CaSTL Seminar Series: Josh Vura-Weis

Abstract: X-ray absorption near edge spectroscopy (XANES or NEXAFS) is a powerful technique for electronic structure determination.  However, widespread use of XANES is limited by the need for synchrotron light sources with tunable x-ray energy. Recent developments in extreme ultraviolet (XUV) light sources using the laser-based technique of high-harmonic generation have enabled core-level spectroscopy to be performed on femtosecond to attosecond timescales.  We have extended the scope of tabletop XUV spectroscopy and demonstrated that M2,3-edge XANES, corresponding to 3p→3d transitions, can reliably measure the electronic structure of first-row transition metal coordination complexes with femtosecond time resolution.  We use this ability to track the excited-state relaxation pathways of photocatalysts and spin crossover complexes.  In semiconductors such as CH3NH3PbI3, distinct signals are observed for photoinduced electrons and holes, allowing the dynamics of each carrier to be tracked independently.  This work establishes extreme ultraviolet spectroscopy as a useful tool for mainstream research in inorganic, organometallic, and materials chemistry.

Bio: Professor Vura-Weis received his B.S. degree in Chemistry from Stanford University in 1999, then worked for several years as a software developer.  The call of the lab beckoned, so he interned with Prof. Ed Solomon for a year to learn how electronic structure calculations can complement sensitive experimental techniques.  He then moved to Northwestern University, where he worked with Profs. Mike Wasielewski and Mark Ratner as an NSF Graduate Research Fellow.  After receiving his Ph.D. in 2009 he moved to Prof Steve Leone’s lab at UC Berkeley as an NSF ACC-F Postdoctoral Fellow.  In 2012 he was awarded the ACS Physical Division Postdoctoral Research Award.  He joined the University of Illinois faculty as an Assistant Professor in Fall 2013.  His group uses advanced laser techniques to study the excited-state electronic and vibrational dynamics of inorganic and organometallic systems.  Since arriving at UIUC, he has been awarded the NSF CAREER, AFOSR Young Investigator, ACS PRF Doctoral New Investigator, and Sloan Fellowship awards.