Rajko Ćosić

Photoabsorption spectra of clusters, N =5–9, have been calculated using a diatomics‐in‐molecules like electronic structure model and a path‐integral Monte Carlo sampling method. A qualitative change in the calculated spectra has been observed at N =9, which has been interpreted in terms of a structural transformation in the clusters consisting in a transition from trimer‐like ionic cores observed for N ≤7 to dimer‐like ionic cores prevailing in through an intermediate state (comparable abundances of both types of ionic cores) observed in . The calculated spectra have been thoroughly compared with an earlier calculation on , , and reported from our group and data available for the same cluster sizes from an experiment.