Stability and structure of cluster ions in the gas phase: Carbon dioxide with Cl−, H3O+, HCO+2, and HCO+

Thermodynamic values for the clustering reactions of carbon dioxide with Cl−, H3O+, HCO+2 , and HCO+ were measured with a pulsed electron-beam high-pressure mass spectrometer. The measured enthalpy changes are reproduced satisfactorily by the ab initio molecular orbital calculations. While Cl−(CO2)n is of the symmetric geometry, H3O+(CO2)n, HCO+2(CO2)n, and HCO+(CO2)n are of the form of the shell plus surroundings. The small fall-off of the bonding energy for the cluster growth is ascribed to the large quadrupole moment of CO2 as well as those on the shell.