bluuebunny/crossref_metadata_2025 huggingface dataset:
Spring Model of Hysteresis Applied to Tape-Wound Cores
Authors: Baldwin John A. , Bayne Jay S. , Calkins Thomas R.
Published: February 2004

The theory of the spring model of hysteresis is compared with experiment for a number of magnetic materials. The properties of the spring model as they relate to minor hysteresis loops are summarized. Loops from tape-wound cores of various materials are compared with these predictions to see if the cores obey the model. It is found that some cores, square orthonol and square Permalloy 80, fit the model quite well. Other cores, round orthonol, supermalloy, and magnesil, deviate considerably from the predictions of the model. It is believed that these cores can be made to obey the model by taking into account an internal self-generated field which acts on the domain walls in addition to the applied field.
Role of Interactions in Magnetic Tapes
Authors: Jaep W. F.
Published: February 2004

Thermodynamic and kinetic considerations applied to an assembly of single domain particles have resulted in a single set of equations that describe such diverse processes as hysteresis, time effects, thermoremanent magnetization, and anhysteretic magnetization. An important feature of this work is the inclusion of particle interactions in a consistent manner through the thermodynamic and kinetic formalism. The mechanism of magnetic processes is attributed completely to the thermal activation of moment reversal and not to interactions. Interactions, however, substantially modify the magnitude of the effects.
Double Extraction of Uniformly Generated Electron-Hole Pairs from Insulators with Noninjecting Contacts
Authors: Goodman Alvin M. , Rose Albert
Published: February 2004

A simple physical model has been used to derive an approximate theory of the double extraction of uniformly generated electron-hole pairs from a photoconductor layer with noninjecting contacts. The theory predicts 4 regimes of current versus applied voltage behavior:

(1) At low voltage, I∝V.

(2) At higher voltage, a transition region between I∝V and I∝V1/2.

(3) At still higher voltage, I∝V1/2.

(4) At very high voltage (above a saturation value), I=constant.

The model relates the extent of these regimes to the physical parameters of the system, viz., μpτp (mobility × lifetime product for holes), μnτn (mobility × lifetime product for electrons), and the layer thickness. Good agreement is obtained between the theory and measurements on lead oxide vidicons. The theory also provides some insight into the nature of the transient phenomena ``red fade'' and ``after image'' sometimes observed in the operation of lead oxide vidicons. At high light excitation levels, space-charge-limited currents are expected. In this case, two regimes of current versus applied voltage behavior can be predicted:

(1) Below a saturation value of voltage, I∝V1/2.

(2) Above a saturation value of voltage, I=constant.

The reasons for the one-half power current-voltage relationships are distinctly different in the μτ-limited and the space-charge-limited cases. In addition, the dependence of current on light intensity in the space-charge-limited case is a three-quarter power relation whereas in the μτ-limited case the dependence is a linear one. Also, the saturation voltage varies as the one-half power of the light intensity in the space-charge-limited case and is independent of the light intensity in the μτ-limited case.
Development of Spark in Air from a Negative Point
Authors: Nasser Essam
Published: February 2004

An old phenomenon used as a new detecting and diagnostic technique has been applied to the study of the voltage breakdown of air between a point cathode and a positive plane. ``Feathers'' were found to propagate at velocities almost 5% of the velocity of light. When they approach the positive plane, they produce ``retrograde streamers'' that bridge the gap and eventually lead to the completion of a plasma channel of high conductivity.
Electron-Beam Plasma-Doping Process
Authors: Myer Jon H.
Published: February 2004

A novel localized doping process using an electron beam as an energy source and a dopant foil as a dopant source is described. Rectifying silicon p-on-n and n-on-p junctions were made. The process presents several attractive features.
Direct and Indirect Optical Energy Gaps of AlAs
Authors: Yim W. Michael
Published: February 2004

Direct and indirect energy gaps of AlAs at 300°K, 3.14 and 2.14 eV, respectively, have been obtained from optical absorption measurements on vapor-grown single-crystalline specimens. The present direct-bandgap value is higher by about 0.2 eV than that previously reported, while the present indirect-bandgap value is in good agreement with a recent value. The optical measurements revealed, in addition to the direct and indirect absorption edges, the existence of an absorption peak due to nonstoichiometry.
Hot-Electron Distribution in n-GaAs Derived from Photoluminescence Measurements with Applied Electric Field
Authors: Southgate P. D. , Hall D. S. , Dreeben A. B.
Published: February 2004

Photoluminescence measurements have been made on thin, epitaxial layers of n-GaAs to which an electric field is applied. Field-dependent spectra are obtained corresponding to band-to-band recombination at 77 and 200°K, and from these the changes in electron distribution function are derived, allowance being made for the distributions of light and heavy holes. A fairly good agreement with theory is obtained, although variations between samples are too great to give clear support to the detailed model of Rees as opposed to the more phenomenologically drifted Maxwellian. The field suppression of the exciton peak is marked and is not adequately explained by present theory.
Nonlinear Faraday Effect in Nonparabolic Semiconductors
Authors: Chakravarti A. K.
Published: February 2004

The distribution function of carriers in a nonparabolic semiconductor subjected to a strong electromagnetic (em) field and a steady magnetic field has been derived, considering polar optical mode and ionized impurity as the sole scattering mechanism of the carrier at electron temperature greater than Debye's temperature. Explicit expressions for the current densities, corresponding to both the modes of propagation, are derived for a moderately strong em wave and then substituted in the general wave equation; the resulting nonlinear second-order differential equations are solved to obtain the expressions for Faraday rotation and ellipticity. It is seen that although the nonparabolicity restricts the heating of carriers, effect of nonlinearity is much more significant at lower frequencies. The present investigation can directly be used to study the effect of em heating on galvanomagnetic phenomena in nonparabolic semiconductors.
Optical Probing of Acoustic Flux Associated with Moving High-Field Domains in Semiconducting CdS Crystals
Authors: Mita Yoh
Published: February 2004

The shape and time-evolution characteristics of strong acoustic flux associated with moving acousto-electric high-field domains were investigated by means of a photoelastic method. The optical measuring system enabled us to determine the shape of the acoustic flux and to obtain quantitative data on its intensity. The width of the acoustic flux was measured to be ranging from 100 μ to several hundred microns, and the flux was found to be lagging behind the high-field domain by several tens of microns. The acoustic flux grew with transit of the high-field domain and tended to saturation. The peak shear stress near saturation was measured above 103 N/cm2, which was sufficient to produce mechanical fracture of the crystals. In many crystals the acoustic fluxes often assumed complicated structures consisting of several peaks. The succeeding peaks grew much faster than the preceding peak. It was shown that the succeeding peaks mainly consisted of lower-frequency acoustic waves compared to the first peak. The experimental results were compared with the results of the computer simulation based on a simple model. Fairly good agreement was found in such characteristics as the formation and relative positions of the acoustic flux and the high-field domain.
Properties of the Alkalis in CdS
Authors: Tell B.
Published: February 2004

Various optical and electrical properties of Na- and Li-diffused samples of CdS have been studied. Samples were prepared under maximum sulfur pressure, both with and without simultaneous donor doping. In the absence of donors, p-type material cannot be obtained, and the specific properties of the alkalis cannot be unraveled. In samples prepared with intentionally added donors, Na and Li are ``good'' acceptors, with a binding energy consistent with previous determinations (∼0.17 eV). Under certain conditions, Li has been shown to act primarily as a donor. The various compensation mechanisms are discussed.
Theoretical Method for Determining the Thickness and Surface Scattering Coefficient of Metal Films
Authors: Fitzgerald P. E. , Leonard W. F.
Published: February 2004

A method to determine the thickness and surface scattering coefficient of metal films from Hall-effect and temperature coefficient of resistance measurements is described. The method is based on the Fuchs-Sondheimer theory for size effects.
Method for Measuring Electrical Resistivity of Anisotropic Materials
Authors: Montgomery H. C.
Published: February 2004

A rectangular prism with edges in principal crystal directions is prepared with electrodes on the corners of one face. Voltage-current ratios for opposite pairs of electrodes permit calculation of components of the resistivity tensor. The method can use small samples, and is best suited to materials describable by two or three tensor components. Examples are given of measurements of V2O3–Cr and oriented amorphous graphite.
Traveling Wave Reflection Methods for Measuring Ultrasonic Attenuation and Velocity in Thin Rods and Wires
Authors: Papadakis Emmanuel P.
Published: February 2004

Two methods are outlined for determining the ultrasonic attenuation in thin rod-shaped specimens bonded to wire transmission lines. One method involves digital (video) pulses or short rf bursts resulting in separated echoes. The other employs rf bursts longer than three round trips in the specimen resulting in overlapped (stepped) echoes from the specimen. Use of three echo amplitudes or three interference steps permits the calculation of the reflection coefficient at the transmission line-specimen junction and the attenuation coefficient in the specimen. Methods for obtaining the travel time in the specimen are also outlined. Three experiments are reported to show the utility of the methods for studying specimens themselves and their environments.
Refraction and Reflection of Surface Acoustic Waves at Boundaries of Layered Anisotropic Substrates: Gold on Lithium Niobate
Authors: Pedinoff M. E. , Waldner M. , Jones W. R.
Published: February 2004

Acoustic surface-wave phenomena similar to optical refraction and reflection occur at boundaries of layered regions. In the case of piezoelectric substrates the anisotropy of the substrate must be considered in determining the reflection and refraction angles at such boundaries. The results of calculations of phase velocity and energy-flow direction as a function of propagation direction for the case of gold films on Y-cut lithium niobate are given. From these results the reflection and refraction angles at the boundaries of layers are determined. The theoretical results are compared with experimental observations of the deflection of surface-wave beams at gold film boundaries. These beam deflections were determined by optical imaging of the surface-wave beams using a laser diffraction technique.
Simple Theory of Acoustic Surface-Wave Amplification Using Very Thin Semiconductor Layers
Authors: Guéret P.
Published: February 2004

A theory of electro-acoustic surface-wave interaction is presented for a layered structure of piezoelectric and semiconductor. The semiconductor is assumed to be thin compared to both the acoustic wavelength and the Debye length. Diffusion has been taken into account in the analysis. Computed curves of gain are given and the dependence of gain on frequency, carrier concentration, drift velocity, and semiconductor thickness is discussed.
Neodymium-Activated Lanthanum Oxysulfide: A New High-Gain Laser Material
Authors: Alves R.V. , Buchanan R.A. , Wickersheim K.A. , Yates E.A.C.
Published: February 2004

We have observed lasing action at 1.075 μ for Nd in La2O2S (LOS). We have measured the lasing transition cross section of LOS: Nd to be σπ=(2.1±0.2)×10−18 cm2 and that of Nd in Y3Al5O12(YAG) to be σ=(5.6±0.6)×10−19 cm2. The stronger pump bands plus the larger lasing cross section for Nd in LOS relative to YAG result in a lower threshold in both pulsed and cw operation. We obtained sufficient data to predict a cw slope efficiency for LOS:Nd 8–12 times greater than YAG:Nd when LOS crystals with an optical quality comparable to YAG become available.
Coincidence Twist Boundaries between Crystalline Smoke Particles
Authors: Chaudhari P. , Matthews J.W.
Published: February 2004

Twist boundaries have been observed on {001} surfaces between crystals of MgO and CdO smoke. Measurements of the angles of twist across several hundred of these boundaries have revealed preferences for boundaries at 16.5°, 22.6°, and 37.3° in MgO and 22.8°, 28.5°, and 37.1° in CdO. These angles agree with those predicted by the coincidence site model to within the accuracy of measurement.
Grain-Boundary Contrast in Field Ion Microscope Images
Authors: French R. D. , Bishop G. H.
Published: February 2004

The contrast in field ion microscope (FIM) images due to [110] symmetric tilt boundaries in a bcc lattice was systematically investigated for misorientations up to 26° by computer image simulation. In low-angle grain boundaries there are three contrast effects: dislocation spirals, cusps in plane edges, and zone line displacement. The way in which those contrast effects develop with increasing tilt angle is discussed and illustrated with image simulations. An important result is that under favorable conditions contrast due to the boundary dislocations could still be resolved in the simulation of the high-angle 26° boundary.
Arc Extinction Phenomena in Vacuum
Authors: Farrall G. A.
Published: February 2004

Experiments have been performed to study the manner in which an arc between copper electrodes in vacuum extinguishes. In an ac circuit where current is limited to less than 1000 A peak, resistively, the extinctions are often prolonged over a period of many microseconds by successive reignitions of the arc caused by circuit-recovery voltage. These reignitions tend to be suppressed by capacitance paralleling the discharge thus raising the current at which the arc is extingusihed. In a similar circuit where the current is limited by inductance, the extinction most often occurs at a minimum in high-frequency oscillations of discharge current superimposed upon the 60-Hz arc current near the end of the half-cycle period. These oscillations occur at a frequency determined by the capacitance in parallel with the gap and the inductance of the wires used to connect the capacitors to the gap. For the inductive circuit with low values of capacitance, the oscillations are not apparent and extinction times of 10−7 to 10−8 sec are observed.
Measurement of the rf Magnetic Field Distribution in a Thermal Induction Plasma
Authors: Eckert H. U.
Published: February 2004

The radial distribution of the rf magnetic field in the equator section of a 25-kW argon induction flame maintained at 2.6 MHz in a 155-mm-wide tube is measured with a 3-mm-diam water-cooled search coil. It is found that in the annular space between plasma flame and inductor coil the field is increased by about 10% from an unperturbed value of 15 A/cm whereas in the flame interior it drops to a value of 0.8 A/cm at the axis. The penetration depth is of the order of 1 cm from which a mean value for the plasma conductivity of 10 mho/cm is estimated. From the field distribution a variation in magnetic pressure over the plasma radius of 16 dyn/cm2 is calculated which is in order-of-magnitude agreement with values quoted in the literature. Probe errors caused by signal averaging, current obstruction, and plasma cooling are discussed and found to be of minor consequences under the test conditions employed.
Thermal Transport Properties of Ordered and Disordered Ni3Fe
Authors: Moore J. P. , Kollie T. G. , Graves R. S. , McElroy D. L.
Published: February 2004

Thermal conductivity λ, electrical resistivity ρ, and Seebeck coefficient S measurements have been made from 80 to 400 K on a Ni3Fe alloy (74.77-at. % Ni and 25.33-at. % Fe) in both disordered and highly ordered states. The effect of lattice disorder is to lower λ and S and increase ρ. Although λ and ρ for the three states studied differ by about 50%, the Lorenz ratios λρ/T are the same to within the combined uncertainty of the measurements. This ratio is near the Sommerfeld value Lo from 200 to 400 K, and the positive deviation from Lo below 200 K indicates a significant lattice component to λ in all states of disorder. The thermal conductivities of the three states of Ni3Fe exhibit peaks between 142 and 175 K. The unusual relative shift of the temperatures of the maximum conductivities is related directly to the large deviation of the electrical resistivity differences from Matthiessen's rule.
Protonic Transport inside Polymeric Membranes
Authors: Wallace Richard A.
Published: February 2004

Electrical conductivity σ of sulfonated polystyrene ion-permeable membranes has been measured from 80 to 160°C to determine the effects of glass transition temperature Tg on protonic transport. Membranes were loosely crosslinked (1%) and contained up to 10% by weight of styrene sulfonic acid. Membrane conductivity increases exponentially with rising temperature as given by σ=σ0exp−E/RT where σ0 is the preexponential factor and E is the apparent activation energy for the protonic conduction process. Activation energy values vary from 11.0 to 16.0 kcal/mole in the glassy state and 15.0 to 22.0 kcal/mole in the rubbery state. Self-diffusion coefficients of hydrogen ions within a typical sulfonated membrane above and below its Tg have been computed. The increase in protonic transport with rising temperature has been interpreted to be chiefly due to increasing concentration and mobility of hydrogen ions.
Temperature Rise and Radial Profiles in CO2 Lasers
Authors: Laderman A. J. , Byron S. R.
Published: February 2004

An analytical model is presented which provides results for the radial distribution in gas temperature, electron density, and current density in conventional electric-discharge CO2–N2–He lasers. The heat-conduction and electron-diffusion equations are solved, and it is shown that (i) the radial electron density distribution differs only slightly from the usual Bessel-function profile for centerline gas temperature up to 600 °K and (ii) the laser gas-temperature profile is essentially independent of pressure and depends only on the total power input per unit length of tube. Calculated centerline-to-wall temperature differences are in good agreement with experiment, falling about 5% above measured values.
Extinction and Absorption Distances of Electrons in Evaporated Gold Crystals
Authors: Krakow W. , Hines R. L.
Published: February 2004

An experimental determination of electron-diffraction-theory extinction and absorption distances ξ200, ξ′0, and ξ′200 of (001) vapor-deposited gold crystals is made by investigating the thickness fringes produced in the electron microscope due to {111} microtwin boundaries present in these crystals. The (200) diffracted beam is investigated for 100-kV electrons and only the (h00) systematic spots are excited. The inelastic scattering contribution to these fringes is eliminated by the variable aperture technique and the intensity distribution due to Bragg-scattered electrons is obtained. Eleven-beam electron-diffraction theory is used to calculate an intensity distribution which is matched to the fringes produced by the elastically scattered electrons at a microtwin boundary.
Luminous Efficiency of the High-Pressure Sodium Lamp
Authors: Ozaki Norihiko
Published: February 2004

The luminous efficiency of the high-pressure sodium lamps (one sodium-xenon lamp and four sodium-mercury-xenon lamps) is measured as a function of the vapor pressure of sodium and of the discharge current. The vapor pressure of sodium is determined from the self-reversal width, which is defined as the distance between both lateral peaks of the self-reversed resonance line of sodium. The self-reversal width becomes large when the vapor pressure increases at a constant discharge current, and when the discharge current decreases at a constant vapor pressure. It is attributed to elevation of the plasma temperature that the luminous efficiency becomes high when the discharge current increases at a constant vapor pressure and when mercury is added to the sodium-xenon plasma. When the discharge current is kept constant, there is an optimum pressure at which the luminous efficiency takes its maximum value. The optimum pressure depends on the discharge current, and it corresponds to the self-reversal width of about 100 Å for every discharge current.
Analysis and Design of Ion-Beam Deposition Apparatus
Authors: Fair Richard B.
Published: February 2004

In order to establish an upper limit on the practicality and usefulness of ion-beam deposition of thin films, an experimental beam-deposition system was assembled which was capable of producing an ideally focused ion beam. The system was designed under the assumptions that the final beam diameter is limited by the thermal velocity spread of the ions and the spherical aberration of the final lens of the optical column. Theoretically, this apparatus is capable of producing a 0.01-cm-diam 6×10−8-A indium ion beam at 100-eV energy. Under these conditions, the predicted deposition sweep velocity would be 0.016 cm/min to produce a 2×10−6-cm-thick indium film. Chromatic aberration was the factor that limited the actual measured spot diameter to 0.075 cm for a beam current of 10−8 A and ion energy of 100 eV. Indium films were deposited in this apparatus with ion energies ranging from 100 to 500 eV (total dose of 7×1017 atom/cm2). Interferometric measurements indicated that these films retained, to some extent, the shapes of the ion distributions across the beam. Sputtering, however, inhibited the complete vertical growth of the deposits. Measurements of the sputtering yield indicated that unity sputtering yield occured at an ion energy of 550 eV, as compared with the predicted energy of 200 eV.
Arsenic Clustering in Silicon
Authors: Schwenker R. O. , Pan E. S. , Lever R. F.
Published: February 2004

Large decreases in the conductivity of arsenic-doped silicon have been observed during 500–970°C heat treatments. The rate of conductivity change depends upon the prior quenching rate from diffusion temperature to room temperature. These conductivity changes are reversed by higher-temperature treatments. The relationship between the electrically active arsenic, as calculated from the conductivity, and the total arsenic is shown to be consistent with a model of substitutional arsenic atoms being nonionized when in a cluster or in a complex involving one or more vacancies.
Growth and Characterization of Liquid-Phase Epitaxial InAs1−xPx
Authors: Antypas G. A. , Yep T. O.
Published: February 2004

Liquid-phase epitaxial layers of InAs1−xPx were grown in the range of 0 < x < 0. 735 on {1̄1̄1̄} InP substrates. The ternary phase diagram was calculated using Darken's quadratic formalism to describe the ternary liquid which is in equilibrium with a regular pseudobinary solid solution. A number of liquidus isotherms were experimentally determined and found to be in good agreement with the calculated phase diagram. The composition of the grown layers was determined by lattice-constant measurements assuming that Vegard's law was obeyed. The band gap was determined by photoluminescence at 77 and 300 °K, and was fitted to the form of Eg = A + Bx + Cx2, where A = 0. 421, B = 0.714, and C = 0. 281 eV at 77 °K. The specimens were n type as determined by Van der Pauw measurements.
Analysis of Gaussian Light by Clipped Photocount Autocorrelation: The Effect of Finite Sampling Times and Incomplete Spatial Coherence
Authors: Koppel Dennis E.
Published: February 2004

The theoretical treatment of clipped photocount autocorrelation of Gaussian light, introduced by Jakeman and Pike, has been extended to include the effects of finite-duration sampling intervals and incomplete spatial coherence. A system of ``interval partitioning'' is used to derive theoretical expressions for 〈Nq(0)N(τ)〉 and 〈N0(0) N0(τ)〉, the single- and double-clipped photocount autocorrelation functions. Here N(t) is the number of photons detected in a sampling interval centered at t and Nq(t) is the clipped count at level q. Each original interval is systematically partitioned in space and time. Multidimensional generating functions are applied to the sets of subintervals with the object of expressing g(1) (t), the first-order field correlation function, in terms of measurable quantities. It is shown that under certain well-defined conditions, 〈Nq(0) N(τ)〉−〈Nq〉〈N〉=γq|g(1)(τ)|2 and 〈1−N0〉−2−[1−2〈N0〉+〈N0(0)N0(τ)〉]−1=φ|g(1)(τ)|2, where, for a given set of experimental parameters, γq and φ can be taken as simple multiplicative factors independent of the delay time τ. For comparative purposes, a similar analysis is performed for the unclipped correlation function 〈N(0)N(τ)〉. Finally, computer calculated values of various quantities of interest are presented for several representative cases.
High-Pressure Equation of State for NaCl, KCl, and CsCl
Authors: Decker D. L.
Published: February 2004

A calculation of the equation of state for NaCl from a Mie-Grüneisen equation was repeated using more accurate values of the zero-pressure compressibility. It was also extended to KCl and CsCl. An analysis of this approach to pressure calibration indicates that it will yield pressures with about the same accuracy as can be presently achieved by experimental measurements above 25 kbar, and thus furnishes a temporary practical pressure scale.
Growth of Ultrathin Gold Crystals
Authors: Krakow W. , Hines R. L.
Published: February 2004

Thin gold crystals are prepared by vapor deposition in an ion-pumped vacuum system onto (100) silver surfaces on rocksalt. The continuity of 15-Å-thick carbon-backed crystals is investigated in the electron microscope for different growth conditions. Specimens made at different thicknesses show that the thinnest stable crystals with areas 1000 Å in diameter free of holes are about 9 Å thick. Diffracted beam intensities of the gold crystals are measured and used with kinematical diffraction contrast theory to obtain an independent measurement of crystal thickness.
Initial Separation of Electrical Contacts Carrying High Currents
Authors: Slade P. G. , Nahemow M. D.
Published: February 2004

An investigation has been made on the initial separation of high-current contact electrodes. Three distinct voltage-time characteristics are observed. Two of these correspond to the formation of a molten-metal bridge and the third corresponds to an abrupt transition from metallic contact to an arc. Two ideal cases are analyzed theoretically from which a model is developed. The model is then related to the three voltage-time characteristics observed.
Velocities of Individual Dislocations in Germanium
Authors: Patel J. R. , Freeland P. E.
Published: February 2004

Dislocation velocities have been measured on loops whose Burgers vectors have been determined by x-ray topography. The new measurements do not agree with earlier work; the reasons for the discrepancy are discussed. The earlier work was also in error because of an incorrect assumption about the Burgers vector of the dislocations. The measured velocity-stress behavior falls into two distinct stress regimes. At low stresses the dislocation velocity depends more strongly on stress than in the high-stress region. The activation energy for dislocation motion depends on stress and varies from 2.9 to 1.5 eV over the stress range 0.6–8 kg/mm2.
Intrinsic Disclinations as Dislocation Sources and Sinks in Surface Crystals
Authors: Harris W. F. , Scriven L. E.
Published: February 2004

An intrinsic disclination (necessarily a wedge disclination) in a surface crystal can act as a source of or sink for dislocations. In so acting the disclination suffers a displacement. An equation is obtained which relates the displacement to the Burgers vectors of dislocations produced or annihilated. Examples involving disclinated square and hexagonal lattices are presented.
Optimization of Multilayer Soap Crystals for Ultrasoft X-Ray Diffraction
Authors: Charles M. W.
Published: February 2004

A detailed program for the optimization of the ultrasoft x-ray reflectivity and resolution of multilayer soap crystals is described which is based on classical x-ray diffraction theory and fundamental data concerning monolayer films. New measurements of the conversion factor (fraction of fatty acid converted to soap in a monolayer formed on a liquid substrate containing metal ions) as a function of the metal-ion concentration and liquid substrate pH have been used as the basis of a logical optimization procedure. Full optimization parameters are given for the lead soaps of melissic, lignoceric, stearic, myristic, and lauric acids which have 2d interplanar spacings of 159.6, 131.5, 100.4, 80.5, and 70.0±0.1 Å, respectively. These crystals have a reproducibility of about 10% (mean deviation from mean reflectivity), except in the case of lead stearate where it is 5%. For each soap the optimum lead concentration in the liquid substrate is 3×10−5 M, the pH of this solution is 6.0, and the dipping speed is 0.2 cm sec−1. The resultant crystal is 100% soap and contains no unconverted acid. The necessary surface pressure and temperature are dependent upon the particular soap being produced. The optimum values which give good reproducibility and high reflectivity, for the acids mentioned above, are (1) temperature: 30, 20, 18, 12, and 12°C; (2) pressure: 40, 35, 32, 20, and 15 dyn cm−1, respectively. The relative reflectivity of crystals containing varying amounts of lead are in agreement with diffraction theory. The absolute reflectivities for different thicknesses of all the optimized crystals are presented for various ultrasoft x-ray emission lines and are shown to be in qualitative, but not quantitative, agreement with theory. Crystals of thickness in excess of about 150 monolayers (75 lattice planes) proved impossible to build. The diffraction half-widths of the crystals are found to be in agreement with theory, and the spectral resolution of the crystals has thus been estimated. In general, this is equal to the effective number of diffracting planes and is thus limited by crystal absorption. Resolving powers of 30–60 can be obtained in the 20–120-Å region for the thickest crystals grown. The peak and integrated reflectivities of these crystals were of the order of 1–5% and 1–4×10−4 rad. Detailed measurements are given for all crystals and a variety of emission lines. Reflectivity data is also presented for beryl and potassium acid phthalate (KAP) crystals and a comparison is made between soap crystals and other possible dispersive elements in the ultrasoft x-ray region. Data is presented on peak-to-background ratios, high-order spectra intensity, and the use of mixed fatty acids to achieve intermediate spacing crystals. Because the optimized crystals contain no unconverted acid, they are shown to be particularly stable to a vacuum environment and rises in temperature up to at least 100°C. Spectra are presented to illustrate the use of multilayer soap crystals in ultrasoft x-ray spectrometry.
Far-Infrared Mixing in High-Purity GaAs
Authors: Lao B. Y. , Litvak M. M.
Published: February 2004

Calculations are presented for various mechanisms by which two-wave and three-wave mixing of far-infrared and millimeter-wave signals in high-purity GaAs might occur. The emphasis is on low IF, about 1 MHz, as detected by photoconductivity. The energy dependence of the carrier-energy relaxation time and the carrier-recombination time is found to be important, but for three-wave mixing, in addition, the hydrogenic donor levels allow mixing by means of photoexcitation and modulation of the level densities, followed by thermal ionization that carries the modulation to the carrier density and the photocurrent.
Extrapolated and Projected Ranges of 4- to 24-MeV Electrons in Elemental Materials
Authors: Tabata Tatsuo , Ito Rinsuke , Okabe Shigeru , Fujita Yoshiaki
Published: February 2004

The extrapolated range Rex and the projected range Rpr of 4- to 24-MeV electrons in Be, Al, Cu, Ag, and Au have been determined from the experimental data for the charge-deposition distribution produced by the electrons in the effectively semiinfinite absorber. While the results for Rex show no significant difference from the data obtained by Harder and Poschet and by Ebert et al. for the absorber configuration of finite slab, the present values of Rpr for the absorbers of high atomic number are slightly smaller than the results of Harder and Poschet. In the energy region considered here, Rex has been found to obey an empirical equation of the form Rex = A(E0−B)C, where A, B, and C are expressed by simple functions of atomic number, and E0 is the incident kinetic energy of the electron. A semiempirical relation previously found between Rpr and the continuous slowing-down approximation range R0 has been modified so as to show a better agreement with the present data.
Scanning Electron Microscope Study of Electrode Damage Due to Nanosecond Arcs
Authors: Augis Jacques A. , Gray Eoin W.
Published: February 2004

The comparison between the observed cathode damage in a short arc (20–100 nsec duration; 0.3 mm long), as observed by a scanning electron microscope, and a model of cathode erosion employing ionic bombardment as the main erosion source leads to the evaluation of the current density in the individual craters comprising the cathode spot. Only order-of-magnitude calculations were possible; however, the main feature was that the current density was found to remain almost constant at a value of 1.9×107 A cm−2 for craters of radius between 0.3 and 1.0 μ. The ratio of the ionic to electronic currents was found to be significantly higher than previously published values for cathode spots.
Measurements of the Gas Temperature in CO2–N2–He and CO2–N2–H2O–He Discharges
Authors: Waszink J. H. , van Vliet J. A. J. M.
Published: February 2004

The gas temperature has been measured at the axis of the positive column of a number of discharges commonly used for CO2 lasers. The measurements have been made with an interferometer. For the first series of measurements the tube is filled initially with 2-Torr CO2 and 4-Torr N2. Next, He is added in steps. In the second series the gas mixture also contains a small amount of H2O vapor. If the power input into the column is kept constant the gas temperature decreases when He is added.
Transversely Pulse-Initiated Chemical Lasers: Atmospheric-Pressure Operation of an HF Laser
Authors: Jacobson T. V. , Kimbell G. H.
Published: February 2004

Chemical laser action at atmospheric pressure has been observed from vibrational-rotational transitions of HF produced by multiple transverse spark discharges in C3H8–He–SF6 mixtures. Lasing action was also observed when C4F8, C2F6, or CF4 replaced the SF6 and H2, CH4, C2H6, or C4H10 replaced C3H8. Peak-pulse powers in excess of 0.5 MW were obtained at low pressures; at atmospheric pressure, peak powers were of the order of 30 kW. In some instances, the laser was superradiant at pressures up to 1 atm. P-branch transitions from the v=3, 2, 1 vibrational levels of HF were observed. The pumping reaction was F + RH = HF† + R.
Experimental Observations and Calculated Band Strengths for the D2 Lyman Band Laser
Authors: Waynant R. W. , Ali A. W. , Julienne P. S.
Published: February 2004

Experimental observations have been made of vacuum ultraviolet laser emission in the Lyman band of D2. Fourteen lines from 1568 to 1614 Å have been measured to have a total peak power of nearly 1 MW in a short (∼ 1 nsec) pulse. To facilitate identification of the laser wavelengths, optical functions were calculated using the adiabatic correction to the usual Born-Oppenheimer approximation. The theory predicts the most probable transitions and these wavelengths agree with experiment to within 0.1–0.2 Å.
Low-Loss Lithium Ferrites for Microwave Latching Applications
Authors: Collins T. , Brown A. E.
Published: February 2004

Two sets of dense kiln-fired lithium ferrite ceramic bodies with 4πMs around 3600 and around 2600 G, respectively, have been prepared with low microwave dielectric losses (tan δ < 0.0005) and high remanence ratios (Br/4πMs = 0.7). These low dielectric losses were obtained by addition of MnO2. For samples which were thicker than 0.25 cm, an anneal in an oxygen atmosphere was required. The lower 4πMs compositions were obtained by substituting titania for part of the iron oxide in the basic lithium ferrite formulation. A number of physical properties were evaluated and the results are presented. These include density 4πMs and Curie temperature. In addition, properties useful for microwave latching applications such as complex dielectric constant and hysteresis characteristics, i.e., ramanent magnetization and coercive force are presented. The temperature variation of the hysteresis properties for selected compositions is also shown.
Properties of the Room-Temperature Electron Trap in Rutile
Authors: Lauer R. B. , Addiss R. R. , Ghosh Amal K.
Published: February 2004

By a combination of thermoluminescence, thermally stimulated current, and photocurrent measurements, the electron trapping parameters of the room-temperature trap in rutile were obtained. The photon-capture cross section and the electron-frequency factor were determined. The values of the electron-capture cross section, the trap density, and the ratio of optical to thermal ionization energies of the trap were calculated. The relation of the trapping center to the photocurrent decay is discussed.
Spatially Damped Temperature Oscillations in a Highly Ionized Plasma Column
Authors: Stefanov B.
Published: February 2004

A time-varying heat flow along a highly ionized plasma column is analyzed theoretically. The diffusion of a locally applied sine-wave temperature disturbance for frequencies up to 106 Hz is shown to be accompanied by a potential disturbance of the same phase, other quantities (such as the density, the velocity, and the ion temperature) having different phase angles and much smaller amplitudes than the electron temperature and the potential. Calculations of the phase lag of the temperature wave along the column are presented and compared with measurements in a highly ionized cesium plasma column for frequencies 102−104 Hz. The measured thermal diffusivity coefficient determining the phase lag agrees with theory within 20%.
Effect of Electric Field Direction on Pulsed Radiation-Induced Current in Crystalline Quartz
Authors: Okabe S. , Tsumori K. , Tabata T. , Kawabata K. , Yoshida T.
Published: February 2004

Dependence upon sample orientation of the pulsed radiation-induced current (RIC) in crystalline quartz has been studied by using 5-μsec pulses of electrons with an energy of 13 MeV. The variation with time of the RIC has been found to depend on the direction of the applied electric field with respect to the c axis of the crystal, but not appreciably on the direction of the incident electron beam. Detailed dependence of the pulsed RIC on the angle θ between the applied electric field and the c axis has been measured also for θ from 0° to 90° at intervals of 15°, and the variation with time of the RIC has been found to be large for θ<60° and very small for θ≥60°. The dependence on θ was confirmed by measuring the average RIC with a picoammeter.
LEED Studies of Oxygen Adsorption on the (111) and (110) Surfaces of Aluminum
Authors: Bedair S. M. , Smith Harold P.
Published: February 2004

Oxygen adsorption at elevated temperatures on clean (111) surfaces of aluminum produced an ordered reconstruction of the surface, whereas similar treatment of the (110) surface produced (311) and (111) facets. Reconstruction on the (111) facets was the same as the (111) surface.
Preparation and Stability of MnBi Thin Films
Authors: Chen Di
Published: February 2004

A method to prepare thin films of MnBi by vapor deposition followed by a fast annealing process is described. Uniform and reproducible MnBi films suitable for magneto-optic applications can be obtained using this technique. Upon quenching from above 360°C, the high-temperature phase can be preserved at room temperature. The stability of this crystallographic phase has been evaluated and an activation energy of 1. 08 eV associated with the phase transformation from the quenched high-temperature phase to the normal low-temperature phase is determined.
Vibrational assignments and torsional barrier heights of some methylsilylchlorides
Authors: Durig J. R. , Hawley C. W.
Published: February 2004

The infrared spectra of gaseous chloromethyl-, dichloromethyl-, and methyldichlorosilane have been obtained from 4000 to 33 cm−1 and the far infrared spectrum of gaseous methylchlorosilane has been recorded from 350 to 33 cm−1. The far infrared spectrum of the low temperature solids (−190°C) have also been recorded from 350 to 33 cm−1. The Raman spectra of the liquids have been measured, with quantitative depolarization ratios, from 4000 to 100 cm−1. Assignments for all of the fundamentals for each of the molecules are proposed on the basis of depolarization ratios, band contours, and group frequencies. The bands corresponding to the torsional modes are assigned as appearing at 172, 177, 175, and 184 cm−1 in the infrared spectra of the solids and give corresponding barriers of 3.00, 3.69, 2.25 and 2.09 kcal/mole for chloromethyl-, dichloromethyl-, metylchloro-, and methyldichlorosilane, respectively. The results are discussed in terms of present theory.
Ion-molecule reactions by a photoionization mass spectrometer. IV. C5-unsaturated hydrocarbons
Authors: Koyano Inosuke , Suzuki Yukio , Tanaka Ikuzo
Published: February 2004

The reactions of parent ions of five pentene isomers and cyclopentene with their corresponding neutral molecules have been studied at 1.7 eV ion exit energy using a photoionization mass spectrometer in the pressure range between 1 and 10 mtorr. Pentene-1 was the most reactive system and 3-methylbutene-1 and 2-methylbutene-2 were much less reactive than others. C5H11+ formation in 2-methylbutene-1 had an exceptionally large cross section and this made the system much more reactive than other branched chain pentenes. Dimeric ions (C10 ions) were detected in all of the systems and no C9 ions were observed in any of the systems. Distribution of C6, C7, and C8 product ions in pentene isomers can be explained by the mechanism proposed by Henis except in the case of 2-methylbutene-2 where some rearrangements in the intermediate are necessary to explain the product distribution. Parent-minus-two reactions occurred in normal chain pentenes but did not in branched chain isomers. Parent-minus-one and parent-plus-one reactions occurred more or less in all of the pentene isomers. In cyclopentene, product distribution was very simple in contrast with the noncyclic pentenes, product ions C6 through C9 being absent. The cross sections of the observed reactions [(M−2)+, (M−1)+, and C10 ion formation], however, were fairly large.
Ultrasound velocity in solid CH4
Authors: Wolf R. P. , Stahl F. A. , Watrous J. A.
Published: February 2004

We have studied the velocity of 4 and 12 MHz longitudinal and transverse sound in polycrystalline solid CH4 from 2 to 77°K, and calculated the adiabatic compressibility, βs, over this range. Near 20.48°K, the temperature of the known upper lambda transition, the velocity curve shows a discontinuity in slope and βs shows a singularity, as would be expected for a lambda-type transition. However, no such anomalies are found near 8°K, the expected temperature of a lower transition. Addition of 1% O2 to CH4 produced indications of an anomaly in the velocity at 8°K, governed by an equilibration time on the order of 15 min.
External heavy atom effects on benzene in rare gas hosts
Authors: Hsu Yei-Ping , Johnson Philip M.
Published: February 2004

A study has been made of the triplet lifetimes and emission spectra of benzene and perdeuterobenzene in various sites in neon, argon, krypton, and xenon hosts. Accurate lifetime measurements show that there is no deuterium effect on the phosphorescence lifetimes in krypton and xenon. One of the sites in argon and krypton has been identified as having threefold symmetry (D3h or C3v), as evidenced by a complete absence of symmetric vibrations. It is shown that the vibrational structure of the phosphorescence from krypton and xenon are very similar, with both symmetric and antisymmetric modes, even though there is a change in the triplet decay rate by a factor of 30. This implies an external heavy atom effect proceeding by both a direct and a vibronic route. The vibronic structure of the phosphorescence varies substantially with the site, indicating a shallow potential in the triplet state which can be easily influenced by the environment.
Electron paramagnetic resonance studies of a viscous nematic liquid crystal. II. Evidence counter to a second-order phase change
Authors: Shutt William E. , Gelerinter Edward , Fryburg George C. , Sheley Curtis F.
Published: February 2004

The ordering in a viscous nematic liquid crystal was studied using vanadylacetylacetonate and several nitroxides as paramagnetic probes. The ordering curve for VAAC at both K-band and X-band shows a slope discontinuity at a reduced temperature of 0.85. This discontinuity is caused by the tumbling time of the VAAC becoming comparable with the hyperfine splitting. The slope discontinuity is not present in the ordering curves of the nitroxides. The results are taken as evidence counter to the presence of a second-order phase transition.
Collisional dissociation of H2+ and H3+ on molecular targets leading to formation of excited hydrogen atoms
Authors: Conrads R. J. , Ford J. C. , Thomas E. W.
Published: February 2004

Experimental measurements have been made of the cross sections for dissociation of fast (100–700 keV) H2+ and H3+ ions to give fast H atoms in the 3s excited state; targets for this work were O2, CO, CO2, CH4, C2H6, and C3H8. The technique involved quantitative measurement of Balmer-alpha radiation emitted from fast moving fragments of the dissociated projectile. Contributions to the Balmer-alpha emission from the 3p and 3d levels were eliminated by a method that utilizes the different lifetimes of the 3s, 3p, and 3d states. It is observed that cross sections for H(3s) formation by dissociation on the hydrocarbons all exhibit essentially the same variation with impact energy and increase in magnitude with the complexity of the target; similar behavior is exhibited by the O2, CO, and CO2 group of targets. Comparison of the various cross sections suggests that one cannot assign an effective cross-section value to the constituent atoms of the target molecule.
Excitation of Group Ia and IIb metal atoms by a Lewis-Rayleigh nitrogen afterglow
Authors: Duthler C. J. , Broida H. P.
Published: February 2004

Relative atomic line intensities have been measured for Group Ia and IIb atoms excited by a Lewis-Rayleigh nitrogen afterglow. From the measured linewidth and lack of pressure dependence of the intensity distributions for Group Ia atoms, it is proposed that the exciting species in the afterglow is N2(A 3Σu+). Pressure dependence of Group IIb atomic line intensities is observed and possible excitation mechanisms and quenching effects are discussed.