Abstract
Ammoniated ammonium ions (NH4+·nNH3, n=0-6) were studied theoretically by molecular orbital calculations and experimentally by observing their formation and decomposition in a corona discharge-jet expansion process. Ab initio calculations were carried out by employing Gaussian 98 program, which gave optimized structures, binding energies, and wave numbers of the symmetric bending mode of the solvent ammonia molecule. Effects of the stagnation pressure of reactant gas and the diameter of the gas expanding pinhole were examined on the size distribution of NH4+·nNH3. It was found that the cluster size n in NH4+·nNH3 increased by one or remained unchanged in the jet expansion process. Effects of discharge current, the pinhole diameter and flight time were examined on the decomposition rate of the ammonia cluster ions. It was deduced that the internal energies of the cluster were mainly determined by the reactions involved in the cluster formation or decomposition.
