摘要:

Experimental line shapes arising from tilted beta‐ray spectrometer sources are compared with analytically derived line shapes. Although the increased scattering in the source at higher tilting angles considerably alters the experimental line shape, the sharp leading edges predicted for the larger angles are largely retained. This is true for electron energies at least as low as 400 kev, even for quite dense sources (5 mg/cm2). An application of the increased resolution resulting from this feature is given.

ISSN:0021-8979    

DOI:10.1063/1.1721431

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The particle sizes of four Fe and two Fe&sngbnd;Co powders with diameters ranging from 200 to 600 angstroms have been determined using electron microscope, x‐ray line broadening, and nitrogen adsorption techniques. Reasonable agreement was found between the electron microscope and the x‐ray methods, while the sizes determined through nitrogen adsorption were in every case larger. A method of dispersing single‐domain ferromagnetic powders for electron microscopy is described.

ISSN:0021-8979    

DOI:10.1063/1.1721432

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Reflection and transmission coefficients are important parameters of a wave‐guide junction. It is shown that these parameters in phase as well as in magnitude may be read directly from a graph. A short‐circuit is moved in one of two wave guides that are connected by the junction, and the corresponding reflection coefficient is measured in the other wave guide as in a standard method. The positions of the short‐circuit, however, are taken equally spaced every ⅛th of a wavelength. When plotted in the complex plane, the corresponding reflection coefficients fall on a circle and the chords joining opposite points intersect at a point that is simply related to the desired parameters.When very accurate measurements are desired, 8 or even 16 short‐circuit positions spaced at116thor132thwavelength can be used. The quality of the chord intersection then gives a control of the experiment by showing systematic or random errors. When the intersection is not perfect, because of random errors, a method of averaging is described that reduces these errors.

ISSN:0021-8979    

DOI:10.1063/1.1721433

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721434

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A replica technique has been developed for the electron microscope study of particles of precipitates formed by mixing solutions of chemical reagents. The replica is formed thermally in a thin film of parlodion. A one‐step, shadowed replica has been found most satisfactory. The technique has been found suitable for studies of the effect of conditions of observation upon the specimen materials, studies of precipitates such as silver chloride which are known to be unstable during direct observation, studies of precipitates as they exist in the mother liquid; and studies which require detailed observation of surfaces.

ISSN:0021-8979    

DOI:10.1063/1.1721435

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The admittance of a gas discharge may be obtained from measuring the ratio of the transmitted power through a microwave cavity to the incident power as a function of signal frequency near the cavity resonance. The method involves balancing the transmitted and incident signals to zero at the cavity resonance after they have passed through two separate receiving systems. When the signal frequency is changed, an attenuator is used to rebalance the two signals. The change in frequency from resonance and the corresponding change in attenuation gives the necessary data which will plot as a straight line whose slope yields the desired information.

ISSN:0021-8979    

DOI:10.1063/1.1721436

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The thermoelectric power of liquid selenium has been measured in the range 250–500°C. Values of activation energies calculated from the temperature dependences of thermoelectric powers and resistivities agree. This activation energy taken as the intrinsic activation energy (or the energy to break the Se&sngbnd;Se bond) is 2.31 ev calculated from data given by Henkels. The mobility of holes in the intrinsic region exceeds that of electrons and has a value (8.4×106)/T32cm2/volt sec, assuming electronic mass.As a further check of the electronic nature of the conduction in the liquid and of theories of conduction in the hexagonal form, preliminary measurements of the thermoelectric power of pure selenium doped with small percentages of As, Sb, and Bi up to 4 percent were made. In the intrinsic region the specimens exhibitedptype conduction, but at lower temperatures the sign of the thermoelectric powers reversed and values became quite large but negative. The crossover point depended qualitatively on the amount of impurity in the correct manner. Thentype conduction is tentatively attributed to donor levels introduced by the normal trivalence of Group Vbelements. Twopelectrons are considered bound in the selenium chain, the third ionized at high temperature.

ISSN:0021-8979    

DOI:10.1063/1.1721437

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721438

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721439

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721441

出版商:AIP    

年代:1953

数据来源: AIP