2011A&A...533L..11L

We report on the millimeter-wave rotational spectrum of protonated sulfur dioxide, HOSO⁺. Ten rotational transitions between 186 and 347GHz have been measured to high accuracy in a negative glow discharge. The present measurements improve the accuracy of the previously reported centimeter-wave spectrum by two orders of magnitude, allowing a frequency calculation of the principal transitions to about 4km/s in equivalent radial velocity near 650GHz, or one linewidth in hot cores and corinos. Owing to the high abundance of sulfur-bearing molecules in many galactic molecular sources, the HOSO⁺ ion is an excellent candidate for detection, especially in hot cores and corinos in which SO₂ and several positive ions are prominent.