Time-resolved fluorescence spectra of europium methylbenzoates（MBA）with 1,10-phenanthroline（phen）have been measured at room temperature.Foreach of the europium chelates,where the ligand triple states lie above the 5D1 level ofEu3-,the spectra providc evidence that the Eu3- 5D0 state is populated by nonradiativeenergy transfer from the higher-lying 5D1,state.The relaxation time for energy decayfrom 5D1 state is measured in the microcrystals to bc of the order of a fewmicroseconds.It is suggested that the ligand C=0 and C=C stretching vibrations andEu-O vibrations,chclate ring and benzene ring vibrations make importantcontributions to the relaxation process.The 5D-1—5D-0 relaxation time of Eu-（p-MBA）3phen is shorter than those of Eu（m-MBA）3phen and Eu（o-MBA）3phensince nonradiative degradation to 5D0 from 5D1 appears to be more strongly influencedby the Eu3+sites in the former.
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