Showing papers by "Solid State Physics Laboratory published in 1978"
TL;DR: In this paper, the Langevin equation for vortex diffusion was used to estimate the dissipation of energy by a thin film of energy on an oscillating planar substrate, both from motion of free vortices and from polarization of bound pairs.
Abstract: Dissipation of energy by a thin film of $^{4}\mathrm{He}$ on an oscillating planar substrate arises both from motion of free vortices and from polarization of bound pairs. Starting from a Langevin equation for vortex diffusion, and taking into account production of free vortices from bound pairs, we estimate this dissipation in various regimes of frequency, amplitude of vibration, and temperature.
174 citations
TL;DR: In this article, the authors investigated the thermostimulated creep of two series of amorphous polyolefins, (CH 2 ) m C (CH 3 ) 2 and ( CH 2 )m C ( CH 3 )( CH 2 CH 3 ), where m = 1, 2 and 3, was investigated from 77 to 350 K.
52 citations
TL;DR: In this paper, surface studies by means of AES and XPS showed that during the activation process of FeTi surface segregation, metallic Fe clusters are formed and catalyze the hydrogen absorption and are the reason for the irreversible change of the magnetic properties of the FeTi upon hydrogenation.
46 citations
TL;DR: In this article, the irreversible change of the magnetic properties of FeTi upon hydrogenation, the activation process and some surface properties were explained by surface segregation, and they showed that the surface of the FeTi is renewed with each cycle of hydrogenation.
38 citations
TL;DR: In this article, a combination of the following techniques is proposed to analyse the infrared plasma reflectivity spectra in semiconductors: (i) Slope Technique, to determine ϵ x (ii) Reflectivity Minimum Technique to determine N/m c and τ (iii) Curve Fitting Technique, including frequency dependence of τ, which seems to be due to two carrier effects in multiple energy band structures.
27 citations
TL;DR: X-ray inelastic scattering experiments on Li for k ⪆ 2 k F show that the plasmons persist in the whole particle-hole continuum with a flat dispersion relation and that a second peak appears for k > 2k F which is unexpected as discussed by the authors.
17 citations
TL;DR: In this paper, the thermally stimulated currents in undoped and copper-doped polyvinyl acetate were studied as a function of the temperature of polarization and the amount of copper doping.
13 citations
TL;DR: In this article, the electrical resistivities of a number of liquid lithium-magnesium alloys, covering the entire composition range, have been measured as a function of temperature from 675°C down to the liquidus.
Abstract: The electrical resistivities of a number of liquid lithium-magnesium alloys, covering the entire composition range, have been measured as a function of temperature from 675°C down to the liquidus. Additionally, for the same alloy compositions, the temperature of the liquidus has been determined. Calculations of the resistivity were carried out within the framework of the diffraction model, using Heine-Abarenkov-Shaw type model potentials with screening according to Toigo and Woodruff. For the partial structure factors, solutions for hard-sphere potentials of the Percus-Yevick equation for binary systems, with suitably chosen hard sphere parameters, were used. On the same basis, calculations of the thermopower were carried out. As for sodium-caesium alloys, the non-local character of the model potential leads to puzzling results.
11 citations
TL;DR: In this paper, a simple method of determining the birefringence of nematic liquid crystals is described, which is based on a combination of two optical techniques and obtained reproducible and accurate results.
Abstract: In this paper we describe a simple method of determining the birefringence of nematic liquid crystals. The method is based on a combination of two optical techniques. For the nematic liquid crystal MBBA, we have obtained reproducible and accurate results.
11 citations
11 citations
TL;DR: In this paper, the elastic constants, magnetic susceptibility, refractive index and density are reported for p,p'-diheptylazobenzene, a non-polar compound.
Abstract: The elastic constants, magnetic susceptibility, refractive index and density are reported for p,p'-diheptylazobenzene. The behaviour of the elastic constants of this non polar compound is very similar to that of related polar compounds. The anisotropy of both the static and the high-frequency permittivity is proportional to the anisotropy of the susceptibility, as observed earlier for the high-frequency permittivity of other nematogenic compounds.
TL;DR: In this article, the electrical resistivities ϱ and their temperature dependences dϱ/d T of liquid K-Rb and Rb-Cs alloys have been determined experimentally.
Abstract: The electrical resistivities ϱ and their temperature dependences dϱ/d T of liquid K-Rb and Rb-Cs alloys have been determined experimentally. Additionally, the resistivities of Na-K alloys were re-investigated in order to check earlier experiments. The results are interpreted theoretically on the basis of the diffraction model.
TL;DR: In this article, the shape of the potential energy well of a number of alkaline-earth oxides is calculated, using the method of Hatcher and Dienes, for a polarizable-pointion model.
Abstract: The shape of the potential energy well of ${\mathrm{Mn}}^{2+}$ as impurity in a number of alkaline-earth oxides is calculated, using the method of Hatcher and Dienes, for a polarizable-point-ion model. Potentials for the Mn-O, Ca-O, Sr-O, and Ba-O repulsion are derived. It is found that an effective charge of $Z=1.6$ on the ions yields results that are in agreement with experiment. In CaO the ${\mathrm{Mn}}^{2+}$ ion occupies a substitutional site. In SrO the site of ${\mathrm{Mn}}^{2+}$ is also substitutional, but the potential well is very flat over a distance of 0.3 \AA{} in the $〈111〉$ direction. BaO: ${\mathrm{Mn}}^{2+}$ is found to be an off-center system. The off-center sites in the $〈111〉$ and $〈110〉$ direction are both 0.5 eV in energy below the ideal lattice site. The displacements of the impurity in the $〈111〉$ and $〈110〉$ directions are 0.6 and 0.8 \AA{}, respectively.
TL;DR: In this paper, a detailed study has been made at temperatures higher than the Curie temperature; it is suggested that the Cr3+ impurities are located at an NH4+ site which is accompanied by two neighboring proton vacancies.
Abstract: Cr3+ impurities in ADP crystals have been investigated employing the EPR technique. A detailed study has been made at temperatures higher than the Curie temperature; it is suggested that the Cr3+ impurities are located at an NH4+ site which is accompanied by two neighboring proton vacancies. This is concluded from the directions of the principal axes with respect to the crystal axes. In the paraelectric phase there is only one type of Cr3+ center but below TC there are two different centers probably due to different arrangements of the H+ vacancies.
Cr3+-Storstellen in ADP-Kristallen wurden mit der EPR-Technik untersucht. Eine ausfuhrliche Untersuchung wurde bei Temperaturen oberhalb der Curietemperatur durchgefuhrt; es wird angenommen, das die Cr3+-Storstelle an einem NH4+-Platz lokalisiert ist, der von zwei benachbarten Protonenleerstellen umgeben ist. Dies wird aus der Richtung der Hauptachsen bezuglich der Kristallachsen geschlossen. In der paramagnetischen Phase existiert nur ein Typ von Cr3+-Zentren; jedoch existieren unterhalb TC zwei verschiedene Zentren, die wahrscheinlich auf unterschiedliche Anordnungen der H+-Leerstellen zuruckgefuhrt werden konnen.
TL;DR: In this article, the shape of the potential well in KF:Na + and KCl:Li + is calculated using the polarizable point ion (PPI) model and the simple shell model (SSM), in combination with a number of potentials describing the short range interaction between the ions.
TL;DR: In this article, the effect of the electric field on the EPR spectra of SrCl2: Mn2+ and Co2+ was investigated and it was shown that the observed effects can be explained at least partly by displacements of the central impurity induced by the electric fields.
TL;DR: In this article, the radial distribution functions of liquid sodium and caesium at 100°C were calculated by the method of molecular dynamics with interionic pair potentials derived from Heine-Abarenkov-Shaw type model potentials.
Abstract: Radial distribution functions of liquid sodium and caesium at 100°C have been calculated by the method of molecular dynamics with interionic pair potentials derived from Heine-Abarenkov-Shaw type model potential. The results were found to be in good agreement with recent experimental data.
TL;DR: The spectral thermal emission from a single crystal of ferromagnetic iron is partially circular polarized as discussed by the authors, and the circular polarization changes sign at 1.6 eV and diminishes above the Curie temperature.
TL;DR: The thermopower of liquid sodium-caesium alloys has been determined experimentally for a number of compositions covering the whole concentration range and at temperatures between 50 and 200°C.
Abstract: The thermopower Q of liquid sodium-caesium alloys has been determined experimentally for a number of compositions covering the whole concentration range and at temperatures between 50 and 200°C. Values of d Q /d T and of d 2 Q /d T 2 were derived. No irregularities of the kind observed earlier for the temperature dependence of the resistivity have been found. Slightly modified Heine-Abarenkov-Shaw model potentials were used for the interpretation of the results. Full inclusion of their non-local character deteriorates the results significantly.
TL;DR: In this article, a new spherical model is proposed, where the transient heating, caused by a laser impact, is represented by the three-dimensional heat pole, and an analytical solution of the thermoelastic pressure wave could be derived.
Abstract: Existing theories on the thermoelastic generation of acoustic waves do not yield satisfactory agreement with experimental data. A new spherical model is therefore proposed, where the transient heating, caused by a laser impact, is represented by the three-dimensional heat pole. An analytical solution of the thermoelastic pressure wave could be derived. The good agreement of our spherical model with the experimental results is demonstrated.
TL;DR: In this paper, the forbidden fine structure transitions of Cr3+ and Fe3+ ions in alum are explained using the general theory of the ESR transitions, and the calculated transition probabilities are in good agreement with previously communicated experimental data.
Abstract: The forbidden fine structure transitions of Cr3+ and Fe3+ ions in alum is explained, using the general theory of the ESR transitions. The calculated transition probabilities are in good agreement with the previously communicated experimental data. The theoretical angular dependence of both, the allowed and forbidden transition probabilities are also presented.
Es werden die verbotenen Feinstruktur-Ubergange von Cr3+ und Fe3+ in Ammoniumalaun mit Hilfe der allgemeinen Theorie der Elektronenspinresonanz-Ubergange erklart. Die berechneten Ubergangswahrscheinlichkeiten stimmen mit den fruher berichteten experimentellen Ergebnissen gut uberein. Die theoretische Winkelabhangigkeit der erlaubten sowie der verbotenen Ubergange wird ebenfalls mitgeteilt.
TL;DR: A computer program for the analysis of integrated circuits (CAIC) is described, which formulates and solves nonlinear equations for dc node voltages and transistor operating points.
Abstract: A computer program for the analysis of integrated circuits (CAIC) is described. The program formulates and solves nonlinear equations for dc node voltages and transistor operating points, generates...
01 Jan 1978
TL;DR: In this article, the photovoltaic-solar thermal (P-ST) system using concentrated solar radiation can be a match to its high "energy collection" efficiency, and the cell requirements for such a system are discussed.
Abstract: The conventional solar cell is considered as a near ideal absorber of the solar radiation. An integrated Photovoltaic-Solar Thermal (P-ST) system using concentrated solar radiation can be a match to its high “energy collection” efficiency. Cell requirements for such a system are discussed. Conventional silicon and hetero-GaAs based cells are promising. Their effective performance under solar concentration is analyzed on the basis of probable panel cost and area. It is shown that even the high technology costly high performance cells promise viable P-ST systems for large-scale harnessing of the solar energy.