Abstract
We present time-resolved UV-pump x-ray probe Auger spectra on 2-thiouracil. A UV induced shift towards higher kinetic energies is observed in the sulfur 2p Auger decay. The difference spectra of pumped and unpumped Auger electrons exhibit ultrafast dynamics in the shift amplitude, in which three phases can be recognized: in the first 100 fs, a shift towards higher kinetic energies is observed, followed by a 400 fs shift back to lower kinetic energies and a 1 ps shift again to higher kinetic energies. We use a simple Coulomb-model, aided by quantum chemical calculations of potential energy states, to deduce a C-S bond expansion within the first 100 fs. The bond elongation triggers internal conversion from the photoexcited S2 to the S1 state, and based on timescales the subsequent dynamics can be interpreted in terms of S1 nuclear relaxation and S1-triplet internal conversion.
Thomas Wolf
Staff Scientist
My research is focused on discovering structure-function relationships in ultrafast photochemistry to better understand and eventually control this type of reactions.