Two-center dielectronic recombination and resonant photoionization

We consider radiative recombination and photoionization in an atomic system, which consists of two subsystems $A$ and $B$. These subsystems are well separated in space and it is supposed that $A$ has a lower ionization potential. In such a case photoionization of $A$ and recombination of an incident electron with $A^{+}$ can be strongly influenced, via two-center electron-electron correlations, by resonant electron dipole transitions induced in $B$. A theoretical description of these two-center resonant dielectronic processes is presented.

Figure 1

Scheme of two-center dielectronic recombination.

Figure 2

Scheme of two-center resonant photoionization.

Figure 3

The ratio between the cross sections for ionization of Li in a Li-He system and for ionization of a separated Li atom. The electromagnetic field is assumed to be linearly polarized along the internuclear vector $\mathbf{R}$. The ratio was calculated for four different internuclear distances $R$ [(a) $R=20$ Å, (b) $R=50$ Å, (c) $R=100$ Å, and (d) $R=200$ Å] and is given as a function of the normalized detuning $X=({\omega }_0-{\omega }_{\mathrm{res}})/{\stackrel{̲}{\Gamma }}_a$ from the resonant frequency ${\omega }_{\mathrm{res}}={\epsilon }_e-{\epsilon }_0\approx 21$ eV corresponding to the $1s^2\hspace{0.5em}{}^{1}S$–$1s2p\hspace{0.5em}{}^{1}P$ transition in He. Solid and dashed curves display results obtained with the electron-electron interaction in the form (17) and (1), respectively.

Figure 4

The ratio between the cross sections for ionization of Li in a Li-He system and for ionization of a separated Li atom. The electromagnetic field is assumed to be linearly polarized and propagate parallel to the internuclear vector $\mathbf{R}$. The ratio was calculated for three different internuclear distances $R$ [(a) $R=50$ Å, (b) $R=100$ Å, and (c) $R=200$ Å] and is given as a function of the normalized detuning $X=({\omega }_0-{\omega }_{\mathrm{res}})/{\stackrel{̲}{\Gamma }}_a$ from the resonant frequency ${\omega }_{\mathrm{res}}={\epsilon }_e-{\epsilon }_0\approx 21$  eV corresponding to the $1s^2\hspace{0.5em}{}^{1}S$–$1s2p\hspace{0.5em}{}^{1}P$ transition in He. Solid and dashed curves display results obtained with and without taking into account the phase difference $\mathit{exp}(-i\mathbf{k}·\mathbf{R})$ between the electromagnetic transitions on the two centers.