Interface Excitons in Krmnen Clusters : The Role of Electron Affinity in the Formation of Electronic Structure

TL;DR

This study investigates how interface excitons form in small Kr clusters embedded in Ne clusters, revealing the influence of electron affinity on their electronic structure and exciton penetration depth.

Contribution

It provides new insights into the formation and size-dependent behavior of interface excitons in Kr/Ne clusters, highlighting the role of electron affinity.

Findings

Interface excitons are observed at the Ne/Kr interface.

Bulk excitons appear only in larger clusters exceeding a critical size.

The penetration depth of interface excitons is approximately 7.0 Å, influenced by electron affinity.

Abstract

The formation of the electronic structure of small Kr_m clusters (m<150) embedded inside Ne_N clusters (1200<N<7500) has been investigated with the help of fluorescence excitation spectroscopy using synchrotron radiation. Electronically excited states, assigned to excitons at the Ne/Kr interface, 1i and 1'i were observed. The absorption bands, which are related to the lowest spin-orbit split atomic Kr 3P1 and 1P1 states, initially appear and shift towards lower energy when the krypton cluster size m increases. The characteristic bulk 1t and 1't excitons appear in the spectra, when the cluster radius exceeds some critical value, R_cl>Delta_1i . Kr clusters comprising up to 70 atoms do not exhibit bulk absorption bands. We suggest that this is due to the penetration of the interface excitons into the Kr_m cluster volume, because of the negative electron affinity of surrounding Ne atoms. From the energy shift of the interface absorption bands with cluster size an unexpectedly large penetration depth of delta_1i =7.0+/-0.1 A is estimated, which can be explained by the interplay between the electron affinities of the guest and the host cluster.