We
use accurate ab initio methodologies at the
coupled cluster level ((R)CCSD(T)) and its explicitly correlated version
((R)CCSD(T)-F12) to investigate the electronic structure, relative
stability, and spectroscopy of the stable isomers of the [S2O2] system and of some of its cations and dications, with
a special focus on the most relevant isomers that could be involved
in terrestrial and planetary atmospheres. This work identifies several
stable isomers (10 neutral, 8 cationic, and 5 dicationic), including trigonal-OSSO, cis-OSSO, and cyc-OSSO. For all these isomers, we calculated geometric parameters,
fragmentation energies, and simple and double ionization energies
of the neutral species. Several structures are identified for the
first time, especially for the ionic species. Computations show that
in addition to cis-OSSO and trans-OSSO proposed for the absorption in the near-UV spectrum of the
Venusian atmosphere other S2O2, S2O2
+, and S2O2
2+ species may contribute. Moreover, the characterization of the stability
of singly and doubly charged S2O2 entities can
also be used for their identification by mass spectrometry and UV
spectroscopy in the laboratory or in planetary atmospheres. In sum,
the quest for the main UV absorber in Venus’ atmosphere is
not over, since the physical chemistry of sulfur oxides in Venus’
atmosphere is far from being understood.