2014ApJ...782...63B -
Astrophys. J., 782, 63 (2014/February-3)
Experimental studies on the formation of D2 O and D2O2by implantation of energetic D+ ions into oxygen ices.
BENNETT C.J., ENNIS C.P. and KAISER R.I.
Abstract (from CDS):
The formation of water (H2O) in the interstellar medium is intrinsically linked to grain-surface chemistry; thought to involve reactions between atomic (or molecular) hydrogen with atomic oxygen (O), molecular oxygen (O2), and ozone (O3). Laboratory precedent suggests that H2 O is produced efficiently when O2ices are exposed to H atoms (∼100 K). This leads to the sequential generation of the hydroxyperoxyl radical (HO2), then hydrogen peroxide (H2O2), and finally H2O and a hydroxyl radical (OH); despite a barrier of ∼2300 K for the last step. Recent detection of the four involved species toward ρ Oph A supports this general scenario; however, the precise formation mechanism remains undetermined. Here, solid O2ice held at 12 K is exposed to a monoenergetic beam of 5 keV D+ ions. Products formed during the irradiation period are monitored through FTIR spectroscopy. O3is observed through seven archetypal absorptions. Three additional bands found at 2583, 2707, and 1195/cm correspond to matrix isolated DO2(ν1) and D2O2(ν1, ν5), and D2 O (ν2), respectively. During subsequent warming, the O2ice sublimates, revealing a broad band at 2472/cm characteristic of amorphous D2O (ν1, ν3). Sublimating D2, D2O, D2O2, and O3products were confirmed through their subsequent detection via quadrupole mass spectrometry. Reaction schemes based on both thermally accessible and suprathermally induced chemistries were developed to fit the observed temporal profiles are used to elucidate possible reaction pathways for the formation of D2-water. Several alternative schemes to the hydrogenation pathway (O2⟶HO2⟶H2O2⟶H2O) were identified; their astrophysical implications are briefly discussed.
Abstract Copyright:
∼
Journal keyword(s):
astrochemistry - cosmic rays - ISM: molecules - methods: laboratory: solid state - molecular processes - radiation mechanisms: non-thermal
Simbad objects:
4
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2014ApJ...782...63B and select 'bookmark this link' or equivalent in the popup menu