Speaker: Christine Joblin, Université de Toulouse, UPS-OMP, IRAP, Toulouse, France

Title: Large carbonaceous molecules in space: observational and laboratory insights

Abstract: The presence of large free-flying carbonaceous molecules in interstellar space was proposedalmost 30 years ago to account for a series of IR emission bands, called the Aromatic Infrared Bands (AIBs); emission from these bands is triggered by the absorption of UV photons from stars. On the basis of spectral agreement and the emission mechanism, polycyclic aromatic hydrocarbons (PAHs) are considered as the best carriers for these features. They are also candidates to account for the famous diffuse interstellar bands, some absorption features that mostlyfall in the visible range.

The identification of interstellar PAHs has motivated a large number of spectroscopic studies in the laboratory. Although the presence of fullerene C₆₀ in the gas-phase was recently demonstrated, not a single individual PAH species has been identified so far. PAHs represent a large class of species and these studies have to be guided by a better understanding on where interstellar PAHs come from and how they evolve due to environmental conditions: ionisation and dissociation upon UV irradiation, interactions with electrons, gas and dust.

In this seminar, I will present our approach that combines astronomical observations, laboratory studies and modelling; which motivates a joint effort between astrophysicists, physicists and chemists. I will describe our experiments using the cold ion trap set-up, PIRENEA, that was specifically designed to study PAH-related species in conditions that approach those found in interstellar space. I will discuss our view on the chemical evolution ofinterstellar PAHs in UV-irradiated environments and show how this view can be rationalized by our experimental and modelling studies.

Coffee/tea and bread rolls will be served from 10:00