Watching vibrational energy flow across a molecular interface
Home page Contact us Directions for visitors Research Projects Dana D. Dlott (Curriculum Vitae) Dana D. Dlott (personal home page) David M. Dlott (personal home page) Group Members Research Publications Research Funding Research Facilities	This work is done in collaboration with the group of Prof. John Deàk and the University of Scranton. Using 3D vibrational spectroscopy, we can directly monitor the flow of vibrational energy through molecules with angstrom spatial resolution. We have directly measured the flow of vibrational energy across a molecular interface between a nonpolar liquid and an aqueous phase. Reverse micelles consist of an interior water nanodroplet surrounded by an amphiphilic surfactant suspended in a nonpolar liquid. In our experiments, the reverse micelles were composed of about 40 water molecules surrounded by AOT surfactant, suspended in CCl4. We used a femtosecond IR pulse to excite either the water nanodroplet or the AOT alkane chains and then watched the energy move. When water was excited, most of the energy was transferred to the AOT sulfate head groups and then out into the CCl4. When CH stretch of AOT was excited, the energy moved into other chain vibrations and out into the CCl4. Ordinary thermal conduction cannot explain our results. Only an analysis of the detailed vibrational energy pathways can explain why when water is heated, the CCl4 is excited faster than when the AOT chains are excited. This is the first experiment to directly measure the dynamics of vibrational energy transfer across a molecular interface. In addition this is the first measurement of the vibrational relaxation of a water nanodroplet. Reference “Vibrational energy transfer across a reverse micelle surfactant layer”, John C. Deàk, Yoonsoo Pang, Timothy D. Sechler, Zhaohui Wang, and Dana D. Dlott, Science 306, 473-476 (2004).	Schematic of Aerosol OT surfactant, an inverse micelle with w = 2, containing ~40 water molecules, suspended in CCl4. At the bottom is the Raman spectrum showing water, AOT and CCl4 transitions. Measuring vibrational energy transfer across an ethanol molecule Time dependence of vibrational energy in an AOT micelle suspended in carbon tetrachloride when the AOT CH stretches are pumped Time dependence of vibrational energy in an AOT micelle suspended in carbon tetrachloride when the water OH stretches are pumped