JMSSJ On-line

JMSSJ On-line, Vol. 48 (2000) No. 4, pp. 254-262

*Ammoniated Ammonium Ions Studied Theoretically and Experimentally, ab initio* Calculation and Tandem Mass Spectrometer Experiments**		>> Full Text PDF >> References
*Yasumasa IKEZOE^a) and Kazuya SUZUKI^a)** ^) Japan Atomic Energy Research Institute (Tokai-mura, Ibaraki 319-1195, Japan)*

Ammoniated ammonium ions (NH₄⁺xnNH₃, 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⁺xnNH₃. It was found that the cluster size n in NH₄⁺xnNH₃ 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.

Key words: Ammonia cluster ion, Molecular orbital calculation, Optimized geometry, Tandem mass spectrometer, Corona discharge-jet expansion, Internal temperature of cluster ions