Reorientational dynamics of 4H-1-benzopyrane-4-thione (BPT) in the S, state, in hydrocarbon solution, is studied from the anisotropy decay of fluorescence upconversion and pump-probe absorption transients with femtosecond time resolution. The anisotropy decay is found to be monoexponential in n-hexane, n-heptane, n-octane, n-decane, n-dodecane and cyclohexane. The dependence of the rotational time constant, tau(or), on the solvent viscosity is approximated by a linear function with a slope of 2.6 +/- 1 ps/cP indicating slip conditions. The decay of orientational anisotropy is observed for the first time for a molecule in the S-2 state. (C) 2004 Elsevier B.V. All rights reserved.