Sub-millimeter-wave spectroscopy of the Ar•H3+ and Ar•D3+ ionic complexes

An investigation of the sub-millimeter-wave spectra of the ionic complexes Ar . H-3(+) and Ar . D-3(+) is presented. These complexes were produced in a negative glow electric discharge, in mixtures of argon with either H-2 or D-2. About 80 new transitions were assigned iu the 455-650 GHz frequency range using a sub-millimeter-wave spectrometer built with Russian made backward wave oscillators (BWO) sources. These measurements enabled us to observe the first K-a = 2 transitions for Ar . H-3(+) and the first K-d = 3 transitions for Ar . D-3(+). Analyses of the line frequencies were carried out using an IAM-Iike approach, which accounts for the large amplitude internal rotation motion displayed by both species. Insights into the geometry of the intermediate configuration for this large amplitude motion were gained. (C) 1998 Academic Press.