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Laboratory Studies of Organic Chemistry in Space A. Ciaravella Palermo, 2014 March 26

InterStellar Medium (ISM) overview ISM composition Dust and Ice Mantles : synthesis of complex molecules Laboratory Astrochemistry: main results Space vs Laboratory conditions IR Spectroscopy (Ices) An experiment step by step

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Laboratory Studies of Organic Chemistry in Space A. Ciaravella Palermo, 2014 March 26

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  1. InterStellar Medium (ISM) overview • ISM composition • Dust and Ice Mantles : synthesis of complex molecules • Laboratory Astrochemistry: main results • Space vs Laboratory conditions • IR Spectroscopy (Ices) • An experiment step by step • Synthesis of organic compounds on the origin of life LaboratoryStudiesofOrganicChemistry in SpaceA. CiaravellaPalermo, 2014 March 26

  2. InterStellar Medium (ISM) • The ISM: • mostly gas and dust existingover a wide range of physical conditions • dust is 1% in mass • half of the ISM mass in our Galaxy is composed by molecule • processed by the radiation field from stars and cosmic rays • Can be devided in 5 components: • “coronal” gas • warm intercloud medium • HII regions • neutral hydrogen (HI) clouds • and complexes of giant molecular clouds (GMCs)

  3. ISM: Hot and Warm Gas • Hot or Coronal gas T ≥ 106 k n ≤ 0.5 cm-3 • Hot gases ejected in stellar explosions and • winds • Observed as ar-UV absorption lines of highly • ionized atoms soft X-ray background VELA (0.1 - 2.4 keV), ROSAT • Warm gas T ≤ 104 k 0.1 ≤ n ≤ 1 cm-3 • The source in not entirely clear • Can be neutral or ionized • Observed as • neutral − n ≈ 1 cm-3 − emission features in HI • Ionized ( UV radiation) − n ≈ 0.1 cm-3 − HII Orion nebula Hubble Space Telescope

  4. Neutral Hydrogen Clouds Almost half of the ISM T < 102 K n ≈ 50 cm-3 Observedin neutral HI 21 cm line Excellent tracers of spiral structure

  5. Molecular Clouds Sites of chemical and dynamical activity leading to star formation H2 is the dominant molecule but CO is used to map the clouds Large variety Diffuse, Giant, Dark, Dense cores T ≤ 10 − 50 K n ≅ 102 – 104 cm-3 sizes 20-200 pc masses 103-107 M mean density 102 cm-3 In cores (~1pc) n ~104 cm-3

  6. A Multi-Wavelenght View of the Milky Way Visible HI 21cm CO 115GHz H2 X-ray Dust extinction Dark regions

  7. ISM Composition • Neutral Atoms: mainly H and He, with signicant amounts of C, N, O • Ions: mainly H+and cations of other abundant elements. • Cations are the dominating ions in ISM • Electrons: from ionization. Free electrons are signicantly abundant. • Small Size Molecules: the most abundant are H2 and CO, but • other small size are present, mainly in molecular clouds. • Larger Molecules: mainly, polycyclic aromatic hydrocarbons PAH • have been found in many places in galaxies. • Dust Particles: small particles 0.01 − 1 μm • Composition Si, Fe, C, and O • Play a crucial role in the formation of molecules

  8. Molecular Clouds: the richest in molecules 1) Medium complexity molecules e. g. CO , NH3, H2O, HCnN (up to n=13) 2) Polycyclic Aromatic Hydrocarbons (PAH) , C C multiple bonds 3) Large partly H saturated molecules( with no C C multiple bonds & > 3 H) Which are the formation routes? 3-body no working in gas phase. 2-body efficient in gas phase for 1) and 2) No gas phase routes for 3) !!! Where and in which conditions complex molecules can be produced? Need for a heterogeneous chemistry

  9. Chemistry in Dust Grain Mantles I Dust grains have icy mantles t ≈ 109/n [yr] Freeze-out time Diffuse ISM n ≈ 102 t ≈ 107 yr too long!! Dense (≥104 cm-3) and cold (10 – 20 K) regions t ≤ 105 yr Ice Mantles Visible C18O N2H+ Evidence for freeze out appear as emission holes in the maps of some molecules

  10. Chemistry in Dust Grain Mantles II Adsorption or sticking efficiency is high for dust grains. Mobilty of particles is necessary for chemical reactions: ✓quantum tunneling, τq =4h/ΔE for H ✓thermal hopping, τh=ν-1exp(TB/T) H adsorption C CO Desorption occurs continuously: ✗ Micro exothermic reaction liberates molecule from surface; ✗ Macro explosive liberation of molecules by mantle destruction by energetic photons or cosmic rays; ✗Violent collective destruction of grains by shock waves O reactions NH3 diffusion Silicate core CO2 H2O CH3OH CH3OH CH4 desorption

  11. Feeding the ISM From Prestellar through the collapsing envelope into a planetary disk

  12. Laboratory Astrochemistry: ICES • 1979 - UV irradiation • ✓Hydrogen lamp 1216 Å 10.6 eV • ✓T higher than today exp • ✓6eV min E for breaking • typical molecular bonds • ~ 1983 - Particle bombardment • effects of sputtering and ionchemistry • mediated by the solar wind and cosmic rays • Energies Few keV to hundred MeV The brightest UV line Ion beam Sample after Zombec handbook

  13. Laboratory Astrochemistry: Results Many of the observed molecules have been produced in laboratory UV CH3OH (Öberg et al 2009) UV NH3:CO (Grim et al 1989) 46 MeV ions H2O:NH3:CO (Pilling et al. 2010)

  14. A Typical Laboratory Setup Gas Inlet Radiation Source Mass Spect, 1 −A gas is deposited on a cold (≤ 15 K) InfraRed transparent substrate 2 −The ice is then irradiated 3 −Ice evolution is followed by means of IR spectroscopy (mostly transmission) 4 −After irradiation the substrate is heated at a rate of 1-2 K min-1 or slower 5 −The ice desorbs and the desorbed species are detected by the Mass Spectrometer 6 − Refractory residue on the substrate IR

  15. LIFE(Light Irradiation Facility for Exochemistry) UV Source ( HI Lyα ) Cold Finger IR Spectrometer Control System Pumping System Gas Line Mass Spectrometer Needle Valve Gas Inlet

  16. Laboratory vs ISM Conditions: I Temperature 4 - 10 K or higher Chamber pressure: early exp. ~10-7mbar today exp. ~10-10 mbar ~5 × 10-11 mbar How many part. cm-3 in the chamber? At sea level ~1bar and Standard Temperature and Pressure (STP) we have In the best case the density inside the chamber is: ≈ 1.3 × 106 particle cm-3 !!!

  17. Laboratory vs ISM Conditions: II In the best case the density inside the chamber is: ≈ 1.3 × 106 particle cm-3 !!! !! MUCH MORE dense (> 104 times) than the average density in ISM This value is closer to: ✔ Dense cores in molecular clouds (where ices form!) ✔ Regions of stellar formations ISM gas is mainly H2 and CO CO /H2 ≈ 10-6 − 10-4 Diffuse to Dense gas

  18. Laboratory vs ISM Conditions: II cont Laboratory Vacuum Composition ISM CO /H2 ≈ 10-6 − 10-4 2 × 10-9 mbar 5.3 × 107 part. cm-3 1.5 × 10-10 mbar 4 × 106 part. cm-3 H2O H2 CO2 CO Lab CO /H2 ≈ 0.4 − 0.5 H2O !!!

  19. Laboratory vs ISM Conditions: III As in the ISM particles in the chamber stick to the ice. Sticking coefficient Smeasures the capability of a given species to stick to a surface S= f (Surf. Cov, T, F, ….) 0 ≤S≤ 1 The time required to accrete Assuming S=1 ~ 28 hours !! Coarse vacuum conditions high deposition of H2O on top of the ice

  20. Laboratory vs ISM Conditions: III cont Radiation fluxes in the lab are orders of magnitude larger than in the space ✖ even if compatible with stellar emission ✖ not much with the fluxes inside the clouds UV X Laboratory chemistry is quick! ✔ Irradiation times range from min to several hours ✔ The same absorbed energy/photon could take several yr ( or much more !!) in space UV space 6< F<2000 eV 108 cm-2 s-1 Lab 1015 cm-2 s-1 103 yr 1 h Molecular clouds are stable over time > 3 × 107 yr

  21. Molecular InfraRed Spectra InfraRed spectra originate from molecules vibrational-rotational modes 101 105 104 cm-1 102 103 Ultraviolet Visible Near InfraRed Far Infrared Microwaves infrared cm 10-1 10-4 10-2 10-3 10-5 λ = 2.5 × 10-4 cm = 4000 cm-1 λ = 2.5 × 10-3 cm = 400 cm-1 ICES Near−IR: Overtone or Harmonic vibrations Mid−IR: Fundamental vibrations Far−IR: Rotational Spectroscopy

  22. InfraRed Spectra d Iλ(0) IR Source Iλ IR Detector Absorption/Transmission coupling of a dipole vibration with the electric field of the infrared radiation Transmittance Absorbance Optical depth molecule & line dependent

  23. Molecular Vibrational Spectra Change in the dipole moment molecular IR band • Not all the molecules are IR active: • H2, N2 are IR inactive • CO2 linear molecule is IR inactive for symmetric • stretch of the O atoms Symmetrical Strecthing Asymmetrical Strecthing Twisting CH2 Wagging Scissoring Rocking

  24. InfraRed Spectra: II The absorption due to a particular dipole oscillation is generally not affected greatly by other atoms present in the molecule. The absorption occurs at ~ the same frequency for all bonds in different molecules. Functional Groups MolecularFingerprints Trasmittance % Wavenumber (cm-1) Bonds with H (vs C, O) higher energies

  25. InfraRed Spectra: III Absorption of C = O occurs always 1680 − 1750 cm-1 O − H “ “ “ 3400 − 3650 cm-1 C = C “ “ “ 1640 − 1680 cm-1

  26. InfraRed Spectra: cont The Column Density molecular mass The ice tickness species density Avogadro number

  27. X-ray Irradiation of Ices X-ray irradiation of ICEs is a new research field • Why X-ray Irradiation ? • Almost all stars are X-ray emitters • Emission varies with age • Young stars X-rays > EUV & vacuum UV • X-rays penetrate deeply in circumstellar regions • inhibited to EUV and UV after Güdel 2003  after Ribas et al. 2005

  28. X-ray Interaction with the Ice UV HI Lyα 10.9 eV interacts with molecular bonds X-rays photons interact with the atoms of the molecules ph 550 eV = 18 eV KE = hν – BE = 501 eV Auger KE = EA- EB - EC Z BE (eV) 1s 2p1/2 2p3/2 C=2p3/2 8 O 532 24 7 B=2p1/2 A=1s 2 e-18 & 501 eV hν < BE atom into an excited state accompained by single electron emission • Interaction of ices with X-rays is a multistep process • Ionization of the atoms in the molecule • Production of secondary e- which in turn interact with the medium

  29. X-ray Irradiation of Ice 1) Irradiation of simple ices: CO, CO2, H2O, CH3OH study the products their dependence from physical parameter 2) Ice mixtures: H2O + CO + NH3, H2O + CH3OH +NH3 …. We will go Through an Experiment National Synchrotron Radiation Research Center (NSRRC-Taiwan) Irradiation of CH3OH ice with 550 eV photons

  30. X-ray Irradiation of CH3OH Ice • Deposited CH3OH Ice @ 10 K • Take a IR spectrum IR 550 eV Photon Flux ~ 4 × 1012 ph cm-2 s-1 • Compute the ice tickness • using the 1026 cm-1 band • Compute the column density • N = 2.08 × 1018 cm-2 • nML= 2080 • d = 1.08 μm

  31. X-ray Irradiation of CH3OH Ice: cont The used flux ~ 4 × 1012 ph cm-2 s-1 is typical of a very active young solar type star ★ log(N ph cm-2 sec-1)  

  32. X-ray Irradiation of CH3OH Ice: cont 1) Start irradiation sequence @ 550 eV : 16, 80, 160,340, 640,960,1200….70m5s 2) Taking IR spectra after each step Many new features

  33. New Species Formic Acid Acetic Acid Glycolaldehyde Alldetected in the ISM Methane Formaldehyde Methyl Fomate Ethanol b blended W weak

  34. New Species: cont Column densities increase with irradiation time (absorbed energy)

  35. Heating the Ice After irradiation the CH3OH ice is heated at a rate of 1 K/min T T CH3OH start desorbing at ~120 K

  36. Residue A refractory residue left on the substrate

  37. X-rays vs Particle & UV • X-ray • Products of irradiation are more similar to e− • More efficient than e− and UV • HCOOCH3 ≈ 10 times more than e− • HCOOCH3 not a product of UV × a Bennet et al. 2007 b Öberg et al 2009

  38. An Inventory of Molecules in Space H2 C3 c-C3H C5 C5H C6H CH3C3N CH3C4H CH3C5N HC9N c-C6H6 HC11N AlF C2H l-C3H C4H l-H2C4 CH2CHCN HC(O)OCH3 CH3CH2CN (CH3)2CO CH3C6H C2H5OCH3  C60 AlCl C2O C3N C4Si C2H4 CH3C2H CH3COOH (CH3)2 O (CH2OH)2 C2H5OCHO n-C3H7CN C70 C2 C2S C3O l-C3H2 CH3CN HC5N C7H CH3CH2OH CH3CH2CHO CH3OC(O)CH3 CH CH2 C3S c-C3H2 CH3NC CH3CHO C6H2 HCN CH+ HCN C2H2 H2CCN CH3O CH3NH2 CH2OHCHO C8H CN HCO NH3 CH4 CH3SH c-C2H4O l-HC6H CH3C(O)NH2 CO HCO+ HCCN HC3N HC3NH+ H2CCHOH CH2CHCHO C8HF CO+ HCS+ HCNH+ HC2NC HC2CHO C6H– CH2CCHCN C3H6 CP HOC+ HNCO HCOOH NH2CHO H2NCH2CN SiC H2O HNCS H2CNH C5N CH3CHNH HCl H2S HOCO+ H2C2O l-HC4H KCl HNC H2CO H2NCN l-HC4N NH HNO H2CN HNC3 c-H2C3O NO MgCN H2CS SiH4 H2CCNH NS MgNC H3O+ H2COH+ C5N– NaClN2H+c-SiC3 C4H– HNCHCN OH N2O CH3 HC(O)CN PN NaCN C3N– HNCNH SO OCS PH3 CH3O SO+ SO2 HCNO NH4± SiN c-SiC2 HOCN H2NCO± SiO CO2 HSCN SiS NH2 H2O2 CS H3+C3H± HF SiCN HMgNC HD AlNC FeO SiNC O2 HCP CF+ CCP SiH AlOH PO H2O+ AlOH2Cl± OH+ KCN CN= FeCN SH± HO2 SH TiO2 HCl± TiO ArH± ≥ 75% contains Carbon The interstellar chemistry is carbon-dominated

  39. Organic Molecules & Origin of Life on Earth Our Solar System was born 4.6 × 109 yr Meteorites, comets etc etc bombardment CONDITIONS NOT CONDUCIVE TO LIFE End of impacts 3.8 × 109 Life started on Earth 3.6 × 109 Only 200 million yr ! 3.55 × 109 yr old fossilized microorganisms (< 10 μm) from the Barberton Greenstone Belt (South Africa).

  40. … if (& oh what a big if) we could conceive in some warm little pond with all sorts of ammonia & phosphoric salts,—light, heat, electricity……a protein compound was chemically formed….(Charles Darwin, 1 Feb 1871, letter to J.D. Hooker) 1953: Miller Experiment CH4, NH3, H2O, H2 Earth atmosphere composition(N2, CO, CO2 H2O) …… too rich of O

  41. Amino Acids in Space ? To date amino acids have not been detectedin the Interstellar Medium. 1999: NASA’s Stardust (http://stardustnext.jpl.nasa.gov) Glycine detection in a samples from comet 81P/Wild 2 (Elsila et al 2009) • Laboratory UV irradiation of ice mixtures: • H2O:CH3OH:NH3:CO:CO2 • glycine, serine, alanine,valine, • aspartic acid, proline (Muñoz-Caro et al 2002) • H2O:CH3OH:NH3:HCN • glycine, serine, alanine, (Bernstein et al 2002)

  42. Amino Acids in Space ? cont ManyComplexmolecules in Space are Prebiotic (i.e. withstructuralelements in common withthosefound in living organisms) • 2002 Hydrogenated sugar, ethylene glycol HOCH2CH2OH • 2004 Interstellar sugar, glycolaldehyde CH2OHCHO • 2006 The largest interstellar molecule with a peptide bond, Acetamide, CH3CONH2 • 2008 A direct precursor of the amino acid glycine, amino acetonitrile NH2CH2CN It is likely that life is a common phenomenon throughout our Universe

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