摘要:

It is pointed out that the use of the usual equations relating to particle motion in a gas in the presence of diffusion and drift can lead to certain paradoxes. Modified equations are derived which resolve these paradoxes and which (among other things) lead to a modification in the form of the equilibrium distribution for particles in a gravitational field. This modification becomes of importance when the particle sedimentation velocity approaches its thermal velocity.

ISSN:0021-8979    

DOI:10.1063/1.336492

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Starting from a simple model of the distributions of charge created in an insulator by bombardment with electrons, the components of the electric field are evaluated by using Maxwell’s equations and image effects. The results are applied to the most common experimental situations: a semi‐infinite sample (i) bounded by a vacuum or (ii) covered by a conducting film, and a sample in the form of a film (iii) unsupported or (iv) covering a conducting substrate. The results are compared to some experimental data concerning, for instance, electromigration and electron‐stimulated desorption. In surface analysis the decay of the Auger signal from ions of opposite charges and the opposite behavior of ions of the same charge are explained. Similar effects observed in electron‐probe microanalysis of glasses are also elucidated. The results concern scanning electron microscopy, transmission electron microscopy, and electron‐beam lithography applied to biological objects, polymers, ceramics, minerals, glasses, and electronic devices. With slight modifications, the same model can be applied to cases of irradiation with ions or x rays. The evolution of the trapped charges with time is suggested, and the need to indicate the electric parameters (&egr; and &ggr;) of the investigated samples is outlined.

ISSN:0021-8979    

DOI:10.1063/1.336493

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new technique for the optical spectroscopy of adsorbed molecules is introduced. It is based on the detection of the phonons emitted during nonradiative relaxation. A high sensitivity was achieved by using superconducting tunnel junctions as detectors. A light power of the order of 1 &mgr;W was sufficient for the spectroscopy of submonolayers of tetracene. Molecules deposited on a cold substrate had a spectrum similar to the one of isolated molecules in a solvent. Deposition, or annealing, at room temperature, however, yielded spectra like those of single crystals.

ISSN:0021-8979    

DOI:10.1063/1.336494

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A series of measurements characterizing ane‐beam pumped ArF* laser was carried out using a 200‐nse‐beam pulse having a rise time of 25 ns at currents up to 50 A/cm2. These pump conditions are relevant for inertial confinement fusion laser drivers. Intrinsic laser efficiencies up to 7.7% and power efficiencies up to 10% were observed. At high pressures (2 atm<P<5 atm) F2/Ar/Ne mixtures performed significantly better than F2/Ar mixtures. Absorption measurements were performed in Ne‐buffered mixtures as a function of pressure, wavelength, and time. It appears that the background absorption peaks at a wavelength of 220 nm and is significantly smaller near 193 nm.

ISSN:0021-8979    

DOI:10.1063/1.336495

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

High‐purity Ge–Se chalcogenide glasses were fabricated using chemical vapor deposition. Gas‐phase GeCl4and SeCl2were used together with H2for the reaction. High transparency was observed over a wide IR region of 2–10 &mgr;m. In addition, it is reported that heat treatment under NH3and CO gas flow has been found to be effective for eliminating oxygen impurities. Using this technique, the oxygen content was reduced to below 1 wt. ppm. These glass compounds are applicable for infrared‐transmitting windows as well as infrared optical fibers.

ISSN:0021-8979    

DOI:10.1063/1.336496

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An As‐S glass fiber with Teflon Fluorinated Ethylene Propylene (FEP) cladding has been fabricated. The transmission range of this fiber was 1–7 &mgr;m with two pronounced absorption peaks at 2.8 and 4.1 &mgr;m. It was found that these absorptions were caused by moisture adsorbed on the surface of the As‐S glass as well as the hydrogen impurity due to the silica ampule. By removing these impurities the absorption loss was reduced and a minimum optical loss of 0.15 dB/m was obtained for this infrared fiber.

ISSN:0021-8979    

DOI:10.1063/1.336497

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Moisture adsorption patches in magnesium‐fluoride spacer layers of metal‐dielectric‐metal interference filters deposited obliquely are known to possess elliptical symmetry. The spatial distribution of light scattered from these patches at normal incidence is shown to exhibit the same elliptical symmetry with the major and minor axes interchanged.

ISSN:0021-8979    

DOI:10.1063/1.336498

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A method is presented for specifying the physically meaningful high‐frequency wave velocity (the geometric limit) in the context of the Keller approximation, which describes wave propagation in a weakly inhomogeneous medium. The root regularly chosen is shown to violate causality of the coherent wave.

ISSN:0021-8979    

DOI:10.1063/1.336499

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

In this paper, we have made a theoretical investigation of third harmonic generation from intensep‐polarized laser radiation in an inhomogeneous laser‐produced plasma. The fluid equations have been employed to obtain the nonlinear response of the plasma electrons. The power conversion efficiency of the generated third harmonic wave depends drastically on the scale length of the plasma inhomogeneity and the angle of incidence of the laser radiation with the density gradient of the plasma.

ISSN:0021-8979    

DOI:10.1063/1.336500

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Electromagnetic surface waves in the rf and microwave frequency range can be used to produce long large/small‐diameter plasma columns. We propose a theory of surface‐wave‐produced plasmas at two different low‐pressure gas‐discharge regimes, diffusion and recombination, respectively. For a given regime the axial plasma density profile is specified by two quantities: a numerical parameter &sgr;=&ohgr;R/c(&ohgr; being the wave frequency,Rthe tube radius, andcdenoting the speed of light) and the collision frequency &ngr; (&ngr;≪&ohgr;). Our theory predicts the magnitude of the axial electron number density gradient. The very good agreement between the experimentally measured plasma density gradients and the theoretically calculated ones for diffusion‐controlled surface‐wave‐produced plasma columns confirms the adequacy of the proposed model.

ISSN:0021-8979    

DOI:10.1063/1.336501

出版商:AIP    

年代:1986

数据来源: AIP