  A novel technique for studying the demixing of binary fluids with nanosecond
time resolution at nanometer spatial resolution is demonstrated. Nanosecond
kinetics of phase separation initial stages in the water/2,6-lutidine mixture
studied through the combination of a laser-induced temperature jump, and
Forster Resonant Excitation Transfer techniques. A pair of chromophores:
8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS) and Coumarin 480 form a FRET pair in
the uniform phase of the mixture and separate into the components of the
mixture in the nonuniform phase. The temperature jump that brings the mixture
into a nonuniform phase is performed by the mid-infrared laser pulse. The
exponential growth stage of phase separation is in the 5 to 20 nanoseconds
range. The demonstrated technique can be applied to a broad range of chemical
and biological systems.
