Emission spectra of three isotopomers of helium hydride (4HeH, 3HeH, and 3HeD) in the visible spectral region have been acquired using proton‐beam irradiation of dense helium gas (150 Torr) at 4.2 K in the presence o...
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Emission spectra of three isotopomers of helium hydride (4HeH, 3HeH, and 3HeD) in the visible spectral region have been acquired using proton‐beam irradiation of dense helium gas (150 Torr) at 4.2 K in the presence of some solid hydrogen or deuterium. Besides the previously reported D? 2Σ+→A? 2Σ+ transition, near 550 nm, a second transition near 640 nm, identified as the D? 2Σ+→B? 2Π, has been acquired and analyzed. The spectroscopic constants for both transitions have been obtained and compared to the theoretical results based on the latest published potential curves. Further insight into the mechanism for forming HeH will be presented, which indicates that the formation process is sensitive to the hydrogen vapor pressure above the solid.
We propose a finite-size scaling hypothesis for the ‘‘singular’’ part of the free-energy density, f(s)(T,H;L), and the correlation function, G(R,T,H;L), of a system with O(n) symmetry (n≥2), confined to geometry ...
We propose a finite-size scaling hypothesis for the ‘‘singular’’ part of the free-energy density, f(s)(T,H;L), and the correlation function, G(R,T,H;L), of a system with O(n) symmetry (n≥2), confined to geometry Ld−d’×∞d’ (d>4, d’≤2) and subjected to periodic boundary conditions. On the basis of this hypothesis, we predict finite-size effects in the zero-field susceptibility, χ(T;L), the correlation length, ξ(T;L), and the ‘‘singular’’ part of the specific heat, c(s)(T;L), in the region of first-order phase transition (T
A numerical integration of the equations of motion of a 17-particle chain with nearest-neighbor linear and cubic forces has been carried out in quadruple-precision FORTRAN over a period of 600 model time units. The ch...
A numerical integration of the equations of motion of a 17-particle chain with nearest-neighbor linear and cubic forces has been carried out in quadruple-precision FORTRAN over a period of 600 model time units. The chain has clamped ends and is excited initially in the 11th mode. The data obtained from the integration constitute a reversible time ensemble. Equilibrium mode energy distributions in this ensemble prove to have a Maxwell-Boltzmann form, and in addition the calculated mode temperatures agree with those obtained from the double-precision statistical ensemble previously reported for the same system and same model parameters [B. I. Henry and J. Grindlay, Physica D 28, 49 (1987)]. It follows that statistical-ensemble averages and time-ensemble averages are equal, and hence the ergodic hypothesis holds for these two data banks.
A scaling hypothesis is set up for the magnetization m(T,H;L) and susceptibility χ(T,H;L) of a finite-sized system, with O(n) symmetry (n≥2), confined to geometry Ld−d’×∞d’(2<d<4,d’≤2) and subjected ...
A scaling hypothesis is set up for the magnetization m(T,H;L) and susceptibility χ(T,H;L) of a finite-sized system, with O(n) symmetry (n≥2), confined to geometry Ld−d’×∞d’(2
The present work examines two aspects of metallic liquid–glass transitions. First, a computerexperiment, consisting of a temperature‐quench Monte Carlo calculation for the liquid–glass transition of Ca0.7Mg0.3, is ...
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The present work examines two aspects of metallic liquid–glass transitions. First, a computerexperiment, consisting of a temperature‐quench Monte Carlo calculation for the liquid–glass transition of Ca0.7Mg0.3, is carried out. A comparison with such calculations for monatomic metals indicates that there is a significant difference in the Wendt and Abraham criterion for monatomic metals and metallic alloys. In addition, a comparison with laboratory experiments indicates that the discrepancies between the Wendt–Abraham parameters obtained in these laboratory experiments and in the computerexperiments can be ascribed to different cooling rates. Second, an analytic study of the pair distribution function near the transition temperature is presented and reproduces the linear temperature dependence of the Wendt–Abraham parameter. This gives a physical picture for this parameter and indicates that the liquid–glass transition is more likely to be a first‐order transition than a second‐order one.
A scanning microscopy workstation has been developed to digitally control a scanning laser microscope and to provide a powerful image processing system to display and process scanning microscope images. The modular ha...
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There are numerous materials and techniques for the fabrication of optical waveguides and opto-electronic circuits, however all structures require knowledge of the guiding properties for the realization of practical d...
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There are numerous materials and techniques for the fabrication of optical waveguides and opto-electronic circuits, however all structures require knowledge of the guiding properties for the realization of practical devices. We have studied in detail the guiding properties of the planar thin film waveguide, from the most basic, three-layer structure to multilayer waveguides. In sections II and III we describe general formulas for the field distributions, the eigenvalue equations from which the propagation constant can be found, and the generalized dispersion properties, which tell us the variation in effective index with respect to any physical parameter upon which the refractive index or thickness of any layer may depend.
The critical curve of a transition of the second kind in an antiferromagnetic superconductor (AFS) with nonmagnetic impurities has been studied. The AFS is described by using the mean-field model given by Nass, Levin,...
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The critical curve of a transition of the second kind in an antiferromagnetic superconductor (AFS) with nonmagnetic impurities has been studied. The AFS is described by using the mean-field model given by Nass, Levin, and Grest and assuming a one-dimensional electron band. We find that the points on the critical curve satisfy the thermodynamic stability condition for 0≤α1τ/Δ0≤5.04 and 0.49≤HQτ/Δ0≤***α1is the inverse lifetime of a conduction electron for nonmagnetic impurity scattering,HQis the antiferromagnetic molecular field, Δ0is the zero-temperature order parameter of a superconductor in the absence ofHQand impurities. Further, α1τand HQτdenote the values of these quantities for points on the critical curve. For α1τ/Δ0>5.04 and HQτ/Δ0>1.64, the phase transition from the superconducting to the normal state is always of the second kind. Some thermal properties of the system near the critical curve have also been investigated and we find that these depends dramatically on the
The spin-lattice relaxation time of the 31P nucleus in the phosphate group of egg yolk phosphatidylcholine multilamellar dispersions has been investigated at four resonant frequencies (38.9, 81.0, 108.9, and 145.7 MHz...
The spin-lattice relaxation time of the 31P nucleus in the phosphate group of egg yolk phosphatidylcholine multilamellar dispersions has been investigated at four resonant frequencies (38.9, 81.0, 108.9, and 145.7 MHz) in the temperature range from -***. to ***. C. The observed frequency dependence of the relaxation indicates that both dipolar relaxation and relaxation due to anisotropic chemical shielding are significant mechanisms. The experimental data have thus been modeled assuming both mechanisms and the analysis has allowed the contribution of each to the relaxation to be determined along with the correlation time for the molecular reorientation as a function of temperature. Dipolar relaxation was found to dominate at low nuclear magnetic resonance frequencies while at high frequencies the anisotropic chemical shift dominates. The correlation time of the phosphate group is on the order of 10-9 s at ***. C and increases to .apprx. 10-7 s at -***. C. It is observed that the freezing of the buffer which occurs at .apprx. -***. C has a significant effect on the phosphate group reorientation. This effect of the freezing is to change the activation energy for the phosphate group reorientation from 16.9 KJ/mol above -***. C to 32.5 KJ/mol below -***. C.
A quantitative relationship has been identified between the deposition parameters and the electrical and optical properties of a-Si:C thin films. The major effects of the deposition parameters derive from their influe...
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A quantitative relationship has been identified between the deposition parameters and the electrical and optical properties of a-Si:C thin films. The major effects of the deposition parameters derive from their influence on the incorporation of water vapour into the films. Even very small changes in the amount of water vapour, as an ambient during deposition, produce very large changes in the electrical and optical properties of the films. An increase in the ambient water vapour pressure from 1 × 10 −8 to 4 × 10 −8 Torr decreases the room temperature conductivity of the resulting films by as much as three orders of magnitude. The important deposition parameters are expressed in terms of a quantity N H 2 O , which represents the actual amount of water which remains in the film.
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