1. L'Equipe Astro-OP est composée de plusieurs groupes de recherche sur le site "Observatoire de Paris", qui travaillent sur cinq grands thèmes : le Milieu InterStellaire (MIS), la formation des étoiles et des systèmes planénaires les étoiles évoluées, formation de la poussière et recyclage des éléments la formation et l'évolution des Galaxies l'Univers primordial, le CMB, gravité et supercordes LAMAp/LERMA, UMR 8112 du CNRS, Observatoire de Paris Université de Cergy-Pontoise, FRANCE Water formation through O 2 +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 1 19 th International Vacuum Congress. Paris, 11/09/2013

2. Outline Background : Water in the interstellar medium Experiments Results: 1- Reflection Absorption Infrared Spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD) analysis of water formation through O 2 +D pathway on: - Silicate surfaces - Solid water ices 2- Chemical desorption process of water product 3- Kinetic model for the O 2 +D reaction during thermal processing Conclusions 2 Cost meeting, 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 H 2 O: 3 × 10 −8 Gas H 2 O: 10 −7 −10 −6 Background Water in in the ISM T gas = 50-100K T dust = 10 K T dust =T gas = 10 K T gas = 10 K 3The Chemical Cosmos, 2 nd- 5 th April 2013

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  H 2 O H + O 2  HO 2 H + HO 2  H 2 O 2 H + H 2 O 2  H 2 O + OH H + OH  H 2 O H + O 3  O 2 + OH H + O 2  HO 2 H + HO 2  H 2 O 2 H + H 2 O 2  H 2 O +OH H+ OH  H 2 O H 2 +OH  H 2 O +H Efficient formation of H 2 O and H 2 O 2 ices at 10 K-28 K in the Multi-layer regime 10- 30 layers of solid O 2 ice 4 19 th International Vacuum Congress. Gas-surface reactions for water formation in the ISM (JAPAN) (LEIDEN) H 2 O 2 / H 2 O > 1 Paris, 11/09/2013 (CERGY + LEIDEN) (CERGY +USA) Tielens & Hagen (1982)

5. The present work O 2 +D pathway in the Sub-monolayer regime Amorphous SILICATE Amorphous H 2 O water ices (~100 nm) film of Olivine (Mg x Fe 1−x ) 2 SiO 4 Thickness~10 Monolayers T surface =10 K (Bare dust)(Icy Mantle) 0<x<1 5 19 th International Vacuum Congress. Paris, 11/09/2013

6. QMS Micro-wave discharge D  diss (D 2 )=70 % T gas =300 K  =3.0×10 12 molecules.cm -2. s -1 O 2 (≤ 1 ML) Temperature Programmed Desorption (TPD) T surface =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) T surface = 10 K 6 19 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

7. Result 1: Water formation on amorphous Silicates Chaabouni et al. J. Chem. Phys (2012) 719 th International Vacuum Congress. RAIR specrta  (-OD) Successive deposition on silicate at 10K 1 min (0.18 ML) O 2 + 4 min (0.65 ML) D-atoms (1 O 2 + 4 D 2 D 2 O ) Low surface coverages RAIRS Silicate at 10 K Integrated areas a) b) c) d) e) f) g)  D 2 O / D 2 O 2  5 D 2 O 2 / D 2 O < 1 Sub-monolayer regime Paris, 11/09/2013 ~ 1 ML D 2 O ice Integrated areas O 2 exposure dose (ML) (D 2 O + D 2 O 2 ) at 2404 cm -1 D 2 O 2 at 2107 cm -1 0 1 2 3 4 5 6 7 8 9 0.200 0.150 0.100 0.050 0.00

8. Result 2: Effect of the substrate on water formation 1 ML (O 2 ) + 24 min (D) / Silicate surface at 10 K 1 ML (O 2 ) + 24 min (D) / Porous ASW H 2 O ice surface at 10 K 1 ML (O 2 ) + 24 min (D) / Non-porous ASW H 2 O ice surface ( prépared at 120 K, cooled to 10K ) ~ 18 % (D 2 O) ~ 50 % (D 2 O) ~ 68 % (D 2 O) Low formation yield of D 2 O water ice on Silicate at 10K Exposure 8 19 th International Vacuum Congress. D 2 O (M20) D 2 O >> D 2 O 2 ( TPD), Ts= [10 K – 220 K] (RAIRS), Ts=10 K D2O D2O ~ 5 % (O 2 ) ~ 18 % (O 2 ) ~ 2 % (O 2 ) Paris, 11/09/2013

9. RESULTS 3: The chemical desorption of water molecules Chemical desorption of D 2 O molecules upon formation on the surface at 10 K 1- Substrate : Silicate 2- Exposure of 1 ML of O 2 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 O 2 ice at 10 K. Surface at 10 K QMS D 1 ML O 2 D 2, D 2 O gas D 2 O gas 19 th International Vacuum Congress. Chemical desorption Accretion 9 Paris, 11/09/2013 Dulieu et al, Sci.Rep. 2013

10. Reactions routes for water formation Silicates T s =10 K D 2 O water formation through the barrierless reaction D + OD D 2 O  H= - 1600 meV D + OD D 2 O E barrier =2000 K Chemical desorption of D 2 O 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 10 19 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)

11. Thermal desorption Kinetic O 2 +D reaction on Silicates Exposure 1 ML (O 2 ) + X (0 min) of D atoms (6 min) (12 min) (24 min) (35 min) 1 ML O 2 + 6 min D 1 ML O 2 +9 min 1 ML O 2 +12 min D 1 ML O 2 +24 min D 1 ML O 2 + 9 min 1 ML O 2 +12 min D 1 ML O 2 +24min D (M 36) 19 th International Vacuum Congress. 1 ML O 2 + 6 min D 1 ML O 2 + 12 min 1 ML O 2 +24min D 1 ML O 2 +35 min D 1 ML O 2 + 12 min 1 ML O 2 +24 min D 1 ML O 2 +35 min D 1 ML O 2 + 6 min D (M 32) ( M 20) (M 36) ( QMS) T S = 10 220 K D 11 Paris, 11/09/2013 TPD

12. eVeV Modeling Kinetic O 2 +D reaction on Silicates H 2 O(g) Chemical desorption rate of D 2 O O 2 + D O 2 D O 2 D +D OD + OD  =0,7 D 2 O 2 1-  =0,3 D 2 O 2 +D D 2 O (solid) + OD OD + D D 2 O (solid) Branching ratio of the reaction Rate constant of reaction with a Barrier Rate constante of reactions without Barrier k k 1 k k k 1219 th International Vacuum Congress. D 2 O (gas) (~ 86 %) (TPD Experiments) Paris, 11/09/2013 (MODEL)

13. Conclusions  The O 2 +D reaction is efficient in the sub-monolayer regime at 10 K (D 2 O >> D 2 O 2 )  The formation yield of D 2 O water ice depends on the grain surfaces. Silicate : OD + D D 2 O OD + D D 2 O Water ices: O 2 + D DO 2 + D OD +OD D 2 O 2 D 2 O (solid) + OD  The formation of the first monolayer of water ice on bare dust silicates requires very long timescales to be grown ( >10 5 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 D D D D 13 19 th International Vacuum Congress. D D O 2 + D DO 2 + D +2D Astrophysical implications: Paris, 11/09/2013 High chemical desorption rate of D 2 O water molecules (~ 90 % ) through the exothermic OD + D reaction. gas

14. Acknowledgments Université de Cergy (LAMAp/LERMA Laboratory) Francois Dulieu Marco Minissale Emanuele Congiu Saoud Baouche Italy, Catania Giulio Manicò (Model) Mario Accolla Valerio Pirronello 1419 th International Vacuum Congress.Paris, 11/09/2013

15. 19 th International Vacuum Congress.15Paris, 11/09/2013

16. L'Equipe Astro-OP est composée de plusieurs groupes de recherche sur le site "Observatoire de Paris", qui travaillent sur cinq grands thèmes : le Milieu InterStellaire (MIS), la formation des étoiles et des systèmes planénaires les étoiles évoluées, formation de la poussière et recyclage des éléments la formation et l'évolution des Galaxies l'Univers primordial, le CMB, gravité et supercordes LAMAp/LERMA, UMR 8112 du CNRS, de l’Observatoire de Paris Université de Cergy Pontoise, France Water formation through O 2 +D pathway on cold silicates and amorphous water surfaces of interstellar interest Henda. Chaabouni 16 19 th International Vacuum Congress.Paris, 11/09/2013

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 Water plays a key roles: - Cooling of dense gas - Collapsing clouds - Process of star formation - Formation of planetary systems Gas H 2 O: 3 × 10 −8 Gas H 2 O: 10 −7 −10 −6 Gas phase formation cannot explain the observed abundances of solid H 2 O in dense clouds. Background Water in in the ISM T gas = 50-100K T dust = 10 K T dust =T gas = 10 K T gas = 10 K 17The Chemical Cosmos, 2 nd- 5 th April 2013

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  H 2 O H + O 2  HO 2 H + HO 2  H 2 O 2 H + H 2 O 2  H 2 O + OH H + OH  H 2 O H + O 3  O 2 + OH H + O 2  HO 2 H + HO 2  H 2 O 2 H + H 2 O 2  H 2 O +OH H+ OH  H 2 O H 2 +OH  H 2 O +H Efficient formation of H 2 O and H 2 O 2 ices at 10 K-28 K in the Multi-layer regime Thick layers of solid O 2 18 19 th International Vacuum Congress. Gas-surface reactions for water formation in the ISM (Tielens & Hagen (1982)) (JAPAN) (LEIDEN) H 2 O 2 / H 2 O > 1 Cuppen et al. PCCP (2010) H + HO 2 --> OH+OH --> H 2 O 2 Paris, 11/09/2013

19. Outline Background : Water in the interstellar medium Experiments Results: 1- Reflection Absorption Infrared Spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD) analysis of water formation through O 2 +D pathway on: - Silicate surfaces - Solid water ices 2- Chemical desorption process of water product 3- Kinetic model for the O 2 +D reaction during thermal processing Conclusions 19 Cost meeting, 2 nd- 5 th April 2013