Plasmonic Resonant Intercluster Coulombic Decay

Light-induced energy confinement in nanoclusters via plasmon excitations influences applications in nanophotonics, photocatalysis, and the design of controlled slow electron sources. The resonant decay of these excitations through the cluster’s ionization continuum provides a unique probe of the collective electronic behavior. However, the transfer of a part of this decay amplitude to the continuum of a second conjugated cluster may offer control and efficacy in sharing the energy nonlocally to instigate remote collective events. With the example of a spherically nested dimer ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$ of two plasmonic systems we find that such a transfer is possible through the resonant intercluster Coulombic decay (RICD) as a fundamental process. This plasmonic RICD signal can be experimentally detected by the photoelectron velocity map imaging technique.

Figure 1

A cartoon to delineate the process of resonant Auger and ICD plasmon decays in ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$, with curved arrows mimicking these decays [Eq. (2)]. The ground state DFT radial potentials of ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$, isolated ${\mathrm{Na}}_{20}$, and empty ${\mathrm{C}}_{240}$ are drawn (solid curves). The corresponding ${\mathrm{Na}}_{20}$ occupied energy levels as well as ${\mathrm{C}}_{240}$ $\pi$ and $\sigma$ occupied band edges, defined by the maximum and minimum angular quantum number ($l$), are shown; among the levels of ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$, the symbols ${\mathrm{Na}}_{20}@$ and $@{\mathrm{C}}_{240}$ are used to distinguish from free system levels. The isosurface orbitals (HOMO, HOMO-6, HOMO-23) from quantum chemical calculations representing the three ${\mathrm{Na}}_{20}@$ states are shown. Inset: The real part of the LR-TDDFT induced radial potential (${\mathrm{V}}_{\mathrm{ind}}$) for ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$.

Figure 2

LR-TDDFT total photoionization cross sections for ${\mathrm{C}}_{240}$, ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$, and ${\mathrm{Na}}_{20}$. Smoothed curves are added to guide the eye for the fullerene systems. The experimental absorption data [23] are included for ${\mathrm{Na}}_{20}$. Inset: The imaginary part of the induced radial potential (${\mathrm{V}}_{\mathrm{ind}}$) for ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$ calculated in LR-TDDFT.

Figure 3

Color-coded cross section maps as a function of photon energy and photoelectron kinetic energy for ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$ (a) and ${\mathrm{C}}_{240}$ (b). The smoothed curves are used to solely capture the plasmon resonance signals and some blur is introduced to highlight the resonance profiles. Plasmonic RICD traces from $1d$ and $1p$ ${\mathrm{Na}}_{20}@$ levels are identified in panel (a) ($1s$ is too weak to show in this scale), while both panels show similar distributions of regular Auger plasmon traces in ${\mathrm{C}}_{240}$ levels within the range shown. Auger traces in both (a) and (b) are somewhat scaled down for better contrast.

Figure 4

All smoothed LR-TDDFT cross section results are used. (a) The total cross sections for ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$ and ${\mathrm{C}}_{240}$ are shown. The values of the fitted parameters, peak energy (${\mathrm{E}}_0$) and width ($\mathrm{\Gamma }$), and oscillator strength (OS) exhausted by the GPR are given. (b) The difference (scaled-down) between ${\mathrm{Na}}_{20}@{\mathrm{C}}_{240}$ and ${\mathrm{C}}_{240}$ results, the raw ${\mathrm{Na}}_{20}$ result (with a slight down-shift for the aid of comparison), and the RICD plasmon feature (${\mathrm{Na}}_{20}@$), shaded to highlight. The fitting parameters and the OS of ${\mathrm{Na}}_{20}@$ are tabulated.