Interatomic-distance dependence of resonant energy-transfer phenomena

It is well known that interatomic or intermolecular interactions driven by two-center electronic dipole-dipole correlations fall off rapidly with the intersite distance. We show, however, that the effective strength of interatomic reaction channels, which are triggered by a resonant field, can exhibit a nonmonotonous distance dependence, being strongly reduced when the atoms come closer. This surprising result is demonstrated by considering resonant two-center photoionization as an example. Our findings are supported by available experimental data.

Figure 1

Scheme of two-center resonant photoionization (2CPI), embedded in a generic potential curve $V_{\mathrm{int}}\left(R\right)$ of a van der Waals dimer $A\text{−}B$. First, atom $B$ is resonantly photoexcited; its subsequent decay by ICD leads to the ionization of atom $A$ via an interatomic dipole-dipole interaction $V_{ee}$. The shape of the potential curve determines at which internuclear distance $R$ the process mostly occurs.