Recombination dynamics of fragments after the photo-dissociation of triiodide in several room temperature ionic liquids (RTILs) was investigated by sub-picosecond transient absorption spectroscopy. It is found that the fragments, diiodide and iodine, exist only as a caged contact pair in most RTILs. In 1-butyl-3-methylimidazolium iodide, however, part of the caged contact pairs escape from the solvent cage and survive for nanoseconds. The kinetics was explained by additional reaction of iodine atom with abundant iodides in the solution. (C) 2010 Elsevier B. V. All rights reserved.