^{2+}$, and ${\mathrm{C}}_{60}^{3+}$ ions in the 17–75 eV energy range show an additional resonance near 40 eV. Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.