Photo-dissociation reaction of bis(p-dimethylaminophenyl) disulfide in ionic liquids was studied by ultrafast transient absorption spectroscopy. Geminate recombination occurred more efficiently in the ionic liquids than in methanol due to the strong cage effect of the ionic liquids. An analysis based on the diffusion limited reaction model was performed to elucidate the recombination dynamics in ionic liquids. The very fast solvation dynamics less than 0.5 ps was observed in viscous solvents together with slow solvation dynamics on nanoseconds time scale. The relation between the solvation dynamics and geminate recombination was discussed. (C) 2013 Elsevier B.V. All rights reserved.