Ultrafast isomerization dynamics of conformer-selected aligned gas-phase molecules

Complex molecules exhibit multiple conformers (structural isomers), even under the cold conditions (~1 K) of a molecular beam. Since the first observation of multiple conformers in the 1980s – for the essential amino acid tryptophan (C11H12N2O2) – the structures of conformers of many molecules have been investigated using advanced spectroscopic techniques. However, while a lot of data on the local minima on the global energy landscape has been collected, little is known on the connecting valleys and transition states on the potential energy landscape, mainly because ultrafast dynamics experiments would average over the effects for the various conformers present in the sample. Moreover, due to the complexity of these molecules, there is usually not enough prior knowledge to unravel the details of (UV/VIS) spectroscopic pump-probe experiments. We have developed methods to spatially separate structural isomers of neutral molecules, using inhomogeneous electric fields, according to their electric dipole moment to mass ratio. These methods are quantum-state selective and very polar samples are created. This allows us to strongly align and orient these samples. We also separate the molecules from the atomic seed gas, avoiding background signals from the atoms which often obscure the molecular signals.

The goal of this project is to create strongly 3D-aligned and oriented samples of individual conformers in order to investigate their ultrafast inter-conversion dynamics using coherent X-ray diffractive imaging, time-resolved X-ray spectroscopy, and X-ray-induced molecular-frame photoelectron angular distributions. Moreover, these complex molecules with many structural isomers are also prototypical versatile molecular switches. A detailed screening of various molecular systems could open new avenues toward applicable molecular switches and especially toward multi-state switches – corresponding to molecules with multiple (> 2) accessible structural isomers.


The aim of this project is to elucidate the intrinsic inter-conversion dynamics of controlled complex molecules.


Within this project the same class of molecules/same molecule will be investigated as in projects P2 and P3. Experiments will be performed at partner institutes, such as spectroscopy for electronic structure information with high-order harmonic photon source at HZB/MBI; molecular-frame photoelectron-angular distributions with synchrotron source (Petra III/BESSY II) and HHG sources (MBI). Complementary information on the geometric structure will be gained in the gas phase (this project) and on the electronic structure (P2, P3) and influence of environments (this project, P2, P3). There will be theoretical support from P10 and methodological synergy with P4, P5 and P8.



Thomas Kierspel


Prof. Dr. J. Küpper

kooptierte Mitarbeiter

Sebastian Trippel, CFEL-CMI


noch nicht festgelegt