title: The methylsulfinyl radical CH3SO examined.
abstract: Methylsulfinyl radical, a key intermediate in marine atmospheric chemistry, plays a central role in the oxidation of dimethyl sulfide. CH3SO has been extensively studied here with ab initio quantum mechanical methods, with methods as complete as CCSDT(Q) in conjunction with basis sets as large as cc-pV(5+d)Z. In this research, we report high-level computations for the ground and first excited electronic states of the methylsulfinyl radical. The structures of the X[combining tilde] (2)A'' and Ã (2)A' states are quite different with S-O distances of 1.499 and 1.652 Å, respectively. The X[combining tilde] to Ã adiabatic energy difference is predicted to be 45.1 kcal mol(-1), compared to 21.1 kcal mol(-1) for the analogous well-characterized methylperoxy radical CH3OO. The CH3SO barrier to internal rotation is 0.92 kcal mol(-1). The unknown X[combining tilde] (2)A'' torsional vibrational frequency τ is predicted to be 142 cm(-1) (harmonic) and 128 cm(-1) (anharmonic). Our predictions of the Ã (2)A' excited state vibrational frequencies are the first to be reported.
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia. ccq@uga.edu.
authors.forename: Marissa L
authors.initials: ML
authors.lastname: Estep
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia. ccq@uga.edu.
authors.forename: Henry F
authors.initials: HF
authors.lastname: Schaefer Iii