Studying ultrafast processes in organic molecules: From UV to XUV and combining experiment with theory
Date | Mo, 06.01.2014 | |
Time | 16.45 | |
Speaker | Thomas Wolf, PULSE Institute, Stanford University and SLAC National Accelerator Laboratory, USA | |
Location | ETH Zurich, Hönggerberg Campus, HPF G6 | |
Program | What happens to small polyenes between photoexcitation and relaxation from the photoexcited state via a conical intersection? Can we observe such processes? In the first part of my talk I want to follow these questions by presenting the results of a combined experimental and theoretical investigation of the molecule hexamethylcyclopentadiene employing time-resolved photoelectron spectroscopy (TRPES) and ab initio multiple spawning simulations on the MS-MR-CASPT2 level of theory. In this molecule, we investigate two general phenomena in excited state dynamics of small polyenes, a seeming spectral shift in time zero of TRPES spectra and an “induction time” prior to excited state depopulation in dynamics simulations. By applying a stepladder-type model, we can connect both phenomena to localization of the dynamics in a specific molecular degree of freedom. This finding seems to be of general value for excited state dynamics of polyenes. In the second part of my talk, I’m going to show first results from my new group at Stanford University. We are currently completing a time-resolved photoelectron and photoion spectrometer, where we can excite molecules with the second and third harmonic and probe them with high harmonics of our Ti:Sapphire laser system. As a test sample we are using the organic dye perylene. I’m going to show first transient data from excitation at 400 nm and ionization with the 9th harmonic. |