Speaker
Description
The presence of interstellar polycyclic aromatic hydrocarbons (PAHs) is inferred from the widespread mid-infrared (IR) emission bands that are observed at 3.3, 6.2, 7.7, 8.6 and 11.2 μm. [1] This IR radiation is emitted as the PAHs cascade down to the ground state after they have been excited by interstellar (vacuum) ultraviolet radiation. [2] PAHs have been observed towards a large number of galactic and extragalactic sources and it has been derived that they constitute up to 15% of the total cosmic carbon budget.
Energetic processing of interstellar polyaromatics may result in ionization and/or dissociation. It has been hypothesized that this chemical evolution is reflected in subtle changes in the interstellar mid-IR emission bands. Observational and laboratory data suggest that dissociation of large interstellar polyaromatics eventually leads to fullerene formation. [3,4] The underlying chemical mechanisms involved in the dissociation of aromatics are not yet understood.
Our group characterizes the dissociation of polyaromatics by means of vacuum ultraviolet synchrotron radiation and mid-infrared free electron laser radiation. By combining these techniques with quantum chemical computations we obtain insight into the isomerization and dissociation at a molecular level of detail. [5-7] I will review our most recent results and will emphasize their importance in light of astronomical observations.
1. Tielens, A. in Annu. Rev. Astron. Astr. Vol. 46 289-337.
2. Allamandola, L. J., Tielens, A. & Barker, J. R. Astrophys. J. Suppl. Ser, 71, 733-775, doi:10.1086/191396 (1989).
3. Berne, O. & Tielens, A. Proc. Natl. Acad. Sci. 109, 401-406, doi:10.1073/pnas.1114207108 (2012).
4. Zhen, J., Castellanos, P., Paardekooper, D. M., Linnartz, H. & Tielens, A. G. G. M. Astrophys. J. Lett. 797, doi:10.1088/2041-8205/797/2/l30 (2014).
5. Bouwman, J., Sztáray, B., Oomens, J., Hemberger, P. & Bodi, A. J. Phys. Chem. A 119, 1127-1136, doi:10.1021/jp5121993 (2015).
6. Bouwman, J., de Haas, A. J. & Oomens, J. Chem. Commun. 52, 2636-2638, doi:10.1039/C5CC10090A (2016).
7. de Haas, A. J., Oomens, J. & Bouwman, J. Phys. Chem. Chem. Phys. 19, 2974-2980, doi:10.1039/C6CP08349H (2017).
