摘要:

A hydrodynamic regime in dynamic scattering has been observed in which the relaxation time depends on the voltage at turnoff. This regime manifests itself, above a threshold voltage, with microscopic regions of increased on‐axis optical density which grow until the whole cell area is converted. It has been found in all nematic materials which exhibit dynamic scattering. With originally perpendicular homeotropic orientation, the speed of relaxation increases with the square of the voltage at turnoff. With originally parallel homeotropic orientation, the speed of relaxation decreases with increasing voltage at turnoff. The timetto fill a given area depends on the current density and the voltage above a second thresholdVm, according to the empirical relationJ(V ‐ Vm)t= const. For MBBA, the second threshold is about 15 V, and the constant 10−3J/cm2. The relation is independent of current density, temperature, and thickness (greater than 10−4cm). This phenomenon may explain variations in response as seen by different workers. A hydrodynamic model is proposed, with contributions attributable to the dielectric anisotropy.

ISSN:0003-6951    

DOI:10.1063/1.1654373

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

When a Si crystal substrate is covered with evaporated Au and heated at relatively low temperatures (100–300 °C) in an oxidizing atmosphere, because of the Si&sngbnd;Au reaction at the interface, a SiO2layer is readily formed over the Au layer. Present Auger spectroscopic study concludes that the reaction induces a Si&sngbnd;Au mixed phase that is almost identical with the Si&sngbnd;Au alloyed phase obtained by heat treatment in a high vacuum at temperatures well above the Si&sngbnd;Au eutectic point (370 °C). The Auger spectra of Si in both the mixed and alloyed phases differ obviously from that of the pure Si crystal.

ISSN:0003-6951    

DOI:10.1063/1.1654374

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Output pulse observations are presented for a helium‐diluted CO2laser pumped by VV (vibration‐vibration) energy transfer from vibrationally excited DF produced by the D2&sngbnd;F2chain reaction. Flash photolysis of the F2served to initiate the reaction. A 290‐cm3reaction chamber containing a 0.5‐atm mixture with mole ratio D2:F2:CO2:He = 0.33:1:8:10 gave a single‐pulse output energy of 2.8 J. Relative to the amount of D2present in the reaction chamber, this corresponds to a chemical efficiency greater than 5%.

ISSN:0003-6951    

DOI:10.1063/1.1654375

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

An investigation has been made of the spontaneous self‐mode‐locking in a transient transversely excited N2laser operating in the first positive system(B3&pgr;g−A 3&Sgr;u+)in molecular nitrogen on the 0–0 band at 1.048 &mgr;m. The laser emission, which had a typical pulse length of 60 nsec, consisted of a train of mode‐locked pulses of about 6‐nsec duration with a peak power of about 0.5 kW.

ISSN:0003-6951    

DOI:10.1063/1.1654376

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

The effect of thick Cs&sngbnd;O layers on photoemission from GaAs and InAs0.4P0.6cathodes is experimentally investigated. Simple empirical relationships between the yield and thickness and between the escape probability and thickness are given.

ISSN:0003-6951    

DOI:10.1063/1.1654377

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Amplitude weighting in an interdigital surface‐wave transducer array may be achieved by misaligning the electrodes with the incident‐wave phase fronts. Since in this method all the electrodes are full aperture, the problems of diffraction loss and phase‐front distortion are avoided. Transducers employing this method of weighting to achieve a flat bandpass response were used to construct delay lines on quartz and lithium niobate, and their performance is shown to be in reasonable agreement with predictions.

ISSN:0003-6951    

DOI:10.1063/1.1654378

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

The voltage drop at a tungsten cathode surrounded by cesium plasma is measured as a function of the current density and temperature of the cathode. Current densities, an order of magnitude higher than predicted by the LangmuirScurves, accompanied with low voltage drops, have been measured for certain cathode temperature regimes. These results seem to be of interest for the emission properties of electrodes in closed‐cycle MHD generators.

ISSN:0003-6951    

DOI:10.1063/1.1654379

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Low‐capacitance (< 10 pF) Pb1−xSnxTe photodiodes operating near 77 °K (areas 1.7 × 10−4cm2) have been obtained via liquid‐phase epitaxial growth of low‐carrier‐concentration material (low 1014cm−3to high 1015cm−3). Response to a mode‐locked 1.06‐&mgr;m Nd:YAG laser with the devices terminated in 50 &OHgr; indicated a frequency response to 400 MHz. With a 14‐&OHgr; load and by exciting a photocurrent with radiation from a CO2laser, the shot noise rolloff point was found to be 1200 MHz. Optimum parameters have not yet been achieved, as evidenced by the increase in frequency response with increase in reverse bias; these results represent only a lower limit to this material's capability.

ISSN:0003-6951    

DOI:10.1063/1.1654380

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Double‐heterostructure diode lasers with Si‐doped active regions have exhibited laser action within the wavelength range 9100–9500 Å under pulsed room‐temperature conditions. Threshold current densities are typically 4 × 103−1.1 × 104A/cm2, and total power conversion efficiencies are ∼ 1–3%.

ISSN:0003-6951    

DOI:10.1063/1.1654381

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Unidirectional solidification of the CrSi2&sngbnd;Si eutectic leads to formation of an oriented array of CrSi2fibers embedded in a matrix of Si. The aligned eutectic is highly anisotropic, with resistivity parallel and perpendicular to the CrSi2fiber alignment axis characterized by&rgr;⊥/&rgr;∥≈ 103−104for a specimen produced from 100‐&OHgr; cm Si and 99.996% iodide chromium.

ISSN:0003-6951    

DOI:10.1063/1.1654382

出版商:AIP    

年代:1972

数据来源: AIP