Collectively enhanced resonant photoionization in a multiatom ensemble

Photoionization of an atom via interatomic correlations to $N$ neighboring atoms may be strongly enhanced due to constructive interference of quantum pathways. The ionization proceeds via resonant photoexcitation of a neighbor atom and subsequent interatomic Coulombic decay. The enhancement can scale with $N^2$, leading to “superenhanced photoionization.”

Figure 1

Scheme of photoionization of atom $A$ in the presence of an external laser field and $N=3$ neighboring atoms $B_j$ ($j=1,2,3$). Apart from the direct photoionization of $A$, there are interatomic channels via photoexcitation of one of the atoms $B_j$ (here $j=3$) and subsequent ICD.

Figure 2

Resonant photoionization of a Li atom in the presence of neighboring He atoms. Shown is the relative enhancement with respect to the photoionization cross section of an isolated Li atom [see Eq. (8)], for various numbers $N$ of He neighbors. The incident photon energy is resonant with the $1s^2{}^{1}S$–$1s2p{}^{1}P$ transition in helium (i.e., $\omega \approx 21.2$ eV). The distance between the Li atom and each of the He atoms is $R\approx 1$ nm and the He atoms are assumed to be located in the plane perpendicular to the photon field polarization. $N=1$ corresponds to the diatomic case considered in Ref. [16]; $N=2$ would be realized, e.g., by a linear chain He-Li-He; and $N=3$ could correspond to a Li atom in the center of an equilateral triangle formed by three He atoms.