Volume 13, Issue 10, 15 November 1968
Index of content:
13(1968); http://dx.doi.org/10.1063/1.1652457View Description Hide Description
Various experimental results are reported on the dc‐induced optical effects in CdS. Possible explanations are also given.
13(1968); http://dx.doi.org/10.1063/1.1652458View Description Hide Description
A high‐power noble gas cw ion laser has been constructed using a tungsten disk structure capable of dissipating over 70 kW of input power. Quasi‐continuous laser outputs in the near ultraviolet have been observed at 3638 and 3511 Å of ArIII and true cw output was obtained at 3507, 4067, and 4131 Å of KrIII. The latter has been identified as a new cw laser line. Over one watt of quasi‐continuous output was demonstrated with the 3638‐Å line. However, high‐power continuous output in the uv is limited by serious optical degradation effects.
13(1968); http://dx.doi.org/10.1063/1.1652459View Description Hide Description
Time‐resolved emission spectra from flashlamp‐pumped organic dye lasers were recorded with an image convertercamera. The characteristics of several dyes are examined and compared. The rhodamine dyes showed uniform spectral output, but other dyes showed irregular time dependent spectral output.
13(1968); http://dx.doi.org/10.1063/1.1652460View Description Hide Description
Previously published data on the conductivity changes induced in rutile (TiO2) by an applied field are reinterpreted in the light of new information on the behavior of donor impurities in this crystal. It is suggested that the large increase in conductivity which is usually observed is electronic in nature, and is due to an increase in H+interstitial concentration. The H is introduced at the anode, probably by electrolysis of H2O, migrates through the crystal under the influence of the applied field, then is neutralized at the cathode and escapes from the crystal. Enhanced conductivity results when migration of H+ near the cathode is inhibited by Ti4+interstitials, thus increasing H+ concentration in the bulk. Other possible mechanisms are considered.
13(1968); http://dx.doi.org/10.1063/1.1652461View Description Hide Description
This paper describes a new form of acoustical and microwave holography which obviates the need for a real or electronically simulated reference wave. The use of linear (rather than square-law) detectors permits recording of the instantaneous non-time-averaged object wave potential within the acoustic or microwave cycle rather than the intensity of the sum of an object wave and a reference wave time-averaged over many cycles. The time at which the recording is made is the reference rather than a real or electronically simulated reference wave. To achieve the effect of a plane reference wave making an angle θ with the hologram plane, it is necessary to record the object wave potential instantaneously along a straight line on the hologram at the same time as the recording line is swept with velocity v across the plane in the direction perpendicular to the line. Then sinθ = a/v, where a is the speed of the acoustic or microwave radiation. The feasibility of this method is demonstrated by recording and reconstructing a 4.8-MHz temporal reference acoustical hologram made with a Sokolov ultrasonic camera system.
13(1968); http://dx.doi.org/10.1063/1.1652462View Description Hide Description
Infrared absorption measurements were made before and after low‐temperature electron irradiations of silicon samples which contained either dispersed oxygen, carbon, or carbon plus oxygen. Two distinctly different centers are formed upon low‐temperature irradiation depending upon the carbon and oxygen content. One center is the well‐known vacancy‐oxygen A‐center defect (836 cm−1) and is formed in oxygen‐containing silicon with a magnitude which is independent of the carbon content. The other center (922 and 932 cm−1) is formed only in silicon crystals which contain both oxygen and carbon. The results indicate that this center is formed by the trapping of a siliconinterstitial at a carbon‐oxygen complex.
13(1968); http://dx.doi.org/10.1063/1.1652463View Description Hide Description
The transient gyromagnetic behavior of the one‐dimensional 180° Bloch walls in thin films is analyzed based on the Landau‐Lifshitz equation for distributed systems. The physical model of gyromagnetic spin motion in the wall is found adequate in explaining wall streaming (or worm motion). The key mechanism is the induction of a large transverse magnetostatic field resulting from discrepancy in switching speeds in the wall and the adjoining regions. The dependence of wall displacement on pulse shapes and film parameters is examined.
13(1968); http://dx.doi.org/10.1063/1.1652464View Description Hide Description
The phenomenon of hydrogen promotion of field evaporation has been applied to the problem of producing stable images of highly perfect goldFIM specimens. Well developed, stable end forms of gold specimens were obtained by first field evaporating the gold specimen in a 0.5% H2–He gas mixture, then removing the hydrogen gas, and finally imaging the surface in a 25% Ne–He gas mixture. The imaging temperature of the specimen was ∼ 16°K. Details of the experimental observations concerning hydrogen promotion of field evaporation, and the characteristics of the gold end form are reported.
13(1968); http://dx.doi.org/10.1063/1.1652466View Description Hide Description
Amplification of longitudinal acoustic waves traveling in a thin piezoelectricceramic plate was achieved by electrically coupling the elastic waves to the drifting carriers in an n‐silicon plate. Amplification up to 15 dB/cm in the 2‐MHz range was obtained, and the system was also operated as a tunable oscillator and mixer in the 0.5‐ to 4‐MHz range. In addition, these experiments also enabled us to measure the drift mobility of majority carriers in silicon.
13(1968); http://dx.doi.org/10.1063/1.1652467View Description Hide Description
The existing theory of electric conduction in solids fitted with blocking contacts has been modified to include the effect of a series resistance. Experimental current‐voltage curves for trigonal Se with indiumelectrodes are reported which show the essential features predicted by our theoretical analysis.
13(1968); http://dx.doi.org/10.1063/1.1652468View Description Hide Description
A new photomultiplier is described in which the recently reported GaP(Cs) material is used for the first dynode to obtain high secondary emission gain. Gain factors of 20 to 40 have been measured resulting in greatly improved performance of the new photomultiplier at very low light levels.
13(1968); http://dx.doi.org/10.1063/1.1652469View Description Hide Description
The performance of a new photomultiplier with high‐gain GaP(Cs) first dynode is described. The photoelectron statistics are degraded by less than 5% as compared with 20% for conventional multipliers. The improved statistics make it possible, for the first time, to distinguish the emission of one, two, and up to five photoelectrons.
ABSOLUTE MEASUREMENT OF SECOND ORDER NONLINEAR COEFFICIENT FOR OPTICAL GENERATION OF MILLIMETER WAVE DIFFERENCE FREQUENCIES IN GaAs13(1968); http://dx.doi.org/10.1063/1.1652470View Description Hide Description
Millimeter wave difference frequencies are generated by mixing adjacent vibrational‐rotational lines of CO2 laser in a GaAs‐filled waveguide designed for phase matched interactions. Absolute values of the nonlinear coefficient at these frequencies are obtained and are found to be larger than that given by the low‐frequency electrooptic coefficient.
13(1968); http://dx.doi.org/10.1063/1.1652471View Description Hide Description
10.6‐μm radiation from a pair of point sources at optical infinity has been mixed with collimated ruby‐laser radiation in Proustite. The sum‐frequency radiation at 6516 Å so produced was then focused with a camera lens to form a visible image of the infrared sources. With a pump‐laser beam divergence of 1.2 mrad the minimum resolvable angular separation of the infrared sources was 15 mrad according to the Rayleigh criterion.
13(1968); http://dx.doi.org/10.1063/1.1652472View Description Hide Description
Strain amplitude dependence of internal friction was measured as a function of the magnetic state in a niobiumsingle crystal. An enhanced dependence is observed in the mixed state, which is attributed to compression and subsequent breakaway of fluxoids from moving dislocations.