摘要:

An alumina‐supported CuCr catalyst was examined with the extended x‐ray absorption fine‐structure (EXAFS) technique. This is a new technique which can determine the chemical states and near‐neighbor environments of the separate Cu and Cr atomic species. Cu was found to occupy both tetrahedral and octahedral sites in the supporting alumina lattice while Cr was found only in octahedral sites. The valence state was Cr+5in the fresh catalyst which changed to Cr+6in the exhaust‐cycled material. Confirmation of the valence state assignment was obtained by EPR. Fourier analysis of the EXAFS produced separate radial structure functions for the Cu and Cr atoms since the experiment measures the properties of the individual atomic species rather than those of the structure as a whole. Significant differences were observed by both techniques between fresh and exhaust‐cycled material.

ISSN:0003-6951    

DOI:10.1063/1.1655087

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Twisted nematic displays have been constructed in areas up to 36 square inches. Alignment of the liquid crystals was achieved by the oblique evaporation of silicon monoxide or gold. The surface deposits were examined by electron microscopy which indicated that mechanical alignment occurred due to the presence of islands and holes on the surface. It was found that the contrast ratio of the display decreased as the evaporating angle decreased.

ISSN:0003-6951    

DOI:10.1063/1.1655088

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

When thin‐film platinum and single‐crystal silicon are interdiffused, [inverted lazy s] 100 Å of SiO2is found at the PtSi surface. The silica protects the silicide from attack by the aqua regia commonly used to remove unreacted Pt. If the silica is stripped, PtSi on Si will dissolve in aqua regia even faster than Pt. These findings are applicable to contact technology for silicon devices and integrated circuits.

ISSN:0003-6951    

DOI:10.1063/1.1655089

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Nonlinear interactions between noncollinear ASW with exact phase matching provide a special kind of convolution and correlation, according to the ratio &ohgr;1/&ohgr;2of the input frequencies. It means that the time scale at the output port depending on this ratio, time compression or expansion can be achieved. The same device can be used for both correlation and convolution with equal NL conversion efficiency.

ISSN:0003-6951    

DOI:10.1063/1.1655090

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Insulator samples of Plexiglas and alumina ceramic in vacuum have been subjected to high‐voltage pulses with rise times of a few nanoseconds. Breakdown paths were inclined to the electric field in the presence of a magnetic field normal to the insulator surface, analogous to the Hall effect for bulk conduction. These results, as well as measurements of the flashover propagation velocity, strongly support a model of the flashover mechanism based on secondary electron emission.

ISSN:0003-6951    

DOI:10.1063/1.1655091

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Neutron emissions from a small 0.34–1.35‐kJ (10–20‐kV) plasma focus in D2ranged between 1.2×106and 2.8×108neutrons per shot. Shapes of the neutron and the hard x‐ray pulses (half‐width [sine wave] 50 ns) agree, coinciding in time with the ``dip'' in thedi/dtpulse. The angular neutron emission appears to follow the assumptions of the target beam model. Optical filament structures in the 30‐ns‐duration focus could not be observed.

ISSN:0003-6951    

DOI:10.1063/1.1655092

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Waveguide structures and couplers for x rays are analyzed. Experimental results are given for the propagation of CuKaradiation in guides made of BN.

ISSN:0003-6951    

DOI:10.1063/1.1655093

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Memory switching has been observed in the surface layers of certain multiphase glasses which have been subject to Na+&rlarr2;Ag+ion exchange followed by a reduction treatment in hydrogen. A possible mechanism is discussed in the light of the microstructural characteristics of these glasses.

ISSN:0003-6951    

DOI:10.1063/1.1655094

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The refractive indices of AlxGa1−xAs samples prepared by liquid‐phase epitaxy were determined from accurate double‐beam reflectance measurements. The variation of the refractive index with photon energy at room temperature was obtained for AlAs mole fractions between 0 ≤x≤ 0.38 in the spectral range 1.2–1.8 eV.

ISSN:0003-6951    

DOI:10.1063/1.1655095

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We have continuously tuned between 7 and 15 &mgr;m by mixing the output of a LiNbO3parametric oscillator in the chalcopyrite AgGaSe2. We have doubled a CO2laser with 2.7% efficiency which agrees very well with the expected efficiency and verifies the high optical quality of the 1.53‐cm‐long AgGaSe2crystal. The measured transparency range, indices of refraction, and nonlinear coefficient ofd36= (3.7 ± 0.6) × 10−11m/V show that AgGaSe2is a useful infrared nonlinear material phase matchable over the entire 3–18‐&mgr;m infrared region.

ISSN:0003-6951    

DOI:10.1063/1.1655096

出版商:AIP    

年代:1974

数据来源: AIP