UV-PHOTOSTIMULATED PRODUCTION OF DEUTERIUM MOLECULES FROM AMORPHOUS D2O ICE AT 12K Naoki WATANABE, Toshikazu HORII, and Akira KOUCHI Institute of Low Temperature Science, Hokkaido University,Sapporo, Hokkaido 060-0819, Japan Production of D2 molecules was observed in vuv-photostimulated reaction of the amorphous D2O ice. D2 yields were measured by a thermal desorption method after the irradiation of 172nm and 126nm photons from excimer lamps onto the thin amorphous ice at 12K. The yields show saturated at long irradiation time. Photon-flux and -energy dependence of the yields implies that the D2-formation reaction is one-photon process and proceeds via the first electronic excited state of condensed heavy water.