1. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Ion Irradiation of Astrophysical Ice Analogues 4 th Annual LEIF Meeting, Belfast Anita Dawes

2. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Introduction Not much is known about the mechanisms involved in solid state chemistry in astrophysical environments. Not much is known about the mechanisms involved in solid state chemistry in astrophysical environments. Over 120 molecular species have been detected in space Over 120 molecular species have been detected in space Abundances and formation cannot be explained by gas phase chemistry Abundances and formation cannot be explained by gas phase chemistry

3. Sun 29 th June 2003 A.Dawes@ucl.ac.uk 234567891011 H2H2 C3C3 c-C 3 H C5C5 C 5 H C 6 H CH 3 C 3 N CH 3 C 4 H CH 3 C 5 N? HC 9 N AlF C2HC2Hl-C 3 H C4HC4Hl-H 2 C 4 CH 2 CHCN HCOOCH 3 CH 3 CH 2 CN (CH 3 ) 2 CO AlCl C2OC2OC 3 N C 4 SiC 2 H 4 CH 3 C2H CH 3 COOH (CH 3 ) 2 O NH 2 CH 2 COOH ? 12 C2C2 C2SC2SC 3 O l-C 3 H 2 CH 3 CNHC 5 N C7HC7HCH 3 CH 2 OH C6H6C6H6 CH CH 2 C 3 S c-C 3 H 2 CH 3 NC NH 2 CH 3 H2C6H2C6 HC 7 N CH + HCNC2H2C2H2 CH 2 CNCH 3 OHHCOCH 3 CH 2 OHCHO C 8 H 13+ CNHCOCH 2 D + ? CH 4 CH 3 SH c-C 2 H 4 O HC 11 N COHCO + HCCN HC 3 NHC 3 NH + CH 2 CHOH PAHs CO + HCS+HCNH + HC 2 NCHC 2 CHO C60 + CPHOC+HNCOHCOOHNH 2 CHO CSi H2OH2O HNCS H 2 CHNC 5 N HCl H2SH2SHOCO + H2C2OH2C2O KCl HNCH 2 COH 2 NCN NHHNOH2CN HNC 3 NO MgCNH 2 CSSiH 4 NS MgNCH3O+H3O+ H 2 COH + NaClN 2 H+NH 3 OHN2ON2OSiC 3 PN NaCN SOOCS SO+ SO 2 SiN c-SiC2 SiO CO 2 SiS NH 2 CSH3+H3+ HFSiCN SH FeOAlNC >120 Interstellar and Circumstellar Molecules National Radio Astronomy Observatory Formic Acid Acetic Acid Glycolaldehyde Benzene Cyanopolyynes Glycine ? http://www.cv.nrao.edu/~awootten/allmols.html

4. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Whittet et.al.A&A 315, L357-L360 (1996) Ices in Space... Gibb et.al. ApJ 536, 347-356 (2000) W33ASpeciesElias16 NGC 7538 IRS 9 GL 7009S W33A GL 2136 Sgr A* Comets H2OH2OH2OH2O100 CO (total) 25161582<125-30 CO (polar) 32-62-- CO (nonpolar) 2214-2--- CO 2 (total) 1822211316143-20 CO 2 (polar) 1814-111314- CO 2 (nonpolar) <18-23<1<1- CH 4 -241.5-21 CH 3 OH <3530186<40.3-5 H 2 CO -4363<3<30.2-1 HCOOH-3-7-30.05 OCS<0.2-0.2 --0.5 NH 3  913-15-20-300.1-1.8 XCN<0.511.53.50.3-0.01-0.4 Gibb et.al. ApJ 536, 347-356 (2000)

5. Sun 29 th June 2003 A.Dawes@ucl.ac.uk PlanetSatelliteIces JupiterIoSO 2, SO 3, H 2 S?, H 2 O? EuropaH 2 O, SO 2, SH, CO 2, CH, XCN, H 2 O 2, H 2 SO 4 GanymedeH 2 O, SO 2, SH, CO 2, CH, XCN, O 2, O 3 CallistoH 2 O, SO 2, SH, CO 2, CH, XCN SaturnMimasH2OH2O EnceladusH2OH2O TethysH2OH2O DioneH 2 O, C, HC, O 3 RheaH 2 O, HC?, O 3 HyperionH2OH2O IapetusH 2 O, C, HC, H 2 S? PhoebeH2OH2O RingsH2OH2O UranusMirandaH 2 O, NH 3 ArielH 2 O, OH? UmbrielH2OH2O TitaniaH 2 O, C, HC, OH? Oberon NeptuneTritonN 2, CH 4, CO, CO 2, H 2 O PlutoCharonH 2 O, NH 3, NH 3 hydrate N 2, CH 4, CO, H 2 O KBO’sH 2 O, HC-ices (CH 4, CH 3 OH), HC, silicates Ices in the outer Solar System

6. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Introduction Not much is known about the mechanisms involved in solid state chemistry in astrophysical environments. Not much is known about the mechanisms involved in solid state chemistry in astrophysical environments. Over 120 molecular species have been detected in space Over 120 molecular species have been detected in space Abundances and formation cannot be explained by gas phase chemistry Abundances and formation cannot be explained by gas phase chemistry Require laboratory data to understand the mechanisms involved in condensed phase molecular formation/destruction. Require laboratory data to understand the mechanisms involved in condensed phase molecular formation/destruction. The nature of ices and their processing depends on the environment in which they are found... The nature of ices and their processing depends on the environment in which they are found...

7. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Radiation Environments The astrophysical ices can be broadly divided into 3 environments: The astrophysical ices can be broadly divided into 3 environments: Icy grain mantles in the ISM Icy grain mantles in the ISM Dense clouds: Lyman- , cosmic rays Dense clouds: Lyman- , cosmic rays Cold diffuse clouds: UV dominated Cold diffuse clouds: UV dominated Cometary ices Cometary ices Oort cloud: cosmic ray dominated Oort cloud: cosmic ray dominated Icy solar system bodies Icy solar system bodies e.g. Mars polar caps: solar wind, solar UV e.g. Mars polar caps: solar wind, solar UV Galilean satellites: magnetospheric ions (dominant) & solar wind – O +, O 2+, O 3+, O 4+, O 6+, S +, S 2+, S 3+, S 4+, S 5+, S 2 +, SO 2 +, Na +, K 2+, C 6+, H 2 O +, H 3 O +, OH +, H +, He +, H 2 + and H 3 + Galilean satellites: magnetospheric ions (dominant) & solar wind – O +, O 2+, O 3+, O 4+, O 6+, S +, S 2+, S 3+, S 4+, S 5+, S 2 +, SO 2 +, Na +, K 2+, C 6+, H 2 O +, H 3 O +, OH +, H +, He +, H 2 + and H 3 + The ices can be physically characterised by the: The ices can be physically characterised by the: Thickness, temperature & composition Thickness, temperature & composition Energy, flux & type of processing radiation Energy, flux & type of processing radiation In our laboratory regime: In our laboratory regime: Ices are already present, i.e. not concerned with ice Ices are already present, i.e. not concerned with ice accretion / formation  thick ice layers (to ignore the effect of the substrate)  thick ice layers (to ignore the effect of the substrate) Ion, photon and electron irradiation Ion, photon and electron irradiation

8. Sun 29 th June 2003 A.Dawes@ucl.ac.uk To pumping station Electrical feed- through Rotary feed- through Detectors (Spectroscopy): UV-VIS / FTIR spectrometer PMT Sources (Spectroscopy): UV-VIS / FTIR spectrometer Synchrotron Liquid Helium / Liquid Nitrogen Cryostat Resistive heater Rhodium-iron RTD CaF 2 substrate Copper sample mount Ion gauge 50.15 Liquid nitrogen exhaust Cryogen inlet via transfer line Temperature controller HV (UHV) chamber: HV (UHV) chamber: P~10 -7 -10 -10 mbar P~10 -7 -10 -10 mbar CaF 2 substrate for transmission spectroscopy CaF 2 substrate for transmission spectroscopy 120 nm – 10  m 120 nm – 10  m Temperature: Temperature: LN2 / LHe cryostat LN2 / LHe cryostat >30 K >30 K Rh-Fe sensor Rh-Fe sensor Resistive coax. Heater Resistive coax. Heater 4 ports 4 ports Sample deposition Sample deposition Spectroscopy Spectroscopy Irradiation Irradiation Transmission spectra recorded vs. wavelength / frequency Transmission spectra recorded vs. wavelength / frequency Portable Apparatus

9. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Sample Preparation Ice layers are vapour deposited directly onto a cold substrate. The gases are prepared in a reservoir prior to dosing Pure gases or mixtures Sample thickness is determined from the pressure of gas deposited. Ice thickness is calibrated by measuring the absorption through the sample (column densities) or analysing interference fringes ~10  m thick CO 2 ice (left) ~3  m thick H 2 O ice (right)

10. Sun 29 th June 2003 A.Dawes@ucl.ac.ukRadiationSourceEnergyPhoton Hydrogen Lamp (on-site not yet in operation) Synchrotron Radiation (Daresbury SRS & Århus ASTRID) Limited Wavelengths (Lyman-  dominated) Tuneable: (3-10eV) (grating monochromator) Electron Electron Gun (on-site not yet in operation) < 20 eV Ion: singly and multiply charged Van de Graff Accelerator (QUB) ECR Ion source (QUB) keV – MeV Low keV Sample Irradiation 1 hour of irradiation in the lab is equivalent to 1000 years irradiation in space!  Once deposited, the samples are irradiated with either photons, ions or electrons The products may be probed at regular intervals by spectroscopy The products may be probed at regular intervals by spectroscopy UV-VIS & VUV : Electronic Structure UV-VIS & VUV : Electronic Structure FTIR : Vibrational Structure FTIR : Vibrational Structure

11. Sun 29 th June 2003 A.Dawes@ucl.ac.uk What are we currently looking at? Study of H 2 O, CO 2 and H 2 O:CO 2 ices Study of H 2 O, CO 2 and H 2 O:CO 2 ices These are two of the most abundant molecules These are two of the most abundant molecules Present in all astrophysical environments (grain mantles, comets, Galilean satellites, Mars & Triton. Present in all astrophysical environments (grain mantles, comets, Galilean satellites, Mars & Triton. Irradiation with ions Irradiation with ions 100 keV H + 100 keV H + Low energy (1-5 keV) singly charged ions Low energy (1-5 keV) singly charged ions Low energy (1-5*q keV) multiply charged ions Low energy (1-5*q keV) multiply charged ions implantation – reactive ions: C + on H 2 O and H + on CO 2 implantation – reactive ions: C + on H 2 O and H + on CO 2 Irradiation with photons Irradiation with photons Zero order Synchrotron radiation Zero order Synchrotron radiation Discrete wavelengths (synchrotron grating monochromator) Discrete wavelengths (synchrotron grating monochromator) Products we are looking for in H 2 O:CO 2 ices: Products we are looking for in H 2 O:CO 2 ices: Carbonic acid (H 2 CO 3 ) Carbonic acid (H 2 CO 3 ) CO, CO 3, H 2 O:CO 2 complex, HCO, O 3 (?) and others (?) CO, CO 3, H 2 O:CO 2 complex, HCO, O 3 (?) and others (?) FTIR spectra FTIR spectra

12. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Irradiation of H 2 O:CO 2 ice at 90 K with 100 keV H + H2OH2O H2OH2O H2OH2O CO 2 13 CO 2 CO 2 H 2 O:CO 2 H2OH2O H2OH2O H2OH2O CO 2 13 CO 2 CO 2 H 2 O:CO 2 H 2 CO 3 (2850) H 2 CO 3 (2580) CO (2140) CO 3 (2044) H 2 CO 3 (1703) H 2 CO 3 (1488) H 2 CO 3 (1295) After 1 hour irradiation

13. Sun 29 th June 2003 A.Dawes@ucl.ac.uk H2OH2O H2OH2O H2OH2O CO 2 13 CO 2 H 2 O:CO 2 H2OH2O H2OH2O H2OH2O CO 2 13 CO 2 H 2 O:CO 2 H 2 CO 3 (2850) H 2 CO 3 (2580) CO (2140) H 2 CO 3 (1703) H 2 CO 3 (1488) H 2 CO 3 (1295) NO CO 3 ! After 0.5 hour irradiation Irradiation of H 2 O:CO 2 ice at 50 K with 5 keV H +

14. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Warm-up after H + Irradiation of H 2 O:CO 2 ice 50 K100 K120 K140 K CO 2 H2OH2O H2OH2O 160 K CO 2 H2OH2O H2OH2O H2OH2O CO Crystalline H 2 O CO 2 H2OH2O 180 K CO 2 H2OH2O H2OH2O H2OH2O CO 200 K H2OH2O H2OH2O H2OH2O CO 2 220 K H2OH2O CO 2 Temp: H 2 CO 3 250 K

15. Sun 29 th June 2003 A.Dawes@ucl.ac.uk H 2 CO 3 yield after irradiation with H +, He +, O + and Ne + (all at 5 keV) Yield depends on: Ion range? Ion range? Reactive, unreactive ion? Reactive, unreactive ion? Low or no yield with multiply charged ions (N 3+, N 5+, N 6+ ) – not shown here: Lack of secondary electrons? Lack of secondary electrons? Small penetration depth? Small penetration depth?

16. Sun 29 th June 2003 A.Dawes@ucl.ac.uk The CO profile The 2152 cm -1 CO feature possible origin: formation at different sites in the ice matrix (substitutional / interstitial) formation at different sites in the ice matrix (substitutional / interstitial) (Sandford et.al. ApJ 329, 498- 510, 1998) CO diffusion into unirradiated ice and interaction with the dangling OH bonds CO diffusion into unirradiated ice and interaction with the dangling OH bonds (Palumbo, J Phys Chem A, 101, 4298-4301, 1997) (Sandford et.al. ApJ 329, 498-510, 1998)

17. Sun 29 th June 2003 A.Dawes@ucl.ac.uk CO formation by irradiation of H 2 O:CO 2 =1 with different ions (5*q keV) at 50K The 2152 cm -1 CO feature : Increases with mass of ion Increases with mass of ion  interstitial ? Increases with decreasing penetration depth of ion Increases with decreasing penetration depth of ion  diffusion ? Repeated experiment at ~ 100 K with heavier ions..... No 2152 feature! Repeated experiment at ~ 100 K with heavier ions..... No 2152 feature!  diffusion ? (CO partially sublimes >27 K) CO H+H+ He + N 3+ O+O+ Ne +

18. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Irradiation of pure H 2 O with 2 keV C + Irradiation time 00:0000:15 00:3000:4501:0001:15 CO Apolar Component Polar Component 2152 cm -1 feature 01:15

19. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Summary of Results... More questions...? CO, CO 3 and H 2 CO 3 were seen after irradiation of H 2 O:CO 2 with 100 keV H + CO, CO 3 and H 2 CO 3 were seen after irradiation of H 2 O:CO 2 with 100 keV H +But... No H 2 CO 3 seen with highly charged ions (or signal too weak?) No H 2 CO 3 seen with highly charged ions (or signal too weak?) Low penetration depth? Low penetration depth? Lack of secondary electrons? Lack of secondary electrons? PE vs KE effect? PE vs KE effect? No CO 3 seen after irradiation of H 2 O:CO 3 with low (<5*q keV) energy/multiply charged ions! No CO 3 seen after irradiation of H 2 O:CO 3 with low (<5*q keV) energy/multiply charged ions! KE vs PE effect? KE vs PE effect? Nuclear vs electronic stopping? Nuclear vs electronic stopping? 2152 cm -1 feature of CO was seen in H 2 O:CO 2 irradiated ice with heavier ions at T<60 K 2152 cm -1 feature of CO was seen in H 2 O:CO 2 irradiated ice with heavier ions at T<60 KBut... 2152 cm -1 feature was not seen in H 2 O:CO 2 irradiated ice with any ion at T > 90 K 2152 cm -1 feature was not seen in H 2 O:CO 2 irradiated ice with any ion at T > 90 K Many more...

20. Sun 29 th June 2003 A.Dawes@ucl.ac.uk To do... Search for Answers! Changing the beam... Singly vs. multiply charged ions Singly vs. multiply charged ions kinetic vs. potential effects? kinetic vs. potential effects? Secondary electrons... Secondary electrons... Different energies Different energies nuclear vs. electronic stopping effect of ions (latter dominates as energy increases) nuclear vs. electronic stopping effect of ions (latter dominates as energy increases) Different ions Different ions Effect of ion mass/momentum/velocity Effect of ion mass/momentum/velocity Reactive / unreactive ions Reactive / unreactive ions Implantation – chemical vs. physical effects Implantation – chemical vs. physical effects Low energy electron irradiation Low energy electron irradiation Secondary electron effect following ion irradiation Secondary electron effect following ion irradiation Ion vs. Photon irradiation Ion vs. Photon irradiation Systematic comparison Systematic comparison Changing the sample... Temperature Temperature Diffusion (e.g. CO) Diffusion (e.g. CO) Activation energy Activation energy Crystalline vs. amorphous ice Crystalline vs. amorphous ice Get down to 10K!! Get down to 10K!! Composition Composition Isotopic substitution to identify reaction pathways Isotopic substitution to identify reaction pathways Ratio of components Ratio of components Structure Structure Porosity Porosity Crystalline vs. amorphous ice Crystalline vs. amorphous ice Thickness Thickness Ion / photon penetration depth Ion / photon penetration depth Implantation Implantation

21. Sun 29 th June 2003 A.Dawes@ucl.ac.uk General Summary More experimental work is needed to fully understand the mechanisms involved in synthesis of molecules under astrophysical environments... More experimental work is needed to fully understand the mechanisms involved in synthesis of molecules under astrophysical environments... The design of the new apparatus allows flexibility to perform a wide variety of experiments, using different sources to irradiate samples and implement a variety of spectroscopic techniques using different instruments. The design of the new apparatus allows flexibility to perform a wide variety of experiments, using different sources to irradiate samples and implement a variety of spectroscopic techniques using different instruments. Ion accelerators – Belfast (singly & multiply charged ions) Ion accelerators – Belfast (singly & multiply charged ions) Synchrotron Sources – Århus & Daresbury (irradiation & spectroscopy... Circular dichroism) Synchrotron Sources – Århus & Daresbury (irradiation & spectroscopy... Circular dichroism) Electron and photon sources Electron and photon sources These experiments will enable us to better understand the processes behind chemical processing if ices in the ISM and the planets, satellites, comets and meteorites within our solar system. (The apparatus can also be adapted to study atmospheric ices e.g. polar stratospheric clouds) These experiments will enable us to better understand the processes behind chemical processing if ices in the ISM and the planets, satellites, comets and meteorites within our solar system. (The apparatus can also be adapted to study atmospheric ices e.g. polar stratospheric clouds) A systematic experimental approach is required to identify reaction pathways and intermediates whilst pinning down the different variables (both sample and irradiation parameters). A systematic experimental approach is required to identify reaction pathways and intermediates whilst pinning down the different variables (both sample and irradiation parameters). Many more experiments to come... Many more experiments to come...

22. Sun 29 th June 2003 A.Dawes@ucl.ac.uk Acknowledgements Nigel Mason Stephen Brotton Mike Davis Philip Holtom Bob McCullough and Ian Williams (QUB) Roland Trassl (Geissen University) S ø ren Vrønning Hoffmann (ASTRID, Århus)