Decorrelation of luminescent decay in energy-transfer upconversion

A method is presented that gives access to an important parameter in the spectroscopic investigation of energy-transfer upconversion (ETU), namely the fraction of ions that fulfill the condition to participate in ETU, independent of the physical nature of this condition. We exploit the fact that downconversion and upconversion luminescence probe different classes of ions. For ions with a qualified energy-level scheme, a simple analytical solution derives. The method is independent of the pump and ETU parameters. (C) 2002 Elsevier Science B.V. All rights reserved.