LAMAp/LERMA, UMR 8112 du CNRS, Observatoire de Paris
Université de Cergy-Pontoise, FRANCE
Water formation through O2+D pathway on cold silicates
and amorphous water surfaces of interstellar interest
Marco. Minissale, François. Dulieu, Emanuele. Congiu, Saoud Baouche.
Giulio. Manicò, Mario. Accolla, Valerio. Pirronello Dipartimento di Fisica ed Astronomia Università degli Studi di Catania, ITALY Dipartimento di Scienze Applicate – Università Parthenope Napoli, ITALY
Henda. Chaabouni
119 th International Vacuum Congress. Paris, 11/09/2013
2
OutlineBackground : Water in the interstellar medium
Experiments
Results:
1- Reflection Absorption Infrared Spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD) analysis of water formation through O2+D pathway on:
- Silicate surfaces - Solid water ices
2- Chemical desorption process of water product
3- Kinetic model for the O2+D reaction during thermal processing
Conclusions Cost meeting, 2 nd- 5 th April 2013
The Chemical Cosmos, 2 nd- 5 th April 2013
3
Detected in the ISM and outside of our Solar System as Gas, and Ice.
Abundant in the Cosmos and the Solar System (planets, comets…).
Star formation region
Gas H2O: 3 × 10−8
Gas H2O: 10−7−10−6
Background Water in in the ISM
Tgas= 50-100K
Tdust= 10 K
Tdust =Tgas= 10 K
Tgas= 10 K
4
Background
Miyauchi et al. Chem.Phys.Lett (2008)
Ioppolo et al. ApJ (2007), PCCP (2010)
Cuppen et al. PCCP (2010)
Previous studies
H + O OH
H + OH H2O
H + O2 HO2
H + HO2 H2O2
H + H2O2 H2O + OH
H + OH H2O
H + O3 O2 + OH
H + O2 HO2
H + HO2 H2O2
H + H2O2 H2O +OH
H+ OH H2O
H2+OH H2O +H
Efficient formation of H2O and H2O2 ices at 10 K-28 K in the Multi-layer regime
10- 30 layers of solid O2 ice
19 th International Vacuum Congress.
Gas-surface reactions for water formation in the ISM
(JAPAN)
(LEIDEN)
H2O2 / H2O > 1
Paris, 11/09/2013
(CERGY + LEIDEN)
(CERGY +USA)
Tielens & Hagen (1982)
5
The present work
O2+D pathway in the Sub-monolayer regime Amorphous SILICATE Amorphous H2O water ices
(~100 nm) film of Olivine (MgxFe 1−x)2SiO4 Thickness~10 Monolayers
Tsurface =10 K
(Bare dust) (Icy Mantle)
0<x<1
19 th International Vacuum Congress.
Paris, 11/09/2013
QMS
Micro-wave discharge
D diss (D2)=70 % Tgas=300 K=3.0×1012 molecules.cm-2.s-1
O2 (≤ 1 ML)
Temperature Programmed Desorption (TPD)
Tsurface=10 K- 220 K
Heating rate = 0.04K/s
(Gas phase detection) Cryocooler 5 K- 350 K
FT-IR
Spectrometer Bruker tensor 27
Reflection Absorption Infra-Red Spectroscopy (RAIRS)
(Insitu Solid phase detection)
MIR: (4000- 600) cm-1
Cryocooler 5 K- 350 K
Experiments
Sample (siliacte, water)Tsurface= 10 K
619 th International Vacuum Congress.
QMS
Triply differentially pumped beam-lines
FORMOLISM set-up, (LERMA/LAMAP, Cergy)
(MCT) Detector
10-11 mbar
83°
Quadrupole Mass Spectrometer QMS
UHV chamber
Paris, 11/09/2013
Result 1: Water formation on amorphous Silicates
Chaabouni et al. J. Chem. Phys (2012)719 th International Vacuum Congress.
RAIR specrta
n (-OD)
Successive deposition on silicate at 10K
1 min (0.18 ML) O2 + 4 min (0.65 ML) D-atoms
(1 O2 + 4 D 2 D2O )
Low surface coverages
RAIRS
Silicate at 10 K
In
tegr
ated
are
as
a)b)
c)d)e)
f)
g)(2 6)n
D2O / D2O2 5
D2O2 / D2O < 1
Sub-monolayer regime
Paris, 11/09/2013
~ 1 ML D2O ice
Inte
grat
ed a
reas
O2 exposure dose (ML)
(D2O + D2O2) at 2404 cm-1
D2O2 at 2107 cm-1
0 1 2 3 4 5 6 7 8 9 0.200
0.150
0.100
0.050
0.00
Result 2: Effect of the substrate on water formation
1 ML (O2) + 24 min (D) / Silicate surface at 10 K 1 ML (O2) + 24 min (D) / Porous ASW H2O ice surface at 10 K 1 ML (O2) + 24 min (D) / Non-porous ASW H2O ice surface (prépared at 120 K, cooled to10K)
~ 18 % (D2O) ~ 50 % (D2O) ~ 68 % (D2O)
Low formation yield of D2O water ice on Silicate at 10K
Exposure
819 th International Vacuum Congress.
D2O >> D2O2
(TPD) , Ts= [10 K – 220 K](RAIRS) , Ts=10 K
D2O
~ 5 % (O2) ~ 18 % (O2) ~ 2 % (O2)
Paris, 11/09/2013
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RESULTS 3: The chemical desorption of water molecules
Chemical desorption of D2O moleculesupon formation on the surface at 10 K
1- Substrate : Silicate2- Exposure of 1 ML of O2 on the surface
3- QMS placed close to the surface
4- Monitoring with the QMS the species desorbing into the gas phase during the exposure of D-atoms on O2 ice at 10 K.
Surface at 10 K
QMS
D
1 ML O2
D2 , D2O gasD2O gas
19 th International Vacuum Congress. Paris, 11/09/2013
Dulieu et al, Sci.Rep . 2013
Reactions routes for water formationSilicates
Ts =10 K
D2O water formation through the barrierless reaction
D + OD D2O
H= -1600 meV
D + OD D2O
Ebarrier=2000 K Chemical desorption of D2O by the exothermic reaction
H= -3700 meV
H=- 3100 meV
H= - 5200 meV 2 D
H= - 5200 meV
OD+OD
D
H= - 2400 meV H= - 4900 meV
Eley-Readel mechanism
1019 th International Vacuum Congress.
Dulieu et al, Sci.Rep . (2013)
Paris, 11/09/2013
Chaabouni et al. J. Chem. Phys (2012)
Cuppen et al. PCCP (2010)
Thermal desorption Kinetic O2+D reaction on Silicates
Exposure 1 ML (O2 ) + X (0 min) of D atoms (6 min) (12 min) (24 min)
(35 min)
1 ML O2+ 6 min D
1 ML O2+9 min
1 ML O2+12 min D
1 ML O2+24 min D
1 ML O2+ 9 min
1 ML O2+12 min D
1 ML O2+24min D
(M 36)
19 th International Vacuum Congress.
1 ML O2+ 6 min D
1 ML O2+ 12 min
1 ML O2+24min D
1 ML O2+35 min D
1 ML O2+ 12 min
1 ML O2+24 min D
1 ML O2+35 min D
1 ML O2+ 6 min D(M 32) (M 20)
(M 36)
(QMS)
TS= 10 220 K
D
11Paris, 11/09/2013
TPD
eV
Modeling Kinetic O2+D reaction on Silicates
H2O(g)
Chemical desorption rate of D2O
O2+ D O2D
O2D +D OD + OD =0,7
D2O2 1-=0,3
D2O2 +D D2O(solid) + OD
OD + D D2O(solid)
Branching ratio of the reaction
Rate constant of reaction with a Barrier
Rate constante of reactions without Barrier
k
k1
k
k
k
1219 th International Vacuum Congress.
D2O(gas)(~ 86 %)
(TPD Experiments)
Paris, 11/09/2013
(MODEL)
13
Conclusions The O2+D reaction is efficient in the sub-monolayer regime at 10 K (D2O >> D2O2) The formation yield of D2O water ice depends on the grain surfaces.
Silicate: OD + D D2O OD + D D2O
Water ices: O2 + D DO2 + D OD +OD D2O2 D2O (solid) + OD
The formation of the first monolayer of water ice on bare dust silicates requires very long timescales to be grown ( >105 years ).
The chemical desorption of water has an impact on the gas phase composition of astrophysical environment, and can affect Stars and Planets formation.
D
19 th International Vacuum Congress.
O2 + D DO2 + D
Astrophysical implications:
Paris, 11/09/2013
High chemical desorption rate of D2O water molecules (~ 90 % ) through the exothermic OD + D reaction.
gas
19 th International Vacuum Congress. 14
Acknowledgments
Université de Cergy(LAMAp/LERMA Laboratory)
Francois DulieuMarco MinissaleEmanuele CongiuSaoud Baouche
Italy, Catania
Giulio Manicò (Model)Mario AccollaValerio Pirronello
Paris, 11/09/2013
19 th International Vacuum Congress. 15Paris, 11/09/2013
LAMAp/LERMA, UMR 8112 du CNRS, de l’Observatoire de Paris
Université de Cergy Pontoise, France
Water formation through O2+D pathway on cold silicates
and amorphous water surfaces of interstellar interest
Henda. Chaabouni
1619 th International Vacuum Congress. Paris, 11/09/2013
The Chemical Cosmos, 2 nd- 5 th April 2013
17
Detected in the ISM and outside of our Solar System as Gas, and Ice coated onto dusts.
The most Abundant component in the Cosmos and the Solar System (planets, comets…).
Star formation region Gas H2O: 3 × 10−8
Gas H2O: 10−7−10−6
Background Water in in the ISM
Tgas= 50-100K
Tdust= 10 K
Tdust =Tgas= 10 K
Tgas= 10 K
18
Background
Miyauchi et al. Chem.Phys.Lett (2008) Oba et al. ApJ (2009)
Ioppolo et al. ApJ (2007), PCCP (2010)
Cuppen et al. PCCP (2010)
Previous studies
H + O OH
H + OH H2O
H + O2 HO2
H + HO2 H2O2
H + H2O2 H2O + OH
H + OH H2O
H + O3 O2 + OH
H + O2 HO2
H + HO2 H2O2
H + H2O2 H2O +OH
H+ OH H2O
H2+OH H2O +H
Efficient formation of H2O and H2O2 ices at 10 K-28 K in the Multi-layer regime
Thick layers of solid O2
19 th International Vacuum Congress.
Gas-surface reactions for water formation in the ISM (Tielens & Hagen (1982))
(JAPAN)
(LEIDEN)
H2O2 / H2O > 1
Cuppen et al. PCCP (2010) H + HO2 --> OH+OH --> H2O2
Paris, 11/09/2013
19
OutlineBackground : Water in the interstellar medium
Experiments
Results:
1- Reflection Absorption Infrared Spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD) analysis of water formation through O2+D pathway on:
- Silicate surfaces - Solid water ices
2- Chemical desorption process of water product
3- Kinetic model for the O2+D reaction during thermal processing
Conclusions Cost meeting, 2 nd- 5 th April 2013