Structure and dynamics of fluorescently labeled complex fluids by Fourier imaging correlation spectroscopy

We present a method of Fourier imaging correlation spectroscopy (FICS) that performs phase-sensitive measurements of modulated optical signals from fl uorescently labeled complex. fluids. FICS experiments probe the time-depend ent trajectory of a spatial Fourier component of the fluid particle density at a specified wave number k, and provide a direct route to the intermedia te scattering function. The FICS approach overcomes signal sensitivity prob lems associated with dynamic light scattering, while offering a means to ac quire time-dependent information about spatial distributions of fluorescent particles, superior in efficiency to direct imaging methods. We describe t he instrumental setup necessary to perform FICS experiments, and outline th e theory that establishes the connection between FICS observables and stati stical mechanical quantities describing liquid state dynamics. Test measure ments on monolayer suspensions of rhodamine labeled polystyrene spheres are detailed.