The efficiency of resonance energy transfer can be used to determine nanometer-scale separations between dye molecules in a donor-acceptor pair. We argue that the standard method for making this determination in single-pair experiments is valid only when excitation by the applied field is much slower than the other photophysical processes in the system. We derive a simple relation between measured transfer efficiency and interdye distance that is valid regardless of excitation rate for a broad class of currently accepted models for dye photophysics. Significant deviations from weak-field results are predicted for typical experimental conditions.
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© 2009 American Institute of Physics.
2009
American Institute of Physics
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