Two‐Step Energy Transfer in Solution

In the presence of terbium ions, a transfer of energy is observed from 4,4′‐dimethoxybenzophenone (DMB) to europium ions. This transfer does not take place in the absence of terbium and it is concluded that the terbium ion serves as an intermediate in the energy transfer. Fluorescence and excitation spectra, fluorescence lifetimes, and time‐resolved excitation spectra are presented to substantiate the proposed nonradiative two‐step energy transfer.