bluuebunny/crossref_metadata_2025 huggingface dataset:
LATENT HARDENING AND THE FLOW STRESS IN COPPER SINGLE CRYSTALS
Authors: Jackson P. J. , Basinski Z. S.
Published: April 2011

The latent hardening produced by straining copper crystals in single glide was investigated by measuring the flow stress on secondary systems. Specimens oriented for slip on these systems were spark cut from large prestrained crystals and tested in tension. These specimens did not always yield on the most highly stressed system; this behavior is a manifestation of the anisotropy introduced by the prestrain and was found only in certain portions of the stereographic projection.When the glide plane was changed, the flow stress increased. The increase ranged from 160% in early stage I to 40% in late stage II, except for systems with Burgers vectors at 90° to the prestrain slip direction, where systematically smaller increases were observed. The flow stress did not increase significantly when only the slip direction was altered.The anisotropy of the flow stress is closely related to the anisotropy of the dislocation distribution produced by single glide. In particular a reasonably good correlation appears to exist between the flow stress and the forest density. The strain rate and temperature sensitivity of the flow stress are unaffected by a change in stress system.The results are discussed in terms of current theories of the flow stress. It is concluded that while impurity interactions may be important in stage I, the flow stress is controlled mainly by forest interactions.
STATISTICAL TREATMENT OF PENETRABLE OBSTACLES
Authors: Kocks U. F.
Published: April 2011

Obstacles to dislocation motion which are pointlike in character, finite in strength, and random in spatial distribution in the slip plane, are treated by statistical methods developed previously for infinitely strong obstacles. Various important length parameters are distinguished and derived as functions of stress: the link length between obstacles relevant in internal friction problems, the passing distance defined by the flow stress, the differential activation length determining the rate dependence of the flow stress, and the free slip distance important in the elastoplastic transition region and in the preexponential factor for thermal activation. The flow stress results agree with those of Foreman and Makin, but the differential activation length and the free slip distance predicted show important effects not previously expected.
STUDY OF DISLOCATIONS IN LIGHTLY DEFORMED COPPER CRYSTALS USING BORRMANN X-RAY TOPOGRAPHY
Authors: Young Jr. F. W. , Sherrill F. A.
Published: April 2011

Copper crystals of dislocation density [Formula: see text] were deformed in compression at resolved stresses 7–22 g/mm2, then irradiated with fast neutrons, either with the stress applied to immobilize the dislocations in their "stress-applied" positions, or with the stress removed to immobilize them in their relaxed positions. The crystals were then sectioned along {111} planes by acid sawing, and these lamellae were examined by Borrmann X-ray topography. In the stress-applied condition the dislocations produced by the stress were long, often > 0.5 cm and lay predominantly in the screw orientation. Dislocation sources, though not identified, appeared to be at or near the crystal surfaces. The dislocation configurations in the "stress-relaxed" condition were markedly different from those in the stress-applied condition. "Bundles" of dislocations and dipoles were observed only in the stress-relaxed condition. It is postulated that dipoles were formed during the relaxation process.
WULFF'S THEOREM AND CERTAIN GREEN'S FUNCTIONS IN DISLOCATION THEORY
Authors: Brown L. M. , Alcock E. , Brown L. M.
Published: April 2011

Certain Green's functions recently proposed for the solution of dislocation problems in anisotropic media by Lothe (1967) and Brown (1967) are used to calculate the energy of interaction between kinks or jogs on a dislocation line and the energy of a general angular loop. The formulae are particularly simple, and are closely related to the problem of calculating the equilibrium shape of a dislocation. In the case of prismatic loops of Frank sessile dislocation in aluminium and copper, it is shown that the theory cannot account for the shape of the loops unless additional terms representing the variation of core energy with orientation of the dislocation line are included.
DISSOCIATED DISLOCATIONS AND THE SCHMID LAW OF RESOLVED SHEAR STRESS IN b.c.c. METALS
Authors: Nabarro F. R. N. , Duncan T. R.
Published: April 2011

The dissociation of screw dislocations on [Formula: see text] planes in a b.c.c. metal can lead to unequal shear stresses for glide in opposite directions, while dissociation on [Formula: see text] planes cannot. Glide will occur in the former configuration only if the radius of the core of a partial dislocation exceeds [Formula: see text] of the radius of a symmetrically dissociated dislocation. If this condition is not satisfied, one partial dislocation runs to infinity before the remaining two coalesce.
DISLOCATION DISTRIBUTION IN DEFORMED SILVER SINGLE CRYSTALS
Authors: Moon D. M. , Robinson W. H.
Published: April 2011

The results of an electron transmission microscopy investigation of silver single crystals deformed in the three stages of the work-hardening curve are described. In stage I edge-dislocation bundles of the primary system form. With continued deformation in stage I more bundles form and the number of dislocations in each bundle increases. The end of stage I is associated with activity on secondary glide systems adjacent to the bundles. During stage II deformation, a cell structure forms and continually decreases in size by the cooperative activity of the primary and secondary systems. This cooperative activity occasionally results in the formation of dense networks of Lomer–Cottrell dislocations in local areas. Often associated with these networks are small stacking-fault tetrahedra believed to result from the stress-induced cross slip of extended dislocations at jogs. The importance of the stacking-fault energy in the deformation of f.c.c. crystals is discussed.
DISLOCATION STRUCTURE IN "AS-GROWN" HIGH-PURITY IRON SINGLE CRYSTALS
Authors: Kadečková S. , Šesták B.
Published: April 2011

The dislocation structure in iron single crystals prepared by two different strain–anneal techniques from the starting material of two different purities is studied by the method of etch pits. Average dislocation densities of 2.6 × 105 to 7 × 105 cm−2 and the absence of subboundaries are observed in single crystals grown statically or dynamically from zone-refined Johnson and Matthey spectrographic iron. The presence of broad subboundaries and average dislocation densities of 8.6 × 105 to 3.3 × 106 cm−2 is characteristic for single crystals grown from the non–zone-refined J. and M. iron. Annealing of "as-grown" crystals does not greatly influence the dislocation structure. It is assumed that the impurities are mainly responsible for the observed dislocation densities.
PLASTICITY OF IRON SINGLE CRYSTALS
Authors: Keh A. S. , Nakada Y.
Published: April 2011

Results accumulated in the past four years on the plastic deformation of iron single crystals are summarized.The work-hardening behavior of iron single crystals depends very much on orientation and temperature. At room temperature, three-stage hardening was observed for single-slip orientations. The work-hardening rates in stages I and II were correlated with the extent of localized secondary slip.Latent hardening was observed in iron crystals. The latent-hardening ratio is about 1.3 and is relatively independent of temperature and choice of latent system.The yield stress of iron single crystals is very dependent on temperature and is also sensitive to orientation at low temperatures and to interstitial content at all temperatures. By adding interstitials to purified crystals, the athermal portion of the flow stress of iron is raised, but its temperature dependence is not altered. Crystals oriented for single slip on the (101) and (112) planes have different temperature dependences of the proportional limit. Similar but small differences in this temperature dependence of proportional limits were observed in crystals oriented for single, double, and multiple slip on {112} planes. These results are explained on the basis of a Peierls mechanism.
MICROSTRAIN BEHAVIOR OF BODY-CENTERED CUBIC METALS
Authors: Meakin J. D.
Published: April 2011

The true elastic limit of high-purity molybdenum, tungsten, and iron is shown to be of the order of 10−5 μ, where μ is the shear modulus. At higher stresses, linear reversible deformation occurs up to total strains of the order 10−3. The strain-rate sensitivity of the flow stress in this region is investigated and a possible rate controlling dislocation mechanism is discussed.
FAULTED DEFECTS AND STACKING-FAULT ENERGY
Authors: Clarebrough L. M. , Humble P. , Loretto M. H.
Published: April 2011

Four direct methods of obtaining values of stacking-fault energy from observation of faulted defects in pure face-centered cubic metals are discussed. It is shown that there is essential agreement between the method based on the observation of threefold nodes and that based on the observation of triangular Frank dislocation loops and stacking-fault tetrahedra in deformed f.c.c. metals, in the range where both methods are applicable. On the other hand, it is shown that the third method, based on the collapse size of stacking-fault tetrahedra in quenched metals, cannot yield even an upper limit. New experimental results show that the fourth method, based on the annealing rate of faulted loops, is applicable only to metals of high stacking-fault energy and then only if jog nucleation and propagation are not rate controlling; for low stacking-fault energy metals, these factors, together with the dislocation energy, must be considered, and cannot be completely taken into account.
RESISTIVITY OF DEFORMED CRYSTALS
Authors: Basinski Z. S. , Saimoto S.
Published: April 2011

The variation of electrical resistivity with deformation, as a function of purity and orientation, has been studied for Cu single crystals deformed in tension and fatigue. In stage I the rate of increase of resistivity depends very strongly on the impurity content, decreasing with increasing purity. In stage II the resistivity increases quadratically with stress, the rate of increase depending on orientation. The resistivity produced by dislocations appears not to be strongly anisotropic. The value of resistivity per unit dislocation is about 1 × 10−19 ΩSi-cm.
CRITICAL RESOLVED SHEAR STRESS OF LEAD
Authors: Weinberg F.
Published: April 2011

Measurements of the critical resolved shear stress of lead are reported as a function of temperature, purity, solute additions, and orientation. By annealing in situ it was found that the value of the CRSS can be reduced, the scatter between specimens decreased, and the same specimen can be tested a number of times.Over the temperature range 4.2 °K to 600 °K (the melting point) the CRSS decreased from 53 g/mm2 to approximately 10 g/mm2. Between 100 °K and 300 °K the temperature dependence of the CRSS is the same as that of the shear modulus.It was found that the CRSS is relatively insensitive to differences in the trace impurity level and to solute additions of 0.1% Sn and 0.02% Cu. Additions of 1.0% Sn appreciably increase the CRSS at low temperatures.The orientation dependence of the CRSS is similar to that shown for copper, with higher values at the edges and corners of the stereographic triangle.Under optimum conditions the average value of the CRSS of lead is 34 g/mm2 at 78 °K. This value is anomalously high when compared to that of copper, using σ α [Formula: see text] for the flow stress to make the comparison.
DISLOCATION DISTRIBUTION IN DEFORMED GERMANIUM
Authors: Alexander H. , Haasen P.
Published: April 2011

The dislocation distribution in germanium single crystals deformed at 520 °C and cooled under load was investigated by electron transmission and etch pitting at different stages of the stress–strain curve. Contrary to the findings of previous investigators, the Peierls force was not found to be strong enough to line up dislocations in close-packed directions. The dislocation arrangement observed in Ge is rather similar to that found in f.c.c. crystals in which a rearrangement of dislocations was prevented. In particular, dislocations have predominantly edge character, lie in stage I mainly in the primary slip planes, interact with dislocations on cross slip planes, and form braids, etc. Forest dislocations are found concentrated in zones almost parallel to certain primary slip planes which primary dislocations seem to avoid.
GRAIN-SIZE DEPENDENCE OF FRACTURE IN COPPER–ALUMINIUM ALLOYS EMBRITTLED BY MERCURY
Authors: Pargeter F. W. J. , Ives M. B.
Published: April 2011

Polycrystalline specimens of α-phase copper–aluminium alloys of varying composition, amalgamated with mercury, have been deformed in tension in a soft tensile machine. In all cases, brittle intergranular failure occurred at stresses and strains below those required for fracture in air, the degree of embrittlement increasing with increasing aluminium content. The alloys having stacking-fault energies less than '~8 erg/cm2 were found to obey quite well the Petch–Stroh relation:[Formula: see text]The other alloys showed deviations from this relation which became more marked with increasing stacking-fault energy. Values of the fracture energy, varying from ~48 erg/cm2 for pure copper to ~470 erg/cm2 for Cu −8 wt.% Al, have been obtained for all of the alloys. These values are only applicable for relatively small grain sizes.The deviation from the Petch–Stroh relation in the high stacking-fault energy alloys is thought to be due to their tendency to show cross-slip and cellular-network formation, rather than coplanar arrays of dislocations as required by the Stroh model. The low stacking-fault energy alloys typically show well-defined pileups and so obey the Petch–Stroh relations, as expected.
THE POLARIZATION CHARACTERISTICS OF Pi-2 MICROPULSATIONS AND THEIR RELATION TO THE DETERMINATION OF POSSIBLE SOURCE MECHANISMS FOR THE PRODUCTION OF NIGHTTIME IMPULSIVE MICROPULSATION ACTIVITY
Authors: Rostoker Gordon
Published: April 2011

From the analysis of 20 separate events it is shown that Pi-2 micropulsations are polarized in an anticlockwise sense in the horizontal plane at northern-hemisphere mid-latitude stations. Combined with the knowledge that in the southern hemisphere polarization is predominantly in the clockwise sense, it can be inferred that at least the last part of the propagation path of the Pi 2 from the auroral zone to the observing station is traversed in the Alfvén mode. The presence of occasional pulsations possessing clockwise polarization in the northern hemisphere and anticlockwise polarization in the southern hemisphere suggests that the Alfvén mode alone is insufficient to explain the mode of propagation of a Pi 2. It is shown how ionospheric screening may influence the direction of polarization of a micropulsation. It is found that the initial kick of a Pi-2 micropulsation is strongly related to the sign of the accompanying geomagnetic bay. Deviations from this trend are discussed and it is shown that the Pi-2 micropulsation train and the initial kick may be considered as two separate effects. A theory for the origin of Pi-2 micropulsations is proposed.
THE EFFECTS OF PARTICLE RADIATION FROM A DISTURBED SUN ON ATMOSPHERIC ELECTRICITY
Authors: Pakiam J. E. , Johnson D. W.
Published: April 2011

In Section I, it is shown, from a consideration of atmospheric-electric theory and of the radiation emitted from a disturbed Sun, that the corpuscular solar radiation has little effect on atmospheric-electric conditions at ground level.Though the aurora and associated bremsstrahlung ionization should have little or no effect at ground level, several observers have found some correlation. For this reason, experimental measurements of potential gradient and air conductivity were taken at Saskatoon and at Churchill to investigate any apparent relationship between the aurora and atmospheric electricity (Section II). Statistical analysis revealed no definite relationship between aurorae and potential gradients or air–earth current densities over the period of a night. Large fluctuations in potential gradient (and often of air conductivity) were encountered at night, sometimes even coincident with the occurrence of aurorae. However, these fluctuations were considered to be due to the formation of space-charge packets due to low wind speeds.
TRIPLET-STATE ROTATIONAL ENERGY LEVELS FOR NEAR-SYMMETRIC ROTOR MOLECULES OF SYMMETRY C2v, D2, AND D2h
Authors: Creutzberg F. , Hougen J. T.
Published: April 2011

The ideas involved in Hund's coupling cases for diatomic molecules are extended to allow the definition of three coupling cases, (a), (ab), and (b), for the triplet states of orthorhombic polyatomic molecules. Case (a) is dealt with by second-order perturbation theory. Case (b) has recently been discussed by Raynes. Case (ab), which can be subdivided into types I, II, and III, is studied by examining the results of numerical calculations for selected values of the rotational constants, rotational quantum numbers, and spin-splitting parameters for a near-prolate rotor. The assignment of symmetry species to the various spin-rotational functions under consideration is described.
ELECTRON TRANSFER TO MULTIPLY CHARGED IONS OF Ar, N2, N, AND O2
Authors: McGowan J. William , Kerwin Larkin
Published: April 2011

Cross sections for the transfer of one and of two electrons to fast doubly charged ions of Ar, O, N2, N, and to the triply charged ion of Ar are presented. The 20/02 reaction of Ar++ in Ar is resonant and smaller than that for Ar+ in Ar. The nonresonant, single-charge transfer process 20/11, even though it is exothermic, required that 12.5 ± 2.0 eV be transferred to the reaction from the kinetic energy of the projectile for the reaction to go. Consequently, the scatter of the fast Ar+ products is very large. Similarly, large scatter is observed for the double-electron transfer to Ar+++ as the ion traverses an argon target. Unlike the above, however, single- and double-electron transfer to O++ from O2 and to N2++ from N2, double transfer from Ar to Ar++, and single and triple transfer from Ar to Ar+++ show but small scatter.
THE 199Hg(n, γ)200Hg REACTION WITH THERMAL NEUTRONS
Authors: Bartholomew G. A. , Naqvi S. I. H. , Gunye M. R. , Earle E. D.
Published: April 2011

Thermal neutron-capture γ rays from 199Hg(n, γ)200Hg were studied with a lithium germanium detector and with angular correlation techniques. Gamma-ray and level energies were determined with accuracies of at best ±3 keV. Spin 0 for the capturing state was confirmed and levels at 1 569, 2 060, 2 369, 2 640, 3 186, 3 269, 3 289, 3 351 keV were assigned spin 1. The 200Hg level scheme is discussed.
RADIATION FROM A STRIP OF ELECTRIC CURRENT IN A MAGNETOIONIC MEDIUM
Authors: Wunsch A. D.
Published: April 2011

The radiation resistance of a strip of electric current immersed in a cold magnetoplasma is investigated. The current is assumed to flow in a direction perpendicular to the static magnetic field. Integral expressions are obtained for the radiation resistance of a Hertzian dipole and for a current strip of finite width and length. Numerical results covering a wide range of frequencies are presented for both of the sources. It is shown that there are two frequency ranges where the radiation resistance of the Hertzian dipole is infinite, while the radiation resistance of the strip is finite everywhere except at the upper hybrid resonance frequency. The way in which the length of the strip influences its radiation resistance is discussed.
NUCLEAR g FACTORS OF THE FIRST EXCITED STATES OF 76Se AND 122Te
Authors: Murray J. , McMath T. A. , Cameron J. A.
Published: April 2011

The nuclear g factors of the first excited states of 76Se and 122Te have been measured by observing the rotation of gamma-ray angular correlations. The perturbing magnetic fields used were the internal fields in dilute iron alloys. The values obtained for the g factors are[Formula: see text]
DIFFRACTION OF A PLANE ELECTROMAGNETIC WAVE BY AN INFINITE SET OF PARALLEL METALLIC PLATES IN AN ANISOTROPIC PLASMA
Authors: Wu C. P.
Published: April 2011

The diffraction of a plane electromagnetic wave by an infinite set of parallel metallic plates is considered. The plates are assumed to be vanishingly thin and infinitely conducting, and are immersed in a cold plasma which is rendered anisotropic by an external magnetostatic field parallel to the edges of the plates. An exact solution is obtained by using the Wiener–Hopf technique for the case in which the fields have no variation in the direction of the external static magnetic field.It is found that, because of the anisotropy of the medium, the reflection becomes nonvanishing for the TM mode incident normally at the interface between the parallel plates and the free plasma regions. Also, the reflection coefficient is no longer an even or odd function of the angle of incidence. When the degree of anisotropy is relatively small, the results practically reduce to those in an isotropic dielectric, except that the phase functions of the reflection and transmission coefficients would experience a rapid variation for small incident angles. Some numerical examples showing the effects of anisotropy are given.
BISTATIC SCATTERING BY A THIN, LOSSY CYLINDRICAL WIRE
Authors: Breithaupt R. W.
Published: April 2011

A variational solution to the problem of bistatic scattering by a thin, lossy, solid, circular wire of length 2l is given. The amplitude of the far scattered electric field is given by an expression stationary for small differences between the assumed and actual axial current distribution. The ratio of absorbed to scattered power is calculated using the forward scattering theorem, and the result compared with that of FitzGerrell. Solutions are given for zero and first-order assumed current distributions.
MULTIPOLARITIES OF PRIMARY γ RAYS IN 199Hg(n, γ)200Hg AND PARITIES OF LEVELS IN 200Hg
Authors: Bartholomew G. A. , Gunye M. R. , Earle E. D.
Published: April 2011

Linear polarization correlation measurements show that the "anomalous intensity" region, Eγ > 4.5 MeV, of the spectrum of γ rays following thermal neutron capture in 199Hg contains predominantly E1 γ rays and that levels at 1.57, 2.06, 2.37, 2.64, 3.19, 3.27, and 3.29 MeV in 200Hg have positive parity.
THE SURFACE TENSION OF LIQUID HELIUM I AND THE LAW OF CORRESPONDING STATES
Authors: Devaraj N. , Hallett A. C. Hollis
Published: April 2011

Measurements have been made by determining the force necessary to break the liquid film between the edge of a suspended metal ring and the liquid surface. The results obtained are about 13% larger than those given by Allen and Misener (1938), and the variation of the surface tension, γ, with temperature T fits quite well the equation γ = 0.600 (1 − T/Tc)1.04 dyne cm−1, where Tc is the critical temperature. Comparison with other liquids has been made following de Boer's formulation of the law of corresponding states, and the reduced equation γ = (γ0*/Tc*n) (Tc* − T*)n describes the results, (γ0*/Tc*n) and n being functions of the quantum parameter Λ*; the classical limit of (γ0*/Tc*n) is found by extrapolation to be 2.2.
ON THE HYPERFINE STRUCTURE OF TRIVALENT CHROMIUM IN A CUBIC ENVIRONMENT
Authors: Woonton G. A. , Dyer Glenn L.
Published: April 2011

Measurements have been made by the Endor technique on the trivalent chromium ion 53Cr present as a dilute substitutional impurity in a magnesium oxide crystal. The energy levels of the ion are described by the spin Hamiltonian:[Formula: see text]Measurements have been made along the cube axes of the crystals and at 45° to the cube axes in a plane that contains two cube axes. Energy levels in these directions are predicted within a probable error of 3 × 103 Hz. The values of the parameters in the spin Hamiltonian have been found to be:[Formula: see text]The operators used in this Hamiltonian are derived and discussed.
NUCLEOSYNTHESIS IN SUPERNOVA SHOCK WAVES
Authors: Truran J. W. , Arnett W. D. , Cameron A. G. W.
Published: April 2011

It is generally assumed that element synthesis will take place readily under the extreme conditions believed to exist in supernova explosions. We have examined the types of thermonuclear reactions that can occur in a supernova shock wave which propagates through the stellar envelope, in which a temperature ~5 × 109 °K may occur for ~10−2 seconds. The calculations are performed using a network of nuclei connected to their neighbors by absorption or emission of neutrons, protons, alpha particles and photons (Truran et al. 1966). The results show that iron-peak elements can be produced by a supernova shock wave, but the iron-peak composition observed in nature is not produced unless some transformation of protons to neutrons has taken place in the material before the passage of the shock wave. Furthermore, a neutron flux sufficient to drive the rapid neutron-capture process is not attained under these conditions in the stellar envelope.
DETECTION AND MEASUREMENT OF PRECURSOR IONIZATION IN AN ELECTROMAGNETIC SHOCK TUBE
Authors: MacVicar-Whelan P. J. , Smy P. R.
Published: April 2011

Precursor ionization in an electromagnetic shock tube has been detected with various devices and measured with a double probe. The electron densities calculated from the double-probe results are in agreement with measurements obtained by other workers with different techniques and the electron temperatures are in the range 1–10 eV. The responses of various detection devices are in agreement with these results.
THE DIELECTRIC CONSTANT OF BROMINE AT MICROWAVE FREQUENCIES
Authors: Dagg I. R. , Reesor G. E. , Doble R. P.
Published: April 2011

Measured values of the real part of the dielectric constant, ε′, and the loss tangent, tan δ, of liquid bromine at 20 °C in the frequency range 8.2–18 GHz are presented. The results for tan δ were obtained by a previously described technique; the results for ε′ were obtained by an improved method herein described. A suggested mechanism for absorption is discussed and the results related to static values and values in the optical range.
A CONJECTURE REGARDING QUANTIZED GRAVITATIONAL THEORY AND THE SIZE OF ELEMENTARY PARTICLES
Authors: Rosen Gerald
Published: April 2011

For the quantum theory of general relativity in the real physical universe with radius of about 1028 cm, the order-of-magnitude analysis in this work leads to a fundamental and characteristic metrical disturbance, with a size of about 10−12 cm. It is possible that such a characteristic metrical disturbance (and the considerable amount of associated gravitational energy) may play an important role in elementary particle structure.
HIGH-FREQUENCY BACKSCATTERING FROM AN ABSORBING INFINITE STRIP WITH ARBITRARY FACE IMPEDANCES
Authors: Bowman John J.
Published: April 2011

Approximate expressions are derived for the high-frequency electromagnetic backscattering from an absorbing infinite strip on which an impedance boundary condition is imposed. Each face of the strip is assumed to possess an arbitrary constant surface impedance not necessarily equal to that of the other face. The problem is treated by a method of successive approximations based on known half-plane solutions; secondary (and in some cases, tertiary) diffraction effects are thereby included. Particularly important is the special case of a perfectly-conducting strip coated on one side with thin layers of highly refractive absorbing materials. Some experimental results of backscattering from an absorber-coated rectangular plate are presented and discussed in the light of the theoretical model.
EFFECT OF TEMPERATURE ON THE PENETRATION OF HEAVY keV IONS IN MONOCRYSTALLINE SOLIDS: II. VARIOUS IONS IN GOLD, ALUMINIUM, AND TUNGSTEN
Authors: Howe L. M. , Channing D. A.
Published: April 2011

The influence of atomic thermal motion on the penetration of various heavy keV ions incident along low index channels of single crystals of gold, aluminium, and tungsten has been investigated over the temperature range 15–295 °K. In general, in gold and aluminium the effect of thermal vibrations on the slowing down of the bombarding ions was quite pronounced, whereas a less marked effect was observed in tungsten. The magnitude of the temperature effect was dependent upon the type of bombarding ion and it is suggested that this is due, to a large extent, to the difference in the relative importance of electronic to nuclear stopping along the channel in the various systems. Thermal effects on the stability of the channeled trajectories are also believed to be important. The penetration of the channeled ions was observed to decrease exponentially with increasing temperature. In addition, the magnitude of the temperature effect was found to be relatively insensitive to the bombardment direction for incidence along the more open channels.
ON THE POLAR IMPURITIES TRAPPED IN AN IONIC CRYSTAL MATRIX
Authors: Chandra Suresh , Agrawal Vinai Krishna
Published: April 2011

A method for obtaining the values of the dipole moment of polar impurities trapped in an ionic crystal matrix has been given. The dipole moment in a crystal matrix is taken to be the sum of the gaseous dipole moment and the induced moments due to the presence of the polarizable ions.
SPIN-LATTICE RELAXATION IN SOLUTIONS OF ELECTROLYTES: I. RELAXATION OF 7Li AND 23Na IN AQUEOUS SOLUTIONS OF ALKALI HALIDES
Authors: Speight P. A. , Armstrong R. L.
Published: April 2011

The concentration dependence of the relaxation rates of 7Li and 23Na ion nuclei in aqueous solutions of alkali halides has been studied at 25 °C, using a pulsed magnetic resonance spectrometer operating at 3.75 MHz. The data are represented by empirical equations of the form:[Formula: see text]where T10−1 is the infinite dilution relaxation rate and C is the solute molarity. The infinite dilution rates are discussed with reference to the theoretical model considered by Hertz (1961). The concentration dependence is analyzed by using an extension of the method introduced by Eisenstadt and Friedman (1966) to include terms quadratic in the solute concentration.
THEORY OF TWO-PHOTON ABSORPTION
Authors: Guccione-Gush R. , Gush H. P. , Kranendonk J. Van
Published: April 2011

The two-photon absorption process is discussed using a density matrix formalism. The electromagnetic field is described by means of coherent states, a technique that permits a simple evaluation of the effect of coherence on the transition probability. It is concluded that the latter is the same for a coherent and an incoherent pulse of radiation. In the case of a stationary field containing many modes, the transition probability is nearly the same in the coherent and incoherent cases, whereas for a single mode the transition probability is twice as high for the incoherent field. These conclusions are independent of the multipole expansion of the interaction Hamiltonian and are valid for electric dipole and higher multipole transitions.
APPROXIMATE MOLECULAR ORBITALS: IV. THE 3dδg AND 4fδu STATES OF H2+
Authors: Cohen M. , McEachran R. P. , McPhee Sheila D.
Published: April 2011

Properties of the lowest even and odd δ states of the hydrogen molecule–ion have been calculated using approximate wave functions. These were derived using a combination of Rayleigh–Schrödinger perturbation theory and variational methods, which have been applied previously to calculate the corresponding wave functions of the lowest σ and π states. Our total molecular energies are in excellent agreement with the recent exact calculations of Hunter and Pritchard (1967). A simple criterion is suggested for judging the accuracy of the approximate orbitals, which indicates that all the molecular properties calculated will be accurate over a wide range of internuclear separations.
NONLINEAR DEMODULATION OF AN AMPLITUDE-MODULATED ELECTROMAGNETIC WAVE IN A PLASMA
Authors: Ram Sant , Arora A. K.
Published: April 2011

In this paper the authors have derived the expression for the electric vector when an amplitude-modulated electromagnetic wave propagates in a nonlinear dispersive medium. Demodulation is obtained in the case of a wave propagating in a nonlinear medium, whereas overmodulation has been obtained when the wave is reflected back in the free space from a plasma free-space interface. Some calculations have been performed in both cases and it has been found that the demodulation decreases with increasing electron density, with increasing index of modulation of the incident wave, and with increasing collision frequency. In the case of reflection the overmodulation is found to decrease with decreasing electron density, increasing index of modulation, and decreasing collision frequency inside the plasma. The calculated results have been presented in the form of tables in the Discussion.
ROTATIONAL ENERGY LEVELS OF STATES AND INTENSITIES IN TRANSITIONS: APPLICATIONS TO SOME HEAVIER HYDRIDES
Authors: Kopp I. , Hougen J. T.
Published: April 2011

Three topics concerning [Formula: see text] states are discussed: (1) The magnitude of the Ω-type splitting in a [Formula: see text] state arising from a Σ state of even multiplicity has been considered and is found to be given to a first approximation by [Formula: see text]. This result leads to the introduction and discussion of a coupling case (a′) for Σ states. (2) Expressions for the Λ-type splitting in a 2Π state and the spin splitting in a 2Σ state (caused by their mutual interaction via spin-orbit coupling) are derived. These expressions are valid when the rotational intervals are small compared to both the spin-orbit interaction and the 2Π−2Σ energy separation, but do not place any restriction on the relative size of the latter two quantities. (3) Branch intensity expressions are presented which apply to any [Formula: see text] transition in which the [Formula: see text] states are not contaminated (due to uncoupling phenomena) by states having a different value of Ω.
ELECTROREFLECTANCE MEASUREMENTS ON GaxIn1−xAs ALLOYS
Authors: Thompson A. G. , Woolley J. C.
Published: April 2011

The electrorellectance of GaAs, InAs, and the GaxIn1−xAs alloys has been measured between 2 and 6 eV at room temperature. The E1, E0′, and E2 transitions and their associated split-off and oscillatory components have been observed, and their behavior as a function of alloy composition is presented. A more detailed account of the band structure of the compounds and their alloys than was obtained by earlier reflectance results is given.
SENSITIZED FLUORESCENCE IN VAPORS OF ALKALI METALS: IX. ENERGY TRANSFER IN COLLISIONS BETWEEN SODIUM AND INERT GAS ATOMS
Authors: Pitre John , Krause L.
Published: April 2011

The total cross sections for inelastic collisions between sodium and inert gas atoms, leading to 3 2P1/2 ↔ 3 2P3/2 excitation transfer in sodium, have been determined in a series of sensitized fluorescence experiments with sodium – inert gas mixtures. The sodium vapor was maintained at a pressure of 5 × 10−7 mm Hg, at which there is no trapping of the resonance radiation, and the inert gas pressures ranged from 0 to 1 mm Hg. The cross sections Q1(3 2P1/2 → 3 2P3/2) and Q2(3 2P1/2 ← 3 2P3/2) are as follows: Na–He, 86.0 and 44.8 Å2; Na–Ne, 67.0 and 35.4 Å2; Na–Ar, 110 and 55.9 Å2; Na–Kr, 85.0 and 43.6 Å2; Na–Xe, 89.8 and 45.6 Å2. The ratios Q1/Q2 are in agreement with the value predicted from the principle of detailed balancing and the cross sections also agree, as to order of magnitude, with some theoretically predicted values.
THE 51V(n, γ)52V REACTION
Authors: Archer N. P. , Kennett T. J.
Published: April 2011

The gamma radiation following thermal neutron capture by vanadium has been studied using a Ge(Li) detector. A separation energy of 7 311 ± 2 keV was determined and the ground-state triplet was observed, confirming levels of 17 and 23 keV. Coincidence measurements were used to assist in the construction of a decay scheme which includes 97% of the total observed intensity. The agreement with (d, p) measurements is very good and permits one to conclude that essentially all of the observed transitions are E1. The lack of any correlation between reduced radiation widths and stripping strengths suggests the absence of direct capture.
EFFECTS OF EXTERNAL AND INTERNAL ELECTRIC FIELDS ON THE BORON ACCEPTOR STATES IN SILICON
Authors: White J. J.
Published: April 2011

Effects of various electrical perturbations on the boron acceptor states in silicon were studied using low-temperature absorption-line measurements.A uniform external electric field was applied to compensated boron-doped silicon and the "Stark effect" on the boron acceptor absorption lines was observed. The Stark shifts of the excited states were quadratic in the applied field. The Stark broadening of the acceptor absorption lines was attributed to an unresolved partial removal of degeneracy of the excited states. The internal Coulomb fields of ionized impurities also perturb neutral acceptor transitions, resulting in (a) "ionized impurity broadening" of the absorption lines by the screened Coulomb fields of thermally ionized impurities in uncompensated Si(B) silicon at T > 50 °K and (b) "compensation effects" on the absorption lines by the unscreened Coulomb fields of compensationally ionized impurities in Si(B, P) silicon at 4 °K. Observations of these two internal Coulomb held effects are related to the external-field Stark effects. The theories of ionized impurity broadening are discussed briefly and the observed properties of a new absorption line due to compensation are reported.
PERIODICAL FLUCTUATION STUDIES OF COSMIC-RAY DIURNAL VARIATIONS DURING THE QUIET-SUN PERIOD 1962–64
Authors: Kodama Masahiro
Published: April 2011

Statistical studies of periodic fluctuations of the cosmic-ray diurnal variation have been performed, using neutron and meson component data obtained by the high-counting-rate cosmic-ray monitors at Deep River. The data cover an interval from May 1962 to October 1964, a period of descending solar activity ending near the solar minimum. It is shown that a 27-day recurrence tendency of the amplitude of the diurnal variation occasionally appears as well as shorter recurrent variations, ranging from one-half to one-sixth of the solar rotation period. The correlations of these fluctuations with some typical solar and terrestrial indices are examined in order to search for possible origins of the shorter recurrent variations. A possible connection with the Kp index exists.
APPROXIMATE MOLECULAR ORBITALS: V. THE 3dδ STATE OF HeH++
Authors: Cohen M. , McEachran R. P. , McPhee Sheila D.
Published: April 2011

The techniques of Rayleigh–Schrödinger perturbation theory and variational methods have been used to obtain an approximate molecular wave function for the lowest δ state of the HeH++ ion. Its accuracy may be judged by a simple criterion proposed in an earlier paper, and molecular properties computed using it should have high accuracy. The main conclusions of this series of papers are reviewed briefly.
RELIABILITY OF ELECTRONIC ENERGY CALCULATIONS BY A MODIFIED LOCAL-ENERGY METHOD
Authors: Rourke T. A. , Stewart E. T.
Published: April 2011

This statistical study of the performance of a modified local-energy method using random selection shows that there is little advantage in using large numbers of electron positions, the quality of the wave functions being a much more significant factor. A relationship is given between the quality of the wave function and the resulting accuracy. Use of as few as 25 sets of electron positions is suggested.A method of avoiding the increase in the calculation time with the size of a system is given and was found to be very accurate in a simple situation.
PRESSURE-INDUCED INFRARED ABSORPTION OF GASEOUS HYDROGEN AND DEUTERIUM AT LOW TEMPERATURES: II. ANALYSIS OF THE BAND PROFILES FOR HYDROGEN
Authors: Watanabe A. , Welsh H. L.
Published: April 2011

Experimental profiles for the pressure-induced fundamental infrared band of hydrogen for a number of temperatures in the range 18–77 °K were analyzed by a computational procedure. Half-widths and peak intensities of 11 components, assumed to have a Boltzmann-modified dispersion line form, were obtained from the analysis. The contributions of the quadrupolar and overlap interactions to the total intensity, as well as their variation with temperature, showed good agreement with theoretical calculations on the exp–4 model.
DEPENDENCE OF THE POSITION OF THE OUTER RADIATION ZONE INTENSITY MAXIMA ON ELECTRON ENERGY AND MAGNETIC ACTIVITY
Authors: McDiarmid I. B. , Burrows J. R.
Published: April 2011

The outer Van Allen radiation zone is characterized by an intensity maximum at values of the magnetic shell parameter Lmax in the range 3.5–6 earth radii. Data from Alouette I and II along with data from other satellites have been used to determine the solar-cycle variation in Lmax as a function of electron energy. During the period 1960–1966, when the yearly mean of the daily KP sum varied from 25 to 14, the average value of Lmax for energetic electrons varied from 3.5 to 4.7 e.r. No change was observed in the average Lmax for 40-keV electrons during the period 1963–1966. The results are interpreted in terms of the diffusion theory of Tverskoy (1965) and imply a decrease in D0, the average diffusion coefficient, of at least a factor of 10 between the years 1960 and 1966.
SURFACE WAVES ALONG AN AXIALLY MAGNETIZED PLASMA COLUMN: I. SYMMETRIC MODES
Authors: Yip G. L. , Seshadri S. R.
Published: April 2011

The characteristics of surface waves excited by an axially oriented point electric dipole situated along the axis of an infinitely long; and axially magnetized column of uniform cold plasma are investigated. The surface waves are found to be slow waves and exist only below the upper hybrid resonant frequency. In the gyromagnetic and plasma resonance regions, the existence of an infinite number of discrete modes is noted. The dispersion curves are presented for different values of the strength of the applied magnetic field and the column radius. Also, the power transported by the surface waves is evaluated and is found to become infinite in the two resonance frequency regions. A technique for the removal of this singularity in the surface wave power is indicated.
TEMPERATURE DEPENDENCE OF PARAMAGNETIC NEUTRON SCATTERING
Authors: Sears V. F.
Published: April 2011

The effect of short-range order on the paramagnetic exchange broadening of magnetic neutron-scattering cross sections is investigated theoretically by expanding the second moment of the energy transfer in inverse powers of the temperature. The results are applied to terbium, where it is found that the first temperature correction gives a substantial improvement in the agreement between theory and experiment.
SUPERNOVA HYDRODYNAMICS AND NUCLEOSYNTHESIS
Authors: Arnett W. David , Cameron A. G. W.
Published: April 2011

The evolution of matter ejected from the [Formula: see text] core of a collapsing massive star is examined with regard to nucleosynthesis. This material is processed to such extreme conditions of temperature and density that a neutron-rich nucléon gas results. Upon expansion and subsequent cooling it appears that sufficient seed nuclei are formed for neutron capture on a fast time scale (r process) to proceed. Excess neutrons decay late in the expansion, but burn-back to 4He is likely. This results in production of nuclear energy late in the expansion, and can provide sufficient thermal energy to explain the observed light output of supernovae in terms of the increasing transparency of a hot expanding mass of gas.
MEAN LIFE OF THE MULTIPLE-POLE RESONANCE
Authors: Gien Tran Teong
Published: April 2011

The mean life of the multiple-pole resonance is calculated by different methods of approach. The inconsistency of the results makes it worthwhile to question the validity of the nonexponential decay laws.
ANHARMONIC CONTRIBUTIONS TO THE BULK MODULUS AND CHARACTERISTIC TEMPERATURES OF NEON AND ARGON AT T = 0 °K
Authors: Brown J. S. , Horton G. K.
Published: April 2011

Anharmonic contributions to the bulk moduli of Ne and Ar are calculated for Lennard-Jones (m–6) potentials and compared with the experimental results at T = 0 °K. We consider direct anharmonic contributions to the bulk moduli and the anharmonic contributions via the use of Brown's (1966) anharmonic potential parameters. Excellent agreement is found with the experimental results of Peterson, Batchelder, and Simmons (1966) and Batchelder, Losee, and Simmons (1967).We also study the effect of the anharmonic parameters on the Debye characteristic temperature obtained from Cν. Improved agreement with the experimental results is found.
STUDY OF THE 31P(n, γ)32P REACTION
Authors: Lycklama H. , Kennett T. J.
Published: April 2011

A total of 64 transitions were observed with an average precision of 2 keV in studying the gamma radiation from the 31P(n, γ)32P reaction using a Ge(Li) spectrometer. The neutron separation energy was measured to be 7 936 ± 1 keV. Comparison with (d, p) results indicates only a weak correlation between (n, γ) and (d, p) reduced widths. The reduced radiation widths follow a x2 distribution of ~2 degrees of freedom.
ORBIT ANALYZER PROBES FOR THE MEASUREMENT OF PLASMA TEMPERATURES
Authors: Loughran D. J. , Schott L. , Skarsgard H. M.
Published: April 2011

An investigation is presented of two different probes, of the magnetic analyzer type, in which the magnetic field used for analysis of the particle orbits is also present in the plasma. Both probes employ a current collector whose distance from the aperture plane is adjustable. One probe (the charge-selective probe) collects charged particles of one sign, while theother (the charge-insensitive probe) collects particles of both signs. Assuming a Maxwell–Boltzmann distribution of electrons, the current collection characteristics are calculated for each probe. The use of these current characteristics for the measurement of the electron temperature is discussed. A procedure is also given for obtaining the mean electron velocity perpendicular to the magnetic field in the case of a non-Maxwellian velocity distribution. Finally, methods for measuring the ion temperature are presented for the special case of a small Debye length compared with the ion Larmor radius.
INFINITE PLANAR AND COLLINEAR ARRAYS OF CYLINDRICAL ANTENNAS
Authors: VanKoughnett A. L.
Published: April 2011

The active impedance and current distribution on a cylindrical antenna in a uniform, infinite, planar or collinear array are examined. A Fourier series for the antenna current is derived by relating the electric field variation in the gaps between adjacent collinear elements to the current. The electric field in the gaps is expanded in a series of Chebyshev polynomials whose coefficients are found by solving the set of algebraic equations obtained by enforcing at a number of points the boundary condition that the current vanish in the gaps between the ends of adjacent elements. The analysis is suitable for any combination of element length and scan angle, provided that the distance between the ends of adjacent collinear elements is comparable to or less than the element length. Results are compared with those based upon sinusoidally distributed currents and discrepancies are noted for arrays with closely spaced collinear elements and for wide H-plane scan angles of planar arrays.
CONSTRUCTION OF RARITA-SCHWINGER FIELDS AND INTERACTION LAGRANGIANS FOR FIELDS WITH ARBITRARY SPIN
Authors: Wilson William A.
Published: April 2011

The formal connection between Rarita-Schwinger fields and fields which have no subsidiary conditions is made, using the Lorentz transformation properties of the fields. By employing this formal connection, the most general interaction Lagrangians, which couple fields with arbitrary spin, are constructed.