Extracting Spectral Dynamics from Single Chromophores in Solution

Fluorescence spectroscopy of single chromophores immobilized on a substrate has provided much fundamental insight, yet the spectral line shapes and dynamics of single chromophores freely diffusing in solution have remained difficult or impossible to measure with conventional linear spectroscopies. Here, we demonstrate an interferometric technique for extracting time dependent single chromophore spectral correlations from intensity correlations in the interference pattern of an ensemble fluorescence spectrum. We apply our technique to solutions of colloidal quantum dots and explore the spectrum of single particles on short time scales not feasible with conventional fluorescence measurements.