Photochemical reaction processes during vacuum-ultraviolet irradiation of water ice

The photoprocesses of water ice play an important role in regions of interstellar space, such as interstellar clouds and outer solar systems. Vacuum-ultraviolet absorption of water ice leads to dissociation of water molecules, and allows subsequent reactions of photoproducts on/in ice. There have been many laboratory studies that identify photoproducts and estimate product yields, reaction mechanisms and energy partitioning in the reaction products. Among them, the experimental approaches aimed at understanding the photoprocesses on the water ice surface can give new insight into the chemical reaction network in interstellar space. In this review, we focus on photochemical processes of water ice relevant to surface astrochemistry following vacuum-ultraviolet photolysis of water ice at a low temperature from a surface reaction dynamics’ point of view.

► A comprehensive reaction processes following vacuum-ultraviolet photolysis of water ice is described. ► Reaction mechanisms are studied from a surface reaction dynamics’ point of view. ► Hot molecules are photodesorbed. ► Experimental studies on vacuum-ultraviolet photochemistry of low temperature water ice are briefly reviewed. ► Surface astrochemistry in regions of interstellar space is discussed.