摘要:

An approximate theory for scattering of elastic waves by general shaped defects has been developed. A defect of arbitrary shape can be represented by a sphereSand a remainder volumeR¯. Using the exact solution for a sphere and treatingR¯as a perturbation, the solution corresponding to the distorted wave Born approximation is obtained. This solution contains nontrivial frequency dependence and phase information. Preliminary comparisons with experiments are presented.

ISSN:0021-8979    

DOI:10.1063/1.329360

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

An estimation theory of the physical variable observed by the system carrying its own fluctuations is developed. The dynamics of the observation system is assumed to be described by a nonlinear Langevin equation. It is shown how the information entropy of the estimation process is decreased through the accumulation of observed data.

ISSN:0021-8979    

DOI:10.1063/1.329361

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We report the design criteria and performance characteristics of a hollow cathode discharge tube developed especially for high‐resolution Doppler‐free laser spectroscopy. The cathode has a large bore diameter (2.7 cm) and operates at a relatively low pressure (0.5 Torr of Ar). Very narrow homogeneous linewidths of refractory element transitions have been observed using this device. It is simple to construct, is easily demountable, and requires a small amount of sample material.

ISSN:0021-8979    

DOI:10.1063/1.329362

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

An x‐ray diagnostic tool was developed for acquiring and interpreting high‐resolution spectra for hot‐plasma emission from selected elements. A convex, curved potassium acid phthalate (KAP) crystal was used to collect spectral data from an exploded‐A1‐wire plasma over a wide exposure latitude with the 001, 002, and the 013 planes simultaneously diffracting. The curved‐crystal diffraction efficiencies were calculated for these three planes in KAP and evaluated with x‐ray line intensities derived from the experimental A1 data. The crystal efficiencies were also computed for two other commonly used acid phthalate crystals rubidium acid phthalate (RAP) and thallium acid phthalate (TAP), to compare with KAP crystals. The calculated efficiencies for the first‐order diffraction in KAP, RAP, and TAP agreed with available experimental data.

ISSN:0021-8979    

DOI:10.1063/1.329363

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The 427.5‐nm radiation emitted from the 6p‖3/2‖2→5s‖3/2‖2transition of krypton was studied using time‐resolved spectroscopic techniques at pressures up to 10 Torr, following excitation with an intense (25 kA) and short (15 ns) burst of 500‐keV electrons. The spontaneous emission probabilityAand the two‐body deactivation rate constantk1of the 6p‖3/2‖2level by ground‐state krypton were found to be 2×107s−1and 2×10−10cm3s−1, respectively. By adding SF6to Kr, at concentrations ranging from 0.05 to 1%, the quenching effect of the 6p‖3/2‖2level by SF6was studied.

ISSN:0021-8979    

DOI:10.1063/1.329364

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Angular distribution of sputtered atoms from polycrystalline metal targets with crystallographic‐preferred orientation was measured for 0.5‐ and 1.0‐keV Ar+ions at incidence angles of 0° and 45°. The distribution was compared with that for a Si (100) single‐crystal target. Atoms sputtered from Au, Pt, Al, and NiFe targets are ejected preferentially in the directions of their close packing in the lattice. For the Si target, the distribution is under cosine. These results are explained in terms of the target‐surface crystal structure during and after ion bombardment. The surface structure for the metal targets remains essentially unchanged, but not for the Si target. Sputtered‐atom ejection along the target normally increases with increasing incident‐ion energy. Even at oblique incidence, heavy‐target atoms such as Au, appear to have preferentially ejected atoms in the close‐packed directions.

ISSN:0021-8979    

DOI:10.1063/1.329365

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Monte Carlo calculations of fast secondary electron production have been performed with a hybrid model for the discrete and continuous energy‐loss processes. The Moller theory was adopted for the differential inelastic scattering cross‐section which determines the production rate of fast secondary electrons. The calculations were made for both a bulk polymethyl methacrylate (PMMA) sample and 4000‐A˚‐thin films of PMMA (with and without a silicon substrate) at 10 and 20 keV. The new model is discussed and comparison made with results obtained from the old model, which is based on the continuous slowing down approximation of Bethe for energy loss and the screened Rutherford equation for elastic angular scattering. The new model predicts a larger absorbed energy density than the old model for an isolated line source exposure on a resist film. The consequences of this fast secondary electron contribution on the ultimate limit in electron lithography is discussed.

ISSN:0021-8979    

DOI:10.1063/1.329366

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The paper takes the space‐charge theory developed by Langmuir and applies it to the accelerating‐field range along with the image‐potential theory suggested by Schottky. The combined theory produces a current‐voltage curve which begins at the zero‐field current and voltage calculated from space‐charge theory, and then gradually approaches the curve generated by Schottky theory. The paper summarizes in a single equation the solution procedure outlined by Langmuir. Based on this equation, the paper discusses the behavior of the current‐voltage curve at the transition points from the exponential range into the space‐charge range and from the space‐charge range into the accelerating field range.

ISSN:0021-8979    

DOI:10.1063/1.329367

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

It is shown that a concave axially symmetric electrostatic mirror can be found with a high enough ratio of chromatic aberration to spherical aberration to allow it to be used as an electron spectrometer. The potential field is given in terms of a finite Fourier‐Bessel series. Using only three nonzero Fourier coefficients, a field can be specified that allows—in the case of a point source located within the mirror field—an energy resolution of 0.003% [full width at half maximum (FWHM)] and a transmission of 0.6% of 2&pgr; steradians to be obtained. This field can be used as a starting point in an optimizing procedure reported earlier by the author, to increase the transmission or adapt the spectrometer for use with sources of finite dimensions.

ISSN:0021-8979    

DOI:10.1063/1.329368

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The magnetostatic field dependence of the threshold current density in a GaAs/AlyGA1‐yAs double‐heterostructure laser is investigated with the aid of the solution of the electron diffusion equation. The reduction of the threshold current density by increasing the magnetic field strength can be significant when the difference in the energy band gap of the active and inactive layers at the heterojunction is small.

ISSN:0021-8979    

DOI:10.1063/1.329354

出版商:AIP    

年代:1981

数据来源: AIP