Observation of small metastable multiply charged CsI clusters embedded inside rare gas clusters

Abstract

Medium size Kr and Ar clusters 〈N〉 ~ 200 – 400 were used to pick up and aggregate CsI molecules. By varying the number of pick-up events it was possible to change the size of the guest cluster and the thickness of the rare gas coverage around the alkali halide cluster. “Soft” single (multiple) ionisation of the alkali halide core was achieved via charge transfer from the primary ionised rare gas shell. It turns out that the rare gas shell controls the vibrational relaxation of CsI cluster ions. Due to cooling by the rare gas shell shallow metastable states of multiply charged CsI clusters can be populated and detected. Clusters as small as Cs₅I ²⁺₃ , Cs₆I ²⁺₅ , Cs₁₃I ³⁺₁₃ and Cs₁₇I ³⁺₁₄ could be observed for the first time. The abundance of these multiply charged clusters steeply decreases if the thickness of rare gas shell shrinks.