Event

Title "What did the metal know, and when did she know it? Ultrafast XUV 

spectroscopy reveals short-lived states in transition metal complexes 

and organohalide perovskites"

Josh Vura-Weis

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.

inquiries rvargas@sas.upenn.edu

Host Dr. Subotnik