Synchrotron x-ray photoemission study of soft x-ray processed ultrathin glycine-water ice films

Journal Article · Sat May 28 00:00:00 EDT 2011 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3591337· OSTI ID:21560280

Tzvetkov, George ^[1]; Netzer, Falko P ^[2]

---

1. Department of Inorganic Chemistry, Faculty of Chemistry, University of Sofia, James Bourchier 1, 1164 Sofia (Bulgaria)
2. Institut fuer Physik, Oberflaechen- und Grenzflaechenphysik, Karl-Franzens Universitaet Graz, A-8010 Graz (Austria)

Ultrathin glycine-water ice films have been prepared in ultrahigh vacuum by condensation of H{sub 2}O and glycine at 90 K on single crystalline alumina surfaces and processed by soft x-ray (610 eV) exposure for up to 60 min. The physicochemical changes in the films were monitored using synchrotron x-ray photoemission spectroscopy. Two films with different amounts of H{sub 2}O have been considered in order to evaluate the influence of the water ice content on the radiation-induced effects. The analysis of C1s, N1s, and O1s spectral regions together with the changes in the valence band spectra indicates that amino acid degradation occurs fast mainly via decarboxylation and deamination of pristine molecules. Enrichment of the x-ray exposed surfaces with fragments with carbon atoms without strong electronegative substituents (C-C and C-H) is documented as well. In the thinner glycine-water ice film (six layers of glycine + six layers of water) the 3D ice suffers strongly from the x-rays and is largely removed from the sample. The rate of photodecomposition of glycine in this film is about 30% higher than for glycine in the thicker film (6 layers of glycine + 60 layers of water). The photoemission results suggest that the destruction of amino acid molecules is caused by the direct interaction with the radiation and that no chemical attack of glycine by the species released by water radiolysis is detected.

• OSTI ID: 21560280
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 20 Vol. 134; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACCELERATORS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AMINO ACIDS
ATOMS
CARBON
CARBOXYLIC ACIDS
CHALCOGENIDES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CRYSTALS
CYCLIC ACCELERATORS
DEAMINATION
DECARBOXYLATION
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION
ENRICHMENT
FILMS
GLYCINE
HYDROGEN COMPOUNDS
ICE
INTERACTIONS
IONIZING RADIATIONS
LAYERS
MOLECULES
MONOCRYSTALS
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOEMISSION
RADIATION EFFECTS
RADIATIONS
RADIOLYSIS
SECONDARY EMISSION
SOFT X RADIATION
SPECTROSCOPY
SURFACES
SYNCHROTRONS
WATER
X RADIATION