Site-selective ionization and relaxation dynamics in heterogeneous nanosystems

We investigated energy and charge transfer mechanisms as well as fragmentation dynamics in site-selectively ionized heterogeneous core-shell clusters using a high-resolution photoelectron-ion coincidence technique. We show that after inner-shell photoionization, energy or charge is transferred to neighboring atoms and that the subsequent charge localization depends on the site of ionization. Cluster bulk ionization leads to more distinct fragmentation channels than surface ionization. We attribute this to different electronic decay, charge localization, and fragmentation times and conclude that charge transfer and fragmentation dynamics are strongly influenced by the environment of the initially ionized atom.

Figure 1

Ion time-of-flight spectra of ArXe cluster fragments after photoexcitation at 110 eV [blue (dark gray) line] measured in coincidence with the angle-resolved detection of an electron compared to a measurement with static extraction fields [thin (light gray) red line]. The inset shows the corresponding Xe $4d$ photoelectron spectrum. The two sharp lines that partially overlap with the $4d_{3/2}$ cluster peak result from fast valence electrons produced by the subsequent photon bunch. The average cluster size $\langle N\rangle$ is smaller than 8000.

Figure 2

Xe $4d_{5/2}$ (left) and Ar $2p_{3/2}$ (right) photoelectron spectra without selection of ionic coincidences (top) and in coincidence with ${\mathrm{Ar}}_2^{+}$, ${\mathrm{Xe}}_2^{+}$, and ${\mathrm{XeAr}}^{+}$ fragments (bottom panels).