VUV photochemistry of PAHs trapped in interstellar water ice

¹ Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
² NASA-Ames Research Center, Space Science Division, Mail Stop 245-6, Moffett Field, CA 94035, USA

Abstract

The mid-infrared emission of Polycyclic Aromatic Hydrocarbons is found in many phases of the interstellar medium. Towards cold dense clouds, however, the emission is heavily quenched. In these regions molecules are found to efficiently freeze-out on interstellar grains forming thin layers of ices. PAHs are highly non-volatile molecules and are also expected to freeze-out. PAHs trapped in interstellar ices are likely to participate in the overall chemistry, leading to the formation of cations and complex molecules in the solid-state. The work presented here aims to experimentally study the chemical reactions that PAHs undergo upon vacuum ultraviolet irradiation when trapped in interstellar H₂O ice.