DETERMINATION OF THE DIFFUSION-COEFFICIENT OF DYE IN SOLUTION AT SINGLE-MOLECULE LEVEL

We have analyzed the width distributions of fluorescence bursts emitte d from single dye in solution, Here we used the confocal microscope co mbined with a short-pulsed diode laser providing an excitation wavelen gth of 638 nm and a repetition rate of 17 MHz. Under the experimental condition that the transit times of dye molecules through a probe spac e were shorter than the average photodestruction time, the data obtain ed using a multichannel scaler showed a linear trend between the photo n counts and the width of fluorescence bursts. From the width distribu tions of burst, the translational diffusion coefficient of JA22 in eth ylene glycol was determined.