摘要:

Static torque curves in 4,4′‐terephthal‐bis (butylaniline) (TBBA) as a function of temperature are reported. In the smecticAphase (between 173 and 199 °C) a simple sinusoidal torque curve is observed as expected. In the smecticCphase (between 144 and 173 °C) the torque curves are no longer sinusoidal. The torque maximum shifts from &pgr;/4 measured from the easy axis to larger angles as the temperature is decreased. Also, rotational hysteresis appears and minor loops are observed. As in the smecticAphase the shape of the torque curves is essentially independent of field, with the torque scaling as the square of the magnetic field. The observed magnetic properties can be understood in terms of the multidomain model for the smecticCphase. Comparison of the calculation with the experimental data allows a determination of the temperature‐dependent cone angle from the torque curves. Assuming a rotational model, the calculated hysteresis is found to be larger than the experimental value.

ISSN:0003-6951    

DOI:10.1063/1.88594

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We have carried out a calculation of the attenuation of Rayleigh surface waves by surface roughness, in the limit where the amplitude of the roughness is small. A Green’s function method has been employed in the work. In this letter, we present a summary of our method along with some principal results.

ISSN:0003-6951    

DOI:10.1063/1.88595

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A new technique using capillary action, capillary liquid epitaxial (CLE) technique, is described for growing a high‐quality LiNbO3thin film onto a LiTaO3substrate. A LiTaO3single‐crystal film, 2 &mgr;m in thickness, was also successfully grown with good epitaxy onto a LiNbO3substrate by this technique. Evaluation of these films by x‐ray measurements and preliminary experimental results on optical waveguide are reported.

ISSN:0003-6951    

DOI:10.1063/1.88596

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Retarding potential and Richardson work functions of 2.28±0.03 and 2.47±0.06 eV, respectively, have been measured for the (100) face of LaB6. Auger electron spectra of the thermally cleaned surface gave a B/La ratio of 2.3–2.6. Mass spectrometric measurements showed the evaporating species from a clean LaB6(100) surface to be atomic La and B in near‐stoichiometric proportions. Activation energies for the vaporization of La and B were 6.3±0.3 and 6.8±0.3 eV, respectively.

ISSN:0003-6951    

DOI:10.1063/1.88597

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

In this letter we derive the stability criterion in discharges where two‐step ionization is dominant. For stable equilibrium the attachment rate has to be greater than or equal totwicethe ionization rate. Two‐step ionization is often dominant in discharge‐pumped visible lasers because of the relatively large number of electronically excited states. Analysis of the KrF laser discharge indicates that two‐step ionization is dominant.

ISSN:0003-6951    

DOI:10.1063/1.88598

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

100 J of 10.6‐&mgr; laser energy produced in a 1.5‐&mgr;s pulse was focused to a 2‐mm‐diam spot by a 50‐cm‐focal‐length mirror. A plasma was created by breakdown in the 70‐ns gain‐switched peak of the pulse where the light flux becomes greater than 1010W/cm2. The plasma column subsequently created in 5–20 Torr of hydrogen by the absorbed light energy was observed by 5‐ns exposure and streak photographs. The aspect of beam trapping is demonstrated by measurements of the transmitted light intensity radial distribution and significant energy absorption is shown by the measurement of transmitted energy.

ISSN:0003-6951    

DOI:10.1063/1.88599

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A considerable increase of the axial electric field together with a modest increase of the electron temperature can be obtained by the introduction of a recombination structure (e.g., glass wool) into the discharge space. The effect is shown by experiments on mercury–rare‐gas discharges and interpreted in terms of enhanced recombination of ions and electrons. As an application, it is shown that the luminous flux per unit volume of usual fluorescent lamps can be doubled, while maintaining high over‐all luminous efficacy. Moreover, the construction of efficient fluorescent lamps with approximately the dimensions of an incandescent lamp has become feasible.

ISSN:0003-6951    

DOI:10.1063/1.88600

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Tensile strength measurements have been made on coated fused silica fibers at gage lengths up to 50 m. At gage lengths between 0.04 and 10 m, the average strength is essentially constant at about 5 GN/m2(700 ksi). At gage lengths greater than 20 m the length dependence becomes important and by 50 m the strength has decreased to about 2 GN/m2(300 ksi). The minimum strength recorded in the testing of samples taken continuously from a length of 1031.6 m was 0.43 GN/m2(64 ksi). A ’’weakest link’’ model appears to be obeyed.

ISSN:0003-6951    

DOI:10.1063/1.88601

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Dark line defects (DLD’s) have been observed in GaP green LED’s under an external mechanical stress. Excitation of minority carriers is essential to DLD formation. DLD is revealed to grow along the ⟨110⟩ direction and to correspond to an array of dislocation etch pits. A ’’traveling dark spot’’ was observed for the first time. It moves as fast as 1 mm/sec and becomes trapped at the edge of DLD, which results in DLD growing. DLD generation depends on both the forward current magnitude and external stress.

ISSN:0003-6951    

DOI:10.1063/1.88575

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Measurements of the diffusion potential, depletion layer width, and bias dependence of quantum efficiency forn‐CdSe/p‐ZnTe heterojunctions are used to construct a band diagram for the junction and to propose a current transport model. A new value of the electron affinity of CdSe is indicated by measurements of the open‐circuit voltage at low temperatures and high intensities. The saturation current densityJ0is controlled by a thermal activation energy of 0.8 eV, corresponding to electron flow to the interface where recombination occurs through interface states. Performance as photovoltaic cells is limited by the short diffusion length of holes in CdSe.

ISSN:0003-6951    

DOI:10.1063/1.88576

出版商:AIP    

年代:1976

数据来源: AIP