A Chemistry Seminar ft: Benjamin G. Levine (Stony Brook) 

Department of Chemistry and Institute for Advanced Computational Science, Stony Brook University, Stony Brook, NY  11794 

Abstract:  Ultrafast laser pulses allow scientists to watch the wave packet motion of a molecule or material following photoexcitation with incredible time resolution.  However, no ultrafast experiment can take a perfect snapshot of the molecular wave packet.  Instead, spectroscopic experiments record a lossy projection of the molecular wave packet.  For this reason, computer simulation has become an essential partner of ultrafast experiment.  Computer simulations can provide a detailed, if approximate, picture of the motions following photoexcitation, explicitly including all nuclear and electronic degrees of freedom.  Working in collaboration with ultrafast spectroscopists, our group has developed novel strategies for simulating and interpreting ultrafast spectra, with an eye toward definitively assigning spectral features to specific molecular motions.  In this talk, I will present two stories of such work.  First, in collaboration with the Allison group at Stony Brook University, we have developed a novel computational strategy for the direct simulation of ultrafast transient absorption spectra.  We will demonstrate how this method may be used to assign spectral features to individual molecular motions in two molecules that undergo excited state proton transfer.  The second story will present our work with the group of Warren Beck at Michigan State University interpreting the two-dimensional electronic spectrum of colloidal CdSe quantum dots undergoing hot carrier cooling, a process that limits the efficiencies of solar cells.  The Beck group’s experiments indicate the existence of coherences between core electronic excitations and ligand vibrational states during relaxation.  By identifying and analyzing conical intersections between potential energy surfaces of quantum dots, we are able to assign the spectral features to specific motions and identify the nature of the observed vibronic coherences. 

Bio: Benjamin G. Levine is a theoretical/computational chemist whose research focuses on developing and applying computational methods for simulating nonradiative processes—physical processes that convert electronic energy into vibrational energy—in molecules and materials.  He earned a B.S. in Chemical Engineering and Ph.D. in Chemistry from University of Illinois at Urbana-Champaign in 2001 and 2007, respectively, doing his Ph.D under Todd J. Martínez.  After performing postdoctoral work at University of Pennsylvania and Temple University in the group of Michael L. Klein, Ben joined Michigan State University as an assistant professor in 2011.  He moved to Stony Brook University as the Institute for Advanced Computational Science Endowed Professor of Chemistry in August 2020.  Ben has over 70 scientific publications.  His work was recognized by the 2017 Journal of Physical Chemistry A/PHYS Lectureship and the 2017 OpenEye Outstanding Junior Faculty Award in Computational Chemistry.