Strongly Enhanced Recombination via Two-Center Electronic Correlations

In the presence of a neighboring atom, electron-ion recombination can proceed resonantly via excitation of an electron in the atom, with subsequent relaxation through radiative decay. It is shown that this two-center dielectronic process can largely dominate over single-center radiative recombination at internuclear distances as large as several nanometers. The relevance of the predicted process is demonstrated by using examples of water-dissolved alkali cations and warm dense matter.

Figure 1

Scheme of two-center dielectronic recombination (2CDR). Depicted is the first step, where an electron is captured at center $A$ with simultaneous excitation of an atom at center $B$. Afterwards, atom $B$ deexcites via photoemission.

Figure 2

Ratio of ${\sigma }_{2\mathrm{CDR}}$ to ${\sigma }_{\mathrm{RR}}^{(A)}$ as a function of internuclear distance. The solid line and the dotted line refer to the system “$e^{-}+{\mathrm{H}}^{+}+{\mathrm{He}}^{+}(1s)$,” with the dotted line including retardation effects. For comparison, the system “$e^{-}+{\mathrm{H}}^{+}+\mathrm{He}(1s^2)$” is described by the dashed line. In both cases, the change of the incident electron energy is assumed to be resonant with the corresponding first dipole-allowed transition energy for the center $B$ (${\epsilon }_{p_i}=1$ and 0.28 a.u., respectively).

Figure 3

Fano profiles for the $2p_0$ (red dashed curves) and $2p_1$ (green dotted curves) intermediate states and for the whole process $e^{-}+{\mathrm{H}}^{+}+{\mathrm{He}}^{+}(1s)\to \mathrm{H}(1s)+{\mathrm{He}}^{+}(1s)+\gamma$ (black solid curves). The internuclear distances are (a) $R=25\mathrm{a}.\mathrm{u}.$ and (b) $R=75\mathrm{a}.\mathrm{u}.$