TIME-RESOLVED SPECTROSCOPY OF SINGLE MOLECULES USING NEAR-FIELD AND FAR-FIELD OPTICS

Room-temperature spectra and excited state lifetimes of single molecul es obtained with conventional, far-field optics are reported, for the first time. The sample was the same as that used in our previous near- field single molecule work, namely 1,1'-dioctadecyl-3,3,3',3'-tetramet hylindo (diI) dispersed in a thin film of polymethylmethacrylate. In a critical comparison of the two methods we have found that superior sp atial resolution and more complete information on the orientation of t he molecule are available with near-field excitation, whereas presentl y, excited state lifetimes can be accurately determined only under far -field illumination. In addition, greater data rates are possible with far-field excitation, without perturbing the molecule. Which method p roves better will depend on the particulars of the system under invest igation.