title: Laboratory detection of protonated SO2 in two isomeric forms.
abstract: By means of Fabry-Pérot Fourier transform microwave spectroscopy, the rotational spectrum of protonated sulfur dioxide in two distinct isomeric forms, a cis- and a trans-geometry, is reported. The search for both isomers was based on theoretical structures obtained at the CCSD(T)/cc-pwCVQZ level of theory corrected for zero-point vibrational effects. At a similarly high level of theory, the cis-isomer is calculated to be the global minimum on the potential energy surface, but the trans-isomer is predicted to lie only a few kcal/mol higher in energy. A total of seven lines, including a- and b-type transitions, has been observed for both isomers, and precise rotational constants have been derived. Because sulfur dioxide, SO(2), is a widespread and very abundant astronomical species, and because it possesses a large proton affinity, HOSO(+) is an excellent candidate for radioastronomical detection.
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA. vlattanzi@cfa.harvard.edu
authors.forename: Valerio
authors.initials: V
authors.lastname: Lattanzi
authors.forename: Patrick
authors.initials: P
authors.lastname: Thaddeus
authors.forename: Michael C
authors.initials: MC
authors.lastname: McCarthy
authors.forename: Sven
authors.initials: S
authors.lastname: Thorwirth