Institution: | * Huygens Astrophysics Laboratory, University of Leiden, Niels, Bohrweg 2, 2300 R, Leiden, The Netherlands ** Service d'Aeronomie, BP 3, 91731, Verrieres-le-Buisson, France *** ESTEC-SAI, Astrophysics Division, 2200 AG, Noordwijk, The Netherlands † Groupe de Physique des Solides, Universite Paris VII, Tour 23, 2 Place Jussieu, 75251, Paris, France |
Abstract: | In various models of interstellar grain chemistry, solid O2 is formed by accretion as well as by surface reactions on grains. In dense molecular cloud models, at a later stage of the evolution, the O2 molecule may become a substantial grain mantle constituent. Since IR dipole vibrational transitions for the homonuclear diatomic molecule O2 are forbidden, the abundance of this potentially important grain mantle component can not be determined. However, embedded in a dirty ice matrix, the fundamental vibration of O2 at 1550 cm−1 becomes observable at 10 K, due to interactions with surrounding molecules, which break the symmetry of molecular oxygen. This process might be applicable for the dust mantle environment of interstellar grains. We have studied the role of solid O2 and O3 in astrophysically relevant ice mixtures and discuss the possible detection of solid O2 and its major photolysis product O3 in interstellar grains, in dense molecular clouds. Both molecules represent a specific target to be observed by the ISO satellite in the near future. |