Layer Of Krypton Research Articles

Solar Pond Window Technology for Energy-Efficient Retrofitting of Buildings: An Experimental and Numerical Investigation

Windows are responsible for an important proportion of heat loss from building envelope due to inadequate insulative characteristics of traditional glazing products. In this respect, advanced glazing solutions are of vital importance to mitigate energy demand of buildings, thus to reduce carbon emissions. Therefore, in this research, a novel glazing technology called solar pond window is introduced, and it is numerically and experimentally investigated for different design configurations. The optimum design of this novel glazing covers four 5-mm-thick glass panes, two 20-mm-thick water layers, and one 20-mm-thick Krypton layer in the middle. The average heat transfer coefficient (U-value) of the optimum case is found to be about 0.40 W/\(\hbox {m}^{2}\) K. If air is used as insulative gas in the interlayer, the U-value of the glazing is determined to be around 0.90 W/\(\hbox {m}^{2}\) K, which is still competitive with the U-value range of argon-filled triple-glazed windows with low-e coatings. The fabrication cost of the optimum design of solar pond window is around €120/\(\hbox {m}^{2}\). Overall, solar pond window technology is a cost-effective and energy-efficient glazing, which has a great potential to be the future of fenestration products as well as being capable of meeting the latest building fabric standards.

Collision-induced light scattering spectra of krypton layer confined between graphite slabs – MD simulation

We have used the molecular dynamics (MD) simulation method to obtain the collision-induced light scattering spectra of the thin krypton layer confined between two parallel graphite slabs. The simulations have been made under constant density, pressure and temperature condition. We have investigated four thin krypton layers of the thickness ranging from 13 to 24 Å. The 2-, 3- and 4-body correlation functions of collision-induced polarizability anisotropy were calculated. The spectra of colliding krypton atoms were simulated as cosine Fourier transform of the total polarizability anisotropy correlation function. The calculated correlation functions and their spectra show substantial dependence on the distance between graphite slabs. The collision-induced light scattering spectrum of krypton bulk sample was also simulated and compared with the krypton layer between graphite walls. The striking differences between these two systems are observed. We have further extended our analysis of krypton movement between graphite slabs by calculating the mean square displacement functions and diffusion coefficients. The decrease of the diffusion of krypton atoms with the increasing distance between graphite walls has been found. The structure of krypton layer has been also investigated by calculating the density profile and pressure tension across the rift. The distance between graphite slabs, for which the highest mobility of krypton's atoms occurred, has been found.

Molecular hydrogen isotopes adsorbed on krypton-preplated graphite

Adsorption of ortho-deuterium and para-hydrogen films on a graphite substrate, preplated with a single atomic layer of krypton, is studied theoretically by means of quantum Monte Carlo simulations at low temperature. Our model explicitly includes substrate corrugation. Energetic and structural properties of these adsorbed films are computed for a range of hydrogen coverages. Thermodynamically stable adsorbed films are solid, with no clear evidence of any liquidlike phase. Quantum exchanges of ortho-deuterium and para-hydrogen are essentially absent in this system, down to zero temperature; consequently, this system displays no superfluidity in this limit. Our simulations provide evidence of a stable domain-wall fluid at low temperature, consistent with recent experimental observations.

Adsorption of para-hydrogen on krypton pre-plated graphite

Adsorption of para-Hydrogen on the surface of graphite pre-plated with a single layer of atomic krypton is studied thoretically by means of Path Integral Ground State Monte Carlo simulations. We compute energetics and density profiles of para-hydrogen, and determine the structure of the adsorbed film for various coverages. Results show that there are two thermodynamically stable monolayer phases of para-hydrogen, both solid. One is commensurate with the krypton layer, the other is incommensurate. No evidence is seen of a thermodynamically stable liquid phase, at zero temperature. These results are qualitatively similar to what is seen for for para-hydrogen on bare graphite. Quantum exchanges of hydrogen molecules are suppressed in this system.

Melting of Krypton Layers Adsorbed in Cylindrical Pores

The mechanism of melting and its correlation to adsorption on cylindrical surfaces of silica-like cylindrical nanopores has been studied for the first time. The size of the pores has been defined by its diameter (4 nm in this work). As an example, we have analyzed krypton atoms as adsorbed system. We have shown, that the layer adsorbed on the surface of the pore has much lower melting temperature (T = 77.5 K) than both the filled pore (T = 90 K) and the bulk system (T = 118 K). The mechanism of melting in the layer is a continuous transition and depends on the vacancy formation. The layering transition changes its character with temperature from a sharp transition below the melting temperature into a continuous one above it.

Calculated phase boundary including corrugation effects for krypton layers physisorbed onto spherical substrates

A molecular-dynamics technique is utilized to calculate the melting curve of submonolayer and complete layers of krypton atoms physisorbed onto a spherical substrate. Two models of the substrate are used. In the first model the substrate is treated as a spherical continuum whose differential elements interact with krypton atoms via Lennard-Jones (LJ) potential. Hysteresis is present in the melting transition for low coverages, which disappears as the melting becomes more gradual near complete coverage. The melting temperature at completion is very sensitive to second-layer promotion, which in turn depends strongly on the radial boundary conditions. In the second model the melting transition is also examined for 100 Kr atoms adsorbed onto spheres that exhibit corrugation in their potential interactions with the asdorbate. Addition of corrugation in the form of a ${\mathrm{C}}_{60}$ lattice effectively serves to merely raise the average LJ substrate sphere density slightly and leave the melting transition unaffected, but replacing the LJ sphere with a cubic carbon lattice raises the melting temperature by about 3 K (4.6%) while dramatically affecting the desorption behavior of the adlayer and lowering its spatial order. Various bond-orientational distributions and snapshot configurations are employed in understanding the completion process.

Predicted properties and melting transition of krypton layers physisorbed onto Lennard-Jones spheres

We report the results of constant-temperature, constant-density, molecular-dynamics simulations of the melting transition of Kr atoms physisorbed onto small Lennard-Jones spheres. Adlayer depletion takes place when free boundary conditions are used but utilization of a soft reflecting shell results in a broad melting transition at around $T=65\mathrm{K}$ without any appreciable hysteresis. We introduce structural and bond-orientational parameters and utilize thermodynamic parameters to monitor the behavior of the system. The spherical geometry causes compression of the neighbor distances with respect to those for the corresponding planar case, causing enhanced interaction of the neighbor shells via interstitials/vacancies, the nature of which is further elucidated using the bond-orientational information. Quantities related to the radial degree of freedom change slowly during melting, and bond-orientational order of the Kr lattice persists well into the fluid.

Effects of under- and overlayers on particle and photon emission from solid argon induced by 2 MeV protons

We studied electron emission, luminescence, and sputtering of thin condensed gas films by 2 MeV protons. For thin Ar films, an external electric field causes nearly complete extraction of excited electrons, hindering hole recombination. This leads to a reduction in luminescence and sputtering. We have observed that overlayers of N2 annul the effects of external electric fields and also that they decrease ion-induced luminescence from the bulk of the Ar films. In related experiments, 20 nm Krypton layers were grown between the metal substrate and the Ar films. We found that these underlayers change the dependence of particle and photon emission on Ar film thickness and dramatically increase electron emission. We discuss these new effects in terms of internal electric fields produced by unbalanced holes and of changed reactions of excitons and holes at the interfaces.

Deuterium monolayers physisorbed on krypton-plated graphite: A two-dimensional Ising system

Neutron-diffraction measurements were used for the first time to investigate the influence of the modification of the graphite substrate potential and of the susbrate symmetry caused by a preadsorbed layer of krypton (Kr). It will be shown that D 2 on Kr/graphite presents a new 2D Ising system. The order-disorder transition of this system has been studied.

Multiple nondissociative scattering of molecules and multiple scattering of ions from a cold metal surface covered with krypton film

Energy spectra of ions emitted from a cold Au surface covered by condensed krypton film at small detection angles θ (including the case of specular reflection) under deuterium-molecule ion bombardment were measured. Two maxima on the energy scale (near the primary energy) were found, and their relative intensity changed according to the law: I 21 ∼ θ −7. Since multiple scattering theory of molecules predicts such a dependence, it is assumed that the observed maxima are connected with multiple nondissociative scattering of D 2 + molecules inside the krypton surface film. Additional experiments with Ar + ion scattering under the same conditions show a splitting of the quasi-single-scattering peak of gold due to multiple scattering of argon ions inside the krypton layer. The maxima in the deuterium energy spectra demonstrate multiple scattering events as well.

Cryogenic targets and related technologies at ILE Osaka University

Described are two approaches to make cryogenic inertial fusion targets that have a uniform solid or liquid fuel layer inside a spherical hollow fuel capsule. One is to utilize low-density, low-atomic-number plastic foam to sustain liquid fuel (foam method) and the other is to initiate a glow discharge in the void of a solid fuel layer to symmetrize the solid layer (plasma layering method). In the foam method, we have successfully made a foam shell with a gas barrier to prevent the fuel from evaporation by means of density-matched emulsion method followed by an interfacial polycondensation method. Foam shells having diameters of 600–1550 μm and wall thicknesses of 10–50 μm were coated with a normal density plastic layer having thickness of 4–10 μm. These foam shells were provided for implosion experiments with the Gekko XII glass laser system. In the plasma layering process, we examined the feasibility of the method by performing experiments using krypton gas and liquid nitrogen. A nonuniform solid krypton layer was redistributed into a uniform one after a 30 min discharge induced by an external 2.45 GHz microwave field. Experimental results on the heat generation in shells indicated that this technique can redistribute 10 K solid fuel into a uniform layer using intermittent discharges.

Structure and morphology of gas phase deposited ice

AbstractAmorphous ice was prepared by deposition of H2O vapour diluted in heat exchange gases such as He or Ar at low temperatures (13 to 45 K). This technique is faster than the deposition of pure H2O vapour. The rapid sticking of condensing molecules on the cold solid leads to a poor short range order inside the grains. The high nucleation rate during vapour deposition results in small grain sizes and microporosity. Structure and morphology of the resulting amorphous ice samples were characterized by x‐ray diffraction. The radial distribution function was calculated from the diffraction data of pure ice and proved to be consistent with the Continuous Random Network model. Diffraction patterns of krypton layers on the amorphous ice reflect the morphology of the substrate: at the beginning micropores with a diameter of 15–20 Å and a volume of 0.045 cm3/g are filled. At higher mass coverages outer grain surfaces and large voids are covered by krypton.

Redistribution of solid fuel in inertial confinement fusion target by plasma

A new technique of applying a high frequency discharge for redistribution of solid deuterium–deuterium (D2) or deuterium–tritium (DT) fuel in a laser fusion target is proposed for future reactor‐class targets. This technique can enhance the beta decay technique which has a long time constant for redistribution of the fuel far below the triple point. A plasma initiated in the central void of the target by glow discharge uniformly heats the inner surface of the fuel ice, and the target is located in an isothermal cooling medium. Resultant higher temperatures at a thicker fuel ice area induce sublimation of the thick fuel ice and condensation of the vapor on a thinner, cold area. This technique is applicable to deuterium fuel in a shell for current implosion experiments. A proof of principle was demonstrated by using krypton gas and liquid nitrogen as substitutes for the D2 or DT fuel and liquid helium, respectively. A smooth solid krypton layer was formed in a glass shell with a gas feeder.

Molecular-dynamics simulation for the dynamic-structure factor of commensurate krypton on graphite.

The dynamic structure factor S(q,\ensuremath{\omega}) for a commensurate layer of krypton on a model graphite surface is calculated from molecular-dynamics simulations. The simulations are carried out at a number of temperatures ranging up to 70 K to assess the thermal variation of S(q,\ensuremath{\omega}). These results are compared with a harmonic-lattice-dynamics calculation of the phonon spectra. The multiphonon content of S(q,\ensuremath{\omega}) is shown to be minor at the temperatures considered. The temperature dependence of the zone-center frequency is attributed to thermal averaging of the substrate corrugation. The results are compared with previous studies of this system and with available experimental data.

Fourier transform infrared study of amorphous N2O4 solid: Destabilization with inert impurities

Amorphous N2O4 solid was formed on predeposited oxygen or krypton layers. Evaporation of the underlying layer and redeposition of the inert impurities resulted in decomposition of the ionic nitrosonium nitrate clusters within the solid nitrogen tetroxide. Infrared features indicate NO+NO−3 decomposition to occur via molecular NONO3 , with NO2 monomers as products. Evaporation of the inert impurities and recooling restored the amorphous N2O4 from which NO+NO−3 was formed again.

Electron spin resonance study of NO 2 adsorbed on [formula omitted] at 20 K

We report a well-resolved ESR signal of 0.01 L NO 2 molecules physisorbcd on a 10 L krypton layer on Ag(110) at 20 K. In situ LEED and AES were used to characterize the surface. To the best of our knowledge, these are the first experiments where surface-analytical methods and ESR in UHV are combined. The analysis of the spectra for low coverage shows that the molecules lie flat on the surface, without molecular rotation. The dependence of the signal on the NO 2 coverage is described. No signal could be seen after adsorption of NO 2 on the clean Ag(110) surface.

Hydrogen atom scattering from physisorbed overlayers: I. Diffraction

Measurements of H-atom diffraction from monolayer and bilayer xenon on graphite are presented. Less complete measurements of krypton, nitrogen and carbon dioxide layers are also given. Because the potentials are quite well known in physisorption, these systems are ideally suited for accurate calculations. The comparison of the diffraction data to close-coupling calculations yields excellent agreement. The procedures developed in the analysis, including a new convolution technique, will be useful in extending the measurements to systems where the potential is less well known. The analysis of the temperature dependence of the diffraction is also accurately modeled, and may serve as a reference system for this type of measurements.

Hydrogen atom scattering from physisorbed overlayers I. Diffraction

Abstract Measurements of H-atom diffraction from monolayer and bilayer xenon on graphite are presented. Less complete measurements of krypton, nitrogen and carbon dioxide layers are also given. Because the potentials are quite well known in physisorption, these systems are ideally suited for accurate calculations. The comparison of the diffraction data to close-coupling calculations yields excellent agreement. The procedures developed in the analysis, including a new convolution technique, will be useful in extending the measurements to systems where the potential is less well known. The analysis of the temperature dependence of the diffraction is also accurately modeled, and may serve as a reference system for this type of measurements.

Dynamics of a krypton-covered graphite slab, and mean-square amplitudes of vibration and thermodynamic functions of krypton and xenon layers adsorbed on the (0001) surface of graphite

Following earlier work on the dynamics of the graphite (0001) free surface [paper I, Phys. Rev. B 23, 4208 (1981)], and of that surface with a registered adsorbed monolayer of xenon [paper II, Phys. Rev. B 24, 6050 (1981)], we present here a full dynamical calculation of a (0001) graphite slab with registered monolayers of krypton adsorbed on its two surfaces. As in II, the krypton-krypton and krypton-carbon interactions are modeled with Lennard-Jones potentials, whereas the carbon-carbon interactions are described by the extended axially symmetric force-constant model of I. The surface-mode spectrum of the krypton-covered graphite slab displays obvious qualitative similarities with that of the xenon-covered graphite slab described in II, but there are also significant quantitative differences. We calculate for both the krypton- and xenon-covered slabs the mean-square amplitudes of vibration (MSA's) and the thermodynamic functions as functions of temperature. For the sizes of crystal that we could handle computationally, the MSA's of the in-plane vibrations $〈{u}_{\ensuremath{\parallel}}^{2}〉$ show the beginnings of the logarithmic dependence on crystal size expected for two-dimensional systems, but this is not yet the case for the MSA's of the out-of-plane vibrations $〈{u}_{\ensuremath{\perp}}^{2}〉$. The most striking difference between krypton and xenon is the large difference in $〈{u}_{\ensuremath{\parallel}}^{2}〉$ between the two cases, resulting from density differences between the registered adsorbed layers and their respective bulk crystals. No absolute measurements of MSA's are presently available for comparison. The adsorbate thermodynamic functions show the behavior expected for a simple two-dimensional crystal. Comparison with experimental quantities for adsorbed systems is made difficult by the fact that the calculations could only be carried out for one density, namely that of the registered monolayer.

Comparative study of the first adsorbed layer of xenon and krypton on boron nitride and graphite

The thermodynamic properties of the first adsorbed layer of xenon and krypton on crystalline boron nitride have been studied between 95 and 125°K and between 77 and 93°K, respectively. They are compared to those previously determined for the first layer of the same gases adsorbed on graphite. With both xenon and krypton the final state of the layer is probably the same as on graphite: a self-determined two-dimensional (2D) solid state having approximately the same density and structure as a (111) plane of the 3D crystal which forms at saturation. As on graphite, the xenon layer also undergoes two successive first-order transitions above a definite temperature: a 2D gas → 2D liquid transition and a 2D liquid → 2D solid transition. But with krypton, only one phase transition has been observed whereas three occur on graphite: two first-order transitions (2D gas → 2D liquid and 2D liquid → 2D localized solid) and a localized → delocalized transition which is of higher order. The only transition observed with krypton on boron nitride is first order, but the nature of this transition has not yet been determined.