Mechanism of superexchange interatomic Coulombic decay in rare-gas clusters

Interatomic Coulombic decay (ICD) is an ultrafast energy transfer process. Via ICD, an excited atom can transfer its excess energy to a neighboring atom which is thus ionized. On the example of the NeHeNe cluster, we recently reported [Phys. Rev. Lett. 119, 083403 (2017)] that the total ICD widths are substantially enhanced in the presence of an ICD inactive atom. The enhancement occurs due to the coupling of the resonance state to intermediate virtual states of the bridge atom—a mechanism named superexchange ICD. In this followup work, we analyze the partial ICD widths in the NeHeNe cluster and show that only some channels are affected by the superexchange ICD process. Furthermore, we consider superexchange ICD in NeHeAr. We show that in this system the enhancement is still present but the energy transfer mediated by the superexchange mechanism is less efficient than in NeHeNe owing to the different ionization potentials of Ar and Ne. The behavior of the computed ICD widths is explained with a simple model based on first-order perturbation theory and a Hartree-Fock-like description of the states.

Figure 1

Comparison between the total decay widths of the ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_{g,u}^{+}$ states in ${\mathrm{Ne}}_2$ (black dashed lines) and NeHeNe (red full lines). Left panel: ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_g^{+}$. Right panel: ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_u^{+}$.

Figure 2

Comparison between the partial decay widths of the ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_{g,u}^{+}$ states in ${\mathrm{Ne}}_2$ (dashed lines) and NeHeNe (full lines) to singlet final states. We show only the channels whose decay widths are enhanced as a result of the superexchange ICD: ${}^1{\mathrm{\Pi }}_g, {}^1{\mathrm{\Pi }}_u$, and ${}^1{\mathrm{\Sigma }}_g^{+}$. Left panel: ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_g^{+}$. Right panel: ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_u^{+}$.

Figure 3

Comparison between the partial decay widths of the ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_{g,u}^{+}$ states in ${\mathrm{Ne}}_2$ (dashed lines) and NeHeNe (full lines) to triplet final states. We show only the channels whose decay widths are enhanced as a result of the superexchange ICD: ${}^3{\mathrm{\Pi }}_g, {}^3{\mathrm{\Pi }}_u$, and ${}^3{\mathrm{\Sigma }}_u^{+}$. Left panel: ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_g^{+}$. Right panel: ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}_u^{+}$.

Figure 4

Comparison between the total decay widths of the ${\mathrm{Ne}}^{+}(2s^{-1}$) ${}^2{\mathrm{\Sigma }}^{+}$ states in NeAr (black dashed line) and NeHeAr (red full line).

Figure 5

Comparison between the partial decay widths of the ${\mathrm{Ne}}^{+}\left(2s^{-1}\right) {}^2{\mathrm{\Sigma }}^{+}$ state in NeAr and NeHeAr to singlet (left panel) and triplet (right panel) final states. We show only the channels whose decay widths are enhanced as a result of the superexchange ICD: ${}^1\mathrm{\Pi }, {}^1{\mathrm{\Sigma }}^{+}$ and ${}^3\mathrm{\Pi }, {}^3{\mathrm{\Sigma }}^{+}$.