摘要:

Impurity diffusion of Na ions along dislocations in LiF has been studied by both dc and transient techniques. The Na impurity is injected into the LiF by plating NaCl on one surface of the LiF and placing a potential across the crystal at an elevated temperature. Large‐scale diffusion with Na dendrite formation is observable in a dc arrangement and the diffusion can be measured by either radioactive tracer methods or measurement of charge transport. Transient experiments yield an activation energy for diffusion of approximately 0.3 eV for both edge and screw dislocations, andD0=0.01 cm2/sec. Analysis of the charge effects in the core of the dislocations leads one to propose a very large vacancy density in the core, and the experiments are even best understood in terms of a hollow of atomic dimensions along the dislocation core.

ISSN:0021-8979    

DOI:10.1063/1.1729291

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Recent interest in the application of infrared and optical masers (lasers) for range measurement, surveillance, welding, and drilling has focused attention on the problem of obtaining high peak‐power pulses of short duration and fast risetime from these quantum devices. Kerr cells, Pockel cells, rotating disks, and mirrors have been used as shutters in the past with varying degrees of success. In this paper, experiments are described that demonstrate an ultrasonic shutter suitable for obtaining giant pulses from a ruby optical maser by utilizing the refraction resulting from the passage of a plane‐parallel light beam through an ultrasonic field whose wavelength is much larger than the width of the light beam. Amplitude, risetime, and pulse duration are comparable with the values reported utilizing a Kerr cell and superior to those reported for rotating mechanical shutters. In addition, the ultrasonic shutter can be utilized to synchronize the usually random output pulses of a ruby optical maser with the ultrasonic frequency.

ISSN:0021-8979    

DOI:10.1063/1.1729292

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The Nernst coefficient, the Hall coefficient, the electrical resistivity, and the Seebeck coefficient have been measured on Te‐ and Se‐doped GaSb between 60° and 800°K. The two minima conduction band model, as applied to the present group of measurements, provides a qualitative description of conditions under which certain scattering mechanisms will dominate the transport phenomena.

ISSN:0021-8979    

DOI:10.1063/1.1729293

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Various factors entering into the continuous operation of optically pumped solid‐state lasers are summarized. Numerical estimates for ruby and for Nd+++‐ activated materials in two types of optical systems suggest that several watts of output power should, ideally, be obtainable when pumping with a 1‐kW Hg arc lamp.

ISSN:0021-8979    

DOI:10.1063/1.1729294

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Saturation magnetizations of V‐Fe and Cr‐Fe alloys were measured and the results used to determine the average atomic magnetic moment. The linear rate of change of the moment with solute concentration,dp¯B/dC, was found to be −3.286 Bohr magnetons per atom in V‐Fe &agr;‐phase alloys. Transformation of an approximately equiatomic alloy to the CsCl‐ordered &agr;′‐phase resulted in a decrease of about 0.4 Bohr magneton in the moment. Subsequent transformation to the &sgr;‐phase lowered it by a factor of three. In Cr‐Fe solid solution alloys,dp¯B/dCwas found to be −2.36 Bohr magnetons per atom.

ISSN:0021-8979    

DOI:10.1063/1.1729295

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Electron microscopical observations of glide dislocations lying in the basal plane of the layer structure GaSe are described. The dislocations are dissociated into partials separated by stacking fault ribbons as wide as 1 &mgr;. Network‐like grids formed from sets of ribbons lying in different glide planes were observed and are analysed in detail. A discussion is given of the contrast effects produced by dislocation dipoles contained in the grids.

ISSN:0021-8979    

DOI:10.1063/1.1729296

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

This paper presents a coupled mode formalism which predicts the effects of rf magnetic fields on the propagating modes of the plasma loaded waveguide. In addition, this formalism provides a simple physical interpretation of the propagation characteristics in terms of the uncoupled modes, which are taken to be the waveguide modes and quasi‐static plasma modes, respectively. The method of obtaining coupled mode equations is given and two typical calculations using the theory are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1729297

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The coefficient of heat transfer between a smooth vertical silver surface and liquid helium is typically 0.020±0.005 W cm−2°K−1for convection and increases in the pool boiling range to 0.22 W cm−2°K−1for 0.040 °K superheat at 4.0°K. The heat transfer rate for pool boiling decreases with decreasing temperature between 4.0° and 2.5°K in proportion to the latent heat of vaporization and inversely as the molar volume of the vapor at the pressure and temperature of the experiment. The superheat in the steady state is determined by the volume rate of gas production at the surface. The hysteretic nature of the heat transfer curves in the boiling range suggests a nucleation mechanism strongly dependent on the thermal history of the specimen.

ISSN:0021-8979    

DOI:10.1063/1.1729298

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The frequency stability of a circularly polarized solid‐state paramagnetic maser oscillator has been observed with the objective of obtaining the information needed to construct a frequency standard with a broad microwave spectral line. The beat frequency between two such masers by using ruby can be made almost free from the variation of the static magnetic field and of the angle between the crystalline axes and the static magnetic field. The stability of the 1.5‐Mc beat frequency is approximately 10−6for short time intervals, and is approximately 10−5for long time intervals. The short‐time stability is limited mainly by the fluctuation of the cavity resonant frequency in the liquid helium. The long‐time stability is determined by the drift of the pump frequency, although the reason for this interrelation is not thoroughly understood. The effect of reflections from the load on frequency is considerably reduced by the unidirectional structure used here, as compared with that to be expected with a reflection type of maser. We also show that the unidirectional maser amplifier can be built with reduced cross section by utilizing dielectric‐loaded circular waveguide.

ISSN:0021-8979    

DOI:10.1063/1.1729299

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The shape of metal‐insulator‐metal potential barriers is derived, including the effects of space charge. For very thin insulating films, the barrier is shown to be essentially rectangular (or trapezoidal if different metals are used on either side of the insulating film). The modification in the rectangular barrier introduced by image forces is derived and shown to be significant for very thin insulating films. Finally, the effect of insulator doping on barrier shape is considered.

ISSN:0021-8979    

DOI:10.1063/1.1729300

出版商:AIP    

年代:1963

数据来源: AIP