AstroPAH: The search for the missing deuterium

"The missing deuterium problem" sounds like it could be a Sherlock Holmes novel, but it is a scientific question in the field of astrochemistry. Ever since the big bang deuterium has been consumed by stars to produce heavier elements such as those contained in the device you are currently reading this on and the carbon that you consist of.

However, some of it has gone missing. Current observations of deuterium levels in the interstellar medium measure less deuterium than expected based on stellar evolution (the deuterium that has been consumed by stars). One hypothesis is that this is caused by the deuterium being locked up in bigger molecules, possibly Polycyclic Aromatic Hydrocarbons (PAHS), which are not directly observed as deuterium. Astronomical observations have shown that deuterated PAHs are present in space, and experiments provide evidence that this is caused by scrambling which ensures that once a deuterium is added to the PAH, it is most likely to lose a hydrogen and stay deuterated, storing the deuterium away.

My work focuses on developping a Kinetic Monte Carlo (KMC) simulator that can evaluate these scrambling and dissociation pathways to explain the mechanism behind this process. PAHMC is a Python implementation initially developed by Emma Carels and expanded by myself. This has shown interesting results already but the simulator is very computationally expensive and the preparation of the input data for the simulator is very labour intensive. For my Master's Thesis I will continue to work on this project with the aims of developing a new Graph-based Kinetic Monte Carlo simulator in Julia to solve issues with the current simulator, and investigate opportunities for automating input data preparation.