bluuebunny/crossref_metadata_2025 huggingface dataset:
Kapitza resistance of cerium ethylsulphate
Authors: Glättli Hans
Published: April 2011

Spin–bath relaxation times τ of cerium ethylsulphate (CeES) immersed in liquid helium have been measured at magnetic fields up to 6 kOe. The electronic spin system of CeES has been heated by pulsed microwave radiation and the return to the equilibrium bath temperature has been monitored, using the optical Faraday rotation. At temperatures below the λ point of liquid helium, τ is a few ms and weakly dependent on magnetic field and temperature. It is assumed that the Kapitza boundary resistance Rk is the limiting factor in the energy transport between the spin system of CeES and the surrounding liquid helium. This assumption is supported by measurements of τ above the λ point between CeES and liquid or gaseous helium. Rk has been calculated from the experimental values of τ using a simple thermodynamical model. The resulting temperature dependence can be fitted with the expression Rk = 30 T−2.4 cm2 °K s (joule)−1 independent of magnetic field. The same model has been applied to PrES, which has been shown previously to exhibit a similar relaxation behavior. The results of Rk are close to those obtained for CeES.
Temperature dependence of the energy gap in superconducting Al–Al2O3–Al tunnel junctions
Authors: Blackford B. L. , March R. H.
Published: April 2011

The most detailed measurements of the energy gap in Al by the tunneling technique have been made using Al–Al2O3-Pb junctions. Determination of the energy gaps from the I–V curves of these junctions is more precise than previous results using Al–Al2O3–Al tunnel junctions. The chief difficulty with the Al–Al2O3–Al junctions has been the lack of definition in the I–V curves, especially near Tc. Al–Al2O3–Al junctions, in which the energy-gap voltages can be read from the I-V curve with very little ambiguity up to T/Tc ≈ 0.99, are reported here. For the majority of the junctions studied, the temperature dependence of the normalized gap Δ(t)/Δ(0) shows very little scatter (T = 0.34 °K to T = Tc) and agrees closely with the BCS theory. However, a consistent small deviation is observed, with the measured gap values being slightly higher than the BCS prediction. The mean value of 2Δ(0)/kBTc obtained from 21 different junctions is 3.53 with an r.m.s. deviation of ± 0.02.
Recovery of electron-irradiated zirconium at low temperatures
Authors: Neely H. H.
Published: April 2011

The low-temperature recovery of the electrical resistivity of polycrystalline zirconium was measured after electron irradiation below 8 °K. The material used in this irradiation was the same low oxygen material (0.015 at.%) used by Swanson to study recovery after deformation at 4.2 °K. Substage IB was found to be only of the order of 4% of the irradiation-induced resistivity change, compared to ~6% observed by Swanson after deformation. Stage I (4.2 to 160 °K) in Zr contains six substages, while stage II (160 to 310 °K) contains only one substage after electron irradiation. While no study of kinetics was made, it seems likely that close pair-annihilation processes are responsible for the recovery spectrum below 118 °K and that longer-range defect migration occurs in the neighborhood of 140 °K.
Optical absorption studies of Co (CH3COO)2∙4H2O
Authors: Narayana P. A. , Mehra A. , Venkateswarlu Putcha
Published: April 2011

The absorption spectrum of Co(CH3COO)2∙4H2O has been studied at room temperature and at 78 °K. The cubic field approximation with Dq = 960 cm−1, B = 850 cm−1, and C = 4.5B is found to give a good fit to the observed band positions. The spin-forbidden transitions from the quartet ground state to upper doublet levels have been observed, and their intensities and positions are discussed.
Absorption spectra of O2 in the a1Δg, , and states
Authors: Alberti F. , Ashby R. A. , Douglas A. E.
Published: April 2011

A number of new absorption bands have been found in the vacuum ultraviolet spectrum of O2 that has been excited by a discharge. The lower states of these bands are the [Formula: see text] and a1Δg states. The analysis of the bands, together with some newly analyzed bands arising from ground-state O2, has allowed us to identify four new electronic states. It has not been possible to assign these states to particular electron configurations of O2.
Effets successifs de l'ammoniaque et de la TEA sur les caractéristiques granulométriques et sensitométriques des cristaux AgBr
Authors: Zizic B. , Demers J. , Demers P.
Published: April 2011

not available
The freezing points of high-purity metals as precision temperature standards. VIIIb. Sb: Liquidus points and alloy melting ranges of seven samples of high-purity antimony; temperature-scale realization and reliability in the range 0–631 °C
Authors: McLaren E. H. , Murdock E. G.
Published: April 2011

An investigation was made of the freezing and melting temperatures of seven samples of high-purity antimony, five with analyzed impurity contents ranging from <0.3 to <0.7 p.p.m. (wt.) and two with impurity contents of ~10 and ~100 p.p.m. (wt.) respectively. The Sb melts had to be deoxidized in situ to eliminate the effect of dissolved oxygen (gaseous or oxide form), which was found to cause large depressions and instabilities in the liquidus-point temperatures. A variation of 0.0026 °C in liquidus point was found among the five purest samples, but the standard deviation for a single determination of the liquidus point realized on outside-nucleated slow induced freezes (ONSIF) of any given sample was [Formula: see text]. The best Sb samples had nonequilibrium alloy melting ranges of a few centidegrees which are distinctly inferior to melting ranges of only a few millidegrees found on samples of Sn, Zn, and Pb with similar analyzed impurity contents: the inferiority is attributed to residual impurity effects in the Sb samples and not to either lag in detector response or anomalous molecular effects in the melting Sb. A value of 630.553 (°C Int./60) was determined for the liquidus point at standard pressure of the purest NRC Sb sample.After establishing the Sb point, eight silica-sheathed standard resistance thermometers were intercompared at the ice, Sn, Cd, Zn, and Sb points to provide information at the highest precision on stabilities of fixed-point realizations and resistance thermometers, inter-thermometer variations, advantages of particular quadratic resistance–temperature interpolation relations, preferred calibrating procedures and thermometer handling techniques, and temperature-scale stability and reliability over the full range 0–631 °C.
A microparticle plasma
Authors: James C. R. , Vermeulen F.
Published: April 2011

A study is made of a cloud composed of microparticles which are individually either positively or negatively charged. The plasma definitions that the total charge of the cloud is zero and the shielding distance is small compared to the dimensions of the system are taken to be satisfied. As a result, it is proposed that the cloud be called a "microparticle plasma". Since the particle sizes vary over a range of values, the cold plasma many-fluid model is used to analyze the problem, with each fluid representing particles of a particular radius. It is assumed that there is a continuum between one fluid and the next. This model has been used to study plasma waves. Microparticle clouds have been set up in our laboratory in an attempt to realize a "microparticle plasma".
Multiple ionization of the rare gases by successive electron impacts (0–250 eV). II. 1S–2S transition in 3He+
Authors: Redhead P. A. , Feser S.
Published: April 2011

The tertiary collision sequence of electrons with helium (He → He+ → He+m(2S) → He2+) has been observed with a trapped-ion mass spectrometer. The variation of He2+ ion current with electron energy shows a threshold at 40.8 eV, and structure, which results from excitation to autoionizing states of the atom below the n = 3 threshold of He+, is observed in the range 45–49 eV. Estimates of the cross section for the 1S–2S transition in He+ lie slightly below the values from close-coupling calculations.
Rigorous wave function for spin- composite particles
Authors: Rosen Gerald
Published: April 2011

A certain composite four-index quantity built up from three constituent spinor wave function solutions to the Dirac equation is shown to transform as a spinor and to satisfy the Dirac equation. This rigorous wave function is therefore associated with a composite relativistic spin-[Formula: see text] particle.
Shock-wave effects arising from the earth's rotation
Authors: Davies David
Published: April 2011

The behavior of shock waves in the atmosphere is governed by eight independent equations. Four of these are the well-known Rankine–Hugoniot equations which express mass and momentum relationships. Two of the other equations, which both involve a Coriolis term, serve to describe the angular momentum relationships. The last two relate to development. All eight equations are derived from Newton's Second Law of Motion and the equation of conservation of mass.
Smooth nucleon–nucleon interactions and meson theory
Authors: Desgrolard Pierre , Pearson J. M. , Saunier Gérard
Published: April 2011

Tabakin and Davies have shown that it is possible to fit the singlet-state nucleon–nucleon data with a potential that is smooth enough to give very small second-order terms in an ordinary perturbation–theoretic treatment of nuclear matter. However, their potential is unrealistic in that the requirements of meson theory are in no way satisfied in the long-range region. It is shown here that a potential whose long-range part conforms to the OBEP of Bryan and Scott can still be made to fit the phase shifts without increasing significantly the second-order terms. Thus, with meson theory being incapable of making an unequivocal statement about the short-range region, it will only be by resorting to the experimental evidence for short-range correlations in nuclei that one will be able to resolve the question as to whether or not an interaction as smooth as the one considered here can be regarded as "real" rather than merely "effective". In any event, the existence of such correlations cannot be inferred from the singlet nucleon–nucleon data.
Boron trifluoride: The analysis of 2v3 and the determination of ζ33
Authors: Brown Chris W. , Overend John
Published: April 2011

The 2v3 bands of 10BF3 and 11BF3 have been studied at high resolution. The experimental values of the Coriolis coefficient ζ33 are 0.7808 ± 0.0036 for 10BF3 and 0.7438 ± 0.0047 for 11BF3. The BF bond length is found to be 1.3102 ± 0.0012 Å. The Coriolis coefficients have been used to fix the E′ species symmetry force constants.
On alpha-decay rates in heavy nuclei
Authors: Scherk L. , Vogt E. W.
Published: April 2011

The alpha-decay rates in heavy nuclei are analyzed by a method in which the decay rates are factored into one-body widths and spectroscopic factors. It is shown that the discrepancy between the absolute values of the experimental alpha-decay rates and those calculated with the nuclear shell model has mainly resided in the incorrect assessment of the one-body widths and that it can be largely removed by a more direct treatment of the average interaction between the alpha particle and the residual nucleus.
Neutron–neutron angular correlation in the reaction 2H(n, p)2n at 14.1 MeV
Authors: Jeremie H. , Miremadi B.
Published: April 2011

The angular correlation between the two outgoing neutrons in the reaction n + d → 2n + p has been measured. One neutron counter was kept in a fixed position at 30° while the other was varied between 22.5° and 67.5°. A maximum in the number of counts was found for 42 ± 7°. A calculation according to the spectator model of Kuckes, Wilson, and Cooper (1961) does not reproduce the experimental results.
A calculation of the production of pions by 450-MeV protons on nuclei
Authors: McMillin D. , Bhargava P. , Lam L. , Vogt E. W.
Published: April 2011

Starting with assumed pion yields in nucleon–nucleon collisions, we consider the influence of the various nuclear effects on the pion yields from the bombardment of various nuclei with 450-MeV protons. In addition to the proton and pion absorption within the nucleus considered by earlier workers, we also include the effects of the momentum distribution and the density distribution of the struck nucleons. The pion absorption, which is density-dependent, is found to dominate the relative yields in various nuclei at these proton energies, using modern densities. We obtain agreement with the measured relative yields as illustrated with the results for pion angle of 21.5° and pion energy of 83 MeV.
Computer studies of channeling of ions in alkali halide lattices
Authors: Torrens Ian McC. , Chadderton Lewis T.
Published: April 2011

The channeling of potassium, sodium, and chlorine ions in potassium chloride and sodium chloride has been investigated by computer simulation techniques. With the model chosen, axial and interplanar channeling occurs for potassium and chlorine ions in potassium chloride and for the smaller sodium ion in sodium chloride. Some events indicate the possibility of energetic sodium ions being displaced from their lattice sites into channels. The channeling process, especially at higher energies, is relatively insensitive to reasonable variations in the ionic interaction potential.
The electrical resistivity of palladium–hydrogen and palladium–deuterium alloys between 4 and 300 °K
Authors: Ho N. S. , Manchester F. D.
Published: April 2011

Measurements of the electrical resistivity of palladium–hydrogen and palladium–deuterium alloys between 4 °K and room temperature, for concentrations between 0 and 0.62 atomic ratio for each alloy, are presented. These results show an anomaly in the resistivity of the Pd–D alloys in addition to the one in the Pd–H alloys previously reported by Schindler, Smith, and Kammer at essentially the same temperature. Some hysteresis has been observed in the resistivity of the alloys as a function of concentration.
Orbit–orbit interaction in positive ions of transition elements
Authors: Thorhallsson Jon , Fraga Serafin
Published: April 2011

The orbit–orbit interaction in a number of positive ions of transition elements has been evaluated from analytical Hartree–Fock functions. This interaction is the same for the various states arising from a given configuration and with the same parent state and, in many cases, of an order of magnitude comparable to the spin–orbit interaction.
Crystal field effects on the inelastic neutron scattering from heavy rare earth metals in the paramagnetic phase
Authors: Woods A. D. B.
Published: April 2011

Expressions which arise in the interpretation of inelastic neutron scattering from hexagonal close packed rare earth metals in the paramagnetic phase are presented and discussed. It is concluded that the fourth- and sixth-order terms which occur in the Hamiltonian describing the crystal field can, in some cases, be as important as the leading second-order term.
Effective parameters for Maxwellian and non-Maxwellian magnetoplasmas
Authors: Bakshi P. M. , Haskell R. E. , Papa R. J.
Published: April 2011

The velocity dependence of the electron–neutral collision frequency may be taken into account by introducing an effective collision frequency and an effective plasma frequency. The properties of these effective parameters are examined for cold, weakly ionized magnetoplasmas. The relationship between these effective parameters and a new collisional response function R(y) is described for Maxwellian distribution functions. For this case of Maxwellian distributions, curves are presented of the effective parameters as a function of frequency for both a pure power-law dependence of collision frequency on electron velocity and for the case of a coupling between two power-law variations. When the a-c. electric field becomes sufficiently strong to alter the form of the isotropic part of the electron distribution function, the effective plasma parameters will become functions of the ellipticity and intensity of the a-c. field. Graphs are presented of the effective parameters as a function of normalized frequency, normalized field strength, and dependence of collision frequency on electron velocity for the case where only pure (unmixed) high-intensity modes are present in the weakly ionized magnetoplasma.
Changement de phases ferroélectriques–antiferroélectriques par l'action d'un champ électrique. Applications aux solutions solides à base de PbZrO3
Authors: Benguigui L.
Published: April 2011

We have studied qualitatively the influence of an electric field on ferroelectric and antiferroelectric structures by means of the phenomenological theory of Landau. We have chosen a simplified example in which the antiferroelectric–ferroelectric phase change takes place without variation of the direction of the polarization. We have been able to show that without field and at increasing temperature, there are four possible cases, exhibiting the following sequences: AF → FE → PR, FE → AF → PR, AF → PR and FE → PR. We have drawn the general pattern of the phase diagrams as a function of the field and the temperature in the four cases. The comparison with the experimental results, chosen among the solid solutions of PbZrO3, shows a satisfactory fit to our theoretical results.
A study of the 4.509-MeV state in 27Al by the 26Mg(p, γ) reaction
Authors: Röpke H. , Lam S. T.
Published: April 2011

The 4.509-MeV state in 21Al has been investigated using the 26Mg(p, γ) reaction at the Ep = 2.174-MeV resonance. On the basis of γ-ray angular distributions, the spin–parity assignment of the resonance (Ex = 10.366 MeV) is found to be 7/2+ and strong evidence is given that the 4.509-MeV state in 27Al has Jπ = 11/2+. The lifetime is found to be τ(4.509) = 340 fs ± 10%. The 8.040-MeV state in 27Al has a spin–parity assignment of 7/2+. Branching ratios are given for the resonance as well as levels above the 4.509-MeV state fed by the resonance.
Vibronically induced Jahn–Teller progressions in the electronic spectrum of iridium hexafluoride
Authors: Brand J. C. D. , Goodman G. L.
Published: April 2011

The absorption of IrF6 vapor between 0.7 and 1.3 μ consists of three distinct electronic transitions connecting the Γ8g ground state with higher Γ6g, Γ8g, and Γ7g states of the (5d f2g)3 configuration. In first approximation, Jahn–Teller forces vanish in the two Γ8g states, while the Γ6g and Γ7g states involve Kramers magnetic degeneracy, which cannot be split by electrostatic forces. Accordingly, no splittings of the ν2(eg) or ν5(f2g) excited states are observed in these spectra, but short progressions in ν5 do appear in the electric-dipole-allowed, vibronic parts of these transitions. These progressions are considered to show that Jahn–Teller anharmonicity can be induced by admixtures of odd-parity, orbitally degenerate electronic states, i.e. by the same mechanism through which these transitions derive their electric-dipole intensity.
Nature of the martensitic transformation in sodium
Authors: Dolling G. , Powell B. M. , Martel P.
Published: April 2011

Measurements have been carried out on selected phonon modes in sodium at temperatures down to 36 °K. No phonon instabilities have been found to be associated with the martensitic transformation in this metal.
Reflectance spectra of some III–V compounds in the vacuum ultraviolet
Authors: Vishnubhatla Sarma S. , Woolley John C.
Published: April 2011

Reflectance spectra in the photon energy range 3.5–7.5 eV have been determined for the compounds GaP, InP, GaAs, InAs, AlSb, GaSb, and InSb, and the positions of the E2, E2 + Δ2, E2 + δ, and four E1′ peaks were observed in most cases. The values of the spin–orbit splittings Δ2, Δ1, ΔL3v, and ΔL3c from the experimental data are found to be in good agreement with the values calculated by Cardona from k∙p analysis.
Study of moving striations in plasmas. I. Measurement of the phase between the variations of several plasma parameters
Authors: Drouet Michel G. , Šicha Miloš
Published: April 2011

The phases between the variations of electron density, electron temperature, plasma potential, electric field, and light intensity have been measured in slow-moving striations in a neon discharge for different values of the discharge current. The reported measurements were made in moving striations artificially excited in the form of both continuous waves and wave of stratification.
Study of moving striations in plasma. II. Investigation of the validity of the microwave and the probe measuring techniques
Authors: Šicha Miloš , Drouet Michel G.
Published: April 2011

Two methods have been proposed recently for the direct oscillographic display of the electron-density variations and of the electron-temperature variations in a plasma. The purpose of this paper is to define some criteria that will establish the validity of these measuring techniques in the actual experimental discharge conditions.
Variation locale de l'état lumineux en diffraction itérée de la figure (sin X)/X par un réseau
Authors: Delisle Claude
Published: April 2011

The diffraction pattern (sin X)/X is formed in the usual way. If one uses x0 and x1 to represent respectively the slit source and objective planes, the diffraction pattern is formed in the x2 plane. A second objective together with a fine slit grating is placed in the x2 plane. The spacing of the slits of the grating is equal to the half-width of the central part of (sin X)/X. An iterated diffraction pattern is formed in the x3 plane, conjugate of the x1 plane. The local variation of intensity at two particular points of the x3 axis is studied as a function of the position of the slit source along the x0 axis perpendicular to the optical axis. Gratings of 2, 3, 4, …, 10 fine slits are considered.
Liquid helium and the properties of a Bose–Einstein gas. II. Effects of finite geometry
Authors: Goble D. F. , Trainor L. E. H.
Published: April 2011

The properties of liquid helium in thin film geometry are studied using both the ideal Bose–Einstein gas and the hard-sphere gas as models. Of particular interest is the occurrence of a statistical correlation length which has roughly the same value in both models and which may help explain some recent experimental results on the behavior of liquid helium in thin films and pores. The limitations of the methods used for the interacting gas are discussed in some detail.
Magnetoresistances and the phonon conductivity of metals
Authors: Witzenburg W. van , Laubitz M. J.
Published: April 2011

The thermal and electrical magnetoresistances of Cu, Ag, Au, and W were measured in the temperature range 80–130 °K. The results for the noble metals were used to establish the validity of the Modified Wiedemann–Franz Law within the experimental accuracy of ±9%. This law was then applied to the results obtained for tungsten to determine its phonon conductivity; in the temperature range investigated, the latter was approximately 0.9 W/cm °K, about 40% of the total thermal conductivity.
Lifetime measurement of the 46-keV state in 76As
Authors: Henry L. C. , Kennett T. J.
Published: April 2011

The lifetime of an excited state of 76As populated in the (n, γ) reaction and observed to decay by 46-keV gamma radiation has been studied, using a multichannel analyzer to record the output of a time-to-amplitude converter. The use of logic modules to determine the differential linearity of the system was studied in detail and is discussed. Experimental findings correlated with results of other studies suggest the following: the lifetime, measured to be 1.93 ± 0.06 μs, is that of the low-lying 46-keV level of 76As characterized by Jπ values of 1+, 2+, or 3 +, strongly populated by direct E1 radiation from the2− and/or 3− capture state and depopulated by E1 radiation to the 2− ground state.
A note on the rotational analysis of the A–X system of the PbBr molecule
Authors: Lal K. M. , Khanna B. N.
Published: April 2011

The rotational structure of the A–X system of the PbBr molecule has been recorded in the second order of a 35-ft concave grating spectrograph at a dispersion of 0.33 Å/mm and the analysis of four bands (3, 2), (2, 2), (4, 2), and (4, 1) has been done. In all, four branches have been observed for each of the bands and they have been explained as the P and R branches due to Pb79Br and Pb18Br. The following constants were obtained:[Formula: see text]
Lifetimes and decay modes of energy levels in 25Mg
Authors: Sharpey-Schafer J. F. , Ollerhead R. W. , Ferguson A. J. , Litherland A. E.
Published: April 2011

Lifetimes of energy levels in 25Mg have been measured using the Doppler-shift attenuation method. The levels were exicted by the 25Mg(p, p′γ) reaction with incident proton energies between 3.8 and 7.0 MeV. The gamma rays were detected in a three-crystal spectrometer consisting of a 40 cm3 Ge(Li) detector surrounded by a large NaI(Tl) crystal in the form of a split annulus. Mean lifetimes found, given in fs, are: τ(1611-keV level) = [Formula: see text], τ(1962) = [Formula: see text], τ(2565) = 59 ± 26, τ(2736) = 288 ± 20, τ(2803) = 27 ± 6, τ(3399) = 33 ± 19, τ(3408) < 20, τ(3903) < 20, τ(3969) = 24 ± 11, τ(4055) = 53 ± 10, and τ(5005) < 26. The decay modes and branching ratios of levels up to 4055-keV excitation are given. The results are compared with the mirror nucleus 25Al and discussed in terms of the collective model.
The operation of a single-electrode coaxial plasma gun
Authors: Pert G. J.
Published: April 2011

The operation of a coaxial-type plasma gun with the central electrode replaced by a pinched gas column was studied by high-speed photography and magnetic probes. It was found that the discharge was unstable after approximately 1.5 μs. and that the plasma slug was not accelerated by the current after this time. Parametric studies indicated that the plasma slug was contaminated with impurities from the insulating back wall of the device.
Spinor space and strong interactions
Authors: Smrz Pavel
Published: April 2011

In order to explain the existence of internal quantum numbers of elementary particles, the ordinary space–time position vector is assumed to be a bilinear combination of two basic spinors. It is shown that this assumption leads to the replacement of the inhomogeneous Lorentz group by the (4 + 1) de Sitter group. Using the idea of external and internal space for the description of strongly interacting particles, the assumption provides a simple way of introducing the internal symmetries. The internal symmetry group SU(3) appears naturally connected with the external space, yielding the Gell-Mann -Okubo mass formula.
Comparison of perturbative and nonperturbative calculations for Urbach's law
Authors: Dunn Dennis , Batra I. P.
Published: April 2011

In many semiconductors and insulators electronic absorption occurs below the direct electron-energy gap, owing (we assume) to the interaction of electrons with optical phonons. In this paper we compare absorption coefficients, over a wide range of interaction strengths, calculated by two different prescriptions. The first method is a perturbative one, which takes into account only one-phonon processes, while the second is a nonperturbative method, which takes into account many-phonon processes.We find that for the (weak) interaction involved in InSb the two methods give essentially the same results for photon energies [Formula: see text] in the interval [Eg – kθ, Eg], where Eg is the energy gap and kθ is the optical phonon energy. For stronger interactions the perturbation results are nowhere applicable.
The decay of 144Pm
Authors: Santhanam S.
Published: April 2011

In the electron-capture decay of 144Pm prepared by (p, 2n) reaction on enriched 145Nd, it is shown that, in addition to the well-known energy levels at 696, 1313, and 1789 keV, two new levels exist, one at 2093 keV, and another at 1509 keV. The state at 2093 keV deexcites with the emission of a 304-keV gamma ray to the 6+ level at 1789 keV, and by a crossover transition to the 4+ level at 1313 keV with the emission of a 780-keV gamma ray. The level at 1509 keV leads to the first excited state (2+) at 696 keV with the emission of a gamma ray of energy 813 keV. The intensities of the 780-, 304-, and 813-keV gamma rays are, respectively, 1.5, ≈ 0.1, and 0.5% of that of the 696-keV gamma ray.
The effect of crystal orientations on fatigue crack growth
Authors: Lardner R. W.
Published: April 2011

A previous theory of fatigue crack growth in metals was based on an analysis of the plastic zone at the tip of a crack in terms of coplanar dislocation arrays. This analysis has been extended to the case of oblique slip planes. It is shown that, for the case of a crack growing in mode 2 through a polycrystal-line material, the average rate of growth through the differing orientations of many grains is almost identical with that obtained by the coplanar analysis.
Slater–Condon parameters for the transition elements, evaluated from analytical Hartree–Fock functions
Authors: Fisk Carolyn , Fraga Serafin
Published: April 2011

The Slater–Condon integrals for the positive ions, neutral atoms, and negative ions from Sc to Zn have been evaluated from analytical Hartree–Fock functions.
Uniaxial magnetic anisotropy in electrodeposited thin films arising from lattice distortion
Authors: Fisher J. E.
Published: April 2011

The usual expression for the magnetocrystalline anisotropy is rewritten for the magnetization referred to the easy axes of the f.c.c. lattice. It is suggested that distortion due to planar film strain produces easy directions different from the [Formula: see text] crystallographic directions and results in the appearance of a large uniaxial anisotropy, Ku, superimposed upon the expected magnetocrystalline anisotropy. A strain of 1 × 10−4 in nickel is considered and is shown to produce a Ku of the order of 105 erg cm−3, comparable with that measured experimentally on electrodeposited (110) single-crystal nickel thin films.
The absorption spectrum of PH in the vacuum ultraviolet
Authors: Balfour W. J. , Douglas A. E.
Published: April 2011

Three new band systems of PH have been observed in absorption following a high current pulsed discharge through PH3. Rotational analyses show that two of these systems have as their lower state the previously unobserved a1Δ state. A third absorption is tentatively attributed to a 3Π ← X3Σ− transition. The constants for the a1Δ state are found to be B0 = 8.440 cm−1, D0 = 4.18 × 10−4 cm−1, and r0 = 1.430 Å.
Velocity and force correlations in H2–He mixtures
Authors: Sears V. F.
Published: April 2011

The fundamental vibrational band of the pressure-induced infrared spectrum of hydrogen in room-temperature helium gas (compressed to twice the density of the normal liquid) is analyzed to determine the force autocorrelation function and, hence, the velocity autocorrelation function and the mean square displacement of a hydrogen molecule as a function of time. The initial curvature of the force autocorrelation function, extrapolated to zero density, yields a value 0.087 for the ratio ρ/σ where ρ is the range of the repulsive core of the intermolecular potential and σ is the diameter of this core. Moment relations, which enable one to determine the parameters in a model introduced recently by Van Kranen-donk, are derived for the force autocorrelation function.
A new spectrum associated with diatomic carbon
Authors: Herzberg G. , Lagerqvist A.
Published: April 2011

A new system of very simple Σ–Σ bands in the region 4800–6000 Å has been observed in flash discharges in CH4, both in absorption and emission. The rotational analysis shows conclusively that the molecule responsible is a diatomic molecule containing two carbon nuclei, a conclusion that is further confirmed by the observation of the corresponding system using 13CH4 instead of 12CH4. Neither the upper nor the lower state is one of the known states of C2. None of the predicted low-lying states of C2 fits the observed new states. Two possibilities remain: either the new system corresponds to two fairly highly excited levels of C2 or it is due to the C2− ion. The latter alternative finds some support in the similarity of the new system to the near ultraviolet bands of N2+ (which has the same number of electrons). However, the doublet splitting required by this interpretation has not been resolved, nor has the study of perturbations in the upper state given clear-cut evidence for doublet structure. On the other hand, a mass-spectrometric investigation of the ions in the flash discharge producing the spectrum shows a strong C2− peak, while C2+ is weak. A definitive answer to the question of the carrier of the new spectrum cannot yet be given.
Neutron activation resonance integrals of 74Se, 78Se, 80Se, 81Br, 127I, 130Te, 138Ba, 140Ce, and 142Ce
Authors: Ricabarra M. D. , Turjanski R. , Ricabarra G. H. , Bigham C. B.
Published: April 2011

A lithium-drift germanium γ-ray spectrometer has been used to make accurate intercomparisons of the ratio of resonance-integral to thermal-activation cross section by measuring cadmium ratios or relative activation rates in two different neutron spectra. The standard, gold, or secondary standard, indium, was mixed uniformly in the samples and the activities resolved with the spectrometer. Expressed as Westcott s0 values, the results relative to s0 = 17.7 for gold were as follows: 74Se = 10.3 ± 0.1, 78Se = 12.3 ± 0.3, 80Se = 2.65 ± 0.02, 81Br = 24.3 ± 0.5, 127I = 27.8 ± 0.5, 130Te = 2.10 ± 0.07, 138Ba = 0.649 ± 0.004, 140Ce = 0.476 ± 0.003, 142Ce = 0.865 ± 0.005.
The conduction processes in silicon nitride
Authors: Kendall E. J. M.
Published: April 2011

The electrical conduction processes through silicon nitride are examined and discussed. Three processes were found to occur: Frenkel–Poole emission, field ionization, and trap hopping. The characteristic constant for the field ionization was found to be lower than expected (~5 × 106 V cm−1), and the thermal activation energy for the trap hopping was between 0.08 and 0.10 eV. The Frenkel–Poole effect indicated trap depths varying from 0.50 to 0.85 eV for various devices, and was more complicated than previously reported. All of the processes were bulk limited. Approximate values of m*/m and the mobility at 300 °K were found to be 0.20 and 0.13 cm2/V s respectively.
Positron–electron scattering and Bhabha exchange effects
Authors: Mendiratta R. G.
Published: April 2011

The study of positron–electron scattering is made using a Wilson cloud chamber to check the presence of Bhabha exchange effects. The observed scattering cross section is more than the value calculated from Moller's theory of positron–electron scattering, where only the Coulomb interaction between the particles is considered. However, the experimental results are in good agreement with the theory if the exchange effects suggested by Bhabha are also included.
Analytic expressions for the thermodynamic functions of superfluid helium
Authors: Singh A. D.
Published: April 2011

Analytic expressions for the thermodynamic functions of superfluid helium are derived by using the experimental dispersion curve for the elementary excitations. The values of the various macroscopic properties calculated this way are in good agreement with those computed by Bendt et al. through numerical integration. This study brings out the relative importance of the various parts of the dispersion curve. The errors made while making the Landau approximations are also brought out.
Vacancy-wind effect in diffusion and deviations from thermodynamic equilibrium conditions
Authors: Manning John R.
Published: April 2011

The vacancy-flow (or "wind") term which appears in kinetic treatments of the diffusion equations is discussed in terms of the vacancy concentrations which appear when a vacancy flow is distorted by an impurity. It is pointed out that this term arises from local distortions in the vacancy-concentration profile and not from any overall deviation of the material from equilibrium vacancy concentrations. Thus, the theory of Kirkaldy and Lane, which considers only net deviations from equilibrium averaged over an entire plane, does not include the vacancy-wind term. Several physical analogies help to describe the basic process. The vacancy-wind term can be large and introduces cross terms in the general thermodynamic equations.The vacancy-wind effect arises from motion of atoms other than the particular diffusing atom. For an accurate kinetic analysis, motion of the diffusing atom itself also must be considered. This motion produces a "mobile-impurity" effect and introduces an additional distortion in the local vacancy distribution. Equations including this effect are discussed. The close relationship between mobile-impurity effects and the correlation factor is shown. For self-diffusion, mobile-impurity and vacancy-wind effects exactly cancel in their influence on vacancy distributions.
Dielectric relaxation of dihalobenzenes. I. Ortho and meta Cl2, Br2, and I2 in benzene solution
Authors: Mansingh Abhai , McLay David B.
Published: April 2011

Dielectric data have been measured for the dilute solutions in benzene at 20.0 °C of the ortho- and meta-isomers of dichlorobenzene, dibromobenzene, and diiodobenzene. The "static" dielectric constants have been measured at 100 kHz, the dielectric constants and losses have been measured at both 9.06 and 21.00 GHz, and the refractive indices have been measured at optical wavelengths. Cole–Cole plots can be fitted to the data to yield mean relaxation times τ0 and distribution parameters α. The values of the relaxation times in the ortho-isomers are 11.8, 14.9, and 20.6 ps for dichlorobenzene, dibromobenzene, and diiodobenzene respectively. The corresponding values for the meta-isomers are 8.6, 10.7, and 13.5 ps respectively, values which increase in the same direction with halogen substituent but which are significantly smaller than the relaxation times for the other isomers. All of these times are of the right order of magnitude for molecular reorientation and there is no evidence for dipole–dipole interactions. Although the nonzero values of the distribution parameters will allow mathematical descriptions in terms of two relaxation times τ1 and τ2, the values derived from two such descriptions yield two unrealistic relaxation times for each molecule. It is concluded that the analysis based on the Cole–Cole plot gives the most meaningful results.
On the thermalization times of positrons in polyatomic gases
Authors: Paul D. A. L. , Leung C. Y.
Published: April 2011

The time taken for positrons from a radioactive source to reach a velocity distribution in the near-thermal range has been measured for mixtures of nitrogen gas with argon, and of methane with argon. An analysis of the shoulder breadths for the free positron components leads to slowing down times of 16 ns for nitrogen and 0.25 ns for methane at densities of 1 amagat. The long slowing time for nitrogen must occur during the last eV or so of slowing and the dominant mode of energy loss is attributable to rotational excitation of the molecules. For methane the slowing to the threshold for vibrational excitation must be extremely rapid, but there is no clearly established mechanism which could account for the remaining energy loss taking place so rapidly.
On the transport properties of a Van der Waals gas near the critical point
Authors: Sobrino Luis de
Published: April 2011

A calculation of the critical anomalies of the transport coefficients of a simple fluid based on a microscopic model of a nonequilibrium Van der Waals gas is presented. It is found that, in the gas region, the anomalous bulk viscosity behaves as (T – Tc)−2. Both the anomalous thermal conductivity and shear viscosity behave as In (T – Tc)−1, but the anomaly in the shear viscosity is much smaller than the anomaly in the thermal conductivity. The results appear to indicate that previous calculations, in which the time dependence of the critical fluctuations is obtained from hydrodynamic equations, are not valid.
Pseudoscalar charge density
Authors: Coombes Charles A.
Published: April 2011

It is shown that a true pseudoscalar charge density—a ψ*ψ which has opposite signs in two regions—can exist. This fact is accomplished by allowing a parity transformation, for which p*p = −1, and by making the operation of hermitian adjoint differ by a minus sign in the two regions. The classical explanation is accomplished by requiring a change in the sign convention used in the two regions connected by the inversion process.
Sensitized fluorescence in vapors of alkali metals. XII. 42P1/2–42P3/2 mixing in potassium, induced in collisions with ground-state rubidium atoms
Authors: Hrycyshyn E. S. , Krause L.
Published: April 2011

The total cross sections for collisions between excited potassium and unexcited rubidium atoms, leading to the transfer of excitation between the 42P states in potassium, have been determined in a sensitized fluorescence experiment. The experiments were carried out at partial pressures of potassium vapor lower than 10−5 mm Hg, at which the imprisonment of resonance radiation may be disregarded. The cross sections Q12″ (42P1/2 → 42P3/2) and Q21″ (42P1/2 ← 42P3/2) equal 260 Å2 and 175 Å2, respectively, and are in the ratio predicted by the principle of detailed balancing.
Production of 8Be in 20 GeV/c proton interactions with the heavy nuclei of nuclear emulsion
Authors: Deka G. C. , Deka K. C.
Published: April 2011

An analysis of 271 collimated pairs of alpha particles of comparable ranges emitted from interactions of 20 GeV/c protons with the heavy nuclei of emulsion has been made; ~90% of these can be interpreted as due to the decay of 8Be in its ground state. The mean Q value (~0.094 MeV) obtained from the analysis is in good agreement with the expected Q value of the reaction 8Be → 24He. The energy and angular distributions of the 8Be nuclei have been compared with the predictions of the nuclear "evaporation" theory. The parameter values for good fit are found to be: T = 10 MeV, V = 10 MeV, and β = 0.015.
Conduction bands of GaSb
Authors: Tongerloo Eric H. van , Woolley John C.
Published: April 2011

Room temperature measurements of free-carrier Faraday rotation have been made on four different single-crystal n-type tellurium-doped samples of GaSb which had been used previously in magnetoresistance measurements. From the combined results for each specimen, values have been calculated for the energy separation of the (000) and [Formula: see text] conduction band minima, ΔE, and the transverse effective-mass ratio of the [Formula: see text] electrons, m1t/m. It is found that ΔE is a function of tellurium content. The value of ΔE at 4.2 °K for an intrinsic sample is hence found to be 0.078 eV. The values obtained for m1t/m, the variation of ΔE with tellurium content (dΔE/dy), and the temperature coefficient of ΔE (dΔE/dT) depend upon the value of the scattering parameter s assumed in the analysis of the room-temperature data. It is shown that the correct value of s lies in the range 0.5 to 1.0 and this gives values for m1t/m = 0.110 and dΔEdy = 0.50 eV/atomic % Te, while dΔE/dT probably lies in the range 0 to −2 × 10−5 eV/°K.
Stability of a cold plasma traversed by two electron beams in the presence of an external magnetic field
Authors: Isaac R. Jayakaran
Published: April 2011

In this paper, the stability of a cold plasma traversed by two electron beams in the presence of an external magnetic field is investigated. Dispersion relations for both longitudinal and transverse modes have been obtained. These dispersion relations have been discussed with respect to the two limiting cases of long- and short-wavelength disturbances. Apart from this, the dispersion relation for transverse modes has been solved numerically for a number of cases. It is found that the system becomes unstable against long-wavelength disturbances while it is stable against short-wavelength disturbances. In particular, for longitudinal modes, those perturbations whose wavelengths are such that their frequencies are near the corresponding frequencies of either of the two beams are found to be unstable. It is also found, numerically, in the case of transverse modes, that under certain conditions there exists a critical value of the wave number α, say α*, such that the system is unstable for the perturbations whose wave numbers satisfy the condition α < α*.
Synthesis of array space factors
Authors: Chow Y. L. , Wu S. C.
Published: April 2011

This report studies the synthesis of array space factors in both main beam and grating lobes. The linear array studied is assumed to be symmetrical. The synthesis is achieved by adjusting both the element excitation and spacing distributions.
Scattering from a conducting cylinder coated with a moving uniaxial medium
Authors: Kong Jin-Au , Cheng David K.
Published: April 2011

The scattering problem of a time-harmonic, plane, electromagnetic wave incident from an isotropic medium normally upon a conducting cylinder coated with a moving uniaxial medium is solved. The solution is facilitated by an equivalence between a general, source-free moving medium and a stationary one which is anisotropic both electrically and magnetically. Both an incident TM wave (parallel polarization) and an incident TE wave (perpendicular polarization) are considered. It is found that axial components of both the electric and the magnetic fields will exist regardless of whether the incident wave is TM or TE. However, when the sheath medium in its rest frame is a uniaxial plasma, an incident TM or TE wave excites only TM or TE fields respectively. Scattering from a moving uniaxial column is treated as a special case.
Conservation of a coherent state distribution
Authors: Webber John C.
Published: April 2011

A certain general P-distribution, which corresponds to a Gaussian distribution as a special case, is found to be conserved, with respect to time, for that general class of Hamiltonians which leave coherent states coherent.
Current distribution in a type II superconducting thin film, and its relevance to the DC superconducting transformer
Authors: Daniels J. M.
Published: April 2011

Using the model of the viscous motion of flux lines in a type II superconductor, an expression is found for the current and field distribution in a superconducting film in the flux-flow regime. The current is peaked near the edges of the strip, the field is constant through the strip, and is very large just outside the strip close to the edges. The presence of this large field could inhibit the movement of vortices in the secondary of a DC transformer if the secondary overlaps the primary laterally.
Beta decay of 87Kr, 88Kr, and 88Rb
Authors: Lycklama H. , Archer N. P. , Kennett T. J.
Published: April 2011

The decay of 1.3 h 87Kr, 2.8 h 88Kr, and 15 min 88Rb to levels in 87Rb, 88Rb, and 88Sr, respectively, has been investigated using high-resolution Ge(Li) detectors, a plastic beta-ray detector, and gamma–gamma as well as beta–gamma coincidence techniques. Isotope separation was achieved using gas-sweeping methods. Consistent level schemes have been constructed for each isotope under study.
Hydrodynamic modes in 3He–4He mixtures at the critical point
Authors: Griffin Allan
Published: April 2011

At the critical mixing point of 3He–4He mixtures, the amplitudes of both the nonpropagating diffusion mode and second sound may become anomalously large. The damping of these two critical modes is discussed on the basis of Khalatnikov's two-fluid hydrodynamics.
Evaluation of the matrix elements and for asymmetric rotors
Authors: Wray J. H.
Published: April 2011

A method of computing the matrix elements [Formula: see text] and [Formula: see text] for asymmetric rotors is presented which utilizes the rigid rotor reduced energies EτJ(κ). The method is formally the same as that of Kivelson and Wilson but differs in the form of the Hamiltonian considered. Explicit solutions of [Formula: see text] and [Formula: see text] are given for those levels for which EτJ(κ) may be given explicitly. These levels are those for which the roots of the reduced energy submatrices can be derived from linear or quadratic factors.