Formation of complex molecules after energetic processing of icy grain mantles

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1 Formation of complex molecules after energetic processing of icy grain mantles Maria Elisabetta Palumbo INAF Osservatorio Astrofisico di Catania

2 Molecules in space

3 Origin of interstellar molecules Gas-phase reactions Solid phase Grain-surface reactions Energetic processing of icy mantles (molecules are released to the gas phase after desorption of ices)

4 Icy grain mantles UV photons Freeze out of gas phase species (CO) Grain surface reactions (H 2 O, CH 3 OH, CH 4, H 2 S) cosmic ions Energetic processing of icy mantles (CO 2, OCS)

5 Abundance of solid-phase molecules (with respect to H 2 O=100) It is generally accepted that other molecules are also present in icy grain mantles

6 Ion beam Vacuum chamber IR spectrometer Vacuum chamber details The sample is processed by energetic ions ( kev) and by UV photons separately or simultaneously. IR spectra are taken before and after processing.

7 column density (molecules/cm 2 ) column density (molecules/cm 2 ) CH 3 OH Palumbo et al. 1999, A&A 342, 551 Baratta et al. 2002, A&A 384, kev He ev photons CH 3 OH dose (ev/16amu) CH4 30 kev He ev photons 30 kev He ev photons H 2 CO dose (ev/16amu)

8 Methyl formate and glycoladehyde Modica and Palumbo 2010 A&A 519, A22

9 Methyl formate in star-forming regions source N(HCOOCH 3 )/N(H 2 ) references Sgr B2 N(LMH) (hot core) Snyder 2006 IRAS B (hot corino) > Remijan & Hollis 2006 NGC 2264 MMS (hot core) ( ) 10-8 Sakai et al N(CO) 10-4 N(H 2 ) (Frerking et al. 1982) N(CH 3 OH) 10-1 N(CO) CO HCO H 2 CO CH 3 O CH 3 OH (Watanabe et al Fuchs et al. 2009) N(CH 3 OH) 10-5 N(H 2 ) N(HCOOCH 3 ) 10-3 N(CH 3 OH) assuming high CO depletion this work N(HCOOCH 3 ) 10-8 N(H 2 ) The amount of methyl formate formed after ion irradiation can account for the observed abundances Modica and Palumbo 2010, A&A 519, A22

10 Ammonium carbamate and ammonium formate Lv et al PCCP 16, 3433

11 Present limits Solid CH 3 OH Species not present before processing CO 20% w.r.t. CH 3 OH H 2 CO 10% CO 2 6% CH 4 5% HCOOCH 3 0.2% (methyl formate) HCOCH 2 OH 0.1% (glycolaldehyde) Modica and Palumbo, 2010

12 WP6. Laboratory Astrophysics Open question: What and how many complex molecules are formed in icy grain mantles by energetic processing? Aim: To build up a new and original experimental set-up that will detect molecules formed after energetic ion bombardment of simple ices, using a combination of laser desorption, He jet cooling and UV-tunable photo-ionization followed by high resolution mass-spectrometric analysis. Gain: Present relative sensitivity (i.e. IR spectroscopy) ~10-3 (column density) Expected relative sensitivity 10-7 (mass abundance)

13 Future experimental procedure Substrate T= K Top view Sample T= K kev ions

14 Future experimental procedure Substrate T= K Top view Time of flight mass spectrometer Processed sample T= K plume Helium jet Pulsed valve He-gas jet Desorption laser Ionization laser

15 Schematic of the new vacuum chamber Pulsed valve position UHV chamber inner diameter 20 cm Desorption laser to the TOF-MS Ion beam line

16 Recruitment 1 PhD student (cycle XXX) Dottorato in Scienza dei Materiali e Nanotecnologie Università degli Studi di Catania 1 post-doc fellow Submission deadline 26 February 2015 at 13.00

17 Acknowledgments Giuseppe Baratta Giuseppe Compagnini Saro Di Benedetto Vincenzo Greco Zuzana Kanuchova Carlotta Scirè Giovanni Strazzulla Alessandra Taffara Riccardo Urso