摘要:

A circular-drive Mössbauer-effect apparatus is described in which the absorber rotates at a fixed speed and the vector character of velocity is used to observe the Mössbauer effect by observing the absorber at varying angles to the emitter. A complete Mössbauer absorption spectrum is thereby recorded without changing the absorber rotation speed.

ISSN:0002-9505    

DOI:10.1119/1.1972877

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

This paper extends the results of the classical derivation of the Kirchhoff-Helmholtz effects on the propagation of sound through fluids in tubes by replacing the ideal gas equation of state with a general equationp = p(ρ, T).

ISSN:0002-9505    

DOI:10.1119/1.1972881

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

About the middle of last century, there were invented several forms of multiple algebra, some of which are extensively used today in mathematical physics. The two types discussed here are quaternions, a quadruple algebra, and vector analysis, a triple algebra. The notations and forms of analysis used in the two systems are contrasted, using for each their representation of scalar and vector products and of Gauss's, Stokes's and Green's theorems. Maxwell made use of the vector part of quaternions in hisTreatise on Electricity, and it was largely due to this that Gibbs came to invent his form of vector analysis. By 1890, about fifty years after the invention of quaternions, it became apparent that Gibbs's vector analysis was being used in place of quaternions, and this gave rise to a heated controversy in the pages ofNature. In the seventy years since this controversy, it is apparent that Gibbs's work and point of view have been completely vindicated.

ISSN:0002-9505    

DOI:10.1119/1.1972885

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

A facet of the development of electromagnetic theory was the choice of a proper notation. This seemingly minor problem generated a large dispute from about 1880 to 1900, reaching a climax in a series of letters inNaturearguing about the relative merits of the quaternion formulation, due to Hamilton and supported by Tait, and the newer vector analysis of Gibbs and Heaviside. This quarrel was carried on at a violent level in many letters inNature.

ISSN:0002-9505    

DOI:10.1119/1.1972887

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

The difference between the electrostatic mass of the classical electronm0, and the electrodynamic mass(4/3)m0, has caused a considerable amount of confusion because the theory of relativity seems to predict that, in the limit of small velocities, the two masses should be the same. It is shown that within the structure of relativity the two masses should not necessarily be the same. The nature of each of the two masses is brought out.

ISSN:0002-9505    

DOI:10.1119/1.1972888

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

The familiar consequences of charge-independence of a nuclear Hamiltonian are derived without introducing the concept of charge space and the extended Pauli principle. Ordinary wave-functions, separately antisymmetric in their protons and neutrons, are used throughout. This has the pedagogical advantage of emphasizing that the physical regularities associated with isobaric spin are consequences of charge-independence alone, and do not depend upon the charge-space formalism.

ISSN:0002-9505    

DOI:10.1119/1.1972889

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

The theories of D. Langmuir and J. R. Pierce on the thermal limitations of electron beam current density have a simple interpretation through geometrical optics and the law of photometric brightness. The brightness law together with Abbe's sine law are sufficient for the design of most electron beams for laboratory experiments. Application of the theory is illustrated for the design of low voltage, high-intensity beams as used in low-energy electron-diffraction experiments.

ISSN:0002-9505    

DOI:10.1119/1.1972890

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

When a potential difference is applied between two electrodes immersed in an electrolyte containing one-ion-type of each polarity, the ratio of the current densities at any point due to the positive and negative charges within the body of the solution is given by the ratio of the drift velocities of the charged carriers. The charge species with the greater drift velocity is associated with the larger fraction of the current density. The fractions of the current density due to the motion of positive and negative charges within the body of the solution are for the most part independent of position, potential difference, and of electrode geometry. These statements apply only when the densities of positive and negative charges are equal. In contrast to the case of electrolytes, there are many cases in gaseous electronics at low current densities where charge neutrality does not hold. In these cases, the fractions of current densities of negative and positive charges are functions of position, electrode geometry, charge production, and loss mechanisms in the gas, and boundary conditions (essentially charge production and loss mechanisms at the electrodes). In a number of cases, these fractions can be calculated without knowledge of the charge carrier velocities in marked contrast to the electrolytic case. In gaseous electronics, it is not true that the more rapidly moving charge species is necessarily responsible for the larger share of the current, either crossing a given plane or averaged over the interelectrode separation. The spatially averaged current fractions furnish revealing information about discharges and are equal to the fractions of currents in an external metallic circuit associated with the motion of the respective ion species. These points are illustrated by a number of steady-state examples encompassing the principal phenomena of gaseous electronics. The discussion is carried out in terms of transference numbers, but it has been found necessary to generalize the concept of transference numbers usually used in chemistry.

ISSN:0002-9505    

DOI:10.1119/1.1972891

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

A somewhat neglected area of research in the optical properties of solids is the study of thermoluminescence. The experimental method is to measure the temperature variation of the fluorescence which results from warming a sample in the dark after excitation by some form of radiation at low temperatures. Its usefulness lies in the information it furnishes concerning defect and impurity energy levels in the band gap in semiconductors and insulators. The experimental results when combined with supplementary data (obtained with the same equipment), yield information concerning the energy distribution of trapping levels and luminescent centers in the material. The relatively small investment required for experimental equipment, the very large range of potential materials for study, and the fact that comparatively little is being done in this field all combine to make thermoluminescence a good possibility for solid-state research in the smaller colleges.

ISSN:0002-9505    

DOI:10.1119/1.1972892

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP

摘要:

A cooled photomultiplier is used to count photons which tunnel through the gap between two prisms in the optical barrier penetration experiment. The transmission is found to be an exponentially decreasing function of gap spacing over the range of spacings measured (̃3 to 9 wavelengths). Furthermore, the strength of the exponential fall-off is in good agreement with the prediction of classical electrodynamics.

ISSN:0002-9505    

DOI:10.1119/1.1972893

出版商:American Association of Physics Teachers    

年代:1966

数据来源: AIP