Small quantum systems research on trans-cis isomerization in molecular photoswitches at the European XFEL

Photoisomerization plays a crucial role in many biological and technological applications. However, the precise mechanism(s) in which molecular photoswitches such as azobenzene undergo photoisomerization is still debated. No previous experimental investigation has revealed the femtosecond nuclear dynamics of photoisomerization.
Kasra Amini from Max Born Institute in Berlin and his team use ultraintense and ultrashort European XFEL pulses at the Small Quantum Systems instrument (SQS) to generate high charge states, ensuring instantaneous charge-up and Coulomb explosion of the molecule. Multicoincidence data revealed the molecular structure from the measured emission direction of fragment ions. Snapshots at different pump-probe delays revealed the photoisomerization mechanisms.