摘要:

Copper was diffused in cadmium sulfide single crystals to determine diffusion coefficients using the radio‐active tracer sectioning technique. Over the temperature range of 450°–750°C, the relationship between temperature and diffusion coefficient was found to beD=1.5×10−3e−17600/RTsquare centimeters per second for diffusion perpendicular to theCaxis. For diffusion parallel to theCaxis, the frequency factor and activation energy were found to be within the experimental accuracy of the corresponding values for perpendicular diffusion. There appears to be no appreciable diffusion anisotropy. Observed surface diffusion was a complicating factor in obtaining data on volume diffusion.

ISSN:0021-8979    

DOI:10.1063/1.1776996

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Most of the AIIIBVsemiconducting compounds have the zincblende crystal structure. This structure is noncentrosymmetric and as a consequence the modulii ofF(hkl) andF(h¯k¯l¯), the geometrical structure factors, have different magnitudes. This difference results in a variation in the integrated intensities of certain x‐ray reflection from opposite sides of samples taken from crystals with the zincblende structure. X‐ray measurements of a series of {111} reflections from opposite sides of an InAs single crystal have been made and related to the etching characteristics of these surfaces.

ISSN:0021-8979    

DOI:10.1063/1.1776997

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Two characteristic temperatures for quartz were determined which, when substituted into the Debye‐Waller formula and then used to compute the ratios of temperature corrected integrated reflection coefficients of various pairs of sets of Bragg planes, gave results in best agreement with experimentally determined ratios. These temperatures are 508±16°K in the direction of the trigonal axis and 452±15°K in any perpendicular direction. Corresponding values obtained from an approximate formula relating characteristic temperatures with elastic constants were 448° and 398°K, respectively. The fairly good agreement between the characteristic temperatures obtained by the two methods seems to support the conjecture that the modification of the Debye theory used gives a fairly good approximate description of the effect of thermal motion on the x‐ray reflectivity of quartz. Calculations based upon the experimentally determined characteristic temperatures indicate that when Bragg spacings are less than about 0.7 A, the reflectivity of quartz at room temperature is reduced to less than half the value that would be obtained if the atoms were rigidly fixed.

ISSN:0021-8979    

DOI:10.1063/1.1776998

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The equations of electrostatic irrotational space‐charge flow are set up in a paraxial manner. Given an arbitrary trajectory, and the potential distribution along that trajectory, the variation of such quantities as potential and beam convergence in the vicinity of the specified trajectory are investigated. A detailed analysis is carried out for beams from a space‐charge‐limited cathode in the form of a cone. The agreement between the paraxial theory and the exact theory for particular beams is investigated. Numerical results are presented for beams from a conical cathode which predict beams with a microperveance of about 15 and a very large area convergence. It is felt that by use of this method much higher perveances and beam convergences could be obtained for hollow and sheet beams than have heretofore been possible.

ISSN:0021-8979    

DOI:10.1063/1.1776999

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In operating a three‐level maser one wishes to know the external magnetic field and crystal orientation necessary to match a given pair of frequencies. In the case of Cr+++a fourth‐degree secular equation determines four energy levels for each value of external fieldHand crystal orientation &thgr;. Determination of the latter two variables, given two desired frequencies of operation, ordinarily involves either the solution of a tremendous number of fourth‐degree equations and extrapolation towards the required solution, or determination of the matching conditions by experimental methods. In the following a method is described, allowing direct calculation ofHand &thgr; for a three‐level ruby maser.

ISSN:0021-8979    

DOI:10.1063/1.1777000

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The second harmonic distortion by a BaTiO3crystal of a small high‐frequency sinusoidal electric field, superimposed on a low‐frequency switching field, is studied by the filter method. From the phase relationship of the second harmonic distortion with respect to the measuring signal, together with the increase of the fundamental component of the capacitive current, it is concluded that the polarizability increases markedly for the backward direction during switching.

ISSN:0021-8979    

DOI:10.1063/1.1777001

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The Schiff expression for the cross section per nucleus, for thin‐target bremsstrahlung into the angular and energy rangesd&thgr;0anddk, is integrated analytically over angle from zero to&thgr;¯0. Results are shown for the caseZ=78,E0−mc2=40 Mev andx¯=0.5, 1, 2, 4, and 8, whereE0−mc2is the kinetic energy of the incoming electron andx¯is the reduced angle&thgr;¯0E0/mc2. The fraction of the total cross section included in a cone of angle&thgr;¯0can be approximated to within 20% byx¯2/(1+x¯2). Atx¯=1, or&thgr;¯0=0.723°, the ratio of energy delivered by photons above (E0−mc2)/2 to that below is 9% greater than for the limiting spectral shape at&thgr;¯0=0, or that given by the Schiff expression at&thgr;0=0, and 13% greater than for the spectrum integrated over all angles. For a target of finite thickness, multiple electron scattering should partially suppress the spectral dependence onx¯.

ISSN:0021-8979    

DOI:10.1063/1.1777002

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A theory of pressure buildup under unipolar ion conduction is presented and verified experimentally. Constriction of the current flow leads to sizeable pressures in insulating liquids.

ISSN:0021-8979    

DOI:10.1063/1.1777003

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

This paper deals with the results of an electron diffraction investigation of the structure of soft magnetic materials which exhibit magnetic annealing. The property of heat treatment in a magnetic field has been found to depend upon the oxygen content present as an impurity and is associated with distinct diffraction phenomena. A structural model based on an interpretation of diffraction results, magnetic properties, and oxygen content is presented.The pertinent conclusions from this study are:1. The ability of soft magnetic alloys containing Fe, Co, and Ni to exhibit magnetic annealing properties is due to oxygen present as an impurity.2. An oxygen content of about 0.001% is sufficient to produce magnetic annealing with the proper heat treatment. An alloy containing only 0.0001% oxygen fails to respond to field heat treatment or is ``dead.''3. The oxygen impurity produces magnetic activity in the alloy crystal (with proper heat treatment) by condensing into the (111) planes of the crystal, thus giving rise to a stacking disorder or fault. The term ``impurity fault'' has been introduced to describe this structural irregularity.4. The oxygen impurity faults are presently thought to be aligned by magnetic annealing and are intimately connected with field heat treatment properties. If sufficient oxygen is available in the crystal, the faults thicken and organize to yield metal oxides.

ISSN:0021-8979    

DOI:10.1063/1.1777004

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Previous work on Alnico single crystals (permanent magnet alloy) showed that magnetic torque reversals are associated with an inhomogeneous structure. More recently, it has been found that alloys of iron, nickel, and cobalt in the Perminvar region also exhibit these torque reversals although the alloys are considered to be solid solutions. An inhomogeneous structure occurs simultaneously with the torque reversals in some of these alloys. The inhomogeneous structure has been observed by means of electron diffraction, and the observations have been interpreted to mean that there are faults in the lattice normal to [111] directions. The faults form in the temperature region where the magnetic field heat treatment is effective and their density is roughly proportional to the response of the magnetic field treatment. When the crystals are not heat treated in a field, the faults are arranged to have cubic symmetry and their magnetic anisotropy has cubic symmetry. When the crystals are heat treated in a magnetic field, electron diffraction indicates that the faults are usually affected also.Evidence has been obtained that small amounts of oxygen as an impurity in Perminvar cause both the faulting and the heat treatment in a magnetic field. An extremely small amount of oxygen (0.0014%) is sufficient to cause such effects.In a more detailed sense we feel that the magnetic anisotropy introduced by heat treatment in a magnetic field probably arises either from short range order within the faults or from the arrangements of the faults each of which is parallel to a (111) into regions whose shape anisotropy is along the direction of the magnetic field.

ISSN:0021-8979    

DOI:10.1063/1.1776971

出版商:AIP    

年代:1959

数据来源: AIP