The 1 6-diphenyl-1 3 5-hexatriene (DPH) triplet decay rate constant in degassed benzene is strongly temperature-dependent Photostationary states for the fluorenone-sensitized photoisomerization of DPH in degassed methylcyclohexane (MCH) favor the all-trans isomer and become richer in the cis isomers as the temperature is increased The results are interpreted in terms of competing decays from equilibrated triplet conformers on the basis of the experimentally derived DPH triplet potential energy surface [Saltiel, J, Crowder, J M, Wang S J Am Chem Soc 1999, 121, 895-902 5352] Calculated geometries and energy differences [B3LYP/6-311+G(d p)] are consistent with the experimental model