Electron driven reactions in complexes embedded in superfluid helium droplets

A thesis submitted to the University of Innsbruck for the doctor degree in Natural Sciences, Physics and New University of Lisbon for the doctor degree in Physics, Atomic and Molecular Physics

The research work performed under the course of this thesis at the Nano-Bio Physics Group of the Institute of Ion Physics and Applied Physics, University of Innsbruck, deals exclusively with electron driven reactions in complexes embedded in helium nanodroplets. Helium nanodroplets provide a special and exotical environment that is not reachable with other techniques. The cold environment of the helium nanodroplets (0.38K), is a perfect tool to study complex systems in their ro-vibrational ground state. Dopants are added to the helium nanodroplets in a pick up cell allowing to control accurately the growing of clusters‘ size in helium droplets. The research activities described in this thesis cover the interaction of low and intermediate energies (0 – 100 eV) electrons with a wide range of simple and complex molecules in a very cold environment. Electron impact ionisation and free electron attachment to different systems were studied. Different halogenated molecules were used to study the size of solvated cations and anions. Clusters of the rare gas argon were also investigated and compared with argon cluster ions formed upon electron impact of pure neutral argon clusters. Several biomolecules and molecules with biological interest have been studied, these including: some amino acids as Glycine, L-alanine and L-serine embedded in helium nanodroplets. Several features were assigned as helium solvation and fragmentation. In the case of L-serine, a magic octamer S8H+ cluster was observed and identified. Free electron attachment experiments to L-serine shows very rich chemistry observed here for the first time in amino acids embedded in helium nanodroplets. Positively and negatively charged ions from He nanodroplets doped with acetic acid were also investigated. Chemistry triggered by low energy electrons was discuss and compared with previous studies especially with single, gas phase molecules. Preliminary studies on L-valine show strong indication for peptide bond formation at cold temperatures and triggered by low electron energy, close to 0 eV.