Radiation effects in water ice: A near-edge x-ray absorption fine structure study

Journal Article · Mon Nov 27 23:00:00 EST 2006 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.2395937· OSTI ID:20864350

Laffon, C; Lacombe, S; Bournel, F; Parent, Ph ^[1]

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1. Laboratoire de Chimie-Physique, Matiere et Rayonnement, UMR 7614, Universite Pierre et Marie Curie et CNRS, 11 Rue Pierre et Marie Curie, 75231 Paris, Cedex 05 (France)

The changes in the structure and composition of vapor-deposited ice films irradiated at 20 K with soft x-ray photons (3-900 eV) and their subsequent evolution with temperatures between 20 and 150 K have been investigated by near-edge x-ray absorption fine structure spectroscopy (NEXAFS) at the oxygen K edge. We observe the hydroxyl OH, the atomic oxygen O, and the hydroperoxyl HO{sub 2} radicals, as well as the oxygen O{sub 2} and hydrogen peroxide H{sub 2}O{sub 2} molecules in irradiated porous amorphous solid water (p-ASW) and crystalline (I{sub cryst}) ice films. The evolution of their concentrations with the temperature indicates that HO{sub 2}, O{sub 2}, and H{sub 2}O{sub 2} result from a simple step reaction fuelled by OH, where O{sub 2} is a product of HO{sub 2} and HO{sub 2} a product of H{sub 2}O{sub 2}. The local order of ice is also modified, whatever the initial structure is. The crystalline ice I{sub cryst} becomes amorphous. The high-density amorphous phase (I{sub a}h) of ice is observed after irradiation of the p-ASW film, whose initial structure is the normal low-density form of the amorphous ice (I{sub a}l). The phase I{sub a}h is thus peculiar to irradiated ice and does not exist in the as-deposited ice films. A new 'very high density' amorphous phase--we call I{sub a}vh--is obtained after warming at 50 K the irradiated p-ASW ice. This phase is stable up to 90 K and partially transforms into crystalline ice at 150 K.

• OSTI ID: 20864350
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 20 Vol. 125; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
AMORPHOUS STATE
FINE STRUCTURE
HYDROGEN PEROXIDE
ICE
IRRADIATION
PHASE TRANSFORMATIONS
PHOTONS
POROUS MATERIALS
RADIATION EFFECTS
RADICALS
REACTION KINETICS
SOFT X RADIATION
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
THIN FILMS
VAPOR DEPOSITED COATINGS
X-RAY SPECTROSCOPY