摘要:

We have measured the contact angle &thgr; of water on silicon and on very thin layers of silicon dioxide grown on silicon. The silicon is hydrophobic and &thgr; is near 90°. Oxides thicker than 30 Å are hydrophilic and &thgr; is near 0°. For intermediate thicknesses, &thgr; varies smoothly between these limits. Our results show that the interaction energy between water and the solid surface depends strongly on the oxide thickness. Consideration of different possible interactions leads us to conclude that this is due to corresponding changes in the structure or composition of the oxide surface.

ISSN:0003-6951    

DOI:10.1063/1.1655297

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The characteristics of a new low‐temperature bolometer, insensitive to magnetic fields, are reported. The bolometer consists of an evaporated CdS film with interdigital electrodes, and the underlying mechanism is attributed to preferential electron‐trapping influences on the dc photoconductivity.

ISSN:0003-6951    

DOI:10.1063/1.1655298

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A novel electrically reversible storage effect in doped nematic liquid crystals is described. The ``off state'' is homeotropic nematic and the ``on state'' a single layer of densely packed spherulites. Both states are stable in time. The effect was observed in a narrow range of pitch and cell thickness combinations, and is interpreted as a nematic‐cholesteric phase transition.

ISSN:0003-6951    

DOI:10.1063/1.1655299

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new technique is presented to study surface absorptive properties by utilizing the interaction of an acoustic surface wave with a radiatively heated surface region. Phase changes are induced in a surface wave onY‐cut quartz by the absorption of 10.6‐&mgr; laser radiation. Quantitative measurements of the process agree with a theory describing the interaction in which there are no free parameters. The sensitivity and response time of this detection process are indicated by phase change signals occurring in a ∼10‐&mgr; absorbing film which correspond to a radiative heating of ∼13 &mgr;J and have a rise time of ∼125 nsec.

ISSN:0003-6951    

DOI:10.1063/1.1655300

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Ion‐induced lattice atom displacements in single‐crystal Al2O3give rise to an optical absorption band at 204 nm as well as to expansion of the implanted volume. The 204‐nm absorption per unit energy into atomic processes is found to increase rapidly with decreasing incident ion mass. In contrast, light ions (H+, D+, He+) show less volume expansion per unit energy into atomic processes than do heavier ions. Furthermore, the volume expansion induced by heavy ion implantation can be completely relieved by H+‐ion implantation or by ionizing electron irradiation (8.16 keV). A simple model characterizes the results. The 204‐nm absorption is found to be proportional to the ion energy into electronic processes, and the expansion is proportional to the ion energy into atomic processes linearly reduced by the ion energy into electronic processes. The implications for defect production in CTR insulators are discussed.

ISSN:0003-6951    

DOI:10.1063/1.1655301

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Density variations in low‐Mach‐number (≤0.3) flowing discharges have been obtained by coupling the fluid mechanics with the plasmadynamics. The coupling occurs through the variation of the electrical conductivity with density. If this variation is known, for a particular lasing mixture, the simple and accurate analysis presented below may be applied.

ISSN:0003-6951    

DOI:10.1063/1.1655302

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The bias dependence of the nonlinear mixing characteristics of metal‐barrier‐metal junction currents is deduced assuming an electron tunneling model. The difference‐frequency beat voltage at frequency &ohgr;1−n&ohgr;2, wherenis an integer and &ohgr;1and &ohgr;2are the assumed frequencies of two induced currents, is found to havenzeros as the diode bias is varied. Recent experimental observations have demonstrated such characteristics.

ISSN:0003-6951    

DOI:10.1063/1.1655303

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

One to four x‐ray spots are always present in hydrogen and deuterium along the z axis during the dense pinch phase; ∼4% argon is required for pinhole photography. Spots have an observed 5–10‐ns lifetime and develop in succession within the first 30 ns of the x‐ray emission. The hard >80‐keV radiation shows the spot time structure and controls the neutron pulse. The x‐ray spots representm= 0 plasma instabilities.

ISSN:0003-6951    

DOI:10.1063/1.1655304

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

High secondary emission ratios have been obtained for the GaN:Cs&sngbnd;O surface. A peak ratio of 51 at 3 keV primary electron energy has been observed. At 20 keV the ratio is 24, compared with 2 when the GaN is uncesiated. Analysis of the data indicates that the diffusion length in the material is between 300 and 800 Å, and the surface escape probability for secondary electrons is 0.36. These results indicate that the GaN:Cs&sngbnd;O surface has been activated to negative electron affinity (NEA).

ISSN:0003-6951    

DOI:10.1063/1.1655305

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A measure of the performance of a magnetohydrodynamic (MHD) generator is the enthalpy extraction (power out/heat in) which generally must exceed 20% to operate efficiently in a thermodynamic Brayton power cycle. For the first time 1.82 MW which represented 19.3% enthalpy extraction was achieved in a nonequilibrium plasma MHD generator. Cold electrodes were used. Theoretical calculations show that 30% enthalpy extraction could be achieved with thermionically emitting electrodes.

ISSN:0003-6951    

DOI:10.1063/1.1655306

出版商:AIP    

年代:1974

数据来源: AIP