Ionization Influence on the Dynamics of Simple Organic Molecules

Sammanfattning: This licentiate thesis is devoted to the investigation of how bonding in simple organic molecules are affected by X-ray beam irradiation. The investigation targets molecules with three carbons as their main-chain structure. The stability of the bonds under ionization are simulated using the SIESTA package. SIESTA is a simulation package that provides molecular dynamics simulations based on density functional theory within the Born-Oppenheimer approximation. The aim of this study is to understand statistically the damaging process and selectivity among different types of bond. As the first targets, 4 hydrocarbons are investigated. They are propane, propene, propyne and propadiene, which have different combinations of single, double and triple bonds as their main-chain structures. Depending on the combinations, the structures can be either symmetric around the central atom or not. The structure of the symmetric molecules propane and propadiene are  stable until charge +3. In contrast, the asymmetric molecules propene and propyne, the  main-chain bonds show a tendency towards a more similar bond-distance as the level of ionization increases. In addition, hydrogens relocation occurs in propene, leading to a symmetric structure. Secondly, the bond fluctuations are investigated among 4 types of three-carbon molecules which have functional parts. Alcohol and carboxyl groups molecules show the stable bond integrities at charging 0 to +2. On the other hand, the carbon-carbon bonds in molecules with  acetyl and ketone groups are broken by ionization. Comparing the 8 kinds of bond breaking processes in these molecules, this statistical study gives an insight to organic molecules bonding systems.