Quantum jumps of single molecules at room temperature

The room temperature dynamics of single fluorescent dye molecules adsorbed on dry surfaces was investigated with submillisecond time resolution. Rapid turn-on and off events that satisfy stochastic statistics of quantum jumps were observed. These jumps were most likely intersystem crossing transitions to the triplet state, individually resolved due to the extended triplet state lifetime tau(off) in the dry condition. Saturation study of such single molecules confirmed the extended tau(off). Distributions in intersystem crossing yield Y-ISC and in tau(off), probably due to different local environment, were measured. Moreover, individual molecules exhibited abrupt changes in tau(off) and Y-ISC, correlated with spectral changes of the molecular emission.