STSM by Helena Levola, Department of Physics and Astronomy, University of Turku (FI) with Fernando Martín, Universidad Autónoma de Madrid (ES)hele-logo
On October 20th, 2014 (5 days)

Theoretical and experimental studies on ionization induced fragmentation of thiophene and L-α-alanine

Radiation induced fragmentation of biomolecules is a widely studied subject due its importance to medical and industrial applications. In addition, these studies provide information about the properties of the molecules as well as quantum mechanical processes involved. Therefore, understanding the phenomena responsible for the radiation damage of biomolecules is of interdisciplinary interest for physicists, chemists, and materials scientists from the basic science point of view.

In this study, we used electron-ion-ion-coincidence measurements to investigate the fragmentation of two organic molecules – L-α-alanine and thiophene – after ionizing them with soft x-ray radiation. The results were compared with theoretical calculations. It was observed that alanine has many different fragmentation pathways, some of them involving multiple dissociation steps. Thiophene, on the other hand, dissociates mainly into two fragments (see figure below).

During this STSM, theoreticians from Universidad Autónoma de Madrid met with the experimentalists of University of Turku to compare their results on the fragmentation of these molecules. The primary purpose of this STSM was to develop a consistent interpretation of the molecular dynamics in medium-sized molecules such as thiophene and alanine that has a common foundation on both the experimental findings and the computational results. To this end, intensive discussions and reviews of both the experimental and theoretical results were held during the STSM, with intervening refinements of the analysis. The results will be published in a joint article about the fragmentation of thiophene, including analysis of the effect of internal energy on the fragmentation. The theoretical analysis of alanine is still to be continued and a joint article about alanine’s fragmentation will be written once the analysis is completed.

hele-imgPEPIPICO maps of alanine (left) and thiophene (right) with the main fragmentation pathways marked.

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