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Coherent Multidimensional Spectroscopy (CMDS) of Quantum Confined Nanostructures John C. Wright, University of Wisconsin-Madison, DMR 0906525.

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  1. Coherent Multidimensional Spectroscopy (CMDS) of Quantum Confined NanostructuresJohn C. Wright, University of Wisconsin-Madison,DMR 0906525 Quantum mechanical effects form the basis for research that promises to dramatically increase solar collection efficiencies of complex nanostructures. However, new technologies are needed to observe these quantum effects so it becomes possible to guide materials chemists’ efforts to make the nanostructures. Recent work shows that CMDS provides this capability. Focusing 3 femtosecond laser pulses into a nanostructure creates new light pulses. CMDS changes the colors and the delay times of 3 femtosecond laser pulses so they excite different quantum states and follow how the states change during the entire progression between their creation and their production of electricity or solar fuels. The pictures show two examples of CMDS on PbSe quantum dots. The top picture shows how the output brightness (red is the brightest) depends on the colors of 2 input beams. Note the new peak that is growing at the left of the main peak. It comes from a new state at the quantum dot surface. The two bright features in the bottom picture show how the two states that are excited by different frequencies along the y-axis are formed and decay along the x-axis. For further information, see references: (1) Pakoulev, A. V.; Block, S. B.; Yurs, L. A.; Mathew, N. A.; Kornau, K. M.; Wright, J. C. Journal of physical chemistry Letters 2010, 1, 822-828. (2) Yurs, L. A.; Block, S. B.; Pakoulev, A. V.; Selinsky, R. S.; Jin, S.; Wright, J. C. Journal of Physical Chemistry C 2011, 115, 22833-22844. (3) Yurs, L. A.; Block, S. B.; Pakoulev, A. V.; Selinsky, R. S.; Jin, S.; Wright, J. C. Journal of Physical Chemistry C 2012, 116, 5546-5553.

  2. Coherent Multidimensional Spectroscopy (CMDS) of Quantum Confined NanostructuresJohn C. Wright, University of Wisconsin-Madison,DMR 0906525 Our CMDS methods involve very new ideas and require dissemination to the scientific and educational community. Our group creates educational materials that visualize important physical processes and incorporates the materials into graduate and undergraduate classes. The left-hand pictures are frames from a video that illustrates our CMDS methods. The top shows three femtosecond light pulses being focused into a sample. The video shows them creating a new light pulse after the sample. CMDS measures the changes in the intensity of this light pulse as a function of the colors and time delays between the three entering pulses. The bottom frame shows the effects of these three light pulses on the quantum states of a hydrogen atom. The video shows how the electron wave function oscillates as it interacts with the electric field of the light pulses. The oscillating electron cloud launches the new light pulse. You can open the URL to see the complete video. http://pubs.acs.org/page/jpclcd/wright-video.html

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