Stimulated emission depletion and fluorescence correlation spectroscopy of a branched quadrupolar chromophore

Abstract

Stimulated emission depletion (STED) and single molecule fluorescence correlation spectroscopy (FCS) are used to determine stimulated emission cross-sections and investigate non-radiative relaxation in a branched quadrupolar chromophore (OM77). The results are used as inputs to simulations of single molecule STED by which the feasibility of STED control of the single molecule fluorescence cycle can be assessed. Single molecule STED in OM77 is shown to be readily achievable; however its effectiveness in reducing triplet trapping is apparently mediated by fast non-radiative relaxation processes other than intersystem crossing and rapid quenching of the triplet state in a non-deoxygenated environment.