It has been proposed that organic molecules required for life on earth may be formed by the radiation processing of molecular ices in space environments, e.g., within our solar system. Such processes can be studied in the laboratory with surface science analytical techniques and by using low-energy electron (LEE) irradiation to simulate the effects of the secondary electrons that are generated in great abundance whenever ionizing radiation interacts with matter. Here we present new measurements of 70 eV LEE irradiation of multilayer films of CH4, 18O2, and CH4/18O2 mixtures (3:1 ratio) at 22 K. The electron stimulated desorption (ESD) yields of cations and anions have been recorded as a function of electron fluence. At low fluence, the prompt desorption of more massive multi-carbon or C—O containing cationic fragments agrees with our earlier measurements. However, new anion ESD signals of C2−, C2H−, and C2H2− from CH4/18O2 mixtures increase with fluence, indicating the gradual synthesis (and subsequent electron-induced fragmentation) of new, more complex species containing several C and possibly O atoms. Comparisons between the temperature programed desorption (TPD) mass spectra of irradiated and unirradiated films show the electron-induced formation of new chemical species, the identities of which are confirmed by reference to the NIST database of electron impact mass spectra and by TPD measurements of films composed of the proposed products. New species observed in the TPD of irradiated mixture films include C3H6, C2H5OH, and C2H6. Furthermore, X-ray photoelectron spectroscopy of irradiated films confirms the formation of C—O, C=O, and O=C—O— bonds of newly formed molecules. Our experiments support the view that secondary LEEs produced by ionizing radiation drive the chemistry in irradiated ices in space, irrespective of the radiation type.
REFERENCES
1.
A. G. G. M.
Tielens
, “The molecular universe
,” Rev. Mod. Phys.
85
, 1021
–1081
(2013
).2.
P.
Ehrenfreund
and S. B.
Charnley
, “Organic molecules in the interstellar medium, comets, and meteorites: A voyage from dark clouds to the early earth
,” Annu. Rev. Astron. Astrophys.
38
, 427
–483
(2000
).3.
S.
Pizzarello
and E.
Shock
, “The organic composition of carbonaceous meteorites: The evolutionary story ahead of biochemistry
,” Cold Spring Harbor Perspect. Biol.
2
, a002105
(2015
).4.
A. S.
Burton
, J. C.
Stern
, J. E.
Elsila
, D. P.
Glavin
, and J. P.
Dworkin
, “Understanding prebiotic chemistry through the analysis of extraterrestrial amino acids and nucleobases in meteorites
,” Chem. Soc. Rev.
41
(16
), 5459
–5472
(2012
).5.
H. S. P.
Müller
, F.
Schlöder
, J.
Stutzki
, and G.
Winnewisser
, “The cologne database for molecular spectroscopy, CDMS: A useful tool for astronomers and spectroscopists
,” J. Mol. Struct.
742
, 215
–227
(2005
).6.
A.
Belloche
, H. S. P.
Müller
, K. M.
Menten
, P.
Schilke
, and C.
Comito
, “Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)
,” Astron. Astrophys.
559
, A47
(2013
).7.
T. E.
Madey
, R. E.
Johnson
, and T. M.
Orlando
, “Far-out surface science: Radiation-induced surface processes in the solar system
,” Surf. Sci.
500
, 838
–858
(2002
).8.
B. W.
Carroll
and D. A.
Ostlie
, An Introduction to Modern Astrophysics
, 2nd ed. (Pearson
, 2007
).9.
C. J.
Bennett
, C.
Pirim
, and T. M.
Orlando
, “Space-weathering of solar system bodies: A laboratory perspective
,” Chem. Rev.
113
, 9086
–9150
(2013
).10.
S. M.
Pimblott
and J. A.
LaVerne
, “Production of low-energy electrons by ionizing radiation
,” Radiat. Phys. Chem.
76
(8-9
), 1244
–1247
(2007
).11.
E.
Böhler
, J.
Warneke
, and P.
Swiderek
, “Control of chemical reactions and synthesis by low-energy electrons
,” Chem. Soc. Rev.
42
, 9219
–9231
(2013
).12.
C. R.
Arumainayagam
, H. L.
Lee
, R. B.
Nelson
, D. R.
Haines
, and R. P.
Gunawardane
, “Low-energy electron-induced reactions in condensed matter
,” Surf. Sci. Rep.
65
, 1
–44
(2010
).13.
M. C.
Boyer
, N.
Rivas
, A. A.
Tran
, C. A.
Verish
, and C. R.
Arumainayagam
, “The role of low-energy (≤20 eV) electrons in astrochemistry
,” Surf. Sci.
652
, 26
(2016
).14.
M. A.
Huels
, L.
Parenteau
, A. D.
Bass
, and L.
Sanche
, “Small steps on the slippery road to life: Molecular synthesis in astrophysical ices initiated by low energy electron impact
,” Int. J. Mass Spectrom.
277
, 256
–261
(2008
).15.
J. H.
Lacy
, J. S.
Carr
, N. J.
Evans
, F.
Baas
, J. M.
Achtermann
, and J. F.
Arens
, “Discovery of interstellar methane—Observations of gaseous and solid CH4 absorption toward young stars in molecular clouds
,” Astrophys. J.
376
, 556
–560
(1991
).16.
R. N.
Clark
, R.
Carlson
, W.
Grundy
, and K.
Noll
, in The Science of Solar System Ices
(Springer-Verlag
, New York
, 2013
).17.
P.
Ehrenfreund
, M.
Spaans
, and N. G.
Holm
, “The evolution of organic matter in space
,” Philos. Trans. R. Soc., A
369
(1936
), 538
–554
(2011
).18.
J. R.
Spencer
, W. M.
Calvin
, and M. J.
Person
, “Charge-coupled device spectra of the Galilean satellites: Molecular oxygen on Ganymede
,” J. Geophys. Res.
100
(E9
), 19049
, (1995
).19.
J. R.
Spencer
and W. M.
Calvin
, “Condensed O[TINF]2[/TINF] on Europa and Callisto
,” Astron. J.
124
, 3400
–3403
(2002
).20.
O.
Mousis
et al., “Methane clathrates in the solar system
,” Astrobiology
15
, 308
–326
(2015
).21.
L.
Sanche
, “Transmission of 0–15 eV monoenergetic electrons through thin-film molecular solids
,” J. Chem. Phys.
71
(12
), 4860
(1979
).22.
G.
Bader
, G.
Perluzzo
, L. G.
Caron
, and L.
Sanche
, “Elastic and inelastic mean-free-path determination in solid xenon from electron transmission experiments
,” Phys. Rev. B
26
(11
), 6019
–6029
(1982
).23.
A.
Bass
, L.
Parenteau
, F.
Weik
, and L.
Sanche
, “The effects of temperature and morphology on electron transmission and stimulated desorption of H from thin hydrocarbon films
,” J. Chem. Phys.
113
(19
), 8746
–8752
(2000
).24.
D. V.
Klyachko
, M. A.
Huels
, and L.
Sanche
, “Halogen anion formation in 5-halouracil films: X rays compared to subionization electrons
,” Radiat. Res.
151
, 177
–187
(1999
).25.
Y.
Yildirim
, M.
Balcan
, A. D.
Bass
, P.
Cloutier
, and L.
Sanche
, “Electron stimulated desorption of anions and cations from condensed allyl glycidyl ether
,” Phys. Chem. Chem. Phys.
12
(28
), 7950
–7958
(2010
).26.
A. D.
Bass
, L.
Parenteau
, M. A.
Huels
, and L.
Sanche
, “Reactive scattering of O- in organic films at subionization collision energies
,” J. Chem. Phys.
109
, 8635
–8640
(1998
).27.
X.
Pan
, H.
Abdoul-Carime
, P.
Cloutier
, A. D.
Bass
, and L.
Sanche
, “D−, O− and OD− desorption induced by low-energy (0–20 eV) electron impact on amorphous D2O films
,” Radiat. Phys. Chem.
72
, 193
–199
(2005
).28.
M. N.
Hedhili
, P.
Cloutier
, A. D.
Bass
, T. E.
Madey
, and L.
Sanche
, “Electron stimulated desorption of anionic fragments from films of pure and electron-irradiated thiophene
,” J. Chem. Phys.
125
, 094704-1
–094704-12
(2006
).29.
I. S.
Gilmore
, Surface Analysis: The Principal Techniques
, 2nd ed. (John Wiley and Sons Ltd.
, 2009
).30.
D.
Briggs
and M. P.
Seah
, Practical Surface Analysis by Auger and X-Ray Photoelectron Spectroscopy
(John Wiley and Sons Ltd.
, 1983
).31.
See http://xpspeak.software.informer.com/4.1/ to download the XPSPeak peak fitting software.
32.
J. P.
Meyburg
, I. I.
Nedrygailov
, E.
Hasselbrink
, and D.
Diesing
, “Thermal desorption spectroscopy from the surfaces of metal-oxide-semiconductor nanostructures
,” Rev. Sci. Instrum.
85
, 104102
(2014
).33.
K. I.
Öberg
, “Photochemistry and astrochemistry: Photochemical pathways to interstellar complex organic molecules
,” Chem. Rev.
17
(116
), 9631
–9663
(2016
).34.
E.
Burean
, I.
Ipolyi
, T.
Hamann
, and P.
Swiderek
, “Thermal desorption spectrometry for identification of products formed by electron-induced reactions
,” Int. J. Mass Spectrom.
277
, 215
–219
(2008
).35.
X.
Pan
, A. D.
Bass
, J. P.
Jay-Gerin
, and L.
Sanche
, “A mechanism for the production of hydrogen peroxide and the hydroperoxyl radical on icy satellites by low-energy electrons
,” Icarus
172
, 521
–525
(2004
).36.
A. D.
Bass
and L.
Sanche
, “Reactions induced by low energy electrons in cryogenic films (review)
,” Low Temp. Phys.
29
, 202
–214
(2003
).37.
L.
Sanche
, L.
Parenteau
, and P.
Cloutier
, “Dissociative attachment reactions in electron stimulated desorption from condensed O2 and O2-doped rare-gas matrices
,” J. Chem. Phys.
91
(4
), 2664
–2674
(1989
).38.
T. E.
Madey
and J. T.
Yates
, “Electron-stimulated desorption as a tool for studies of chemisorption: A review
,” J. Vac. Sci. Technol., A
8
, 525
(1971
).39.
M. A.
Huels
, L.
Parenteau
, and L.
Sanche
, “Substrate dependence of electron-stimulated O− yields from dissociative electron attachment to physisorbed O2
,” J. Chem. Phys.
100
(5
), 3940
–3956
(1994
).40.
P.
Rowntree
, L.
Parenteau
, and L.
Sanche
, “Electron stimulated desorption via dissociative attachment in amorphous H2O
,” J. Chem. Phys.
94
, 8570
–8576
(1991
).41.
K. M. A.
Refaey
and J. L.
Franklin
, “Endoergic ion—Molecule-collision processes of negative ions. III. Collisions of I− on O2, CO, and CO2
,” Int. J. Mass Spectrom. Ion Phys.
20
, 19
–32
(1976
).42.
M.
Knapp
, O.
Echt
, D.
Kreisle
, T. D.
Märk
, and E.
Recknagel
, “Formation of long-lived CO−2, N2O−, and their dimer anions, by electron attachment to van der Waals clusters
,” Chem. Phys. Lett.
126
(3-4
), 225
–231
(1986
).43.
F. H.
Dorman
, “Negative fragment ions from resonance capture processes
,” J. Chem. Phys.
44
, 3856
–3863
(1966
).44.
P.
Rowntree
, L.
Parenteau
, and L.
Sanche
, “Anion yields produced by low-energy electron impact on condensed hydrocarbon films
,” J. Phys. Chem.
95
(12
), 4902
–4909
(1991
).45.
B. C.
Ibănescu
, O.
May
, A.
Monney
, and M.
Allan
, “Electron-induced chemistry of alcohols
,” Phys. Chem. Chem. Phys.
9
, 3163
–3173
(2007
).46.
B. C.
Ibănescu
and M.
Allan
, “Selective cleavage of the C–O bonds in alcohols and asymmetric ethers by dissociative electron attachment
,” Phys. Chem. Chem. Phys.
11
(35
), 7640
(2009
).47.
O.
Karis
et al., “Manifestation of the paramagnetic splitting of physisorbed O2 in core and valence spectroscopies
,” Surf. Sci.
352-354
, 511
–517
(1996
).48.
A. F.
Lee
, D. E.
Gawthrope
, N. J.
Hart
, and K.
Wilson
, “A fast XPS study of the surface chemistry of ethanol over Pt{111}
,” Surf. Sci.
548
, 200
–208
(2004
).49.
See http://webbook.nist.gov/chemistry/ for the NIST Chemistry webbook (NIST Standard Reference Database Number 69).
50.
B. M.
Jones
and R. I.
Kaiser
, “Application of reflectron time-of-flight mass spectroscopy in the analysis of astrophysically relevant ices exposed to ionization radiation: Methane (CH4) and D4-methane (CD4) as a case study
,” J. Phys. Chem. Lett.
4
(11
), 1965
–1971
(2013
).51.
C. J.
Bennett
, C. S.
Jamieson
, Y.
Osamura
, and R. I.
Kaiser
, “Laboratory studies on the irradiation of methane in interstellar, cometary, and solar system ices
,” Astrophys. J.
653
, 792
–811
(2006
).52.
A. L. F.
Barros
et al., “Cosmic ray impact on astrophysical ices: Laboratory studies on heavy ion irradiation of methane
,” Astron. Astrophys.
531
, A160
(2011
).53.
G. A.
Baratta
, G.
Leto
, and M. E.
Palumbo
, “A comparison of ion irradiation and UV photolysis of CH4 and CH3OH
,” Astron. Astrophys.
384
, 343
(2002
).54.
S.
Kundu
, V. S.
Prabhudesai
, and E.
Krishnakumar
, “Low energy electron induced C–H activation reactions in methane containing ices
,” J. Phys. Chem. C
121
, 22862
–22871
(2017
).© 2017 Author(s).
2017
Author(s)
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