摘要:

Micron‐sized particles (0.3 to 15 &mgr; in radius) of metals such as aluminum, carbonyl nickel, molybdenum; semiconductors such as magnetite and zirconium hydride; and insulators such as aluminum oxide, silicon oxide, and eccospheres are charged by contact electrification in electric fields up to 8000 V in a 0.3‐cm gap. The charges are measured with a drift‐tube detector and a quadrupole mass spectrometer and compared with a theoretical value which includes the contact potential and the electric field. Experimentally, the contact charge is quite important for particles less than one micron in radius, but relatively unimportant for larger particles. The experimental values are in good agreement with the calculated values for the range of materials and particle sizes studied.

ISSN:0021-8979    

DOI:10.1063/1.1713799

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A method for determining electron density in cylindrical plasma columns uses surface wave resonances which occur when the length of plasma column is an integral multiple of the half‐wavelength of the surface wave. One type of resonance is in an axially symmetric mode, the other in a dipolar mode. A theory is given for the relation of resonance frequency to electron plasma frequency. Experiments were carried out with both propagation modes excited simultaneously; the axially symmetric resonances are at much lower frequencies than the electron plasma.

ISSN:0021-8979    

DOI:10.1063/1.1713800

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Previous work by the authors indicated that the penetration depth of krypton ions into the molybdenum cathode of a glow discharge tube operated at 150 V was the order of 104Å after a 24‐h bombardment (C. Y. Bartholomew and A. R. LaPadula, J. Appl. Phys.31, 445 (1960)]. Additional results indicate that this penetration depth increases with time of operation of the discharge. A diffusion‐like process appears to be dominant in the initial period of bombardment, but later the removal of surface layers by sputtering becomes dominant. The penetration reaches a steady‐state condition after a sufficient period of bombardment.

ISSN:0021-8979    

DOI:10.1063/1.1713801

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Properties of a moving striation in the positive column of a dc glow discharge are investigated using a pulsed microwave technique. The electron density and the power absorption in various portions of the striation are determined from the time‐resolved resonant curves of a microwave cavity containing the discharge, and the variation of the electron temperature is inferred from the absorption measurement. The results of the measurement show a large degree of variation of both the temperature and the density within one cycle of the striation. The variation of the light intensity measured with a photomultiplier tube is observed to be in phase with the temperature. These results are consistent with the Langmuir probe data and results of other microwave measurements previously reported.

ISSN:0021-8979    

DOI:10.1063/1.1713802

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Protons, electrons, and primary x rays were used to excite characteristic x radiation from individual specimens of Ti, Cr, Fe, Cu, Ge, Zr, and Au. X‐ray yield expressed as (photons /sr)/ quantum increased with quantum energy in a similar manner for protons in the range about 1 MeV and electrons in the range about 50 keV. For primary x‐ray excitation, the yield decreased with increasing quantum energy, a relationship opposite to that for proton or electron excitation. It appears that the relative values of photo‐electric absorption and scattering must be quite different for x rays and electrons to account for their opposite relationship of yield vs energy.

ISSN:0021-8979    

DOI:10.1063/1.1713803

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

This paper investigates problems associated with multimode oscillations in semiconductor lasers. In particular, even in semiconductors there can exist a spatially nonuniform distribution of excess electrons and holes because a given mode de‐excites electrons most strongly at antinodes and not at all at nodes of the electric vector. This nonuniform distribution encourages the oscillation of other modes which have a different distribution of the electric field vector and which, in particular, have finite electric fields at nodes of the first oscillating mode. Diffusion of electrons and holes tends to wipe out nonuniform carrier distributions. For low temperatures, this diffusion is relatively slow, and for current densities only moderately above the threshold, several modes may oscillate simultaneously. At higher temperatures the suppression of additional modes is much more effective. Because of the complexity of the calculations, the present work had to be restricted to Fabry‐Perot type modes and relatively low power levels. Comparisons are made between theory and experiments.

ISSN:0021-8979    

DOI:10.1063/1.1713804

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The emission of electrons from metals can be excited through a variety of treatments and stimulated by thermal energy and as shown only recently, by high‐intensity ultrasound. Investigations were carried out on disks of 99.999% pure aluminum and aluminum 6061, exposed to acoustic irradiation up to 100 W/cm2at 20 kc/sec. The peak emission at certain intensity levels of the acoustic field is presented, compared with emission from thermal stimulation, and discussed from the viewpoint of acoustic activation of lattice defects in metal crystals.

ISSN:0021-8979    

DOI:10.1063/1.1713805

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

An analytical model is described in which the time‐averaged charge of adsorbed particles is a function of the energy of transition between atomic and ionic states, as in a thermally ionized gas. This relation is used to determine the dipole moment of the adsorbed layer, including the effect of depolarization by adjacent charges. An expression is obtained which relates the emission properties to the temperature, degree of surface coverage, and basic properties of the substrate and adsorbate. Through estimation of the atom adsorption energy, a relationship is obtained which gives a good correlation of most available data for the emission properties of surfaces immersed in cesium vapor.

ISSN:0021-8979    

DOI:10.1063/1.1713806

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The optical transmission of a xenon flashtube has been measured at wavelengths from 2500 to 10 000 Å and at currents up to 5000 A/cm2. It is found that the absorption increases with current and with wavelength. Above about 5000 Å and a current of 4000 A/cm2, a discharge tube 1 cm thick is nearly opaque. At shorter wavelengths or lower currents, the discharge is fairly transparent.

ISSN:0021-8979    

DOI:10.1063/1.1713807

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Experiments are reported in which (1) the resistivity has been measured as a function of the angle between the magnetic field direction and the current direction and as a function of the thickness in 82% Ni‐18% Fe thin films, (2) the ferromagnetic resistance anisotropy in these films has been measured as a function of thickness, (3) the anisotropy in the fractional magnetoresistance has been measured as a function of thickness in these films, and (4) the anisotropy in the fractional magnetoresistance of films ranging in composition from 65% Ni‐35% Fe to 92% Ni‐8% Fe has been measured. The angular dependence of the resistivity agreed with theoretical predictions, provided suitable values are assumed for the mean free path and bulk resistivity of the films. The ferromagnetic resistance anisotropy appears to be independent of film thickness in the range from 75 to 2500 Å. The anisotropy in fractional magnetoresistance is lower than in bulk due to an abnormally high value for the resistivity of the zero magnetostrictive films studied. Nonzero magnetostrictive films also exhibit anomalies when the anisotropy in fractional magnetoresistance is compared with that in bulk material. A simple analytic expression relating these resistance anomalies to the magnetostriction parameter for the films is explained in terms of the magnetostriction of the films and the fact that they are attached to the substrate.

ISSN:0021-8979    

DOI:10.1063/1.1713808

出版商:AIP    

年代:1964

数据来源: AIP