Tunneling motion in ArH+3 and isotopomers from the analysis of their rotational spectra

Abstract

The millimeter and submillimeter wave spectra of different H/D isotopomers of ArH+3 were investigated. The ionic clusters were produced inside a negative glow extended by a magnetic field, in Ar/H2/D2 mixtures. Most of the observed rotational lines were split by internal motion and spin statistical weights as well as intensity ratios for the components were determined from symmetry considerations. The splittings were interpreted in terms of internal motion of the H+3 triangle. In a first step, the usual rigid top-rigid frame model was used to reproduce the order of magnitude of the splittings. In a second step, a more refined model, which accounts for the flexibility of the top and the frame, led to a better calculation of the observed splittings in ArH+3 and ArD+3.