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PhD Thesis: Energetic processing of complex molecules in the gas phase
  Thesis defense

Wednesday 31 January 2018
from 13:00 to 17:00
at FB52
Speaker : Michael Wolf (Stockholm University, Department of Physics)
Abstract : Collisions between molecules and gas phase targets often lead to various intriguing processes. Such collisions may induce fragmentation of molecules that can be divided into different subsets depending on the projectile, target, and collision energy. One major part of the present research is the exploration of astrophysical relevant collision mechanisms. In collisions between polycyclic aromatic hydrocarbon (PAH) molecules or fullerenes with, for example, helium, nuclear stopping can lead to the prompt knockout of a carbon atom from the molecule. Such a vacancy in the molecular carbon backbone can be highly reactive, and lead to the formation of larger molecules. The energy dependencies of such processes are important for the understanding of astrochemical molecular growth processes, which in turn may lead to the formation of larger and more complex molecules in space. In addition, hydrogenation of PAHs changes their structures and internal properties, including their resistance against fragmentation. To better understand the effects of hydrogenation on the fragmentation of PAHs, low energy photofragmentation experiments are presented along with the collision experiments, and a detailed comparison is made between the effects of these different types of energy transfer processes. Besides astrophysically relevant research, studies on the response of biomolecules to collisions with gas phase targets are presented. Here, the energy dependence for formation of the protonated n-butyl β-ionone Schiff base through electrocyclization of the protonated n-butylamine Schiff base of all-trans-retinal in collisions is presented. The latter is a model compound for all-trans-retinal, the chromophore of the light sensitive opsin proteins, and such studies are essential for the understanding of the operation of mammal vision. While our collision studies are very successful, they are sometimes also limited by the experimental timescale. Therefore, we have constructed an experimental setup for ion storage and fragmentation analysis. The goal of this new experiment is to store internally hot fragments to investigate their behavior on extended timescales and as functions of internal excitation energies. Stockholm 2018

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