The crystal structure of fluorocarbonylsulfenyl chloride, FC(O)SCl, was detd. by x-ray diffraction anal. from crystals obtained at low temp. using a miniature zone melting procedure. The mol. exhibits only 1 form with Cs symmetry: the C:O double bond syn with respect to the S-Cl single bond. The matrix Raman spectrum of FC(O)SCl shows features originated by 2 conformers, which are in equil. in the gas phase. Irradn. of the Ar matrix with UV light of l<300 nm produces randomization. The pre-resonance Raman effect was detd. for the mol. Its extension is assocd. with the planarity of the mol. and it is related to the p p* transition in the chromophore. Theor. calcns. reproduce both exptl. parameters and vibrational data.