摘要:

A simple yet exact method of solving the Schrodinger equation across an arbitrary one‐dimensional piecewise‐linear potential is described. It is based on the analytical solution of the Schrodinger equation across a linear potential, where the solution can be expressed as a linear combination of the Airy functions. Proper boundary conditions are imposed at the interface between adjacent linear intervals of the potential, and a transfer‐matrix procedure is utilized in the derivation. The quantum mechanical transmission coefficient across a potential barrier and eigenenergies of a potential well can also be easily calculated using this method.

ISSN:0021-8979    

DOI:10.1063/1.337788

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A revised fringe equation is proposed for the hook method in anomalous dispersion for the case of thick plate compensation. The derivation is based on the equality of transit times through the interferometer arms, which results in a revised expression for the optical path difference of the plate. As a result, an apparent fringe order inconsistency in the traditional derivation is resolved, and the interpretation of the hook constant is clarified.

ISSN:0021-8979    

DOI:10.1063/1.337291

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The spatial distribution and absolute values of the stopping power of the rare gases Kr, Ar, and Ne were determined in 250‐kV electron beam excited gas mixtures. The measured values were compared with 1D and 3D Monte Carlo code calculations. Excellent agreement was found in all cases.

ISSN:0021-8979    

DOI:10.1063/1.337292

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A trapped distribution of low‐energy electrons was used to alleviate spherical aberration in a solenoidal magnetic lens. The space‐charge‐correction method has potential application to the focusing of heavy, negatively charged particles such as H−ions. In the geometry investigated, the field contributions from trapped electrons cancel net electric fields along magnetic flux surfaces. The lens magnetic fields therefore define equipotential surfaces. Experimental results were obtained using a 10‐keV electron beam as a nondestructive probe in a solenoid lens with 65‐G peak field. Annular distributions of trapped electrons were achieved that were stable against the diochotron instability. Deflections of the probe beam were consistent with theoretical predictions. The peak focused current density of the 10‐keV beam was improved twentyfold with the addition of trapped electrons in the lens.

ISSN:0021-8979    

DOI:10.1063/1.337293

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The structure or the near‐zone field transmitted through an electrically small aperture in a perfectly conducting plane is investigated. We dwell on two issues that are of importance to engineers analyzing small aperture problems. The first question addressed is how far should one recede from the aperture in order to justifiably use the well‐known aperture dipole approximations. Alternatively, how close may a source or a backing object be located without appreciably effecting the aperture quasistatic field distributions. The second consideration is to what distance the radiation emanating from the aperture remains collimated and how strongly is the near‐field intensity dependent upon distance. The model used for our calculation is that of a small circular aperture for which the quasistatic aperture field distributions are analytically derivable. It is presumed that this should give an indication of the near‐zone field characteristics to be expected in the general case.

ISSN:0021-8979    

DOI:10.1063/1.337294

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A calculation is presented of spontaneous radiation emitted by an electron beam passing through a continuously rotating quadrupole magnetic undulator. It is shown that radiation spectrum emitted in forward direction of beam propagation has four peaks, corresponding to four betatron frequencies. Utilizing the Madey theorem, a stimulated emission is calculated and presented as gain versus frequency curves, for different values of the quadrupole magnetic field. A free‐electron laser operating at two or three radiation frequencies with a quadrupole magnetic wiggler is suggested.

ISSN:0021-8979    

DOI:10.1063/1.337295

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report the fabrication procedure and properties of optical nonlinear guided wave structures consisting of a thin film of Corning 7059 glass deposited on the surface of CdSxSe1−xdoped glass. The limiting action in power‐dependent prism coupling in the structures produced is described. The nonlinear prism coupling is used to evaluate both the sign and the steady‐state value of the intensity‐dependent refractive index of the substrate. For the glass used the nonlinearity is negative and its value is in the range of 10−10m2/W.

ISSN:0021-8979    

DOI:10.1063/1.337296

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A thin wafer of polycrystalline Si was mounted on the cathode of a small cylindrical plasma cell which consisted of two flat stainless steel electrodes and a piece of alumina tubing. A discharge was supported by a slow flow of Ar, and short pulses of SF6and O2were injected simultaneously into the Ar stream. The contents of the plasma cell were sampled continuously, and analyzed by mass spectrometer. The concentration transients of various species resulting from the SF6and O2pulses were measured as a function of time. The maxima of the SiF+3transients and thus the etching rates were found to depend on oxygen concentrations in the mixtures, but far less so than the atomic fluorine concentrations, as reported by others. By contrast, the maxima of several S–F and S–O–F species concentrations depended very strongly on O2concentrations. It is concluded that neither atomic fluorine, nor any one of the other observed species can be the sole important reactive species in the etching reaction studied. The experimental results also bear on the fate of SiF2initially formed and thus illustrate the potential of the pulse injection method used in mechanistic studies.

ISSN:0021-8979    

DOI:10.1063/1.337246

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A method is developed to calculate the depth distribution of the local stoichiometric disturbance (SD) resulting from ion implantation in binary‐compound substrates. The calculation includes first‐order recoils considering projected range straggle of projectiles and recoils and lateral straggle of recoils. The method uses tabulated final‐range statistics to infer the projectile range distributions at intermediate energies. This approach greatly simplifies the calculation with little compromise on accuracy as compared to existing procedures. As an illustration, the SD profile is calculated for implantation of boron, silicon, and aluminum in silicon carbide. The results for the latter case suggest that the SD may be responsible for otherwise unexplained distortions in the annealed aluminum profile. A comparison with calculations by other investigators using the Boltzmann transport equation shows good agreement.

ISSN:0021-8979    

DOI:10.1063/1.337247

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The microstructure of a fiber‐reinforced composite material can be characterized in terms of a set ofn‐point matrix probability functionsSnwhich give the probability of findingnpoints all in the matrix phase. From a knowledge of these functions one can place rigorous upper and lower bounds on effective thermal, electrical, and mechanical properties of the composite. Third‐ and fourth‐order bounds derived by Milton involve threefold integrals over the three‐point matrix functionS3. Exact analytic determination ofS3is impossible except in idealized cases, and the highly oscillatory nature of the integrands makes numerical integration costly and time consuming. In this paper we discuss an approximation toS3in terms of the two‐point functionS2, which is often quite easy to determine. We show that in this approximation the bounds can be expressed in terms oftwofoldintegrals for which the integrands are mostly of one sign, and which can be evaluated very cheaply to a high degree of precision. For a model microstructure in which the inclusions consist of fully penetrable cylinders, we compare our approximate results with the exact results. Agreement is excellent.

ISSN:0021-8979    

DOI:10.1063/1.337248

出版商:AIP    

年代:1986

数据来源: AIP