Theoretical investigations of ozone vibrational relaxation and oxygen atom diffusion rates in Ar and xenon matrixes

1993 ◽  
Vol 97 (47) ◽  
pp. 12134-12143 ◽  
Author(s):  
M. Beth Ford ◽  
Angel D. Foxworthy ◽  
G. J. Mains ◽  
Lionel M. Raff
Keyword(s):  
Oxygen Atom ◽  
Vibrational Relaxation ◽  
Atom Diffusion ◽  
Theoretical Investigations ◽  
Diffusion Rates

Theoretical Investigations of Hydrogen Atom Diffusion Rates in Xenon Matrixes

1994 ◽  
Vol 98 (51) ◽  
pp. 13766-13771 ◽  
Author(s):  
Martin D. Perry ◽  
Gilbert J. Mains ◽  
Lionel M. Raff
Keyword(s):  
Hydrogen Atom ◽  
Atom Diffusion ◽  
Theoretical Investigations ◽  
Diffusion Rates

Oxygen atom diffusion-driven anomalous Hall behavior in Co/Pt multilayers

2015 ◽  
Vol 579 ◽  
pp. 123-126 ◽  
Author(s):  
Shao-Long Jiang ◽  
Xi Chen ◽  
Jing-Yan Zhang ◽  
Guang Yang ◽  
Jiao Teng ◽  
...  
Keyword(s):  
Oxygen Atom ◽  
Atom Diffusion

Interstitial-oxygen-atom diffusion in MgO

1996 ◽  
Vol 53 (12) ◽  
pp. 7731-7735 ◽  
Author(s):  
T. Brudevoll ◽  
E. A. Kotomin ◽  
N. E. Christensen
Keyword(s):  
Oxygen Atom ◽  
Interstitial Oxygen ◽  
Atom Diffusion

scholarly journals Efficient diffusive mechanisms of O atoms at very low temperatures on surfaces of astrophysical interest

2014 ◽  
Vol 168 ◽  
pp. 151-166 ◽  
Author(s):  
Emanuele Congiu ◽  
Marco Minissale ◽  
Saoud Baouche ◽  
Henda Chaabouni ◽  
Audrey Moudens ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Interstellar Dust ◽  
Oxidation Reactions ◽  
Weakly Bound ◽  
Water Ice ◽  
Atom Diffusion ◽  
Interstellar Dust Grains ◽  
Diffusion Rates ◽  
Experimental Values ◽  
Simple Reduction

At the low temperatures of interstellar dust grains, it is well established that surface chemistry proceeds via diffusive mechanisms of H atoms weakly bound (physisorbed) to the surface. Until recently, however, it was unknown whether atoms heavier than hydrogen could diffuse rapidly enough on interstellar grains to react with other accreted species. In addition, models still require simple reduction as well as oxidation reactions to occur on grains to explain the abundances of various molecules. In this paper we investigate O-atom diffusion and reactivity on a variety of astrophysically relevant surfaces (water ice of three different morphologies, silicate, and graphite) in the 6.5–25 K temperature range. Experimental values were used to derive a diffusion law that emphasizes that O atoms diffuse by quantum mechanical tunnelling at temperatures as low as 6.5 K. The rates of diffusion on each surface, based on modelling results, were calculated and an empirical law is given as a function of the surface temperature. The relative diffusion rates are kH2Oice > ksil > kgraph ≫ kexpected. The implications of efficient O-atom diffusion over astrophysically relevant time-scales are discussed. Our findings show that O atoms can scan any available reaction partners (e.g., either another H atom, if available, or a surface radical like O or OH) at a faster rate than that of accretion. Also, as dense clouds mature, H2 becomes far more abundant than H and the O : H ratio grows, and the reactivity of O atoms on grains is such that O becomes one of the dominant reactive partners together with H.

scholarly journals Measurement of oxygen atom diffusion in Nb and Ta by anelastic spectroscopy

2005 ◽  
Vol 8 (3) ◽  
pp. 239-243 ◽  
Author(s):  
Luciano Henrique de Almeida ◽  
Kelly Cristina Cezaretto Pires ◽  
Carlos Roberto Grandini ◽  
Odila Florêncio
Keyword(s):  
Oxygen Atom ◽  
Atom Diffusion

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

A study of twinning in YBa2Cu3O7−x by large-angle convergent-beam electron diffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 20-21
Author(s):  
P.A. Midgley ◽  
R. Vincent ◽  
D. Cherns
Keyword(s):  
Electron Diffraction ◽  
Oxygen Atom ◽  
Strain Field ◽  
Large Angle ◽  
Convergent Beam Electron Diffraction ◽  
Orthorhombic Distortion ◽  
Beam Electron ◽  
Resultant Powder ◽  
Convergent Beam ◽  
Mesh Grid

The oxygenation of YBa2Cu3O7−x (YBCO) leads to an orthorhombic distortion of the unit cell to accommodate the extra oxygen atom. This makes the formation of twins energetically favourable with CuO4 planar unit chains running alternately along the a and b axes of the parent tetragonal structure. The geometry of this twinning is such that four possible twin variants may co-exist with the twin boundaries lying in the (110) or (110) planes of the deformed structure. The traces of these planes are not mutually perpendicular and thus the crystal is strained to allow for the mismatch. It is to the nature of this strain field that this work has been addressed.Sintered samples were prepared by crushing and dispersing the resultant powder onto a very fine Cu mesh grid. Single crystals were chemically thinned to perforation. No discernible artefacts were seen and similar results were obtained with either method.

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