The photophysics of gas phase europium chelates. I. Temperature dependence of luminescence

Luminescence lifetimes for two gas europium chelate complexes have been measured as a function of gas temperature. Following ligand excitation the rate constant for Eu(+3) 5D0→7F2 in both molecules shows an Arrhenius temperature dependence. An activation energy of 5100 cm−1 is obtained for europium (3+) tris-1, 1, 1, 2, 2, 3, 3-heptafluoro-7, 7-dimethyl-4, 6,-octanedione, Eu(fod)3, and 4100 cm−1 is obtained for the activation energy of europium (3+) tris-2, 2, 6, 6,-tetramethyl-3, 5-heptanedione, Eu(thd)3. The quantum yield for production of molecules in the luminescing Eu(+3) 5D0 state is found to be independent of temperature when either Eu(thd)3 or Eu(fod)3 is excited in the ultraviolet absorption bands of the ligands.