Abstract：

　　In the near-perfect vacuum of the Inter-Stellar Medium (ISM) a wide variety of complex organic molecules, including pre-biotics, are observed, which should have been frozen onto surfaces of dust grains at their thermal temperature of ~15K [1].  Complex molecules are most likely formed when mixtures of solid-phase small molecules covering dust grains are exposed to bond-breaking vacuum ultraviolet radiation [2].  How do the new molecules get free of the ice mantles?  Despite the importance and apparent simplicity of this question, very little information pertaining to the molecular-scale mechanism of desorption from molecular ice is available, due to the experimental and theoretical complexity of condensed phase dynamics [3].   In this talk, special aspects [4] of the velocity map imaging [5] method, which has revolutionized gas-phase research [6], will be exploited to reveal the mechanism for VUV photon induced desorption of the fragile molecule ozone formed by photochemistry at a molecular oxygen surface.  Relevance of our method to astrochemical conditions, and to studies of other molecular ice systems will be discussed.

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