摘要:

In this paper the definitive work of Stevenson for the Rayleigh series expansion of electromagnetic scattering from homogeneous scatterers is extended to inhomogeneous scatterers. Furthermore, it is shown that a determination of the strength of the multipoles induced by the incident radiation is sufficient to determine the far field and therefore the scattering cross section, without relying on an awkward expansion and subsequent matching of far and near fields. The calculations are thus enormously simplified.

ISSN:0021-8979    

DOI:10.1063/1.1659753

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Solutions are obtained for the electromagnetic field propagating in a gas in which the electron density and electric field strength are interdependent. The solutions are specialized to study the reflection and transmission of electromagnetic waves by a nonlinear gaseous slab. For a given slab thickness we find that no matter how large we make the incident power, the transmitted power cannot exceed the finite limiting value, which can be calculated from our theory.

ISSN:0021-8979    

DOI:10.1063/1.1659754

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Ion sampling measurements have been made on cesium plasmas for normalized pressures from 10−4to 1 Torr using dc as well as rf excitation. For dc discharges, sampling was undertaken through both the anode and the cathode. The major cesium ions observed were Cs+,Cs2+, andCs3+. Measurements were made of the ion current ratios,I(Cs2+)/I(Cs+)andI(Cs3+)/I(Cs2+)as a function of normalized pressure. Comparison of the observed dependencies with those predicted using steady‐state kinetics provides estimates of the rate coefficients of the following reactions:Cs**+Cs→K2Cs2++e,K2&tgr;≃2×10−15 cm3,Cs++2Cs→&bgr;Cs2++Cs,&bgr;≃1.5×10−29 cm6/sec,Cs2++2Cs→&ggr;Cs3++Cs,&ggr;≃3×10−29 cm6/sec, andCs3++e→&agr;33Cs+h&ngr;3,&agr;3≃2×10−8 cm3/sec.

ISSN:0021-8979    

DOI:10.1063/1.1659755

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Mass‐identified measurements of the time dependence of the density of atomic neon ions in decaying plasmas are reported. The conversion of Ne+intoNe2+occurs by the three‐body reactionNe++2Ne→Ne2++Neat a rate given by the rate constantK=7.7×10−32cm6sec−1in good agreement with the value reported by Smith and Cromey. The measured value of mobility of Ne+ions in neon &mgr;0(Ne+) = 4.0 cm2V−1sec−1at a temperature of 300°K is in agreement with the values obtained by other techniques.

ISSN:0021-8979    

DOI:10.1063/1.1659756

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Magnetic domains existing during the magnetization reversal in oriented low‐temperature phase MnBi films have been observed at room temperature by decorating the domains with iron particles obtained and brought onto the film investigated by evaporating iron in an argon atmosphere onto the film. By making a carbon replica of the film surface, the domains can be observed electron microscopically. The resolution obtained is 0.05 &mgr;m. The domain width in a 100‐nm‐thick MnBi film without applied field is approximately 0.35 &mgr;m. It increases with decreasing film thickness. Before the films reach saturation, bubble domains with diameters smaller than 0.5 &mgr;m are observed. Along minor hysteresis loops, filament domain configurations are observed. The width of the filament domains decreases with increasing strength of a field applied perpendicular to the film plane. The width is approximately 0.1 &mgr;m in a 90‐nm‐thick MnBi film with an applied field of 344 kA/m. The wall‐energy density in MnBi film is estimated to be 2×10−3W sec/m2.

ISSN:0021-8979    

DOI:10.1063/1.1659757

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Microwave absorption and emission and electron temperatures of a nonuniform axially magnetized afterglow plasma column in a waveguide geometry have been investigated experimentally. Frequency &ohgr; and magnetic field &ohgr;care chosen to satisfy the upper‐hybrid resonance condition&ohgr;2=&ohgr;c2+&ohgr;p2(r), where &ohgr;p(r) is the local electron plasma frequency. Nearly perfect absorption is observed in the range of upper‐hybrid frequencies, while at other frequencies the absorption coefficient is essentially zero. The sharp absorption onset at the maximum upper‐hybrid frequency yields an accurate measure for the peak electron density. Density decay and profile in the plasma column are observed—the latter using a new technique. In the range of high absorption the noise emission approaches the blackbody limit. The electron temperature is measured with a radiometer and a reference noise source in a new technique yielding both spatial and time dependence without perturbing the plasma. The time resolution is obtained by a sampling technique. The spatial resolution results from the fact that upper‐hybrid resonance absorption and emission are confined to a narrow resonant layer. This property is also used to heat the electrons locally and observe the thermalization process.

ISSN:0021-8979    

DOI:10.1063/1.1659758

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Two electrodes are considered in an axisymmetric configuration: a central cathode rod and a ringlike coaxial anode, with a relatively small axial displacement. This assembly is mounted on an insulated plenum, fed by a gas pulse. In coincidence, an electrical power pulse (currents up to 50 000 A, powers up to 10 MW) is delivered to the electrodes with a duration of 1 to 2 msec. It is demonstrated that, under well‐defined conditions, the resulting impulse has a predominantly self‐magnetic origin. Individual impulses are experimentally determined by means of angular momentum measurements of an inertial platform, free of any parasitic impulses. The experimental results are shown to be in good agreement with analytical predictions. It is found that the self‐magnetic impulse is directly proportional to the time integral of the square of the current. The proportionality coefficient is shown to depend only on the anode‐to‐cathode ratio of radii. This coefficient is also shown to be insensitive to other details of the configuration and, especially, independent of both the kind and flow rate of the gas feed.

ISSN:0021-8979    

DOI:10.1063/1.1659759

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

We report experiments on three‐pulse echoes in rare‐gas magnetoplasmas. The results are consistent with a periodic perturbation in frequency space of the electron density. If this perturbation is due to a diffusion in physical space of ``hot'' electron bands, then it is not a simple diffusion governed by electron‐neutral collisions. We observe absorption and emission which are periodically modulated after the application of two shortS‐band pulses. The clear connection between our measurements of echo amplitudes and of emission and absorption spectra shows that these experiments will be useful tests of future three‐pulse echo theories.

ISSN:0021-8979    

DOI:10.1063/1.1659760

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The optical properties of Dow Corning‐704 and ‐705 diffusion‐pump oils have been measured from 2→10.6 eV using a closed‐cell technique. The data are interpreted in terms of molecular excitations of &pgr;, &sgr;, and nonbonding electrons in the complex pump oil molecules and in terms of collective oscillations of electrons in the liquids. The optical constants of Dow Corning‐200, another silicone oil, and liquid benzene from 2→10.6 eV are also presented for use in the interpretation of the pump oil data.

ISSN:0021-8979    

DOI:10.1063/1.1659761

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The optical properties of Dow Corning‐704 and ‐705 diffusion‐pump oils have been measured from 4→24.8 eV using an open‐dish technique. These are the first liquids for which optical constants have been obtained above 11.8 eV. In the region above 10.6 eV, the real part of the dielectric constant is structureless. A collective oscillation involving &pgr; and &sgr; electrons is seen in the region between 21→25 eV. Sum rule calculations indicate approximately 130 as the effective number of electrons per molecule participating in absorption processes up to 25 eV.

ISSN:0021-8979    

DOI:10.1063/1.1659762

出版商:AIP    

年代:1971

数据来源: AIP