摘要:

The diffusion charging of aerosol particles by unipolar ions has been studied experimentally over the pressure range, 0.0311 to 0.960 atm, using monodispersed aerosols of di‐octyl phthalate. The ratio,a/&lgr;, of the particle radius to the mean free path of ions has been varied over the range from 1.0 to 66. Within the accuracy of the experiments, the particle charge has been found to be independent of the ratio,a/&lgr;, and well represented by the equation,np=9.00Dpln (1+1.02×10−5N0tDp), wherenpis the number of elementary units of charge acquired by the particle,Dpis the diameter of the particle in microns,N0is the number concentration of the ions to which the particle has been exposed in ions/cc, andtis the charging time in seconds. This equation agrees with a theoretical equation derived by White when the molecular weights of the positive ions used in the charging experiments are assumed to be equal to 16 times that of air or 460.

ISSN:0021-8979    

DOI:10.1063/1.1709728

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

In the absolute method for determining thermal conductivityK, the difference in temperature between two points along a rod is measured under conditions of steady‐state flow of heat. The thermal diffusivity &kgr; may also be determined from measurements of the time required for this temperature difference to decrease to half the steady‐state value when the source of heat is removed. FromKand &kgr; data, the specific heat may be calculated, using the general relationshipC=K/&kgr;&rgr;, where &rgr; is the density. The technique permits determination ofK, &kgr;, andCwith a single, small specimen having a wide range ofKand &kgr;. By observing simple experimental precautions, agreement to within 5%–10% has been obtained, for neodymium‐doped yttrium oxide, betweenCvalues calculated fromKand &kgr; data and those derived from calorimetric data.

ISSN:0021-8979    

DOI:10.1063/1.1709729

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The thermal conductivities of Y2O3, Y2O3:Nd3+, Y3Al5O12:Nd3+, and LaF3have been measured from 77°–300°K by a steady‐heat‐flow method. The densities of these crystals and of LaF3:Nd3+have been determined in the same temperature range, using x‐ray methods. Using this information and specific heat data from a variety of sources, the thermal diffusivities of these materials have been calculated. Although the diffusivity of pure yttrium oxide is somewhat higher than that of pure yttrium aluminum garnet, introduction of about 1 mole % of neodymium into both these compounds leads to crystals with diffusivities approximating that of undoped YAG. The diffusivity of doped yttrium oxide and YAG (about 0.05–0.06 cm2/sec at room temperature) is about three times that found for undoped lanthanum fluoride. The relative ease with which heat may be removed from Nd‐doped Y2O3and YAG suggests their use in lasers to diminish time variations in the width of the beam.

ISSN:0021-8979    

DOI:10.1063/1.1709730

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The temperature dependence of the relative sputtering yields of Ge (100), (110), and (111) surfaces for various kinds of noble gas bombarding ions, bombarding ion energies, and bombarding ion fluxes has been investigated. Instantaneous relative yields were obtained by using the spectroscopic emission technique. The dependence of the annealing temperature on the bombarding ion energy and flux can be interpreted in terms of a simplified model where the rate of defect production equals the rate of defect annealing at the annealing temperature. The width of the transition region increases with decreasing bombarding ion energy and mass.

ISSN:0021-8979    

DOI:10.1063/1.1709731

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Light intensity modulators have been developed using single‐domain lithium tantalate as the electro‐optic material. A broadband transistor amplifier which can develop 0.2‐W output power drives the modulator sample which presents a capacitive load of 5 pF. Approximately 80% modulation is achieved from dc to 220 Mc/sec, when the light is made to traverse the sample twice. The modulation bandwidth is limited by the transistor amplifier. Very little acoustic ringing is observed when the modulator is used as a fast light switch.

ISSN:0021-8979    

DOI:10.1063/1.1709732

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

For equivalent values of plastic strain, the dislocation density and point‐defect concentration following deformation by the propagation of high‐amplitude shock waves (70 to 330 kbar) through high‐purity polycrystalline nickel are appreciably larger than as a result of cold rolling near 0°C. Based on the electrical‐resistivity change in recovery state III and IV, it is concluded that vacancies rather than interstitials are the predominant point defects formed. The ratio of the two types of defects that are formed appears to be essentially strain‐rate independent. The dominant point‐defect formation mechanism is believed to consist of the nonconservative motion of jogs on screw (or mixed‐character) dislocations. The observed enhanced formation of point defects as a result of shock deformation is explained as the result of the increasing efficiency of this process with increasing dislocation velocity.

ISSN:0021-8979    

DOI:10.1063/1.1709733

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A study has been made of the temperature dependence of the lifetime and Hall coefficient inp‐ andn‐type InSb with extrinsic carrier concentrations ranging respectively from 1×1013to 4×1015cm–3and from 2×1012to 5×1014cm–3, the lifetime having been measured by means of the phase‐shift method. The lifetime data confirm that the interband Auger process is the limiting recombination process in InSb for temperatures above 150°K. Below 150°K both the lifetime and Hall data are generally consistent with a model consisting of two sets of single‐level, donor‐like recombination centers, rather than with a model of a single set of divalent, donor‐like centers as used in a previous work. The energy levels of these centers are located at 0.071 eV and 0.11 eV above the valence band. Subsequent bombardment of ap‐type and ann‐type sample with 11‐Mev electrons produced an increase in the number of recombination centers having the same properties as those occurring before bombardment. It is concluded that the recombination centers inas‐grown crystals are lattice defects of a simple nature, and that there are grounds for believing that associated with the two energy levels are two different sets of defects rather than a single set.

ISSN:0021-8979    

DOI:10.1063/1.1709734

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The thermal-expansion and room-temperature lattice constants were determined for several phosphates and arsenates isomorphous to KH2PO4. From these data, the lattice constants were calculated at the ferroelectric antiferroelectric temperature. They show a nearly identicalc/aratio for the compounds of any given alkali ion and a change ofc/aratio with the ionic radius of the alkali ion. The size of the expansion anomalies at the transition are markedly affected by deuteration. The anomalies in the ammonium compounds are larger by an order of magnitude than those for the ferroelectric alkali compounds. Temperature hysteresis measurements indicate that the transition in KD2PO4is probably second order.

ISSN:0021-8979    

DOI:10.1063/1.1709735

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The transient response of the current to an applied voltage step is analyzed for the range of time approaching equilibrium, using a perturbation scheme applied to the steady‐state equations. A modal equation is developed from which an infinite set of decaying, oscillatory modes are shown to exist. The time constant for the system is shown to be approximately one‐fourth of the transit time associated with one‐carrier space‐charge‐limited currents.

ISSN:0021-8979    

DOI:10.1063/1.1709736

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Crystallization of thin layers of vitreous Se induced by exposing the surface to various inorganic and organic solvent vapors, e.g., carbon disulfide, trichloroethylene, isopropyl acetate, has been studied at room temperature. It is noted that the morphology of the crystallites obtained and the various growth features observed are essentially the same for the different chemical vapors used and are similar to growth of Se crystals by evaporation. Different experimental conditions seem only to change the distribution of the relative abundances of the various morphologies and the time needed for achieving a certain extent of crystallization. The mechanisms of crystal growth in this case, as visualized through the various growth features at intermediate stages, are remarkably similar to growth by vapor deposition of Au and Ag films on single‐crystalline substrates.

ISSN:0021-8979    

DOI:10.1063/1.1709737

出版商:AIP    

年代:1967

数据来源: AIP