Real-time picosecond measurements of electronic energy transfer from DODCI to malachite green and DQOCI

Singlet-singlet resonance energy transfers from DODCI (donor) to malachite green and to DQOCI in ethanolic solutions have been investigated with a real-time picosecond streak-camera (time-resolution 3–5 ps) operating at a repetition rate of 140 MHz, in synchronism with the pulse train from a mode-locked cw dye laser used as excitation source. Acceptor concentrations from 10^?5 M to 7.5 × 10^?3 M were studied and average R_o values of 45.6 Å for malachite green and 61.8 Å for DQOCI are obtained from the directly measured fluorescence decay curves. Departure from Förster kinetics is seen at the lower acceptor concentrations employed.