scholarly journals The theory of the change in resistance in a magnetic field

1934 ◽  
Vol 145 (854) ◽  
pp. 268-277 ◽  
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Periodic Potential ◽  
Quadratic Function ◽  
Modern Theory ◽  
Quantum Numbers ◽  
Wrong Direction ◽  
Constant Potential ◽  
The Subject ◽  
Experimental Values

The resistance of a metal is in general increased by a magnetic field. For sufficiently small magnetic fields this dependence may, of course, be expressed by the equation ∆R/R = BH 2 . The calculation of the coefficient B has been the subject of many previous investigations. Sommerfeld has shown that if the electrons are regarded as moving in a constant potential, then the theoretical value of B is 10,000 times smaller than the observed value, and the temperature dependence is in the wrong direction. Peierls has suggested that the correct magnitude of B may be obtained if cognizance is taken of the fact that the electrons are moving in a periodic potential, as is usual in the modern theory of metals. Moreover, he has shown that the correct temperature dependence will then be obtained. Blochinzev and Nordheim have recently investigated in detail the charge of resistance of divalent metals from this standpoint. The periodicity of the lattice was, however, introduced in quite an idealized manner. In place of an actual metal they considered a simple cubic lattice. The surface of the Fermi distribution was assumed to be composed of sections each of which was a quadratic function of the quantum numbers ξ, η , ζ. The coefficient B was obtained in terms of the Fourier coefficient of the potential energy of an electron in the lattice, V 100 . Agreement with the experimental values of B was obtained by taking |V 100 | as small as several hundredths of an electron volt, while the correct value must be of the order of 1 volt. Since in their model B varies inversely as the square of |V 100 |, the comparison with experiment is far from satisfactory.

scholarly journals On the Pressure and Temperature Dependence of the Absorption Coefficient of NH3

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
F. Aousgi ◽  
S. Hadded ◽  
H. Aroui
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Absorption Coefficient ◽  
Temperature Dependence ◽  
Quadratic Function ◽  
Fourier Transform Spectrometer ◽  
Absorption Coefficients ◽  
Linear Evolution ◽  
Exponential Law ◽  
Quantum Numbers

The effects of pressure and temperature on the absorption coefficient of ammonia (NH3) gas self-perturbed and perturbed by nitrogen (N2) gas have been measured. We varied the gas pressure from 10 to 160 Torr and the temperature from 235 to 296 K in order to study the absorption coefficient at the center and the wings of lines in the ν4 band of NH3. These measurements were made using a high resolution (0.0038 cm-1) Bruker Fourier-transform spectrometer. These spectra have been analyzed using the method of multipressure technique permitting to succeed to an evolution of the absorption coefficient with the pressure and the quantum numbers J and K of the NH3 molecule. The results show that the absorption coefficient varies as a quadratic function of the pressure at the center of a given line. However, it has a linear evolution in the wings of the line. Moreover, the absorption coefficients are inversely proportional to temperature in the wings when NH3 lines are broadened by N2. The retrieved values of these coefficients were used to derive the temperature dependence of N2 broadening NH3 lines. The absorption coefficients were shown to fit closely the well-known exponential law.

Materials for Electron Beam Information Storage

1969 ◽  
Vol 27 ◽  
pp. 152-153 ◽  
Author(s):  
D. E. Speliotis
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Recent Literature ◽  
Electron Beams ◽  
Information Storage ◽  
The Subject ◽  
The Magnetic Field

The interaction of electron beams with a large variety of materials for information storage has been the subject of numerous proposals and studies in the recent literature. The materials range from photographic to thermoplastic and magnetic, and the interactions with the electron beam for writing and reading the information utilize the energy, or the current, or even the magnetic field associated with the electron beam.

MATHEMATICAL MODELING OF TEMPERATURE EFFECT ON THE FAN CHART OF MAGNETOABSORPTION SPECTRUM IN SEMICONDUCTORS

2019 ◽  
pp. 104-115
Author(s):  
G. Gulyamov ◽  
U. I. Erkaboev ◽  
A. G. Gulyamov
Keyword(s):  
Mathematical Modeling ◽  
Magnetic Field ◽  
Temperature Dependence ◽  
Density Of States ◽  
Landau Levels ◽  
Joint Density ◽  
Narrow Gap ◽  
Narrow Gap Semiconductors ◽  
Dispersion Law ◽  
The Magnetic Field

The article considers the oscillations of interband magneto-optical absorption in semiconductors with the Kane dispersion law. We have compared the changes in oscillations of the joint density of states with respect to the photon energy for different Landau levels in parabolic and non-parabolic zones. An analytical expression is obtained for the oscillation of the combined density of states in narrow-gap semiconductors. We have calculated the dependence of the maximum photon energy on the magnetic field at different temperatures. A theoretical study of the band structure showed that the magnetoabsorption oscillations decrease with an increase in temperature, and the photon energies nonlinearly depend on a strong magnetic field. The article proposes a simple method for calculating the oscillation of joint density of states in a quantizing magnetic field with the non-quadratic dispersion law. The temperature dependence of the oscillations joint density of states in semiconductors with non-parabolic dispersion law is obtained. Moreover, the article studies the temperature dependence of the band gap in a strong magnetic field with the non-quadratic dispersion law. The method is applied to the research of the magnetic absorption in narrow-gap semiconductors with nonparabolic dispersion law. It is shown that as the temperature increases, Landau levels are washed away due to thermal broadening and density of states turns into a density of states without a magnetic field. Using the mathematical model, the temperature dependence of the density distribution of energy states in strong magnetic fields is considered. It is shown that the continuous spectrum of the density of states, measured at the temperature of liquid nitrogen, at low temperatures turns into discrete Landau levels. Mathematical modeling of processes using experimental values of the continuous spectrum of the density of states makes it possible to calculate discrete Landau levels. We have created the three-dimensional fan chart of magneto optical oscillations of semiconductors with considering for the joint density of energy states. For a nonquadratic dispersion law, the maximum frequency of the absorbed light and the width of the forbidden band are shown to depend nonlinearly on the magnetic field. Modeling the temperature  dependence allowed us to determine the Landau levels in semiconductors in a wide temperature spectrum. Using the proposed model, the experimental results obtained for narrow-gap semiconductors are analyzed. The theoretical results are compared with experimental results.

Temperature Dependences in the O + OH → O2 + H Reaction. Quasiclassical Trajectory Calculation

1993 ◽  
Vol 58 (2) ◽  
pp. 234-243 ◽  
Author(s):  
Viliam Klimo ◽  
Martina Bittererová ◽  
Stanislav Biskupič ◽  
Ján Urban ◽  
Miroslav Micov
Keyword(s):  
Temperature Dependence ◽  
Energy Surface ◽  
Analytical Form ◽  
Mean Values ◽  
Quantum Numbers ◽  
Mean Lifetime ◽  
Temperature Dependences ◽  
Quasiclassical Trajectory Calculation ◽  
The Mean ◽  
Combustion Processes

The reaction O + OH → O2 + H in conditions of combustion of hydrocarbons and polymers was modelled by using the method of quasiclassical trajectories. The potential energy surface was determined by the multiconfiguration interaction method and fitted with the analytical form of the extended LEPS function. Attention was paid to the mean values of the vibrational and rotational quantum numbers of O2 molecules and their temperature dependence. The temperature dependence of the mean lifetime of the OOH collision complex was also examined. The calculated rate constants were analyzed and compared with the experimental data over the temperature region of the combustion processes.

Quantum Theory

2017 ◽  
Author(s):  
Frank S. Levin
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Uncertainty Principle ◽  
Quantum Spin ◽  
Quantum States ◽  
Wave Functions ◽  
Symbolic Representations ◽  
Quantum Numbers ◽  
The Subject ◽  
Heisenberg's Uncertainty Principle

The subject of Chapter 8 is the fundamental principles of quantum theory, the abstract extension of quantum mechanics. Two of the entities explored are kets and operators, with kets being representations of quantum states as well as a source of wave functions. The quantum box and quantum spin kets are specified, as are the quantum numbers that identify them. Operators are introduced and defined in part as the symbolic representations of observable quantities such as position, momentum and quantum spin. Eigenvalues and eigenkets are defined and discussed, with the former identified as the possible outcomes of a measurement. Bras, the counterpart to kets, are introduced as the means of forming probability amplitudes from kets. Products of operators are examined, as is their role underpinning Heisenberg’s Uncertainty Principle. A variety of symbol manipulations are presented. How measurements are believed to collapse linear superpositions to one term of the sum is explored.

scholarly journals Art. II.—Some Suggestions of Origin in Indian Architecture

1888 ◽  
Vol 20 (1) ◽  
pp. 49-71
Author(s):  
William Simpson
Keyword(s):  
Great Achievement ◽  
Indian Architecture ◽  
Wrong Direction ◽  
The Subject

When Mr. Fergusson commenced the study of Indian Architecture, nothing was really known on the subject. He had first to collect the materials, and after years of work he was able at last to leave the Architecture of India in a classified form. This was in itself a great achievement for one man to do. But he did more than this. He traced back the developments of form and construction in many cases to their early beginnings, and thus gave us their origin. It is only when this has been accomplished that we can truly say “we know” any particular style of architecture. We have still some very interesting problems of this kind to work out in regard to India; and suggestions regarding them, even although they should ultimately be found to have pointed in the wrong direction, may yet be useful in many ways; such speculations may call the attention of men in India to the information that is required, and by this means we have the chance of receiving knowledge. I have often discussed some of these questions of origin with Mr. Fergusson, and he used to refer to some of the unexplored parts of India, where he thought some remains of the older forms of Architecture might yet be found, which would throw light on what we wanted. His mode of expressing himself was, “If some man, with the necessary knowledge, and with an eye in his head, could be sent,” he felt certain that there are old temples in many parts not yet discovered that would clear up most of the doubtful points.

Temperature dependence of the magnetic-field-induced strain of NiMnGa in the presence of an acoustic drive

2008 ◽  
Vol 104 (3) ◽  
pp. 033918 ◽  
Author(s):  
Bradley W. Peterson ◽  
Samuel M. Allen ◽  
Robert C. O’Handley
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
The Magnetic Field

Toward a Modern Theory of Rhetoric: A Tagmemic Contribution

1965 ◽  
Vol 35 (4) ◽  
pp. 450-468 ◽  
Author(s):  
Richard Young ◽  
Alton Becker
Keyword(s):  
Subject Matter ◽  
Linguistic Theory ◽  
Modern Theory ◽  
New Approach ◽  
The Subject

The authors undertake first to define the subject matter of rhetoric as it has been traditionally understood and then to illustrate how aspects of one linguistic theory,tagmemics, can form the basis for a new approach to rhetorical problems

scholarly journals The general proof of certain fundamental equations in the theory of metallic conduction

1934 ◽  
Vol 144 (851) ◽  
pp. 101-117 ◽  
Keyword(s):  
Wave Equation ◽  
Periodic Potential ◽  
Thermal Motion ◽  
Electronic Conduction ◽  
Modern Theory ◽  
General Proof ◽  
Metallic Conduction ◽  
Fundamental Equations

In the modern theory of electronic conduction the electrons are considered, when the thermal motion of the lattice is neglected, as moving in a periodic potential with the property V ( x + la , y + ma , z + na ) = V ( x, y, z ). The wave equation for an electron in this field is { h 2/8π2 m ∇ 2 + E K - V} ψ K = 0. Block has shown that this equation has solutions of the form ψ K = e i K.R U K (R), where U K has the periodicity of the lattice.

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