title: Reaction kinetics and isotope effect of water formation by the surface reaction of solid H2O2 with H atoms at low temperatures.
abstract: We performed laboratory experiments on the formation of water and its isotopologues by surface reactions of hydrogen peroxide (H2O2) with hydrogen (H) atoms and their deuterated counterparts (D2O2, D) at 10-30 K. High-purity H2O2 (> 95%) was prepared in situ by the codeposition of molecular oxygen and H atoms at relatively high temperatures (45-50 K). We determined that the high-purity H2O2 solid reacts with both H and deuterium (D) atoms at 10-30 K despite the large activation barriers (-2000 K). Moreover, the reaction rate for H atoms is approximately 45 times faster than that for D atoms at 15 K. Thus, the observed large isotope effect indicates that these reactions occurred through quantum tunneling. We propose that the observed HDO/H2O ratio in molecular clouds might be a good tool for the estimation of the atomic D/H ratio in those environments.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Oba
authors.forename: Kazuya
authors.initials: K
authors.lastname: Osaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Watanabe
authors.forename: Takeshi
authors.initials: T
authors.lastname: Chigai
authors.forename: Akira
authors.initials: A
authors.lastname: Kouchi