摘要:

Reflection coefficients and complete angular distributions have been measured at angles of incidence between normal and near grazing for thermal beams of RbI molecules which were scattered from clean and beam‐covered NaCl (100) surfaces. For fixed angles of incidence and scattering the intensity of scattered molecules was measured as a function of coverage of RbI on the sodium chloride surfaces. Dynamics of the gas‐surface interactions are discussed and a mechanism for condensation of RbI is proposed.

ISSN:0021-8979    

DOI:10.1063/1.335972

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Direct writing of micron‐sized features in self‐developing photoresists is demonstrated using less than 1 mW of cw ultraviolet light at 257 nm. No energy density or intensity thresholds for ablation are observed. Ablation depth depends only on the deposited energy density and is independent of the rate of deposition; that is, the self‐developing process is reciprocal. We have determined that an environment containing oxygen is necessary for complete self‐developing; in the absence of O2the process is self‐limiting. Patterns created in poly(methyl methacrylate) have been faithfully reproduced into silicon substrates using reactive‐ion etching.

ISSN:0021-8979    

DOI:10.1063/1.335973

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The influence of a strong laser field on the optical absorption edge of a direct‐gap magnetic semiconductor is considered. It is shown that as the strong laser intensity increases the absorption coefficient is modified so as to give rise to an absorption tail below the free‐field forbidden gap. An application is made for the case of the EuO.

ISSN:0021-8979    

DOI:10.1063/1.335974

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The results of acoustic and photoacoustic testing of an uncoupled Helmholtz resonator suggest its utilization as an open photoacoustic cell. Although signal levels are lower in our cell than in small closed cells, this type of resonator produces very low coherent noise if light scattering by the sample is negligible. The resonator is free of static pressure fluctuation problems as well.

ISSN:0021-8979    

DOI:10.1063/1.335975

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A numerical calculation of the complex eigenfrequencies of prolate spheroids and ellipsoids, and of finite‐length circular cylinders undergoing acoustic or electromagnetic eigenvibrations is reported. While mainly longitudinal eigenvibrations have been studied previously, here we obtained eigenfrequencies of vibrations which contain azimuthal components. These give rise (e.g., for the case of a cylinder) to helical surface waves, and we were able to interpret the corresponding eigenfrequencies in terms of resonances caused by the phase matching of such surface waves as they repeatedly engulf, and propagate around, the vibrating object. Phase and group velocities and absorption coefficients of the surface waves are obtained numerically from the set of complex eigenfrequencies.

ISSN:0021-8979    

DOI:10.1063/1.335976

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Optimal control theory is used to determine the piston trajectory which yields maximum power output for a model which incorporates the diesel engine’s major irreversibilities. Optimal trajectories were obtained for the cases of unconstrained and constrained piston acceleration. Optimizing the path for our standard engine increased both the net work output per cycle and the net efficiency by about 10%.

ISSN:0021-8979    

DOI:10.1063/1.335977

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The effects of excitation frequency (10 kHz–25 MHz) on plasma etching, voltage‐current characteristics, emission spectra, and ion densities and energies in the sheath of chlorine plasmas, have been studied at 0.3 Torr using several techniques. Emission spectra and mass spectral analysis of ions extracted from the sheath region show a dramatic increase in the Cl+signal as frequency is lowered through the ion–transit frequency near ∼1 MHz. Concurrently, the voltage at constant power and energy of ions impinging on the electrodes increase dramatically, while the etch rate of poly‐Si increases due to ion‐enhanced reactions. The Cl+2ion density and degree of Cl2dissociation to Cl atoms were found to be roughly frequency independent.

ISSN:0021-8979    

DOI:10.1063/1.335978

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The transport system of intense light ion beams through plasma channels is considered in the reactor system. Channel parameters for the beam transport are determined by diode brightness, pellet requirements, and channel constraints. We considered the desirable reactor parameters and the transportable power window. We have studied most of the single‐channel formation by the laser initiation, the beam transport in this channel, and the multiple‐channel formation within this window. Uniform and stable plasma channels were formed in 10–40 Torr of ethylene gas by the guidance of the CO2laser with up to 1‐m length. Ion beams were injected to this channel from a pinch‐reflex ion diode on the Reiden IV generator. High total transport efficiencies of up to 70% were achieved. Beam orbits, estimated from the post‐transported beam pattern on the detector film with energy resolution, were in good agreement with the calculation in the center current mode. We proposed the uniform irradiation reactor channel system using the dodecahedral arrangement so as to satisfy the transportable window constraints. A triple plasma channel was also formed as a simulational model of an overlap channel system. A desirable channel system is expected from experiments and calculations when channels and return paths are alternately arranged.

ISSN:0021-8979    

DOI:10.1063/1.335979

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In a free‐electron laser with a long, linear wiggler, the external focusing required to keep the electron beam from dispersing can seriously degrade the performance of the laser. The transverse focusing modulates the longitudinal velocity of each electron, periodically and nonadiabatically changing the phase of the electron with respect to the electromagnetic wave. Phase changes of order unity over a betatron period can strongly detrap or debunch electrons and greatly reduce the gain of a linear wiggler amplifier. The modulation of the electron’s longitudinal velocity can be prevented if focusing in the plane of the electron’s wiggle motion is provided by parabolically curved magnet pole faces. The focusing and resonance effects of curved pole faces are analytically calculated and numerically confirmed. Numerical simulations of linear wiggler amplifiers are presented to illustrate the effect of the curved pole faces on amplifier performance.

ISSN:0021-8979    

DOI:10.1063/1.335980

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It has been shown recently that steep optical thresholds can occur in twisted nematic configurations with tilted boundary conditions. This is the case when the twist angle &fgr; is between &pgr; and 2&pgr;. We have derived an analytical expression for this threshold, utilizing the results from a numerical evaluation of director patterns with a computer program. The consequences of the dependence of the threshold on the relevant physical parameters are discussed and the theory is compared with experimental data. Also we point out the differences with respect to the threshold equation for the conventional 90°‐twisted nematic configuration.

ISSN:0021-8979    

DOI:10.1063/1.335981

出版商:AIP    

年代:1985

数据来源: AIP