Ultraviolet absorption bands of [Cs_n+1I_n]⁺ (n<14) clusters

Starting from the large photofragmentation cross sections recently reported for mass-selected alkali-halide clusters [1], we have obtained, for the first time, optical absorption spectra for Cs_n+1I_n⁺ clusters in the ultraviolet charge-transfer bands. In this short report we focus on the spectra of n=4, 6 and 13 which start to show absorption between the lowest charge-transfer band of the diatomic (ca. 3.8 eV) and that of the bulk (ca. 5.9 eV). The spectral features are analyzed for these sizes and correlated to their structures qualitatively as a preliminary model.