UV photoprocessing of icy dust grains induces desorption and dissociation. Photodesorption offers a non-thermal mechanism that is relevant to explain the gas-to-ice balance observed for small molecules. Photodissociation produces radical species that desorb from or diffuse over the ice surface, reacting with other species and participating in solid state reactions that offer pathways towards molecular complexity. Studies of these fundamental processes in the past have been performed using broadband (microwave driven H2 discharge) lamps peaking around 10.2 eV (Ly-a). Using also monochromatic vacuum UV light, available from the beamline DESIRS at the synchrotron facility SOLEIL, it is also possible to resonantly excite specific solid state processes. This provides detailed and valuable information on the underlying molecular mechanisms. This talk reviews recent experiments that focus on wavelength dependent photodesorption of CO, N2, O2, and water. It discusses the potential role of co-desorption, illustrates the role water plays in the ice upon vacuum UV irradiation, and presents the idea of a (partially) wavelength dependent chemistry in space.ReferencesE.C. Fayolle et al. Astrophys. J. Lett. 739 (2011) L36; M. Bertin et al. Phys. Chem. Chem. Phys. 14 (2012) 9929; E.C. Fayolle et al. Astron. Astrophys., submitted; K.I. Oberg et al. ApJ 693 (2009) 1209; K.I. Oberg et al. Astron. Astrophys. 504 (2009) 891.

UV photoprocessing of interstellar ice analogs

246th National Meeting (2013)

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