Millimeter-wave spectroscopy of SHD2+ and its symmetric isotopologues: Determination of the molecular structure of the sulfonium ion

The asymmetric species SHD2+, produced in a magnetically confined negative glow discharge, was spectroscopically observed for the first time by measuring its pure rotational spectrum by means of a submillimeter-wave source-modulated spectrometer. In addition, the J = 2 ← 1 to 4 ← 3 transitions of SD3+ and 34SD3+, and the J = 1 ← 0 and 2 ← 1 lines of SH3+ and 34SH3+ were measured in the 290-654 GHz frequency region. All the determined rotational constants allowed to calculate the molecular structure of the sulfonium ion at various levels of description of the contribution of zero-point vibrations. The rm method of Watson et al. [J.K. Watson, A. Roytburg, W. Ulrich, J. Mol. Spectrosc. 196 (1999) 102-119] has confirmed to be a quite straightforward procedure to estimate, from ground state rotational constants, structural parameters very close to the equilibrium values.