Search results for "amorphous"
showing 10 items of 790 documents
Post UV irradiation annealing of E’ centers in silica controlled by H2 diffusion
2004
Abstract We investigate the isothermal annealing of E′ centers generated by UV photons (266 nm) of a pulsed Nd:YAG laser in two natural silica types differing for their OH content. Electron spin resonance and absorption spectra recorded at room temperature at different delays from the laser exposure evidenced a partial reduction of E′ centers, more pronounced in the wet silica. These post irradiation kinetics complete within 10 5 s, regardless the silica type, and they are consistent with a diffusion limited reaction between the E′ centers and the molecular hydrogen H 2 . Analysis of our data is done by theoretical fits using the Waite's equation and compared with the H 2 diffusion paramete…
Myoglobin embedded in saccharide amorphous matrices: water-dependent domains evidenced by small angle X-ray scattering
2010
We report Small Angle X-ray Scattering (SAXS) measurements performed on samples of carboxy-myoglobin (MbCO) embedded in low-water trehalose glasses. Results showed that, in such samples, "low-protein" trehalose-water domains are present, surrounded by a protein-trehalose-water background; such finding is supported by Infrared Spectroscopy (FTIR) measurements. These domains, which do not appear in the absence of the protein and in analogous sucrose systems, preferentially incorporate the incoming water at the onset of rehydration, and disappear following large hydration. This observation suggests that, in organisms under anhydrobiosis, analogous domains could play a buffering role against th…
Identification of strong and weak interacting two level systems in KBr:CN
2010
Tunneling two level systems (TLSs) are believed to be the source of phenomena such as the universal low temperature properties in disordered and amorphous solids, and $1/f$ noise. The existence of these phenomena in a large variety of dissimilar physical systems testifies for the universal nature of the TLSs, which however, is not yet known. Following a recent suggestion that attributes the low temperature TLSs to inversion pairs [M. Schechter and P.C.E. Stamp, arXiv:0910.1283.] we calculate explicitly the TLS-phonon coupling of inversion symmetric and asymmetric TLSs in a given disordered crystal. Our work (a) estimates parameters that support the theory in M. Schechter and P.C.E. Stamp, a…
Influence of an Electron Beam Exposure on the Surface Plasmon Resonance of Gold Nanoparticles
2013
Electron beam imaging is a common technique used for characterizing the morphology of plasmonic nanostructures. During the imaging process, the electron beam interacts with traces of organic material in the chamber and produces a well-know layer of amorphous carbon over the specimen under investigation. In this paper, we investigate the effect of this carbon adsorbate on the spectral position of the surface plasmon in individual gold nanoparticles as a function of electron exposure dose. We find an optimum dose for which the plasmonic response of the nanoparticle is not affected by the imaging process. The final publication is available at link.springer.com
Oxygen Exchange at the Internal Surface of AmorphousSiO2Studied by Photoluminescence of Isotopically Labeled Oxygen Molecules
2009
The exchange between lattice and interstitial oxygen species in an oxide was studied by the $^{16}\mathrm{O}\mathrm{\text{\ensuremath{-}}}^{18}\mathrm{O}$ isotope shift of the ${a}^{1}{\ensuremath{\Delta}}_{g}(v=0)\ensuremath{\rightarrow}{X}^{3}{\ensuremath{\Sigma}}_{g}^{\ensuremath{-}}(v=1)$ infrared photoluminescence band of the oxygen molecules (${\mathrm{O}}_{2}$) incorporated into the interstitial voids of amorphous ${\mathrm{SiO}}_{2}$ ($a\mathrm{\text{\ensuremath{-}}}{\mathrm{SiO}}_{2}$) by thermal annealing in $^{18}\mathrm{O}_{2}$ gas. A large site to site variation of the oxygen exchange rate, originating from structural disorder of $a\mathrm{\text{\ensuremath{-}}}{\mathrm{SiO}}_{…
Interaction of two-level systems in amorphous materials with arbitrary phonon fields
2006
To describe the interaction of the two level systems (TLSs) of an amorphous solid with arbitrary strain fields, we introduce a generalization of the standard interaction Hamiltonian. In this new model, the interaction strength depends on the orientation of the TLS with respect to the strain field through a $6\times 6$ symmetric tensor of deformation potential parameters, $[R]$. Taking into account the isotropy of the amorphous solid, we deduce that $[R]$ has only two independent parameters. We show how these two parameters can be calculated from experimental data and we prove that for any amorphous bulk material the average coupling of TLSs with longitudinal phonons is always stronger than …
Fluctuating hydrodynamics and diffusion in amorphous solids
1994
The fluctuating hydrodynamic description for an isotropic fluid is extended to include the displacement field u, reflecting the freezing of the local structures in an amorphous solid. The fluctuating nonlinear equations for the set of hydrodynamic variables including u has been obtained. The role of u is manifested through its longitudinal part, i.e., \ensuremath{\nabla}\ensuremath{\cdot}u, in terms of which we define the variable c(x,t). It refers to the diffusion of the free volume or vacancies, signifying configurational rearrangements in the amorphous solid. The analysis here shows that one recovers the earlier result obtained by Das and Mazenko [Phys. Rev. A 34, 2265 (1986)] for mode c…
Unraveling exciton dynamics in amorphous silicon dioxide: Interpretation of the optical features from 8 to 11 eV.
2011
Physical review / B 83, 174201 (2011). doi:10.1103/PhysRevB.83.174201
In situobservation of the formation, diffusion, and reactions of hydrogenous species inF2-laser-irradiatedSiO2glass using a pump-and-probe technique
2006
We quantitatively studied the formation, diffusion, and reactions of mobile interstitial hydrogen atoms $({\mathrm{H}}^{0})$ and molecules $({\mathrm{H}}_{2})$ in ${\mathrm{F}}_{2}$-laser-irradiated silica $(\mathrm{Si}{\mathrm{O}}_{2})$ glass between 10 and $330\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Two key techniques were used: single-pulse ${\mathrm{F}}_{2}$ laser photolysis of silanol (SiOH) groups to selectively create pairs of ${\mathrm{H}}^{0}$ and oxygen dangling bonds (nonbridging oxygen hole centers, NBOHC), and in situ photoluminescence measurements of NBOHCs to monitor their reactions with ${\mathrm{H}}^{0}$ and ${\mathrm{H}}_{2}$ as a function of time and temperature. A smalle…
Corrigendum: Fabrication and heating rate study of microscopic surface electrode ion traps
2012
We report heating rate measurements in a microfabricated goldon-sapphire surface electrode ion trap with a trapping height of approximately 240 μm. Using the Doppler recooling method, we characterize the trap heating rates over an extended region of the trap. The noise spectral density of the trap falls in the range of noise spectra reported in ion traps at room temperature. We find that during the first months of operation, the heating rates increase by approximately one order of magnitude. The increase in heating rates is largest in the ion-loading region of the trap, providing a strong hint that surface contamination plays a major role for excessive heating rates. We discuss data found i…