title: Reaction Sites of CO on Size-Selected Silicon Oxide Cluster Anions: A Model Study of Chemistry in the Interstellar Environment.
abstract: We present reactions of size-selected free silicon oxide cluster anions, SinOm(-) (n = 3-7, 2n - 1 ≤ m ≤ 2n + 2), with a CO gas. Adsorption of CO on SinOm(-) is observed as a major reaction channel. The rate constant of the adsorption reaction is high for the oxygen-rich clusters with m ≥ 2n + 1, whereas almost no reaction product is observed for m ≤ 2n. DFT calculations revealed that a pair of dangling O atoms on 4-fold-coordinated Si atoms plays a key role, which is the adsorption site of CO on SinOm(-). Bond formation between CO and one of the dangling O atoms is associated with electron transfer from the CO molecule to the other dangling O atom. The present findings give molecular-level insights into adsorption of CO molecules on silicates in the interstellar environment.
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Arakawa
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamane
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Terasaki