IR Spectroscopy and physicochemical effects on astrophysical ices produced by energetic ions collisions Ana Lucia de Barros Physics Department Centro Federal de Educação Tecnológica Celso Suckow da Fonseca Rio de Janeiro, Brazil Guilherme C. Almeida Physics Department Pontifícia Universidade Católica Rio de Janeiro, Brazil Cíntia A. P. da Costa Physics Department Pontifícia Universidade Católica Rio de Janeiro, Brazil Enio F. da Silveria Physics Department Pontifícia Universidade Católica Rio de Janeiro, Brazil INTERNATIONAL SYMPOSIUM AND WORKSHOP ON ASTROCHEMISTRY ISWA Campinas July 2016
Astrophysical ices Orion Nebula The grains are covered with an icy mantle formed from simple molecules (H 2 O, CO, CO 2, O, CH 4, etc). Energetic processes induced by: - photons, - electrons (high and low-energy), - ions (cosmic rays, solar wind). Carina Nebula NASA website NASA website Irradiation induces chemical modification and desorption of species from the ice.
Astrophysical ices: energetic processes state of the art Projectiles: photons (e.g. new molecules, destruction/formation cross sections, photodesorption ) H 2 O:CH 3 OH:NH 3 :CO:CO 2 Muñoz Caro et al., Nature 416 (2002) 403 electrons (low and high energy range) (e.g. same as Photons) ~1-20 ev CH 3 COOH:NH 3 Lafosse et al., PCCP 8 (2006) 5564 ions (mainly H, He, C, O ions in ~50 kev and ~2 MeV energy range) (e.g. new molecules, destruction/formation cross sections, sputtering) In this work H + and He + at 1.5 MeV H 2 O Strazzulla & Baratta, Europhysics Letter 18 (1992) 517
PUC Van de Graaff Accelerator Rio de Janeiro, Brazil INTERNATIONAL SYMPOSIUM AND WORKSHOP ON ASTROCHEMISTRY ISWA Campinas July 2016
PUC Van de Graaff Accelerator FTIR Beamline UHV Chamber Overview
Experimental details Substrate Kbr window Temperature T = 10 K FTIR spectrometer cryostat irradiation/analysis chamber connection to beam line Pressure in irradiation chamber ~ 2 x 10-8 mbar (~10 K) Samples (ices- O) - in situ gas deposition - thickness ~ 0.1-2 mm (10 16-10 17 molecules/cm 2 ) - ion penetration depth > ice thickness Ion beam - 1.5 MeV H + and He + - flux ~10 9 ion/cm 2 s - fluence up to 2.0 x 10 13 ions/cm 2 INTERNATIONAL SYMPOSIUM AND WORKSHOP ON ASTROCHEMISTRY ISWA Campinas July 2016
Irradiation Process SALT WINDOWS INFRARED DETECTOR O ICE INFRARED SOURCE GAS INLET CRYOSTAT H + or He + BEAM VACUUM PUMP http://www.astrochem.org/sci_img/chamberschematic.jpg
Absorbance Absrobance(peak area) FTIR spectrum of O ice 3.0 100 2.5 2.0 H + N O 2 He + Non irradiated c = 1.07x10-11 cm 2 d = 2.05x10-12 cm 2 3 1.5 3 + 2 2 1 + 2 2 1.0 10 1 + 3 1 1 2 2 0.5 N(0) =ln10. Sp /A p = 2.26 x1018 v 0 1 2 3 4 5 6 7 8 9 10 11 3500 3000 Fluence 2500 (10 11 2000 ions cm -2 ) 1500 1000 Wavenumbers (cm -1 ) Absorbance d N ln(10) A( cm / molecule ) Abs( ) total band absorbance A integrated absorbance
Absorbance Observed Daughter Species O 0.8 O O 3 O 4 0.6 O O O N 4 5 2 O 5 3 O 2 0.4 0.2 0.0 1750 1700 1650 1600 1550 1500 1450 1400 1350 1300 1250 Wavenumbers (cm -1 ) INTERNATIONAL SYMPOSIUM AND WORKSHOP ON ASTROCHEMISTRY ISWA Campinas July 2016
Column density (10 16 molecules cm -2 ) Daughter Species 1.5 MeV H + O 100 10 H + NO 2 NO O 3 1 O 2 O 3 O 4 0.1 O 5 0.01 0 2 4 6 8 10 12 Fluence (10 11 ions cm -2 )
Column density (10 16 molecules/cm 2 ) Daughter Species 1.5 MeV He + O 1 He + NO 2 NO O 3 O 2 0.1 O 3 O 4 0.01 O 5 1E-3 0.00 0.01 0.02 0.03 0.04 Fluence (10 11 ions cm -2 )
Column density (10 17 molecules/cm 2 ) Precursors Integrated (Destruction + Formation) Cross Sections 4 3.5 3 Destruction d 2.5 2 1.5 O 1 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 )
Column density (10 16 molecules/cm 2 ) Column density (10 17 molecules/cm 2 ) Precursors Integrated (Destruction + Formation) Cross Sections 4 3.5 3 Destruction d 2.5 2 1.5 O 3.0 2.5 1 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 ) 2.0 1.5 N x O y 1.0 0.5 f Formation 0.0 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 ) N x O y (Formation + Destruction) Cross Sections
Column density (10 16 molecules/cm 2 ) Column density (10 17 molecules/cm 2 ) Precursors Integrated (Destruction + Formation) Cross Sections 4 3.5 3 Destruction d 2.5 2 1.5 O 3,0 2,5 Destruction 1 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 ) 2,0 1,5 N x O y 1,0 0,5 f Formation 0,0 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 ) N x O y (Formation + Destruction) Cross Sections
Column density (10 16 molecules/cm 2 ) Column density (10 17 molecules/cm 2 ) CH Precursors 3 OH Integrated (Destruction + + Formation) Cross Cross Sections 4 3,5 3 Destruction d 2,5 2 Formation f 1,5 O 3,0 2,5 Destruction 1 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 ) 2,0 1,5 N x O y 1,0 0,5 f Formation 0,0 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 )
Column density (10 16 molecules/cm 2 ) Column density (10 17 molecules/cm 2 ) Precursors Integrated (Destruction + Formation) Cross Sections 4 3,5 3 2,5 2 Destruction d Formation f regeneration of O from its daughter molecules 1,5 O 3,0 2,5 Destruction 1 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 ) 2,0 1,5 N x O y 1,0 0,5 f Formation 0,0 0 2 4 6 8 10 12 14 Fluence (10 15 impacts/cm 2 )
Average (integrated) Cross Sections E in = 1.5 MeV H + 0 dn df i j i f, ijn j Li d, i N i Y i H 2 O O 100Å N i is the column density of molecular species i; f and d formation and destruction cross sections; L i and Y i are their layering and sputtering yields; Approximate Equations... Precursor molecule Daughter molecule dn df dnk f, k1n1 d, k N df k 1 f,1k Nk d,1n1 k There is no chemical reaction between daughter species!!!!!
Cross Sections Destruction and formation cross-sections (10-14 cm 2 ) of O with H + Molecules 10 K at 1.5 MeV Formation cross-section Destruction crosssection Precursor O - (2.1 ± 0.5) NO 2 (1.1 ± 0.2) (1.3 ± 0.2) O 2 (0.09 ± 0.01) (3.1 ± 0.6) Daughters NO (0.54 ± 0.08) (1.0 ± 0.5) S.08 O 3 (0.25 ± 0.02) (5.4 ± 0.7) O 4 (0.03 ± 0.01) (3.8 ± 0.8) O 5 (0.02 ± 0.01) (3.3 ± 0.8) O 3 (0.05 ± 0.02) (4.8 ± 0.4) de Barros et al., in press
The dissociation cross-sections due to 4 projectiles at different energies are determined, assuming validity of the d ~ S e 2/3 power law. 10 O d = a S e 2/3 136 Xe 26+ 90 MeV d x 10-13 cm 2 ) 1 H + 1.5 MeV He + 1.5 MeV N + 1.5 MeV 10 100 1000 S e (ev.10-15 / atoms/cm 2 ) INTERNATIONAL SYMPOSIUM AND WORKSHOP ON ASTROCHEMISTRY ISWA Campinas July 2016
Summary Our experiments demonstrate that 1.5 MeV ion irradiation of nitrous oxide with H + leads to production of molecules NO 2, O 2, NO, O 3, O 4, O 5 and O 3 ; The most abundant daughter species are NO 2 and NO; Same results where observed for the He + beam irradiation; The formation and destruction cross sections of both ion beams where determined; For the O matrix, the dependence of the destruction cross section on the stopping power is found to follow a power law, i.e., σ d S e n, where n 2/3. INTERNATIONAL SYMPOSIUM AND WORKSHOP ON ASTROCHEMISTRY ISWA Campinas July 2016
Acknowledgments Thank you