Direct observation of intramolecular energy transfer by selective picosecond laser excitation of a single chromophore in jet-cooled molecules

Here we report on the direct observation of time-resolved formation of a product of intramolecular energy transfer in isolated, jet-cooled A^*-CH_2-CH_2-CH_2-B. The anthracene chromophore (A) was excited by picosecond pulses, and the transfer of energy was probed at various excess energies by observing the emission arising from the exciplex formed between B (dimethyl aniline) and A^*. The threshold is at 3 kcal/mole.