Topic: What did the metals know, and when did they know it? Ultrafast XUV spectroscopy reveals short-lived states in transition metal complexes and organohalide perovskites

Speaker: Professor Joshua Vura-Weis - University of Illinois at Urbana-Champaign

Host: Professor Jim McCusker

Date: Thursday, November 21, 2019

Time: 4:10 PM

Location: 136 CEM

More Information:

What did the metals know, and when did they know it? 

Ultrafast XUV spectroscopy reveals short-lived states in transition metal complexes and organohalide perovskites

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 M_2,3-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.