The vibrational and electronic spectra of hexafluorothioacetone, (CF3)(2)CS, a novel blue gas, have been studied. Ab initio calculations of the vibrational properties of CF3COF, CF3CSF, and (CF3)(2)CO were used to establish the feasibility and effectiveness of using theoretical predictions in the analysis of the spectra of perfluorinated compounds. These predictions have allowed us to obtain revised interpretations of the spectra of trifluoroacetyl fluoride and trifluorothioacetyl fluoride that are consistent with both experiment and theory and have allowed us to confirm a previous theoretical and experimental study of the spectrum of hexafluoroacetone. Similar calculations on hexafluorothioacetone predicted a ground state of C-2 symmetry, with the CF3 groups staggered in an antieclipsed configuration and a pattern of vibrational frequencies similar to that of hexafluoroacetone. The gas phase and argon matrix infrared spectra and the Raman spectrum of hexafluorothioacetone were analyzed with the aid of the ab initio predictions and 20 of the 24 fundamentals were assigned. The blue color of the compound originates from very weak T-1-S-0 (800-675 nm) and S-1-S-0 (725-400 nm) transitions in the visible due to the n-pi* electron promotion. Promotion of an electron from the pi to the pi* orbital gives rise to a very strong electronic transition in the 230-190 nm region of the ultraviolet. No emission was observed on laser excitation of hexafluorothioacetone in the visible.