Infrared and ab Initio Study of the Chloride - Ammonia Anion Complex

Abstract

The infrared spectrum of the Cl--NH3 anion complex has been recorded in the 2900-3450 cm-1 range by monitoring the infrared-induced production of Cl- anion fragments in a tandem mass spectrometer. The spectrum features an intense band centered at 3140 cm-1, which is shifted by 196 cm-1 to lower frequency with respect to the ammonia ν1 band (3336.2 cm-1). Two much weaker peaks are observed at 3270 and 3340 cm-1. Ab initio calculations performed at the MP2(full)/aug-cc-pVTZ level indicate that the complex possesses a Cs proton-bound minimum-energy structure, and yield vibrational frequencies and intensities that accord with the infrared data. Barriers, calculated at the MP4SDTQ(full)/aug-cc-pV..