The cluster formation in supercritical carbon dioxide

Ab initio calculations using flexible basis sets and including the effects of electron correlation are used to examine various possible structures for (CO2)-n anionic clusters. These calculations reveal that the symmetrical D2d (CO2)2- dimer appears as the core of anionic clusters with 27 clusters. Milliken net charge distribution analysis for anionic clusters with 2<n<7 showed that the extra electron is mainly localized on a dimer core with D2d geometry while for n≥7 clusters electron is shared between all molecules of the cluster. It has been shown that when cluster size increases from 6 to 7 there appears crossover from localized to delocalized behavior for the extra electron. We have proposed that the potential in which this extra electron is moving can be presented by δ-like potential well which is different from zero in thin layer with radius r equal to radius of the cluster anions (CO2)7- and (CO2)13-. On the basis of this model, the photodetachment cross sections of (CO2)7- and (CO2)13-. are calculated as a function of photoelectron energy for the electron in s-like state. (author)