Two-Center Resonant Photoionization

Photoionization of an atom $A$, in the presence of a neighboring atom $B$, can proceed both directly and via resonant excitation of $B$ with subsequent energy transfer to $A$ through two-center electron-electron correlation. We show that in such a case the photoionization process can be very strongly enhanced and acquire interesting characteristic features, both in its time development and the electron spectrum.

Figure 1

Scheme of two-center resonant photoionization (2CPI).

Figure 2

The ratios $p^{2\mathrm{CPI}}/p^{(i)}$ (solid curve) and $p^{(ii)}/p^{(i)}$ (dashed curve) for a Li-He system at $R=10\AA$.

Figure 3

Ionization probability for Li in the presence of He as a function of time. $F_0={10}^{-4}\mathrm{a}.\mathrm{u}.$, the field frequency is resonant to the $1s^2{}^{1}S-1s2p{}^{1}P$ transition in He. The solid, dash and dot curves display results for $R=5$, 7.5, and 10 Å, respectively. For comparison, the ionization probability for an isolated Li atom in the same EM field is shown by the dash-dotted curve.

Figure 4

Energy spectrum of the emitted electrons, as a function of $\Delta ={\epsilon }_p-{\epsilon }_0-{\omega }_0$, for the same atomic system and field as in Fig. 3, $R=5\AA$ and $T=920\mathrm{ps}$.