Study of I−(CO2)n, Br−(CO2)n, and I−(N2O)n clusters by anion photoelectron spectroscopy

Photoelectron spectra of the I−(CO2)n=1–13, I−(N2O)n=1–12, and Br−(CO2)n=1–11 clusters are presented. The spectra provide information about the stepwise solvation of the bromide and iodide anions and about the size of the first solvation shells in these clusters. The data suggest that significantly different solute–solvent interactions exist in the three sets of clusters studied here. The X−(CO2)n spectra exhibit resolved progressions which are assigned to in-phase CO2 solvent bending vibrations in the neutral clusters. These vibrations are excited by photodetachment of anion clusters in which the CO2 molecules are distorted from linearity by a charge-quadrupole interaction. The I−(N2O)n spectra do not show any vibrational structure, presumably because the weaker ion–solvent interactions are insufficient to distort the N2O molecules.