Formation of molecular hydrogenFormation of molecular hydrogenin the interstellar mediumin the interstellar medium

Jean Louis LEMAIRE

LAMAp/LERMA

Observatoire de Paris & Université de Cergy-Pontoise

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

It could appear at first sight that formation of molecular hydrogen in the interstellar medium (ISM) has nothing to see with the title of the conference.

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

International Conference on Nano-Materials and Renewable Energies

Formation of molecular hydrogenFormation of molecular hydrogenin the interstellar mediumin the interstellar medium

They are in fact two links, even if the first of them is daring.

The first one deals with renewable energies …

but on an astronomical time scale !!

- When AGB stars become Super Novae, they expel their material out in the space and part of it (the rest is gas) constitutes the interstellar dust grains mainly made of silicates, SiC and carbonaceous material.

- Much later on, when this material, coming from several such explosions, is gathered together with the pervading atomic hydrogen in giant clouds, - it starts to form a wealth of molecules (starting with the more simple H2, then promoting more complex ones … up to prebiotic ones) and - when gravitation enters at play inside denser clumps of materials, new stars may form.

… and renewed energy will arise out of these stars !an ITERative process

.International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

+ Extra-galactic infall Schematic diagramSchematic diagram

massive stars enrich the material with

heavy elements

* At every stages of star formation and evolution, gas and dust material are recycled back into the Interstellar Medium (ISM). * Through nucleosynthesis,

Time evolution

fast

slow

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010Planetary Nebulae

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

The archetype of a star forming region:OMC1Orion Molecular Cloud

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

OMC1Orion Molecular Cloud

VLT ESO (UT4 + adaptive optics)

False color RGB Image:M, L and K band

False color RGB image(in red): 2.12 µm (K-band)H2 1-0 S(0) emission (in blue and green):Nearby continuum emission

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Class Material Signatures (abs., emi.)bare material- Silicates Olivine (MgxFe1-x)2 SiO4 9.7 and 18 µm bands

- Graphite the more active to form H2 217.5 nm bump

- Amorphous carbon and HAC 7.6 µm bands

active catalyst- PAHs 3.3, 6.2, 7.7 and 11.3 µm

- SiC 11.4 µm

- MgS 30 µm

core + ice mantle material (UV processed or not)- Ice covered grains

CO, H2O, NH3, CH4, CO2, N2

Methanol 3.1, 4.6, 6.0, 6.85 µm

- Refractory organics covered grains 3.4, 6.0 µm

Grains origin: Novae, Supernovae, ejected stellar matter

Composition and physical/chemical state of the interstellar grains

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Cosmic Dust Grains:

- Composed of particles which arefrom a few molecules to 0.1 mm in size- Solid, crystalline, porous, fluffy

…..Extremely large grains

asteroids planetesimals Here is an ELG !!

Chondrite interplanetary dust particlePorous Smooth

1 km

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Forsterite has an unusually high melting temperature at atmospheric pressure, almost 1900°C, but the melting temperature of Fayalite is much lower (about 1200°C). The melting temperature varies smoothly between the two endmembers, as do other properties.

Olivine incorporates only minor amounts of elements other than oxygen, silicon, magnesium, and iron. Manganese and nickel commonly are the additional elements present in highest concentrations.

The mineral olivine (gem-quality called peridot) is a magnesium iron silicate with the formula

(Mgx,Fe(1-x))2SiO4

It is one of the most common minerals on Earth, and has also been identified in meteorites, the Moon, Mars, in the dust of comet Wild 2, and within the core of comet Tempel.

The ratio of magnesium and iron varies between the two endmembers of the solid solution series: Forsterite (Mg-endmember, x=1) and Fayalite (Fe-endmember, x=0).

Crystal system: orthorhombicThe atomic scale structure of olivine looking along the a axis. Oxygen is shown in red, silicon in pink, and magnesium/iron in blue. A projection of the unit cell is shown by the black rectangle

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

-Silicates comprise the majority of the earth's crust, as well as most planets and moons. -Silicate compounds, including the minerals, consist of silicate anions whose charge is balanced by various cations.

- Then silicates have specific spectroscopic signatures which can be observed in space and recreated in the laboratory.

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

SiCSiCWhile rare on Earth, silicon carbide is remarkably common in space.

It is a common form of stardust found around carbon-rich stars, and examples of this stardust have been found in pristine condition in primitive (unaltered) meteorites.

The silicon carbide found in space and in meteorites is almost exclusively the beta-polymorph.

Analysis of SiC grains found in the Murchison carbonaceous chondrite meteorite has revealed anomalous isotopic ratios of carbon and silicon, indicating an origin from outside the solar system; 99% of these SiC grains originate around carbon-rich asymptotic giant branch stars.SiC is commonly found around these stars as deduced from their infrared spectra.

In the early stages of star formation, molecules will form:- either in the gas phase - or, for many of them, at the surface of the nano- or micro-material forming the dust grains.

The first of them is molecular hydrogen.

Numerous diagnostics & techniques are now currently used to show how such formation reactions proceed, involving:

- Atomic and molecular physics, - Surface science

- Solid state physicsand by the more recent ones: STM techniques (at low temperature)

Theoretical works are also necessary to explain the mechanisms involved.

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

H2 formation on surfacesSummaryThe gas-grain surface interaction is the main route for the molecule formation in the ISM- Gould and Salpeter (1963)

Interstellar grains acts as catalysts- from the very simple H2 formation- to the more complex chemistry

The kinetics of the reaction under interstellar conditions is still not well understood- experimental aspects

- what is a real interstellar grain ?

- how to work in the laboratory under interstellar conditions ?Low flux (<1012 atoms/cm2/sec) and Ek (10-300 K) of H atomsLow sample temperature (5-40 K), Low background pressure (10-10 torr)- theoretical aspects

what are the physical and chemical mechanisms involved ?what formalism to use to give account of them ?

- Morphology- Porosity- Binding energy- Mobility- Sticking- Bare or ice covered- ……

Grain surface characteristics:Atoms or molecules characteristics and interaction with the surface:

* morphology (crystalline, micro- or poly- crystalline, amorphous)* role of the defects* porosity (dense / fluffy), area/unit vol.* bare grain size distribution (0.01 to 0.5 µm)* surface temperature* adsorption processes* type of interaction with the surface (physi- vs. chemi-sorption)* binding sites and energies* ice morphologies and surface coverage (ice mantles, mixtures)

* flux of incoming atoms, kinetic temperature* sticking coefficient* mobility, time scales: residence time, migration time (10-12 to 10-3 s)* formation processes* recombination efficiency

* desorption kinetics (thermally activated mobility?) * Ev,j & Ek

H2 formation on surfaces Experimental aspects

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Formation of H2 molecules on grains

H

Adsorption ( flux, sticking ?…)from the gas phase onto the grain

H

Diffusion (mobility ?)

HDesorption

Formation reaction

Desorption(residence time ?)

Formation

T ?Composition ?Morphology ?Coverage ?

HH

H

H

H

Formation process ISM dynamics (results from the balance between internal pressure and gravitational forces)

Nascent H2 with internal energy H2 will cool through

radiation of IR photonsThe molecular cloud collapse more readily

Nascent H2 with large translational and small internal energyand/or grain heating Heating of the cloudSlow collapse of the molecular cloud

Thermal accomodationand/or sticking

Formation energy partition4.5 eV

Ev,J ?

Ek ? Grain heating ?

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Interaction of atoms and molecules with surfaces:* physisorption (vdW interaction)* chemisorption (covalent bond)

Surfaces, H2 formation Theoretical aspectsReaction mechanisms

- Eley-Rideal (prompt mechanism)occur at high H atom coverage rate creates "hot" H2

- Harris-Kasemo (hot atom mechanism)several bounces before prompt reactionoccur at low and high H atom coverage ratecreates "hot" H2

- Langmuir-Hinshelwood(migration mechanism by tunneling or thermal hooping)occur at low and high H atom coverage rate creates H2 at surface temperature

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Formation of molecular hydrogenon a silicate surface

Experiment

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

"FORMOLISM"  experimental setup

Atomic hydrogen source

“FORMOLISM” experimental set up

0 – UHV chamber (~10-10 mbar)

1 - Substrate: - Amorphous silicate. - Temperature controlled (>5.5K).

2 – Exposure (with 1 or 2 beams) to:- molecules (MW discharge off)- atoms and molecules

(MW discharge on)

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

(MW discharge on)

Beam shutter: ON or OFF

Beam 1: can be temperaturecontrolled (20 – 300K)

Diagnostics

QMSSimultaneous measurementsduring beam exposure and after exposure during the heating ramp (TPD)(Thermally Programmed Desorption)

– QMS (Mass selective) in a remote location

– REMPI-TOF MS Laser detection [Quantum state selective: (v,J)]

– Infrared spectroscopy RAIRS (not used in this experiment)

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Diagnostics

UV Laser

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Simultaneous measurementsduring beam exposure and after exposure during the heating ramp (TPD)(Thermally Programmed Desorption)

– QMS (Mass selective) in a remote location

– REMPI-TOF MS Laser detection [Quantum state selective: (v,J)]The laser is tuned to the specific Q(J") [X(v",J")-EF(v',J')] transitions in orderto measure the X(v",J") population

– Infrared spectroscopy RAIRS (not used in this experiment)

micro-capillary array doser(+ translation)

Time of Flight Mass Spectrometer

cold head+ thermal shield(+translation)

Quadrupole Mass Spectrometer(+ translation + rotation)

RAIRS diagnostic(KBr windows)

Inside of the UHV chamber (as seen from the molecular or atomic gas beams entrance window) International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Silicate sampleSilicate sampleCryo generatorCryo generatorTTss=6-150K=6-150Kcleaning: 800 Kcleaning: 800 Ktemperatures measurementstemperatures measurementsand regulationsand regulations

H/HH/H22

D/DD/D22

UV laser beamfocused in front of the surface

Nd:YAG laser + Dye laser

1.064µm x 2 … 600-300-200 nm

REMPI + Time of Flight Mass Spectrometer (TOF-MS)quantum states discrimination

Excitation 2.45 GHz

Time of flight

HDHD++, H, H22++

,, DD22++ (v,J) signal(v,J) signal

Acceler.

Extract.

MCP

Ultra High Vacuum Chamber (<10-10 mbar, n~106cm-3) pumping: primary, turbomlecular, ionic, titanium sublimation. baking up at 150°C for ~100 hours

Experiment scheme Experiment scheme Diagnostics methods with state specific resolution

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Transition Q(J")

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Formation of molecular hydrogenon a silicate surface

Experiment

paper in preparation

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Toward chemical complexity

O2 Beam (40 % dissociation)Initially 100 O2 moleculesFinally: 60 O2 and 80 O

D2 Beam (60 % dissociation)

Substrate: - Silicates: to be done- Water ice: Dulieu et al, A&A,

2009

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

H, O, N and C Interaction and Reactivity on Surfaces,H, O, N and C Interaction and Reactivity on Surfaces,in Laboratory to explain what is observed in Spacein Laboratory to explain what is observed in Space

Water formationWater formation

Molecules in Space & Laboratory, Paris, May 2007, JL Lemaire

Suggested mechanisms (theoretician view)

Tielens & Hagen 1982 Stantcheva et al 2002

Kaufman et al. 2005

In situ observations with STMof molecular formation on graphite

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

H on HOPG

High Coverage

Medium Coverage

80 x 72 Å2

171 x 155 Å2

Low Coverage

103 x 114 Å2

Vt~800mV, It~0.15-0.2nALiv Hornekær, 2009, iNano Aarhus

H chemisorbed on HOPG

Rauls

Work on graphitic surfacesChemisorption - basal plane: Jeloica & Sidis, Chem. Phys. Lett. 300, 157 (1999)Chemisorption at defects: Sha et al, Surface Science 496, 318 (2002)

Sha et al, J. Am. Chem. Soc. 126, 13095 (2004)Güttler et al, Surface Science 570, 218 (2004)

Chemisorbed states on graphite: Cazaux & Tielens, Astrophys. J. 604, 222 (2004)

Dimer formation

Hornekær et al. Phys. Rev. Lett. 97, 186102 (2006)

In situ observations with STMof molecular formation on other surfaces

(Graphene, Silicene, silicates …)studying mainly

interaction and reactivity with H and O

Project of collaboration between CEA, CINAM and our team

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

S. Baouche, M. Chehrouri, H. Chaabouni, H. Mokrane S. Baouche, M. Chehrouri, H. Chaabouni, H. Mokrane E. Somson, S. DianaE. Somson, S. Diana

and G. Vidali (Syracuse University NY USA and G. Vidali (Syracuse University NY USA as visiting professoras visiting professor))

Thanks to all who have performed the work onthe formation of vibrationnaly excited H2 formation

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

and thank you for your attention

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Website: http://www.u-cergy.fr/LERMA-LAMAP/Head of Laboratory: JL Lemaire (jean-louis.lemaire@obspm.fr)

Fundamental research: Laboratory AstrophysicsAimed at explaining how stars are forming,

from the first molecules to the more evolved ones.

Several fields involved:Atomic & Molecular Physics, Surface science, Chemistry, Astrophysics &

AstrochemistryOMC1 (VLT-UT4-NACO)

Laboratoire Atomes et Molécules en Astrophysique (LAMAp)Université de Cergy-Pontoise (UCP)

FORMOLISM experiment at the Cergy Laboratory "SOLEIL" synchrotronDESIRS beam-line

Scanning Tunneling Microscope(CERGY + CEA collaboration)

Laboratoire associé au LERMA UMR 8112 du CNRS Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique

Observatoire de Paris + Université Pierre et Marie Curie + Université de Cergy-Pontoise + Ecole Normale supérieure+ collaboration with CEA

PhD project:The LAMAp/LERMA group (managed by both the Observatoire de Paris and the Université de Cergy-Pontoise) opens a position for a PhD student in the project:

Gas-grains interaction and reactivity forming moleculesGas-grains interaction and reactivity forming moleculesin inter- and circum-stellar conditionsin inter- and circum-stellar conditions

Starting Date: 01/02/2010 (then immediately available) Duration: 36 monthsCandidate: Physics, Physical chemistry or Astrophysics MSc.D.

All nationalities eligible, according to the EU mobility criteria (then French nationals escepted).

Funding program: European FP7-ITN 7th Framework Programme - Initial Training Networks) LASSIE (Laboratory Astrochemical Surface Science In Europe) project (PI: Prof. McCoustra Edinburgh)

+ ANR (Agence Nationale de la Recherche) + SESAME (CR Ile de France) contractGross salary ~36 k€ per year. Additional travel allowance to participate in the network meetings.

Responsible Scientist: Prof. Jean Louis Lemaire (jean-louis.lemaire@obspm.fr)

Theme: Laboratory astrophysics (atomic & molecular physics and surface science for astrophysics)Short description: A laboratory research project to study the reactions leading to molecular hydrogen and small molecule formation on inter- and circum-stellar dust analogues (silicates, carbonaceous materials and ices) under ultrahigh vacuum and ultralow temperature conditions.

Web pages: http://www.u-cergy.fr/LERMA-LAMAP/International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

PhD project: The LAMAp/LERMA group (managed by both the Observatoire de Paris and the Université de Cergy-Pontoise) opens a position for a PhD student in the project:

Gas-grains interaction and reactivity forming moleculesGas-grains interaction and reactivity forming moleculesin inter- and circum-stellar conditionsin inter- and circum-stellar conditions

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Project description:- Study of the atomic and molecular mechanisms as well as of the reactions pathways involved in the molecular formation within inter- and circum-stellar conditions, in the framework of gas/surface interactions and heterogeneous catalysis. - Interaction and reactivity of H, O and N (under atomic and/or molecular forms) on surfaces simulating interstellar dust grains, either dry ones (silicates or carbonaceous materials of different morphologies, material pertinent to diffuse clouds) or covered with icy mantle (water, CO …, material pertinent to dark clouds).We are in particular interested in the formation of H2, H2O, CO2 …

- Experiments are performed using the "FORMOLISM" experimental setup: a sample maintained at very low temperature is irradiated in an ultra high vacuum chamber by atomic and molecular beams. Three spectroscopic diagnostics are used to detect and characterize the molecular formation:1) TPD-MS (thermally programmed desorption mass spectroscopy) to monitor the desorption kinetics of a given species (irrespective of its quantum state), using a QMS (quadrupole mass spectrometer)2) REMPI-TOF-MS Laser spectroscopy (resonantly enhanced multiphoton ionization associated with time of flight mass spectroscopy) allowing rovibrational quantum states discrimination. This diagnostic is mainly used for H 2 formation studies.

3) RAIRS (reflection absorption infrared spectroscopy) is implemented to diagnose both the ice structure and the molecules formed on the surface as well as their physical/chemical evolution during TPD heating. 4) STM in the near future for in situ formation observations.- The main aim of the project is to provide fundamental data and information on gas/surface interactions necessary to the modeling of astrophysical environments. Such models are designed to interpret astronomical and radio astronomical observations (Spitzer, Herschel, ALMA).Scientific environment: Responsible Scientist: Prof. Jean Louis Lemaire (jean-louis.lemaire@obspm.fr)An active collaboration exists between our research team and V Pirronello (Catania) and G Vidali (Syracuse USA). Theoretical aspects of gas interactions with model surfaces are treated by both the LCAM (Orsay) and the LERMA (Meudon) theoretician groups.

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Study and importanceCosmic dust was once solely an annoyance to astronomers, as it obscures objects they wish to observe. When infrared astronomy began, those previously annoying dust particles were observed to be significant and vital components of astrophysical processes.For example, cosmic dust can drive the mass loss when a star is nearing the end of its life, play a part in the early stages of star formation, and form planets. In our own solar system, dust plays a major role in the zodiacal light, Saturn's B Ring spokes, the outer diffuse planetary rings at Jupiter, Saturn, Uranus and Neptune, and comets.The study of dust is a many-faceted research topic that brings together different scientific fields: physics (solid-state, electromagnetic theory, surface physics, statistical physics, thermal physics), fractal mathematics, chemistry (chemical reactions on grain surfaces), meteoritics, as well as every branch of astronomy and astrophysics.[1] These disparate research areas can be linked by the following theme: the cosmic dust particles evolve cyclically; chemically, physically and dynamically. The evolution of dust traces out paths in which the universe recycles material, in processes analogous to the daily recycling steps with which many people are familiar: production, storage, processing, collection, consumption, and discarding. Observations and measurements of cosmic dust in different regions provide an important insight into the universe's recycling processes; in the clouds of the diffuse interstellar medium, in molecular clouds, in the circumstellar dust of young stellar objects, and in planetary systems such as our own solar system, where astronomers consider dust as in its most recycled state. The astronomers accumulate observational ‘snapshots’ of dust at different stages of its life and, over time, form a more complete movie of the universe's complicated recycling steps.The detection of cosmic dust points to another facet of cosmic dust research: dust acting as photons. Once cosmic dust is detected, the scientific problem to be solved is an inverse problem to determine what processes brought that encoded photon-like object (dust) to the detector. Parameters such as the particle's initial motion, material properties, intervening plasma and magnetic field determined the dust particle's arrival at the dust detector. Slightly changing any of these parameters can give significantly different dust dynamical behavior. Therefore one can learn about where that object came from, and what is (in) the intervening medium.Some bulk properties of cosmic dustCosmic dust is made of dust grains and aggregates of dust grains. These particles are irregularly-shaped with porosity ranging from fluffy to compact. The composition, size, and other properties depends on where the dust is found, and conversely, a compositional analysis of a dust particle can reveal much about the dust particle's origin. General diffuse interstellar medium dust, dust grains in dense clouds, planetary rings dust, and circumstellar dust, are each different in their characteristics. For example, grains in dense clouds have acquired a mantle of ice and on average are larger than dust particles in the diffuse interstellar medium. Interplanetary dust particles (IDPs) are generally larger still.In circumstellar dust, astronomers have found molecular signatures of CO, silicon carbide, amorphous silicate, polycyclic aromatic hydrocarbons, water ice, and polyformaldehyde, among others. (In the diffuse interstellar medium, there is evidence for silicate and carbon grains.) Cometary dust is generally different (with overlap) from asteroidal dust. Asteroidal dust resembles carbonaceous chondritic meteorites, and cometary dust resembles interstellar grains, which can include the elements: silicates, polycyclic aromatic hydrocarbons, and water ice.

Dust grain formationThe large grains start with the silicate particles forming in the atmospheres of cool stars, and carbon grains in the atmospheres of cool carbon stars. Stars that have evolved off the main sequence and have entered the giant phase of their evolution are a major source of dust grains in galaxies. Star dust, sung and written in the popular media, is a colloquial term referring to the birthplace of most dust grains in the Universe. If one indeed traces the origin of the elements out of which human bodies are made, they are star dust.Astronomers know that the dust is formed in the envelopes of late-evolved stars from specific observational signatures. An (infrared) 9.7 micrometre emission silicate signature is observed for cool evolved (oxygen-rich giant) stars. And an (infrared) 11.5 micrometre emission silicon carbide signature is observed for cool evolved (carbon-rich giant) stars. These help provide evidence that the small silicate particles in space came from the outer envelopes (ejecta) of these stars.It is believed that conditions in interstellar space are generally not suitable for the formation of silicate cores. The arguments are that: given an observed typical grain diameter a, the time for a grain to attain a, and given the temperature of interstellar gas, it would take considerably longer than the age of the universe for interstellar grains to form. Furthermore, grains are seen to form in the vicinity of nearby stars in real-time, meaning in a) nova and supernova ejecta, and b) R Coronae Borealis, which seem to eject discrete clouds containing both gas and dust.Most dust in our solar system is highly processed dust, recycled from the material out of which our solar system formed and subsequently collected in the planetesimals, and leftover solid material (for example: comets and asteroids), and reformed in each of those bodies' collisional lifetimes. During our solar system's formation history, the most abundant element was (and still is) H2. The metallic elements: magnesium, silicon, and iron, which are the principal ingredients of rocky planets, condensed into solids at the highest temperatures. The range of elements of the solar nebula between H 2 and (Mg, Si, Fe) is not known well (Wood, J., 1999). Some molecules such as CO, N2, NH3, and free oxygen, existed in a gas phase. Some molecules, for example, graphite (C) and SiC condensed into solid grains. Some molecules also formed complex organic compounds and some molecules formed frozen ice mantles, of which either could coat the "refractory" (Mg, Si, Fe) grain cores.The formation of these molecules was determined, in large part, by the temperature of the solar nebula. Since the temperature of the solar nebula decreased with heliocentric distance, scientists can infer a dust grain's origin(s) with knowledge of the grain's materials. Some materials could only have been formed at high temperatures, while other grain materials could only have been formed at much lower temperatures. The materials in a single interplanetary dust particle often show that the grain elements formed in different locations and at different times in the solar nebula. Most of the matter present in the original solar nebula has since disappeared; drawn into the Sun, expelled into interstellar space, or reprocessed, for example, as part of the planets, asteroids or comets.

Interstellar Grain Material

H2 (HD, D2) Formation H2 (HD, D2) desorption

PhysisorptionPolycristalline silicates Pirronello et al. 1997(telluric olivine)

Amorphous carbon Pirronello et al. 1999

Amorphous water ice Manico et al. 2001Roser et al. 2002, 2003 Hornekaer et al. 2003 Hornekaer et al. 2005Perets et al. 2005, 2007 Amiaud et al. 2007 Dulieu et al. 2005

Amiaud et al. 2006, 2008Amorphous silicates(Fex, Mg1-x)2SiO4, x=0.5 Vidali et al. 2007

0<x<1 Vidali et al. (submitted)

Graphite Creighan et al. 2006Islam et al. 2007Latimer et al. 2008

ChemisorptionGraphite Zecho et al. 2002, 2003, 2004 Hornekaer et al. 2006

Güttler et al. 2004

Revue de Projet JLL – 22/11/2007

Techniques of surface science (Woodruff & Delchar 1994)

Zecho et al. 2002

HD TPD signal

H2 formation on dust grains under PDR and post-shock conditions

Position de l'équipe dans la concurrence internationalePosition de l'équipe dans la concurrence internationale

Travaux expérimentaux sur la formation de H2 (HD, D2)

Syracuse + Catania team (Vidali G. , USA + Pirronello V., It) 1997 TPDSilicates (Olivine), carbone amorphe, glace d'eau, de CO et de CO2

Formation de HD

Odense team (Baurichter A. & Hornekaer L., Dk) 2003 TPDGlace d'eauFormation de HD, désorption de D2

HOPGraphite, Ek(q) de H2 (D2) 2006 LAAD

UC London team (Price S., UK) 1999 REMPI-TOFGraphite (15K)Formation de H2 et HD, diagnostic (v,j)

Observatoire de Paris & Cergy-Pontoise team (Lemaire JL, Fr) 2005 TPD, REMPI-TOF, 2009 RAIRS & … STM 200x

Formation de molécules simples et complexes sur des glaces d'eauFormation de D2, désorption H2, HD, D2 et de mélanges, énergies d'adsorption, diagnostic (v,j), ortho/para

Waterloo team (Govers T., Ca) 1980 BolométrieCinétique de physisorption, H2 et D2

Aarhus team (Hornekaer L. & Besenbacher F., Dk) 2006 STMHOPGraphite, in situ formation de D2

Bayreuth team (Zecho T., Küppers J., G) 2002 TPD, ELS, HREELSHOPGraphite 2006 STMFormation de H2 et D2

chimisorbéphysisorbé

N'est plusen activité

V. Pirronello:Collaboration très active avec Cergy

Activité arrêtée,déplacée à Aarhus(Cf. infra) Postdoc=notre 1er doc.

Postdoc=notre 1er doc.Retour ?

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Cosmic dust was once solely an annoyance to astronomers, as it obscures objects they wish to observe. When infrared astronomy began, those previously annoying dust particles were observed to be significant and vital components of astrophysical processes.For example, cosmic dust can drive the mass loss when a star is nearing the end of its life, play a part in the early stages of star formation, and form planets. In our own solar system, dust plays a major role in the zodiacal light, Saturn's B Ring spokes, the outer diffuse planetary rings at Jupiter, Saturn, Uranus and Neptune, and comets.The study of dust is a many-faceted research topic that brings together different scientific fields: physics (solid-state, electromagnetic theory, surface physics, statistical physics, thermal physics), fractal mathematics, chemistry (chemical reactions on grain surfaces), meteoritics, as well as every branch of astronomy and astrophysics.[1] These disparate research areas can be linked by the following theme: the cosmic dust particles evolve cyclically; chemically, physically and dynamically. The evolution of dust traces out paths in which the universe recycles material, in processes analogous to the daily recycling steps with which many people are familiar: production, storage, processing, collection, consumption, and discarding. Observations and measurements of cosmic dust in different regions provide an important insight into the universe's recycling processes; in the clouds of the diffuse interstellar medium, in molecular clouds, in the circumstellar dust of young stellar objects, and in planetary systems such as our own solar system, where astronomers consider dust as in its most recycled state. The astronomers accumulate observational ‘snapshots’ of dust at different stages of its life and, over time, form a more complete movie of the universe's complicated recycling steps.The detection of cosmic dust points to another facet of cosmic dust research: dust acting as photons. Once cosmic dust is detected, the scientific problem to be solved is an inverse problem to determine what processes brought that encoded photon-like object (dust) to the detector. Parameters such as the particle's initial motion, material properties, intervening plasma and magnetic field determined the dust particle's arrival at the dust detector. Slightly changing any of these parameters can give significantly different dust dynamical behavior. Therefore one can learn about where that object came from, and what is (in) the intervening medium.

Cosmic dust is a type of dust composed of particles in space which are

from a few molecules to 0.1 mm in size

Cosmic dust can be further distinguished by its astronomical location: intergalactic dust, interstellar dust, interplanetary dust (such as in the zodiacal cloud) and circumplanetary dust (such as in a planetary ring).

In our own Solar System, causes the zodiacal light. Sources include:comet dust,asteroidal dust,

dust from the Kuiper belt, andinterstellar dust passing through our solar system.

The terminology has no specific application for describing materials found on the planet Earth, other than in the most general sense that all elements with an atomic mass higher than hydrogen are believed to be formed in the core of stars via stellar nucleosynthesis and supernova nucleosynthesis events.As such all elements that exist can be indiscriminately considered to be a form of "cosmic dust".

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

Cosmic dust of the Andromeda Galaxy as revealed in infrared light by Infrared Space Telescope (Spitzer, Herschel) Cosmic dust of the Horsehead Nebula as revealed by the Hubble Space Telescope (HST)

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

- The structural properties of cosmic dust has been improved by observations at higher spectral resolution and in a wider range of wavelengths. - However, the formation and processing of main dust components in different astrophysical environments is not yet completely understood.- Spectroscopy is a main tool to characterize dust analog materials and to monitor ongoing structural transformations and provides also the major link to astronomical observations and the tool for identification of cosmic dust properties. - There is a lot of laboratory work to re-create cosmic dust analogs and to study thermal, UV and ion irradiation processing in order to understand cosmic dust formation and processing in space.

International Conference on Nano-Materials and Renewable Energies (ICNMRE) Safi (Morocco) July 2010

A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxidesSilicates comprise the majority of the earth's crust, as well as most planets and moons. Sand, Portland cement, and thousands of minerals are examples of silicates.

Silicate compounds, including the minerals, consist of silicate anions whose charge is balanced by various cations. Myriad silicate anions can exist, and each can form compounds with many different cations.

Mineralogically, silicate minerals are divided according to structure of their silicate anion into the following groups:

Nesosilicates (lone tetrahedron) - [SiO4]4−, eg olivine. Sorosilicates (double tetrahedra) - [Si2O7]

6−, eg epidote, melilite group. Cyclosilicates (rings) - [SinO3n] 2n−, eg tourmaline group. Inosilicates (single chain) - [SinO3n] 2n-, eg pyroxene group. Inosilicates(double chain) - [Si4nO11n] 6n−, eg amphibole group. Phyllosilicates (sheets) - [Si2nO5n] 6n−, eg micas and clays. Tectosilicates (3D framework) - [AlxSiyO2(x+y)] x−, eg quartz, feldspars, zeolites.

MC