bluuebunny/crossref_metadata_2025 huggingface dataset:
RADIATION EFFECTS IN PRECISION RESISTANCE THERMOMETRY: I. RADIATION LOSSES IN TRANSPARENT THERMOMETER SHEATHS
Authors: McLaren E. H. , Murdock E. G.
Published: April 2011

Standard platinum resistance thermometers that are constructed with transparent sheaths of fused silica or pyrex glass are subject to thermal losses arising from losses of visible and near-infrared radiation up (piping) and through these sheaths. This heat loss may introduce substantial errors in temperature determinations; e.g. 0.084, 0.015, and 0.001 1 °C at the Sb, Zn, and Sn fixed-temperature points for a fused-silica sheath, or 0.000 2 °C at the Zn and Sn points for a pyrex sheath. This effect has been investigated in detail for thermometers of various types at the Sb, Zn, and Sn points, and it has been shown that simple stem radiation-traps, consisting of a blackening or roughening of the smooth outer surface of the thermometer sheaths, will eliminate these errors and greatly improve the immersion characteristics of the thermometers.Suitable radiation-trapping should be incorporated on the stems of every transparent-sheathed standard platinum resistance thermometer; without strong evidence to the contrary, radiation loss errors of the orders of magnitude cited above should be suspected in reported measurements involving resistance thermometers having unprotected transparent fused-silica sheaths.
APPROXIMATE MOLECULAR ORBITALS: II. THE 2pπu AND 3dπg STATES OF H2+
Authors: Cohen M. , Dorrell Brenda H. , McEachran R. P.
Published: April 2011

Simple analytic wave functions for the lowest even and odd π states of H2+ have been obtained by the procedures described in the first paper of this series. Their accuracy is somewhat higher than that of the lowest σ states treated earlier.
HARTREE–FOCK WAVE FUNCTIONS FOR EXCITED STATES: II. SIMPLIFICATION OF THE ORBITAL EQUATIONS
Authors: Cohen Maurice , Kelly Paul S.
Published: April 2011

Hartree–Fock wave functions have been calculated for a number of excited states of the helium sequence, the wave functions being constrained to be orthogonal to all lower state functions. The effect of choosing the inner 1s orbital so that the orthogonality constraint is satisfied automatically has been examined, and it is shown that such a choice has a very small effect on the total energy. An extension to heavier systems is proposed.
SOME CHARACTERISTICS OF THE LOWER HYBRID RESONANCE NOISE BANDS OBSERVED BY THE ALOUETTE I SATELLITE
Authors: McEwen D. J. , Barrington R. E.
Published: April 2011

An investigation has been made of the occurrence as a function of latitude and time of lower hybrid resonance (LHR) noise bands as recorded during 1963 and 1964 by the very-low-frequency receiver aboard the Alouette I satellite. Two different types of LHR noise are observed—polar and mid-latitude. Polar LHR noise bands, with the maximum frequency of occurrence at about 75° invariant latitude, are observed approximately one half of the time throughout the year and during both night and day. Mid-latitude LHR noise bands have a maximum frequency of occurrence at about 55° and are observed mainly during the months of June–October and primarily at night. The differences in appearance and occurrence of these two types of LHR noise suggest different excitation mechanisms.
THE EFFECT OF RESONANCE SCATTERING ON THE CRITICAL TEMPERATURE OF ANISOTROPIC SUPERCONDUCTORS
Authors: Zuckermann M. J. , Singh A. D.
Published: April 2011

In a previous paper, the effect of a nonmagnetic resonant d orbital (bound to a transition-metal impurity) on a simple isotropic superconductor was discussed. It was shown that the critical temperature Te of such an alloy suffered an initial linear decrease proportional to the impurity concentration NI. The resulting curve of Te versus NI remains linear for experimentally realizable values of the impurity concentration. However, this is not borne out experimentally and one reason for the discrepancy is that the anisotropy of the superconductor was not taken into account theoretically. In this paper, it is shown that the change in Te due to the presence of nonmagnetic transition-metal impurities is given by the sum of three terms, as follows: (a) the isotropic term due to the interaction of the d orbital with the conduction electrons found in the previous paper, (b) the usual term due to the "anisotropic effect" of Markowitz and Kadanoff (1963), and (c) a cross term between the resonance scattering and the anisotropic scattering. The term (c) is shown to be very small compared with (a) and (b) and hence the procedure for comparison with experiment used by Boato et al. (1966) is justified in our approximation.
TUNNELING INVESTIGATION OF ENERGY-GAP ANISOTROPY IN SUPERCONDUCTORS
Authors: Campbell C. K. , Walmsley D. G.
Published: April 2011

Tunneling measurements of the energy gaps at T ≈ 1.2 °K in thick [Formula: see text] and thin [Formula: see text] films of aluminium, lead, indium, and tin are reported. The thin films have isotropic gaps consistent with the Anderson theory of dirty superconductors; the thick films all exhibit behavior that may be interpreted as due to the existence of multiple gaps.
THE b1Σ+–X3Σ− BAND SYSTEM OF NCl
Authors: Colin R. , Jones W. E.
Published: April 2011

When a mixture of N2 and Cl2 is pumped rapidly through a mild microwave discharge, an orange afterglow is observed downstream from the discharge. The spectrum of this weak emission consists of a prominent double-headed band, the strongest head lying at 6 648.6 Å, and a number of weaker similar bands forming three sequences. Observed isotopic shifts have been used to identify the emitter as NCl. The rotational analysis of the strongest (0–0) band, photographed with high resolution, shows that these bands represent the b1Σ+–X3Σ− transition of the NCl molecule. The vibrational and rotational constants were determined for both states; we find ωe′ = 935.6 cm−1, ωo″ = 827.0 cm−1, γ0′ = 1.565 3 Å, and γ0″ = 1.608 3 Å.
ON THE ANALYSIS OF GLOW CURVES
Authors: Kelly P. J. , Laubitz M. J.
Published: April 2011

Exact expressions for trap depths are derived from the analysis of first-order and second-order theoretical glow curves. These expressions are compared with some of the currently used approximate expressions and it is shown that errors in trap-depth energies of 20% or more are possible when some of the latter are used. A method of analyzing complex glow curves is also presented and discussed.
EXCITED STATES OF 16O IN THE HARTREE–FOCK (H F) APPROXIMATION
Authors: Muthukrishnan R.
Published: April 2011

The intrinsic 4-particle – 4-hole state of 16O is calculated in the Hartree–Fock approximation. The energy and single-particle levels are compared with previous calculations and some observations regarding the two-nucleon interaction are made.
ON THE ROLE OF STACKING FAULTS IN SOME PROBLEMS OF GLIDE AND TWINNING IN CUBIC METALS
Authors: Escaig B. , Fontaine G. , Friedel J.
Published: April 2011

The possible role of stacking faults is discussed in some problems of glide and twinning of cubic metals, especially at low temperatures.The first part analyzes a model for the thermal variation of macroyield in b.c.c. metals. If one assumes that the dislocations of such metals split along either the (110) or the (112) planes, the screw dislocations will be sessile. The strong temperature variation of macroyield could be due to the thermally activated slip of such screws, previously developed at lower stresses during the less temperature-dependent microyield. Reasonably high stacking-fault energies are required for satisfactory numerical fits.The second part studies the influence of a dense dislocation network on the propagation of a stacking fault. The friction force acting on the partial that propagates the fault must be taken into account when deducing a stacking-fault energy from the stress at which stacking faults develop in a strongly work-hardened (f.c.c.) metal. The trails of dipoles left at each tree crossed should prevent any creation of point defects; they should lead, after the faults have propagated some length, to its multiplication into a twin or martensitic lamella. The analogies with problems of slip bauds and dipole formation in easy glide are stressed.
APPLICATION OF X-RAY TOPOGRAPHY TO THE ANALYSIS OF THE DISLOCATION ARRANGEMENT IN DEFORMED COPPER SINGLE CRYSTALS
Authors: Wilkens M.
Published: April 2011

The paper deals with the application of Berg–Barrett X-ray topography to deformed copper single crystals. The imaged surfaces were sectioned from the deformed bulk crystals parallel to low-index planes.In stage I of the work-hardening curve, the braids of primary edge-dislocation dipoles, well known from electron transmission microscopy, have been observed over lengths of several tenths of a millimeter. Whereas in stage 1 the slip appears to be rather homogeneous and without strong interaction between primary and secondary slip systems, the transition region to stage 11 displays, as a characteristic feature, a systematic interaction of both types of slip systems, giving rise to layer-like dislocation structures about parallel to the primary slip plane. These layers, as in stage 11, are connected with a special type of lattice rotation. In stage II, dislocation walls or wall fragments perpendicular to the primary slip direction are observed. Generally, these walls are accompanied on either side by an extended region with an excess density of primary edge dislocation of one sign ("kink-walls"). As an example, the excess density at a flow stress τ ≈ 1–2 kg/mm2 is found to be of the order of 108/cm2.
THE DEFORMATION OF NIOBIUM SINGLE CRYSTALS
Authors: Foxall R. A. , Duesbery M. S. , Hirsch P. B.
Published: April 2011

Various orientations of single crystals of niobium, purified by ultra-high vacuum annealing, have been tested in compression at 295 °K and in tension at temperatures between 77 °K and 295 °K. The shear stress – shear strain curves show three-stage hardening in a manner similar to f.c.c. crystals. Analysis of the orientation dependence of the operative slip system suggests an asymmetry in the critical resolved shear stress for slip on {112} planes which increases with decreasing temperature. Explanations for this in terms of the various ways in which a [Formula: see text] type screw dislocation can dissociate have been proposed. It is found that dissociation on two {112} planes or composite dissociation on {110} and {112} planes leads to a satisfactory qualitative explanation of the experimental results.The dislocation distribution occurring as a function of strain has been studied for crystals of a single glide orientation deformed in tension at 295 °K. [Formula: see text] sections from crystals deformed into stage I contain clusters of primary edge dipoles. The density of secondary dislocations is low (~10%). Sections from crystals deformed into stage II were chosen such that the three-dimensional nature of the dislocation arrays could be investigated. The distribution shows strong similarities to those observed in copper crystals (Steeds 1966), i.e. edge multipole walls, tilt and twist boundaries. The density of secondary dislocations is high, being of the same order as the primary density.
DISLOCATION CONTRIBUTION TO THE FLOW STRESS OF POLYCRYSTALLINE IRON
Authors: McLean D.
Published: April 2011

New information confirms the existing evidence that, after subtracting any friction stress, the flow stress during cold work and creep of polycrystalline iron is determined mainly by the attractive junctions and general stress field of the three-dimensional dislocation network. Thus, recent experiments show none of the preference among the dislocations for the screw orientation that would be expected if jogs in screw dislocations were a main factor, and the grain boundaries during cold work and the subboundaries during creep also have no direct influence. On the other hand, the three-dimensional network is of the tightly linked type envisaged by this theory, and therefore contains a concentration of attractive junctions as well as of dislocations which fits the theory. The unevenness of the three-dimensional network, when the well-known cellular dislocation pattern has developed, does not affect the quantitative relationship between flow stress and network density, probably because it is the average density which is always measured and the weakest links which always determine the flow stress. The average proportionate contributions to the flow stress from the various sources are more or less calculable, but the actual contributions at individual weak links must vary greatly.
DEFORMATION OF ALUMINIUM AT HIGH TEMPERATURES AND STRAIN RATES
Authors: McQueen H. J. , Wong W. A. , Jonas J. J.
Published: April 2011

The steady-state flow stress, σ, of commercial purity aluminium was determined by extrusion over a range of temperatures, T, from 255–616 °C, and strain rates, [Formula: see text], between 0.1–10 sec−1. The data are shown to fit the relationship[Formula: see text]where A, α, and n′ are constants. The activation energy, ΔH, for aluminium extrusion was determined to be 41.8 kcal/mole, a value somewhat higher than that of self-diffusion. The dislocation substructures produced during extrusion were examined by transmission electron microscopy. The equilibrium subgrain size was found to vary inversely with the logarithm of the Zener–Hollomon parameter, [Formula: see text], and with the extrusion flow stress.
OBSERVATION OF THE TRANSVERSE STERN–GERLACH EFFECT IN NEUTRAL POTASSIUM
Authors: Bloom Myer , Enga Eric , Lew Hin
Published: April 2011

A successful transverse Stern–Gerlach experiment has been performed, using a beam of neutral potassium atoms and an inhomogeneous time-dependent magnetic field of the form[Formula: see text]A classical analysis of the Stern–Gerlach experiment is given for a rotating inhomogeneous magnetic field. In general, when space quantization is achieved, the spins are quantized along the effective magnetic field in the reference frame rotating with angular velocity ω about the z axis. For ω = 0, the direction of quantization is the z axis (conventional Stern–Gerlach experiment), while at resonance (ω = −γH0) the direction of quantization is the x axis in the rotating reference frame (transverse Stern–Gerlach experiment). The experiment, which was performed at 7.2 Mc, is described in detail.
PROTON-NUCLEUS REACTION CROSS SECTIONS COMPUTED FROM ELASTIC-SCATTERING DATA
Authors: Sannes F. , Stairs D. G.
Published: April 2011

Proton-nucleus reaction cross sections in the energy region from 90 to 300 MeV are computed from elastic-scattering data. The interference of the nuclear scattering amplitude with the calculable Coulomb scattering amplitude determines the magnitude and phase of the nuclear amplitude when the differential elastic-scattering cross section is known. The reaction cross section is then obtained by an application of the optical theorem.
NEW HIGH-SPIN LEVELS IN 20Ne
Authors: Kuehner J. A. , Almqvist E.
Published: April 2011

Levels of 20Ne at excitation energies of 10.57, 12.19, and 13.39 MeV have been formed in the 12C(12C, α)20Ne reaction. Angular correlations of deexciting alpha particles have been measured, leading to spin and parity assignments of 4+, 6 +, and 7−, respectively. Level energy systematics and systematics of reduced alpha-particle widths suggest that these levels be associated with rotational bands.
RESPONSE OF MU-MESON DETECTORS DEEP IN THE ATMOSPHERE TO PRIMARY COSMIC-RAY PARTICLES OF MAGNETIC RIGIDITY BETWEEN 10 AND 25 GV
Authors: Mathews T. , Sivjee G. G.
Published: April 2011

The cosmic-ray mu-meson intensities at three different altitudes at the equator were measured as a function of zenith and azimuth angles by means of a portable scintillation counter telescope of semi-opening angles 23°. The data were analyzed to assess the effects of differences in pi- and mu-meson decay rates on the intensity of the penetrating ionizing component at different zenith angles. It was found that the changes of intensity as a function of zenith angles could be attributed almost entirely to differences in atmospheric absorption, provided that at all zenith angles the threshold rigidities were the same. Hence the intensities measured at different zenith angles in the east–west plane at the equator could be corrected to remove the atmospheric effects and the corrected data used for determining the response of meson detectors at sea level to particles of rigidity up to 25 GV. The response curve thus obtained is presented and compared with that obtained from sea-level latitude surveys by means of ionization chambers.
STUDY OF SOME 20Ne LEVELS BY RADIATIVE CAPTURE
Authors: Litherland A. E. , Ollerhead R. W. , Smulders P. J. M. , Alexander T. K. , Broude C. , Ferguson A. J. , Kuehner J. A.
Published: April 2011

Four resonances in the reactions 16O(α, γ)20Ne and 4He(16O, γ)20Ne have been studied using gas targets of oxygen and helium. Resonances at 5.374, 6.930, and 7.940 MeV alpha-particle bombarding energy had been observed previously using the first reaction. In this experiment, an additional resonance was found at 5.075-MeV alpha-particle bombarding energy. This resonance level decays by a prominent cascade of gamma rays through the 4+, 4.25-MeV level in 20Ne and can be identified with a 6+, 8.79-MeV level in 20Ne observed previously in the 12C(12C, α)20Ne reaction. A comparison of the yield of the new resonance with one previously reported gives a value of ωγ = 1.8 ± 0.4 eV, which implies an E2 strength of 28 ± 6 Weisskopf units for the 6+ to 4+ transition.
A STATISTICAL THEORY OF APERTURE SYNTHESIS
Authors: Gagnon Ralph J.
Published: April 2011

The usual methods of interferometry make use of the Fourier transform relationship which holds between a radio-noise brightness distribution and the complex visibility function which is measured with a pair of antennas. The visibility function is a function of the distance or base line between the antennas. If it were known for all base lines, then the brightness distribution could be found by Fourier inversion. Unfortunately, the visibility function is not known for all base lines and the Fourier inversion is not unique. If the observer wishes to interpret his data by displaying a single possible brightness distribution, then he must choose from the infinite set of brightness distributions which could have produced his data. Previously, the author suggested that this be accomplished by representing the set of possible distributions as a statistical ensemble, and making the choice on a statistical basis so as to minimize the expected mean-square error.In the present communication, the results of the previous paper are presented for the two-dimensional case. The inversion formulas are worked out in detail for the cases of uniform point-source distributions in a square (or rectangle) and in a circular disk, and also for a point-source distribution with a Gaussian envelope taper. It is shown how to extend the point-source results to a distribution of nonpoint sources, and as an example the inversion equations are computed for the case of a distribution of Gaussian-shaped sources distributed with a Gaussian amplitude or density envelope. Finally, the appropriate inversion equations are derived for an observed visibility function which is contaminated with additive zero-mean Gaussian random noise, uncorrelated with the true visibility function.
SOME DYNAMICAL PROPERTIES OF THE ISING FERROMAGNET
Authors: Matsudaira Noboru
Published: April 2011

Time-dependent statistics of the Ising model proposed by Glauber for the one-dimensional chain are extended to the example of a two-dimensional square lattice. Each spin is assumed to change its state through the interaction with a heat bath. The equations of motion for both the single spin and the spin correlation functions are solved approximately by using a decoupling procedure where the many-body correlation functions are taken as sums of products of pair correlation functions. As a special case, our theory allows the approximate calculation of the equilibrium properties of the system and it turns out that, in this case, our result is an improvement over the Bethe approximation. Both the frequency-dependent magnetic susceptibility and the decay of the magnetic moment to the equilibrium state are calculated above and below the Curie temperature. The fluctuation–dissipation theorem developed by Glauber for the linear chain is shown to hold in the two-dimensional case also.
APPROXIMATE MOLECULAR ORBITALS: III. THE 1sσ AND 2pπ STATES OF HeH++
Authors: Cohen M. , McEachran R. P. , McPhee Sheila D.
Published: April 2011

A combination of Rayleigh–Schrödinger perturbation theory and variational techniques, previously used to calculate the wave functions of the lowest σ and π states of H2+ has been applied to the 1sσ and 2pπ states of HeH++. The accuracy of the resulting approximate wave functions is demonstrated by comparing a number of quantities calculated with them with the corresponding exact values.
HYPERFINE STRUCTURE IN THE GROUND CONFIGURATION OF BISMUTH
Authors: Dickie L. O. , Kelly F. M.
Published: April 2011

The hyperfine structure of the 2D3/2 and 2P1/2 levels of the 6p3 ground configuration of Bi I has been determined from the h.f.s. of the λ 4 722 Å and λ 4 121 Å lines of the arc spectrum. The spectrum was excited in a liquid nitrogen cooled hollow cathode source and the structure resolved with a Fabry–Pérot interferometer. The hyperfine interaction constants and the quadrupole moment have been calculated as follows: for 2D3/2,[Formula: see text]
THE ABSORPTION SPECTRUM OF CF2
Authors: Mathews C. Weldon
Published: April 2011

The absorption spectrum of CF2 in the 2 500 Å region has been photographed at high dispersion, and the rotational structure of a number of bands has been analyzed. The analysis of the well-resolved subbands establishes that these are perpendicular- rather than parallel-type bands, as previously assigned. Further analysis shows that the upper and lower electronic states are of 1B1 and 1A1symmetries respectively, corresponding to a transition moment that is perpendicular to the plane of the molecule. In the upper electronic state, r0(CF) = 1.32 Å and [Formula: see text], while in the ground state, r0(CF) = 1.300 Å and [Formula: see text]. An investigation of the vibrational structure of the band system has shown that the vibrational numbering in ν2′ must be increased by one unit from earlier assignments, thus placing the 000–000 band near 2 687 Å (37 220 cm−1). A search between 1 300 and 8 500 Å showed two new band systems near 1 350 and 1 500 Å which have been assigned tentatively to the CF2 molecule.
COMPARATIVE STUDY OF PHYSICAL PROPERTIES OF SOME ISOELECTRONIC SYSTEMS
Authors: Valdemoro Carmela , Fraga Serafin
Published: April 2011

Various physical quantities (diamagnetic susceptibilities, nuclear magnetic shielding constants, magnetic hyperfine-structure constants, orbit–orbit interaction, spin–orbit coupling constants, and scattering factors) have been evaluated for some Ne-like and Ar-like ions from Hartree–Fock functions.
INTERACTION BETWEEN POLARIZATION WAVES AND SPIN WAVES IN MAGNETODIELECTRICS
Authors: Shukla G. C. , Sinha K. P.
Published: April 2011

Microscopic mechanisms of interactions between magnons and optical phonons in antiferro- and ferri-magnetic ionic dielectrics are formulated. Following some earlier work, this is achieved by taking cognizance of the mixing of the excited orbital states with the ground orbital states of the magnetic ions due to lattice vibrations.It is found that the processes which involve splitting of an optical phonon into two magnons are most important for the exchange of energy between the spin and lattice systems. Relaxation frequencies for such processes for antiferro- and ferri-magnetic systems at various temperatures are calculated. In the systems under consideration, processes involving acoustic phonon–magnon interaction dominate below 10 °K; however, the optical phonon–magnon contribution becomes quite appreciable around 25 °K.
THE TEMPERATURE DEPENDENCE OF THE HALF-WIDTHS OF INTERNAL ABSORPTION LINES IN BORON-DOPED SILICON
Authors: Parsons R. R. , Bichard J. W.
Published: April 2011

For boron-doped silicon at temperatures less than 60 °K, half-width measurements for those absorption peaks corresponding to transitions from the ground state to the 2P′ and 3P′ internal states are presented. These half-widths are attributed to concentration and electron–phonon lifetime effects. The major contribution to the phonon broadening appears to be due to electron–phonon coupling of the internal states to the P3/2 Bloch states.
SCATTERING OF ELECTROMAGNETIC WAVES BY A MOVING CYLINDER IN FREE SPACE
Authors: Lee S. W. , Mittra R.
Published: April 2011

Scattering of electromagnetic waves by a moving cylinder in free space is studied by an application of Lorentz transformation. It is shown that the solution in the transformed coordinates can be derived readily from a knowledge of the solution of the corresponding stationary problem. Several important characteristics of the scattered far-fields are investigated in detail for a cylinder of small radius. These include the calculation of the far-field patterns and the angular dependence of the Doppler shift.
THE EFFECT OF MAGNETIC ELEMENT IMPURITIES ON THE RESISTIVITY OF SEMICONDUCTORS
Authors: Narasimhan K. S. V. L. , Sinha K. P.
Published: April 2011

A theoretical analysis of the effect of magnetic element impurities on the resistivity of semiconductors is discussed. The theory of Kondo has been suitably modified. The important processes consist of third-order terms in perturbation theory which correspond to two spin-flip exchange processes followed or preceded by one Coulomb or exchange process without spin flip. This leads to a simple result ρ = aT3/2 – cbT7/2, where the first term refers to the ordinary phonon scattering and the second one to the spin-dependent scattering.
ROCKET STUDIES OF ISOLATED IONOSPHERIC IRREGULARITIES
Authors: Mason K. H. , Tull E. H. , Forsyth P. A.
Published: April 2011

It has been shown previously that ground-based observations of the relative phase, or direction-of-arrival, of radio signals propagated through the ionosphere from artificial satellites provide a useful extension to existing techniques for the study of ionospheric irregularities. This technique has now been extended to observations of the auroral ionosphere using small transmitters ejected from two rockets launched at Fort Churchill, Manitoba. Observations were also made on beacon signals from the Alouette I satellite as it passed over Fort Churchill and these revealed large irregularities in the F region but no similar irregularities in the E region. Nevertheless, when transmitters were placed between the E and the F regions, large E-region irregularities (1–2 km in diameter) having excess electron densities of the order of 2 × 1011 m−3 were clearly revealed. The background ionization, though not measured, was probably of about the same magnitude. These preliminary observations raise a number of questions which need further investigation.
THE PAIR DISTRIBUTION FUNCTION OF AN INTERACTING ELECTRON GAS
Authors: Geldart D. J. W.
Published: April 2011

The pair distribution function, in the limit of zero separation, of an interacting electron gas at high and metallic densities is investigated by many-body perturbation theory. It is shown that the usual methods for maintaining self-consistency in approximate calculations violate, in general, the nonnegativity of the pair distribution function. In particular, the Pauli principle yields a rigorous sum rule for the parallel spin density fluctuation propagator which is not satisfied. Upper and lower bounds on one-loop and multiloop contributions to the pair distribution functions are given. These bounds are used to discuss correlation corrections. An improved wave-number dependence is given for Hubbard's (1957) approximation to the screening function and numerical results are given for a simple class of exchange corrections.
TRANSITION DENSITIES OF DIPOLE EXCITATIONS IN NUCLEI WITH N > Z
Authors: Goulard B. , Fallieros S.
Published: April 2011

The transition charge densities characterizing the excitation of nuclear dipole states are discussed. The splitting of the dipole strength into two components of different isospin is emphasized. The results are illustrated for the specific case of the nucleus 90Zr.
MEASUREMENT OF SPIN-PHONON TRANSITION PROBABILITIES IN POTASSIUM CHROMICYANIDE
Authors: Weissfloch C. F.
Published: April 2011

An experimental method based on the technique of microwave pumping was used to measure spin-phonon transition probabilities in dilute potassium chromi-cyanide. The set of numerical values obtained appears to indicate that the spin-lattice relaxation by the direct process of the cyanide-coordinated Cr3+ ion violates the quadrupolar selection rules. This behavior is in disagreement with the Kronig – Van Vleck theory, but is not contradicted by the experimental results of other workers.
PHONON-ASSISTED MAGNETO ABSORPTION IN DIRECT-BAND SEMICONDUCTORS
Authors: Batra I. P. , Haering R. R.
Published: April 2011

In polar semiconductors with direct energy gaps, optical absorption is observed for photons with energies well below that corresponding to the energy gap. It is now established that the absorption tail (Urbach's law) is due to indirect phonon-assisted optical transitions involving the absorption of one or more optical phonons of energy kθ. In the present paper we have considered the effect of a magnetic field on the optical absorption in that region of the Urbach tail where second-order processes are dominant. In contrast to the normal direct interband absorption coefficient, the absorption reflects the Landau level structure of valence band and conduction band separately. A discussion is given of the conditions under which such an effect should be observable.
EARLY AND MAIN SEQUENCE EVOLUTION OF STARS IN THE RANGE 0.5 TO 100 SOLAR MASSES
Authors: Ezer Dilhan , Cameron A. G. W.
Published: April 2011

The evolutionary study previously carried out for the sun has been extended to stars of 0.5, 0.7, 2, 5, 10, 20, 50, and 100 solar masses. The evolutionary calculations were started at the threshold of energy stability, carried through the approach to the main sequence, and (with the exception of the 100 solar-mass model) through the depletion of hydrogen on the main sequence. All models were observed to have a completely convective Hayashi phase. There was general agreement, in the appropriate mass range, with the evolutionary studies of Iben, the discrepancies apparently resulting from different opacities used in the calculations. Lines of equal evolutionary age in a Hertzsprung–Russell diagram constructed from these calculations do not agree with the observations of Walker, probably because of the neglect of mass loss and rotation in the early stellar evolutionary histories.
NUCLEAR SPIN RELAXATION IN GASEOUS METHANE AND ITS DEUTERATED MODIFICATIONS
Authors: Bloom Myer , Bridges Frank , Hardy Walter N.
Published: April 2011

The spin-lattice relaxation time T1 for protons and deuterons in CH4, CH3D, CH2D2, CHD3, and CD4 has been measured as a function of density ρ and temperature T for 0.1 Amagat [Formula: see text] Amagats and [Formula: see text] The results are interpreted, using the approximation that the correlation function of each operator in the angular momentum coordinates is expressed as a product of the free molecule correlation function and an exponentially decaying function of time. The proton spin relaxation is found to be due to the spin-rotation interaction, while the deuteron spin relaxation is due to the intramolecular quadrupolar interaction.
THERMOELECTRIC PROPERTIES OF n-TYPE Bi2Te3–Bi2Se3 ALLOYS
Authors: Champness C. H. , Muir W. B. , Chiang P. T.
Published: April 2011

Room temperature measurements of the Seebeck coefficient (α), electrical conductivity (σ), thermal conductivity (κ), and thermoelectric figure of merit (Z) were made on samples of n-type Bi2Te3–Bi2Se3 pseudobinary alloys over the whole composition range. To obtain maximum Z, doping was carried out at each composition by the addition of CuBr (donor) from 0 to 66 mole% Bi2Se3 and by lead and excess Se (acceptors) thereafter. Experimentally determined values of the materials parameter β were found to saturate (β∞) at high conductivity in a given alloy and close relationship was found between β∞ and Zmax The optimized values of σ, κ, and CuBr-dopant concentration were found to show a maximum at 33 mole% Bi2Se3, while the optimized value of α showed a minimum at this composition. These results, together with the fact that no maximum was observed in σ at constant α (i.e., constant carrier concentration), suggest that a maximum in the carrier concentration occurs in optimized material at this composition. Further support for this was provided by the observed variation of σ with α at a given composition which was found to be more consistent with a minimum in the apparent energy gap near 33% Bi2Se3 rather than the maximum reported by other workers.
LASER-INDUCED PHOTOCONDUCTIVITY IN SILICATE GLASSES BY MULTIPHOTON EXCITATION, A PRECURSOR OF DIELECTRIC BREAKDOWN AND MECHANICAL DAMAGE
Authors: Sharma Bhim S. , Rieckhoff Klaus E.
Published: April 2011

A Q-switched ruby laser is used to induce photoconductivity in soda glass, fused quartz, and quartz crystal. The number of charge carriers produced per laser pulse of 1027 photons cm−2 s−1 is accounted for by multiphoton ionization of nonbridging oxygens in the silicon oxygen network. The relative magnitude of the effect proves that photoconductivity does not result from the ionization of sodium in glass as extensively quoted in the existing literature. The lifetime of the charge carriers produced is estimated to be 10−5 s. Arguments to the effect that this photoconductivity is the primary cause of dielectric breakdown and damage in glasses under excitation by a Q-switched laser are presented.
ON THE CALCULATION OF THE FUNDAMENTAL MODE OF THE ONE-VELOCITY NEUTRON TRANSPORT OPERATOR
Authors: Bansal N. K. , Ghatak A. K.
Published: April 2011

We report here some results on the asymptotic behavior of a neutron pulse injected into a slab using monoenergetic transport theory including the effects of the anisotropic scattering cross section in the laboratory system. The calculations were performed in the P1 and P3 approximations. These results are compared with the exact numerical calculations and with the recent pulsed neutron experiments in fast nonmultiplying nonmoderating assemblies where the decay of an essentially monoenergetic burst of neutrons is studied.
THERMAL CONDUCTIVITY AND ELECTRICAL RESISTIVITY OF HIGH-PURITY COPPER FROM 78 TO 400 °K
Authors: Moore J. P. , McElroy D. L. , Graves R. S.
Published: April 2011

A guarded-axial heat-flow technique for accurately measuring thermal conductivity, electrical resistivity, and Seebeck coefficient from 78 to 400 °K on small rod samples is described in detail. Results on a 99.999% pure polycrystalline copper specimen (ρ273.16°K/ρ4.2°K = 9.0 × 102) are compared with the results of previous investigators.The behavior of the electrical resistivity and the thermal conductivity is discussed in terms of existing theoretical equations. Although copper is a relatively simple monovalent metal, little agreement between the experimental thermal conductivity results and theory was found. The behavior of the experimental electrical resistivity from 100 to 1 200 °K was explained in terms of an approximation to the Bloch-Grüneisen equation.
NORMAL MODES, CORIOLIS COUPLING, AND CENTRIFUGAL DISTORTION IN MOLECULES WITH NEARLY FREE INTERNAL ROTATION: CH3—C≡C—CH3 AND CH3—C≡C—SiH3
Authors: Bunker P. R. , Hougen J. T.
Published: April 2011

In 1964 Duncan determined force fields for the molecules CH3—C≡C—CH3 and CH3—C≡C—SiH3 under the assumption that the force constants were not dependent on the torsional angle γ. In the first half of this paper we determine the quantitative effect of adding various γ-dependent force constants to Duncan's force field for CH3—C≡C—CH3. The results lead to complications concerning the symmetry species of the normal coordinates, the magnitude of the Coriolis coupling constants, and the calculation of the energy levels. The possible avoidance of these complications is discussed.In the second half of the paper a formalism is set up relating the rotational and torsional centrifugal distortion constants to the vibrational force field for certain molecules with nearly free internal rotation. Duncan's force field for CH3—C≡C—SiH3 is used to calculate some centrifugal distortion constants for that molecule and for CH3—C≡C—SiD3 on the assumption of completely free internal rotation. Good agreement is obtained between the quantities calculated here and the observed quantities determined by Kirchhoff and Lide.
SQUARE-WELL FLUID AT LOW DENSITIES
Authors: Barker J. A. , Henderson D.
Published: April 2011

Values for the radial distribution function and the direct correlation function at low densities and for the first five virial coefficients are obtained for a fluid of molecules interacting according to the square-well potential when the width of the attractive well is half the radius of the hard core. It is found that the higher-order coefficients are surprisingly large and, as a result, the virial series fails to converge even at temperatures and volumes significantly greater than the critical temperature and volume. Comparisons of these exact virial coefficients with those given by several approximate theories are made. Values are also given for the first five virial coefficients when the width of the attractive well is equal to the radius of the hard core.
THE ADMITTANCE OF AN INFINITE CYLINDRICAL ANTENNA IN A LOSSY INCOMPRESSIBLE, ANISOTROPIC PLASMA
Authors: Miller Edmund K.
Published: April 2011

A numerical investigation of the admittance of an infinite, circular cylindrical antenna excited at a circumferential gap of nonzero thickness, and immersed in a lossy incompressible magnetoplasma with the antenna parallel to the static magnetic field is described. A concentric free-space layer (the vacuum sheath) which separates the antenna from the external uniform plasma is included in the analysis to approximate the positive ion sheath which may form about a body at floating potential in a warm plasma. The numerical results for the antenna admittance show that: (1) in the absence of a sheath, a sharp admittance maximum is found at the electron cyclotron frequency, with the maximum more pronounced when the plasma frequency exceeds the cyclotron frequency than for the converse case; (2) the vacuum sheath shifts upward in frequency and reduces in amplitude the admittance maximum which occurs for the sheathless case at the cyclotron frequency; (3) a kink or minimum in the admittance is found at the plasma frequency.
The ranges of 5-80 keV deuterium ions in gold and aluminium
Authors: Freeman N. J. , Latimer I. D.
Published: April 2011

The depth distribution of deuterium in metal targets has been measured by sputtering the metal surface with a 60 keV Bi beam and monitoring the partial pressure of deuterium released into the target chamber with an MS 10 mass spectrometer. No significant differences were found for the distributions from D+, D2+, and D3+ bombardments with 20 and 30 keV energy per incident atom.The sputtering coefficient, measured by the loss in weight of a target, was used to calculate ranges for the energy interval 5–80 keV. These are compared with previous experimental and theoretical values.
Influence of lattice structure on motion of positrons and electrons through single crystals
Authors: Uggerhøj E. , Andersen J. U.
Published: April 2011

The emission yield from single crystals doped with β emitters is investigated. In the axis direction, energetic electrons emitted from a lattice position show a peak in yield up to 2.4 times the normal yield, whereas positrons emitted from the same positions show a dip by a factor of 4 from the normal yield. Electrons emitted from interstitial positions show no peak in yield. Energetic electrons transmitted through a thin single crystal experience increased multiple scattering when the incoming beam is aligned with an axis direction. The influence of atomic planes on the motion of electrons and positrons is also investigated. Furthermore, the electron peak and positron dip have been used for the localization of foreign atoms in single crystals.
Range measurements in oriented tungsten single crystals. III. The influence of temperature on the maximum range
Authors: Davies J. A. , Eriksson L. , Whitton J. L.
Published: April 2011

The maximum range, Rmax, of 42K ions along the [Formula: see text] axis in tungsten has been measured over the temperature region 30–725 °K, by means of the anodizing/stripping technique. The results show that Rmax is completely independent of the lattice temperature, within an experimental precision of ± 3%. The prominent supertail (~10%) observed in 42K range distributions at 30 °K interferes with the evaluation of Rmax. This tail, however, can be completely suppressed by subsequently bombarding the crystal with a higher dose (3 × 1015/cm2) of Ne ions of similar energy while still at ~30 °K.The main conclusions derived from this series of three papers on range measurements in tungsten single crystals are briefly outlined. We find that Rmax is an extremely useful experimental parameter for characterizing the range distribution of channeled ions. Its value in tungsten is determined almost entirely by electronic stopping, except at energies less than a few keV. The electronic stopping powers derived from the energy dependence of Rmax agree roughly with theoretical predictions; however, the observed stopping power values exhibit large oscillations about the smooth theoretically predicted dependence on Z1, the atomic number of the projectile. An adequate explanation of these Z1 oscillations is not yet available.
Implantation profiles of 32P channeled into silicon crystals
Authors: Dearnaley G. , Freeman J. H. , Gard G. A. , Wilkins M. A.
Published: April 2011

Concentration profiles of 32P ions implanted into silicon crystals have been studied over the energy range 10–110 keV, using an electromagnetic separator. Beam directions near the major channeling axes [Formula: see text] and [Formula: see text] were chosen. After implantation, the profiles were determined by the method of anodic stripping, and the beta activity of each oxide layer removed was measured in a low-background proportional counter. Concentration profiles were studied as a function of the ion energy, crystal orientation, crystal temperature, and ion dose. Precise crystal orientation was achieved by a proton-channeling technique making use of protons of around 10 MeV energy from the Harwell tandem generator. The maximum penetration of channeled ions along the [Formula: see text] axis was found to vary with the energy, E, approximately as E0.6. Significant temperature effects were observed, and the influence of radiation damage on ion channeling was studied and is related to other observations.
Inert gas diffusion and radiation damage in ionic crystals and sinters following ion bombardment
Authors: Matzke Hj.
Published: April 2011

A review is given of radiation damage and diffusion phenomena in a large variety of ionic crystals (oxides and halides) and two metals following ion bombardment. Ion beams of both light and heavy nuclides between mass number 3 (tritium) and 222 (emanation) were employed. The ion doses varied between 104 and 1017 ions/cm2. Four different experimental techniques were used to detect gross structural radiation damage following bombardment: reflection electron diffraction, measurement of ranges or penetration profiles, electron microscopy in transmission or using replica techniques, and gas release measurements at low temperatures. In general, materials having cubic lattice structures were shown to be more stable than anisotropic substances.Minor local damage (such as point defects, defect clusters or voids, dislocations and loops) was studied by its interaction with rare gases or other volatile elements (Br, Rb, Cs). For the heavy rare gases (Kr, Xe, Em) and low bombardment doses, volume diffusion was observed starting between 0.4 and 0.5 of the melting point, Tm, on the absolute temperature scale. The activation enthalpies ΔH were about 80 ± 10% of those for the self-diffusion of the less mobile lattice ions and were related to Tm via ΔH = (1.4 ± 0.2) × 10−3Tm eV = (32 ± 4) Tm kcal/mole. For the diffusion mechanism, a relation with self-diffusion is suggested, the gas most probably migrating in small vacancy clusters.
The 4509-keV level in 27Al
Authors: Häusser O. , Pelte D. , Sharpey-Schafer J. F.
Published: April 2011

Levels in 27Al below 4.6 MeV have been studied by triple angular correlations. The 4509-keV level was found to have a probable spin value of 11/2. The quadrupole/dipole mixing ratio for the 4509 → 3003 (11/2 = 9/2) transition was then found to be −0.58 ± 0.08. The value J = 9/2 for the spin of the 3003-keV level has been confirmed. Both levels are likely to belong to a rotational band with a predominant K value of 5/2.
Theory of collision-induced translational absorption
Authors: Sears V. F.
Published: April 2011

A theory of the line shape for collision-induced translational absorption in rare-gas mixtures is developed. The reduced line-shape function is expanded in terms of the quantity ρ/σ, typically of the order of 0.1, where ρ is the range of the induced dipole moment and σ is the size of the repulsive core of the interatomic potential. The calculation is based on the special properties of the exponential model for the induced electric dipole moment. The temperature is assumed to be sufficiently high that the motion of the atoms can be treated classically, while the density is assumed to be sufficiently low that only binary collisions are important and intercollisional correlation effects are negligible over the frequency range of interest. A least-squares comparison of theory with experiment yields values for ρ and the magnitude of the induced moment for Ne–Ar and He–Ar pairs.
Intercollisional interference effects in pressure-induced infrared spectra
Authors: Kranendonk J. Van
Published: April 2011

The dip observed in the Q branch of the pressure-induced vibrational spectra at high densities is shown to be an interference effect due to the correlations existing between the dipole moments induced in successive binary collisions. A similar dip is predicted to exist in the translational spectra of inertgas mixtures at zero frequency. This intercollisional interference effect has the same origin as the dip in the spectral density of the intermolecular force, discussed by Purcell in connection with nuclear electric dipole relaxation. The effect does not occur for the anisotropic part of the induced dipole moments, and this explains the observed absence of any splitting of the S lines and of the QQ component of the Q branch of the induced infrared spectra.
Study of extensive air showers at Mount Norikura. III. Core structure and high-energy events
Authors: Miyake S. , Hinotani K. , Ito N. , Kino S. , Sasaki H. , Yoshii H. , Sakuyama H. , Kato E.
Published: April 2011

An area of 3 × 4 m2 is covered by 48 plastic scintillators above and below a water tank 2 m in depth. From maps of the charged-particle density and the energy-flow density in the core region, properties of EAS cores and of the high-energy nucleon component have been studied. About 25% of observed cores show the complicated structure of a "multiple core". These can be understood as due to effects of high-energy nuclear particles having large transverse momenta of several GeV/c to a few tens of GeV/c. The frequency of occurrence of such events increases with the size of EAS only slowly, but it decreases rapidly with increasing distance between the main cores and subcores. There is no clear distinction in the average lateral density distribution of charged particles between these multiple-core EAS and ordinary EAS at points distant from the cores.Comparing the particle density in both layers of detectors (top and bottom), the activity of cores has been studied. This fluctuates more than would be expected from the lateral structure of the showers.