Showing papers by "Solid State Physics Laboratory published in 1979"
TL;DR: In this article, a review discusses the progress which has been made through the use of a large number of different techniques to study the properties of small metallic particles. But the results of these studies are limited.
Abstract: Small metallic particles with diameters in the range 1–100 nm have interesting properties which can sometimes be very different from those of bulk metals. Such colloidal particles play an important part in fields which range from catalysis to radiation damage in compound solids, and also have an intrinsic interest since in some respects they can be regarded as a state of matter intermediate between that of a molecule and a solid. In ionic crystals colloids can be produced either by irradiation or by the introduction of a stoichiometric excess of the metal constituent. In either case the colloids form as a result of the aggregation of fundamental point defects, but it is only fairly recently that a reasonably coherent picture of these processes has emerged and the properties of the colloids have been related to those of small metallic particles studied for other reasons. This review discusses the progress which has been made through the use of a large number of different techniques to study the pr...
242 citations
TL;DR: In this paper, the transformation from the as-quenched amorphous to the crystalline state of the MG 2605 was followed isothermally at relatively low temperatures (580 to 630 K) with Mossbauer-effect spectroscopy (MES).
Abstract: The transformation from the as-quenched amorphous to the crystalline state of ${\mathrm{Fe}}_{80}$${\mathrm{B}}_{20}$ was followed isothermally at relatively low temperatures (580 to 630 K) with M\"ossbauer-effect spectroscopy (MES). Both the Allied Chemical Metglas 2605 ${\mathrm{Fe}}_{80}$${\mathrm{B}}_{20}$ and twin-roller quenched (RQ) ${\mathrm{Fe}}_{80}$${\mathrm{B}}_{20}$ were studied. Before the onset of crystallization the M\"ossbauer recoil-free fraction of the $^{57}\mathrm{Fe}$ nuclei was constant but it increased by about 15% during crystallization. This implies that on the average the Fe atoms are more firmly bound in the crystalline than in the amorphous state. From a combination of MES, x-ray diffraction, and optical microscopy it was found that (a) the MG 2605 ribbons are rather inhomogeneous in the sense that 10% to 15% of the ribbon cross section is considerably more resistant to crystallization than the remaining part, (b) no such inhomogeneity is present in the RQ ribbons, (c) the crystallization takes place by the eutectic type of reaction, the crystallization products are $\ensuremath{\alpha}$-Fe and the (metastable) tetragonal ${\mathrm{Fe}}_{3}$B compound, and (d) a quantitative analysis of the kinetics of the transformation suggests that crystallization occurs only by the growth of (crystalline) nuclei which are already present in the as-quenched amorphous material.
63 citations
TL;DR: In this article, a model of the smectic C phase is proposed in which the tilt is thought to originate from the forces between dipoles and induced dipoles, where the rotation about the long axis is assumed to be free.
Abstract: A model of the smectic C phase is proposed in which the tilt is thought to originate from the forces between dipoles and induced dipoles. The rotation about the long axis is assumed to be free. Three ordered phases are found corresponding with the smectic C phase, the smectic A phase and the nematic phase. The entropy of packing plays an important role in the mechanism of the smectic C-smectic A phase transition. This transition is not of the usual order-disorder type.
35 citations
TL;DR: In this article, the anisotropy of the diamagnetic susceptibility, the density and the entropy change at the nematic-isotropic transition of a number of structurally related Schiff's bases are reported.
Abstract: The anisotropy of the diamagnetic susceptibility, the density and the entropy change at the nematic-isotropic transition of a number of structurally related Schiff's bases are reported. Order parameters have been calculated from the anisotropies of the susceptibility. The results indicate that there is a close correspondence between the order parameter and the relative volume change at the nematic-isotropic transition. The experimental data suggest that there exists considerable flexibility of the alkylene chains both in the nematic and isotropic phases. The experimentally observed trends can be understood within the framework of theoretical models, which take account of molecular flexibility.
32 citations
TL;DR: In this article, the elastic constants of a number of nematic liquid crystals with relatively rigid molecular structures were investigated and it was shown conclusively that the ratio of the bend and splay elastic constants K 3 / K 1 increase with increasing length to width ratio.
31 citations
TL;DR: In this paper, a hollow metallic waveguide resonator with deep periodic corrugations was used for the pulsed operation of an optically pumped CH 3 F 496 μm distributed feedback (DFB) gas laser.
31 citations
TL;DR: In this paper, the structure of liquid sodium-caesium alloys has been investigated for a large number of compositions covering the whole concentration range using X-ray as well as neutron diffraction techniques.
Abstract: The structure of liquid sodium-caesium alloys has been investigated for a large number of compositions covering the whole concentration range. X-ray as well as neutron diffraction techniques were employed. Special attention has been paid to the small-angle region of the diffraction pattern. The long-wavelength limit of the structure factor has been interpreted by applying a model proposed by Bhatia and March. Appreciable concentration fluctuations, indicating a tendency to phase separation, occur in the liquid. The size of the clusters was estimated using Guinier's model. For a few concentrations, molecular dynamics computer simulations have been carried out. Different models for evaluating the three partial structure factors have been considered.
28 citations
24 citations
TL;DR: In this paper, a comparison of the detectivities, D,′ and the depletion layer capacitance per unit area, (C/A), of various diodes has been made at 77K.
17 citations
TL;DR: In this paper, the cholesteric state and its distortion free energy were discussed in terms of a molecular model, and the influence of packing entropy was analyzed for the temperature dependence of the pitch and elastic constants.
17 citations
TL;DR: Polarized absorption spectra parallel to a - and b -crystal axes of the single crystal of indole between 2600-3000 A at 90°K have been investigated.
TL;DR: In this article, the elastic constants of Schiffs bases were investigated in terms of the theory of Priest and it was shown that the elastic constant is related to the molecular dimensions and can be understood qualitatively in terms the theory.
Abstract: Experimental values are reported for the elastic constants of a number of Schiffs bases. The ratio K3,/Kl, is found to decrease with increasing alkyl chain length. The results indicate that the elastic constants are related to the molecular dimensions and can be understood qualitatively in terms of the theory of Priest.
TL;DR: In this article, a transversely excited HCN laser with u.v.preionization is described and the influence of auxiliary discharge on the laser medium is discussed and the results obtained with laser gas mixtures CH 3 CN-He, (CN) 2 -H 2 -He and HCN-CH 4 -He are presented.
TL;DR: A slightly modified version of the Maier-Saupe model is presented in this paper, which relies on the introduction of a spherical constraint and can be easily solved analytically in the mean field approximation.
Abstract: A slightly modified version of the Maier-Saupe model is presented. As a result of this modification, that relies on the introduction of a spherical constraint, the model can be easily solved analytically in the mean field approximation. Simple expressions result for the relevant thermodynamic quantities, e.g. the temperature dependence of the order parameter. Consequently the thermodynamic properties of the original model can be understood without any appreciable numerical effort. The method can be applied to other models as well. As an example we shortly deal with the Meyer-Lubensky model of the nematic to smectic A transition.
TL;DR: In this paper, the chiral smectic C phase was discussed using a simple molecular model and the helix was expressed in terms of the tilt angle and the smectric order parameter.
TL;DR: The spin lattice relaxation time of deuterium in Pd (D/Pd = 0.70) is measured as a function of temperature in this article, and the activation energy for the diffusion of deutium atoms is obtained and compared with that of hydrogen in β-PdH.
Abstract: The spin lattice relaxation time of deuterium in Pd (D/Pd = 0.70) is measured as a function of temperature. The activation energy for the diffusion of deuterium atoms is obtained and compared with that of hydrogen in β-PdH. By comparing the experimental quadrupole coupling constant with the theoretical one, informations are obtained about the configuration of the deuterium atoms in palladium.
On a fait des mesures de temps de relaxation spin reseau du deuterium en Pd (D/Pd = 0,70) en fonction de la temperature. L'energie d'activation obtenue pour la diffusion des atomes de deuterium a ete comparee a celle de l'hydrogene en β-PdH. La comparison de la constante experimentale du couplage quadrupolaire avec sa valeur theorique, donne des informations sur la configuration des atomes de deuterium dans le palladium.
TL;DR: In this paper, a comparative study of natural and deuterated polysterene has been performed by thermally stimulated currents (TSC), and a TSC peak is observed whose relaxation times obey an Arrhenius equation.
TL;DR: In this paper, the Maier-Saupe model in terms of the random-phase approximation is given and the influence of the range of the intermolecular potential is analyzed.
Abstract: A calculation of the Maier-Saupe model is given in terms of the random-phase approximation. The influence of the range of the intermolecular potential is analyzed. Notably, attention is paid to short-range-order effects in the isotropic phase. It appears that light-scattering data can be understood using a short-range potential.
TL;DR: In this article, three possible explanations are discussed to understand the helix inversion in a number of binary cholesteric-nematic mixtures, including the one described in this paper.
TL;DR: In this paper, the authors report new results of EPR experiments on orthorhombic Gd 3+ - M + complexes (M = Na, K, Rb and Ag) in SrF 2.
TL;DR: In this article, it was shown that by allowing the carrier relaxation time in the Drude theory to be frequency-dependent, an overall improvement in the agreement between the theoretical and experimental variation of conductivity of p-Si is obtained.
TL;DR: A comparative study of low density polyethylene (LDPE) and HDPE of different surface morphologies was carried out using the depolarization thermocurrent (DTC) technique as mentioned in this paper.
TL;DR: In this paper, the steady hydrodynamic problem of a single-rudder ship moving in a shallow canal of rectangular cross-section is considered, where the ship-rudders system is considered as a slender body with a hinged fin.
Abstract: This report deals with the steady hydrodynamic problem of a single-rudder ship moving in a shallow canal of rectangular cross section. The ship-rudder system is considered as a slender body with a hinged fin. The theoretical model can be used to compute the lateral forces induced by the canal walls, the sway angle and rudder deflection required to cancel the effects of these forces, and the course-keeping stability. No numerical results are given.
TL;DR: In this article, the authors developed a nomograph for direct evaluation of various parameters at 77K of Schottky barrier infrared detectors, which can also be used for other temperatures.
TL;DR: In this paper, thin films of As2S3 were vacuum evaporated on Germanium single crystals as well as on chemically deposited photosensitive PbS films and the sealing properties of A2,S3 films were found to be satisfactory.
Abstract: Thin films of As2S3 were vacuum evaporated on Germanium single crystals as well as on chemically deposited photosensitive PbS films. Films thicknesses were controlled with the quartz crystal monitor, for making Ge filters for different selective IR regions. The sealing properties of A2,S3 films deposited on sensitised photoconductive PbS films were found to be satisfactory. The transmission electron micrographs have been taken to investigate the structure of the films deposited at different temperatures.
TL;DR: In this paper, SiO was vacuum evaporated in the presence of ionised oxygen at a pressure of l 0 -5 torr, and films were deposited on NaCl single crystals held at ambient to 200°C temperature.
Abstract: Silicon monoxide was vacuum evaporated in the presence of ionised oxygen at a pressure ~l0–5 torr. Films were deposited on NaCl single crystals held at ambient to 200°C temperature. Ionised oxygen was produced with the help of a specially made discharge tube. Conversion of SiO to SiO2 was evaluated by infrared absorption spectra. The magnitude of absorption bands due to different oxides in the region 700 to 1400 cm–1 yield information about the film composition.