The effects of many-body interactions in the static structure of dense gaseous krypton (for 0.9-2.1 rho(c), where rho(c) is the critical density) and xenon (for 2.2-2.6 rho(c)) were investigated in the momentum transf...
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The effects of many-body interactions in the static structure of dense gaseous krypton (for 0.9-2.1 rho(c), where rho(c) is the critical density) and xenon (for 2.2-2.6 rho(c)) were investigated in the momentum transfer range 4 less than or equal to Q less than or equal to 42 nm(-1), through comparisons of the measured structure factors S(Q) with those calculated through the MHNC-CRS integral equation by Reatto and Tau. One property investigated is the small increase in the effective atomic diameter with increasing density. While the observed variation, as determined through the position of the main diffraction maxima, is similar to that given by the inclusion of the Axilrod-Teller triple-diploe interaction in the calculation, further small deviations exist which indicate the need for additional many-body terms.
Dynamic light scattering is an established technique for measuring the average size and size distribution of particles in a suspension. The technique has the advantage of being fast and non-invasive, but it does requi...
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Dynamic light scattering is an established technique for measuring the average size and size distribution of particles in a suspension. The technique has the advantage of being fast and non-invasive, but it does require low particle concentrations. As well, dynamic light scattering results are often open to misinterpretation if one is unaware of the state of the sample and the method of data analysis. The following discussion reviews some of the basic concepts of dynamic light scattering and outlines some of the pitfalls that are often encountered in data interpretation. A modification of dynamic light scattering, diffusing wave spectroscopy, can be used to obtain approximate size information at higher particle concentrations. The fundamentals of this new technique are summarized.
The effect of polydispersity on the isotropic-nematic phase transition of rigid rods is analyzed in terms of a second-order perturbation theory, in which the width σ of an arbitrary number fraction is used as a pertu...
The effect of polydispersity on the isotropic-nematic phase transition of rigid rods is analyzed in terms of a second-order perturbation theory, in which the width σ of an arbitrary number fraction is used as a perturbation parameter. These results show that the isotropic-nematic phase transition takes place at the isotropic density nI, where nIL¯N2D=4.189(1+2.128σ2), and the nematic density nN, where nNL¯N2D=5.336(1+1.655σ2), with D and L¯N being the diameter and the number-averaged length of rods in the nematic phase. At the transition density, the weight- and number-averaged orientation order parameters have the values SW=0.7922+1.1333σ2 and SL=0.7922+0.816σ2; the ratio between the number-averaged length of rods in the isotropic phase, L¯I, and that in the nematic phase, L¯N, is L¯I/L¯N=1-1.844σ2. These perturbation results are compared with the numerical solution of the equilibrium conditions for the isotropic-nematic transition of rods obeying two modeled number fraction distributions.
We examine possible nematic to smectic and nematic to columnar phase transitions for binary mixtures of perfectly parallel aligned hard cylinders with equal diameters but different lengths by using the free-energy fun...
We examine possible nematic to smectic and nematic to columnar phase transitions for binary mixtures of perfectly parallel aligned hard cylinders with equal diameters but different lengths by using the free-energy functional within the third virial coefficient approximation. The regions of stability are located and the phase diagram of the system is calculated for different values of the ratio of the two cylindrical lengths. The nematic phase can directly transform into the columnar phase for values with a length ratio smaller than 0.635, showing that dispersity in molecular length can stabilize columnar versus smectic ordering of these mixtures.
The equations of motion of the Hénon-Heiles model have been numerically integrated for 100 different starting conditions on the critical energy surface E=1/6. The truncation error in the data was monitored using ...
The equations of motion of the Hénon-Heiles model have been numerically integrated for 100 different starting conditions on the critical energy surface E=1/6. The truncation error in the data was monitored using the separation in phase space of two numerical histories with the same initial conditions, based on different time steps, h=2−13 and h’=2−14. From the data for which the truncation error is less than 1% it is found that the 100 histories fall into three categories, (a) regular (or quasiperiodic), (b) irregular (or chaotic), and (c) regular-irregular. The three-dimensional phase space portraits prove to be the most useful tool in distinguishing between regular and irregular behavior. In category (c) the orbit switches reversibly from (to) regular to (from) irregular behavior. The data suggest that all 100 orbits, followed for long enough times, will show regular-irregular behavior and moreover the phase points in these orbits will spend, on average, equal amounts of time in the quasiperiodic and chaotic regimes.
The self-consistent-field model for K shakeoff in β± decay and electron-capture decay is extended to deal with the processes of L shakeoff accompanying K capture and K shakeoff accompanying L capture. The result...
The self-consistent-field model for K shakeoff in β± decay and electron-capture decay is extended to deal with the processes of L shakeoff accompanying K capture and K shakeoff accompanying L capture. The results indicate that many-body effects play an important role and reduce the shakeoff probability.
Samples of solid deuterium, cooled below 4.2 K, and irradiated by 15 MeV protons, will spontaneously flash. The flash-spectrum occurs in the near infrared with a maximum close to 920 nm. The flash intensity is two to ...
Samples of solid deuterium, cooled below 4.2 K, and irradiated by 15 MeV protons, will spontaneously flash. The flash-spectrum occurs in the near infrared with a maximum close to 920 nm. The flash intensity is two to three orders of magnitude greater than a steady-state emission observed in the same spectral region. The flash frequency is 1 every 1 to 3 min after several hours of irradiation of 10 nA/cm2. Heat pulses have been detected accompanying many of the flashes and both can be stimulated by the application of external heat triggers. Following the optical flash, the steady-state emission intensity decreases by an amount that is wavelength dependent. While it is thought that these flashes are caused by atomic association in the solid, the species responsible for the optical emission is uncertain as is the transition itself.
Effect of J term in the t-t'-J model on the Fermi surface, density of states and the Drude plasma frequency have been studied. The J term is treated within the uniform bond theory of Affleck and Marston [Phys. Rev...
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Effect of J term in the t-t'-J model on the Fermi surface, density of states and the Drude plasma frequency have been studied. The J term is treated within the uniform bond theory of Affleck and Marston [Phys. Rev. B39, 11538 (1989)]. Inclusion of the J term succeeds in removing the Brinkman-Rice divergence in the density of states at Fermi energy but fails to obtain an insulating state at zero doping. We have also shown that an exact treatment of the J term does indeed lead to an insulating' state at half-filling.
Methods of standardization in quantitative micro-PIXE analysis are reviewed and various issues that bear on analytical accuracy are explored;pertinent recent work on Si(Li) X-ray detector response is included and some...
Methods of standardization in quantitative micro-PIXE analysis are reviewed and various issues that bear on analytical accuracy are explored;pertinent recent work on Si(Li) X-ray detector response is included and some geochemical examples are drawn upon. Extension of the GUPIX software to deal with multilayer targets, including secondary fluorescence within and between layers, is reported;analytical examples include alloy foils and multilayer solar cell structures.
Making use of the Poisson summation formula in m dimensions, a class of phase-modulated lattice sums is evaluated analytically. The resulting formulas provide a broad generalization of the results reported previously ...
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Making use of the Poisson summation formula in m dimensions, a class of phase-modulated lattice sums is evaluated analytically. The resulting formulas provide a broad generalization of the results reported previously and are of considerable use in the analysis of finite-size effects in systems undergoing phase transitions, especially when the boundary conditions imposed are other than periodic.
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