The ultrafast thermal relaxation of reversed micelles in n-octane/AOT/water (where AOT denotes sodium di-2-ethylhexyl sulfosuccinate) microemulsions was investigated by time-resolved infrared pump-probe spectroscopy. This picosecond cooling process can be described in terms of heat diffusion, demonstrating a new method to determine the nanometer radii of the water droplets. The reverse micelles are stable against transient temperatures far above the equilibrium stability range. The amphiphilic interface layer (AOT) seems to provide an efficient heat contact between the water and the nonpolar solvent.

Efficient intermolecular energy transfer between the C–Br stretching modes ν2 and ν5 of bromoform molecules in the liquid phase has been observed directly in time-resolved experiments applying vibrational pump–probe spectroscopy with picosecond laser pulses. An analysis of results on CHBr3, CDBr3, and an isotopic mixture of both yields a typical time constant of 25±15 ps for this rather efficient, near-resonant intermolecular relaxation channel. Additional new details about the intramolecular pathways of vibrational energy relaxation have been determined for the pure substances.

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