HSCO^+^ and DSCO^+^ lines

This class of molecules is also pivotal for the determination of important physical parameters for the ISM evolution (e.g. gas ionisation fraction) or as tracers of non-polar, hence not directly observable, species. The identification of these molecular species through radioastronomical observations is directly linked to a precise laboratory spectral characterisation.

The goal of the present work is to extend the laboratory measurements of the pure rotational spectrum of the ground electronic state of protonated carbonyl sulfide (HSCO^+^) and its deuterium substituted isotopomer (DSCO^+^). At the same time, we show how implementing different laboratory techniques allows the determination of different spectroscopical properties of asymmetric-top protonated species. Three different high-resolution experiments were involved to detected for the first time the b-type rotational spectrum of HSCO^+^, and to extend, well into the sub-millimeter region, the a-type spectrum of the same molecular species and DSCO^+^.