On October 17, 2025, Klara Raspe, PhD student in the Collaborative Research Centre LiMatI, successfully defended her doctoral thesis.
In her dissertation, Klara Raspe investigated how matter on the nanometer scale responds to strong laser fields. When ultrashort laser pulses interact with clusters consisting of a few to several thousand atoms, a so-called nanoplasma is formed — a highly dynamic state of matter governed by the interaction between electrons, ions, and the laser field.
To gain a deeper understanding of the underlying processes, Ms. Raspe advanced experimental techniques that allow a comprehensive characterization of the emission of fast electrons and highly charged, energetic ions resulting from the Coulomb explosion of the nanoplasma.
In experiments with argon clusters, she demonstrated the transition from surface- to volume-driven expansion by employing a laser-intensity-selective analysis of the measurements. By preparing targets in an ion trap, she succeeded for the first time in studying the nanoplasma dynamics of mass-selected metal clusters. The results reveal, among other findings, how increasing cluster size leads to a transition from a partially to a fully ionized nanoplasma.
Using pump–probe techniques, Ms. Raspe further showed that the measured energy spectra provide insights into the original structural properties of the clusters. Her work impressively demonstrates how the electron dynamics of a nanoplasma can be controlled through plasmon-enhanced energy absorption.
The Collaborative Research Center LiMatI warmly congratulates Klara Raspe on her outstanding doctoral achievement and wishes her all the best for her future scientific career.