Photoinduced chemical reactions of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF,6,]) were studied by laser photolysis at a wavelength of 266 nm. Excited triplet state,3,[bmim],+*, was observed, radical cation [bmim],2+,·, and neutral [bmim],·, radical via photoionization were also formed. Energy transfer from ,3,[bmim],+*, to β-carotene was confirmed. Oxidation via one electron transfer from TMPD to ,3,[bmim],+*, was also observed and the rate constant was determined to be 1.2 × 10,5, L·mol,-1,·s,-1,. The reaction of [bmim][PF,6,] with hydrated electron (e,aq,-,) was confirmed by laser photolysis in aqueous solution.