bluuebunny/crossref_metadata_2025 huggingface dataset:
The infrared and ultraviolet absorption spectra of diimide (N2H2)
Authors: Trombetti A.
Published: April 2011

The infrared spectrum of N2H2 in the 3.1 μ region and the ultraviolet spectra of N2H2 and N2D2 have been examined. The analysis of the infrared spectrum indicates that N2H2 in the ground state has a planar trans-conformation with with rN−N = 1.238 ± 0.007 Å and [Formula: see text], assuming rN−H to be between 1.05 and 1.08 Å. In the vacuum ultraviolet spectrum near 1700 Å, progressions of bands with spacings of 1180 and 950 cm−1 have been observed for N2H2 and N2D2, respectively. From the intensity alternation in the J structure of the vacuum ultraviolet spectrum it seems to follow that the electronic ground state of N2H2 is not totally symmetric.
On the Green-function theory of the spin- Heisenberg ferromagnet
Authors: Dembinski S. T.
Published: April 2011

A new first-order decoupling scheme for the Green function appearing in the theory of the spin-[Formula: see text] Heisenberg ferromagnet is introduced. At low temperatures the magnetization has no spurious term in T3 and the coefficient of the term in T4 is within a few percent of the Dyson exact result. The Curie temperature is equal to the random phase approximation Curie temperature.
On the instability of synchrotron radiation
Authors: Fung P. C. W.
Published: April 2011

In a system of isotropic relativistic electrons which is embedded in a cold ambient magnetoactive plasma, the growth rate of synchrotron radiation at wave normal angle θ = 90° is derived by means of the classical kinetic approach. It is shown that the result is identical with that obtained from the quantum treatment. Two errors occurring in the literature of synchrotron radiation are pointed out. The growth rate is computed for the case of monoenergetic electrons as an example.
The spark spectra of zinc. II. Zinc III
Authors: Dick K. A.
Published: April 2011

The energy levels of zinc III have been revised and extended as a result of improved wavelengths of the spectral lines, particularly those in the vacuum ultraviolet. Of the 70 levels listed in Atomic Energy Levels (Moore 1952), 37 have been retained in the present analysis, although the designations of 14 of these have been changed. An additional 233 levels are established. The new scheme results in 1279 line classifications in the region from λ 383 Å to λ 6270 Å. A value of 320 390 cm−1 is given for the ionization potential of Zn III.
A covariant treatment of relativistic plasma oscillations
Authors: Tam Kwok-Kee
Published: April 2011

A covariant theory of plasma oscillations in the absence of an external field is formulated by considering a plasma as the limit of an infinite number of relativistic streams.
Hard-sphere Bose gas model for superfluid helium
Authors: Singh A. D.
Published: April 2011

The density dependence of the properties of a dense hard-sphere Bose gas are calculated. The double-time, retarded Green functions and the t-matrix approach are used to derive the energy spectrum of the elementary excitations. This energy spectrum is then used to calculate the various macroscopic properties of the system. The usefulness of the hard-sphere Bose gas model for understanding the pressure dependence of the properties of superfluid helium is brought out.
Electric dipole moment of a nucleon
Authors: Gourishankar Radha
Published: April 2011

New upper limits for the electric dipole moment of a nucleon are obtained in a model proposed earlier, using the present experimental data on K2 → 2π decays.
Gamma rays from inelastic scattering of 2.9-MeV neutrons by 55Mn, 59Co, 63Cu, 65Cu, 139La, and 141Pr
Authors: Daniels J. M. , Felsteiner J.
Published: April 2011

Gamma rays produced by inelastic scattering of 2.9-MeV neutrons on 55Mn, 59Co, 63Cu, 65Cu, 139La, and 141Pr were observed, using a lithium-drifted germanium detector. Coincidences between these gamma rays were observed, using a sodium iodide detector and a lithium-drifted germanium detector. It was possible to resolve gamma rays, hitherto unresolved, to determine their energies to within ±1 keV in most cases, and to determine their relative intensities to within ±30%.From the energies of the gamma rays and the knowledge of which gamma rays are in coincidence, level diagrams were constructed for these nuclei. There was no reason to dispute the presently accepted level scheme for 55Mn, 59Co, 63Cu, and 65Cu, but the energies of the known levels were determined with greater precision. Two new levels, at 1685 and 1715 keV, are proposed for 139La, and four new levels, at 1117, 1350, 1437, and 1451 keV, are proposed for 141Pr. The decay of 141Nd to 141Pr was examined, and the previously published decay scheme was confirmed. In addition, another weak K-capture branch, to a level at 1437 keV, was found. No evidence is seen for the previously suggested levels at 880 keV in 141Pr and at 800 keV in 139La.The relative production rates of the excited states of all these nuclei were fitted to the Hauser–Feshbach model of inelastic neutron scattering. The earlier determinations of the spins of the first four excited states of 55Mn are confirmed and a spin of 9/2 is suggested for the level at 1883 keV. Spins are suggested for all the levels of 59Co, up to and including the level at 1745 keV. These differ from all the three previously published spin determinations. The spin assignments previously published for the first three excited states of 63Cu and 65Cu are confirmed and spins are suggested for the next three excited states. For both 139La and 141Pr, only the spins of the ground state and the first excited state were known; in each case spins are suggested for the next six excited states.
On the theory of VLF propagation for a step model of the nonuniform earth–ionosphere wave guide
Authors: Wait James R.
Published: April 2011

Reflections in a curved model of the earth–ionosphere are considered for the case where the reflecting height is discontinuous. Explicit formulas are given for calculating the conversion coefficients for an incident mode of order m, a reflected mode of order n, and a transmitted mode of order q. It is shown that the usual neglect of reflected modes has some justification.
An experimental and theoretical study of the momentum distribution of two photon annihilating positron–electron pairs in methane
Authors: Chuang S. Y. , Holt W. H. , Hogg B. G.
Published: April 2011

The momentum distributions of annihilating positron–electron pairs have been measured in liquid and solid methane. Calculated momentum distributions generally assume that the positron wave function ψ+ = 1. This low-momentum, plane-wave representation of the positron is inadequate to describe the experimental distribution for high momenta. A ψ+ obtained by numerical integration of the ground-state radial Schrödinger equation is employed in the calculation and a good fit is observed with experiment for all momentum values.
Behavior of hydrogen in ion sources with hot filaments at very low pressures
Authors: Hobson J. P. , Earnshaw J. W.
Published: April 2011

Experiments designed to establish the approximate magnitudes of the physical processes occurring in ion sources with hot filaments at pressures of hydrogen near 10−11 Torr are described. The objective has been to provide the user of such ion sources with a dynamic description of their behavior as measuring instruments for very low pressures of hydrogen. The measurements were carried out in ultrahigh vacuum apparatus of conventional design near background conditions. It was found that behavior was dominated by a surface phase of hydrogen on the walls and on the electron collector. This surface phase is in quasi-equilibrium with the gas phase and contains orders of magnitude more hydrogen than the gas phase. This large reservoir of hydrogen is very sensitive to small thermal changes. Electron bombardment of the electron collector of the ion source generates a current identified as protons, which is modulated in the modulated Bayard–Alpert gauge as if it were a true ion current from the gas phase.
Dipole matrix elements for vibration–rotation lines in the 2–0 band of the hydrogen bromide molecule
Authors: Rao B. Sesh , Lindquist LuVerne H.
Published: April 2011

The equivalent widths, the line strengths, and the squares of the dipole matrix elements of the 2–0 vibration–rotation band lines of the H79Br molecule are measured. The measurements are made on a high-resolution infrared grating spectrometer which could completely resolve the two isotopic lines of H79Br and H81Br. This is the first time the high-resolution work on the intensities of the HBr molecule has ever been presented. The present data are compared with the earlier work obtained using a low-resolution spectrometer. It is found that the present values are considerably less than the earlier low-resolution values. The discrepancy between the two sets of results is attributed to the lack of resolution in the earlier investigations.
Experimental determination of the dipole moments of the X(2Σ+) and B(2Σ+) states of the CN molecule
Authors: Thomson Ritchie , Dalby F. W.
Published: April 2011

From observation of the electronic emission spectrum in high electric fields, the dipole moments of the X(2Σ+) and B(2Σ+) states of the CN molecule have been determined to be 1.45 ± 0.08 and 1.15 ± 0.08 debye, respectively. The relative signs of the dipole moments in these two states are shown to be opposite.
Mass distribution of meteoroids as determined by radar observations of underdense meteor trails
Authors: McIntosh B. A. , Šimek M.
Published: April 2011

The amplitudes of meteor echoes recorded on high-power radar equipment at Springhill Meteor Observatory have been measured for 57 samples of about 500 meteors each, obtained at various times of day on at least 1 day per month. The number of echoes as a function of echo amplitude is represented by a power law and the exponent in this relation calculated for each sample. Within the limits of error, no strong diurnal or seasonal variations in this exponent have been found. Similarly, there are no significant changes in the exponent when the data are divided into groups according to the height at which the echoes occurred and also according to the distance from the radar to meteor trail.Calibration of the equipment and the methods employed in obtaining and reducing the data are treated in detail. Theory relating the number distribution of echo amplitudes to the distribution of meteoroid masses is reviewed and assessed critically.A best value for the average mass index, s, of the sporadic meteor population in the range from 7th to 10th magnitude is s = 2.3 ± 0.1. The dispersion of individual sample values of s is about ± 0.3.
An analysis of the profile of the pressure-induced pure rotational spectrum of hydrogen gas
Authors: Mactaggart John W. , Hunt James L.
Published: April 2011

The pure rotational infrared absorption band of hydrogen has been investigated in the frequency region 500 to 1400 cm−1. Measurements have been made at densities of up to 100 amagat units and at temperatures of 298, 195, and 77 °K. A blue frequency shift, similar to the shift of the S(0) line observed by Bosomworth and Gush, of the S(1) line of 8 ± 3 cm−1 has been observed. An analysis of the profile has resulted in an individual S line profile which represents the high-frequency wing of the line by a "power law" rather than an exponential shape as presented previously by Bosomworth and Gush.
Primary energy estimation in interactions of 22.8 GeV/c protons with nucleons and light emulsion nuclei
Authors: Bhowmik B. , Shivpuri R. K.
Published: April 2011

In the present work, the validity of the Castagnoli's formula has been tested for primary energy estimation in the case of p–N and p – light nucleus collisions. By eliminating the contribution of the persisting primary in the angular distribution, a better estimate of the primary energy has been obtained. In the case of p–N collisions, a good agreement with the actual value of the primary energy has been obtained for ns > 4 events and a large disagreement for [Formula: see text] events. The latter observation has been explained on the basis of a peripheral mechanism of particle production for such events. In the case of p – light nucleus collisions, the underestimation of the primary energy for high-multiplicity events has been explained as being due to the occurrence of secondary collisions inside the nucleus.
Prediction of a metastable Y0* baryon
Authors: Rosen Gerald
Published: April 2011

On the basis of an empirical mass formula for the baryon octuplet and baryon resonance decuplet, the existence of a metastable [Formula: see text] unitary singlet baryon state with a mass greater than about 2500 MeV is conjectured. Predominantly the I = Y = 0 octuplet member but with a small admixture of the unitary singlet, the Λ baryon would appear as a superposition of the unitary states. The complementary baryon, a metastable [Formula: see text] Y0* composed mainly of the unitary singlet, is predicted.
Vapor pressure of liquid argon, krypton, and xenon
Authors: Bowman D. H. , Aziz Ronald A. , Lim C. C.
Published: April 2011

The vapor pressure of liquid argon, krypton, and xenon was measured from below the normal boiling temperature to close to the critical temperature. Functional relations were fitted by a multiple regression analysis to the experimental data. Data of other authors are compared directly with the results presented here.Comparison of the vapor pressure curves for the three liquids showed that the classical corresponding states principle was obeyed only poorly and that it was necessary to include quantum corrections in comparing the reduced curves. The adjusted reduction factors agreed reasonably well with those found from vapor pressure analysis by other workers. De Boer plots on the basis of our potential parameters are more linear than those using the parameters of Boato and Casanova.
Pressure dependence of nuclear quadrupole relaxation. I. 63Cu relaxation in cuprous oxide
Authors: Armstrong R. L. , Jeffrey K. R.
Published: April 2011

The pressure dependence of the nuclear spin lattice relaxation time of the 63Cu nuclei in a powdered sample of cuprous oxide is reported at two temperatures for hydrostatic pressures in the range 1 to 5000 kg cm−2. It is shown that the experimental value of T1 at atmospheric pressure can be accounted for on the basis of an ionic point charge model for cuprous oxide. The variation of T1 with pressure is discussed on the basis of this model.
Nozzle beam technique for mapping low density gas flows
Authors: LeRoy R. L. , Govers T. R. , Deckers J. M.
Published: April 2011

A collimated nozzle beam is used to probe the exhaust of a converging nozzle operated at Knudsen numbers ranging from 0.73 to 0.044. The results illustrate the expected transition from free molecular to isentropic flow. The technique is sensitive to densities as low as 3 × 1011 molecules cm−3.
Application des miroirs électrostatiques à l'élimination de l'effet chromatique dans les spectromètres magnétiques. Première partie: théorie linéaire
Authors: Baril Marcel
Published: April 2011

Combining an energy-dispersive element with a magnetic prism results in an achromatic mass dispersive instrument, if parameters are chosen appropriately. A plane electrostatic mirror has been chosen as the energy-dispersive element. Trajectories are described in terms of lateral, angular, and energy variations about the principal trajectory. Achromatism and conjugate plane conditions have been calculated by the powerful method of matrix algebra. The first order theory is given in this article (part one), the second order term will be studied in part two which will be published later.
Propagation of high-frequency waves in a plasma
Authors: Sharma S. R.
Published: April 2011

Propagation of high-frequency waves in an unbounded electron-plasma system is examined with the aid of the first three moment equations. The heat-flow tensor is neglected and the effect of collisions is taken into account through appropriate relaxation terms. Assuming an isotropic pressure in the equilibrium, it is shown that the perturbed pressure tensor shows a marked deviation from the isotropic nature if the propagation frequency is higher than the pressure relaxation frequency. A new treatment is presented for the description of transverse waves. The general dispersion relation is derived and is examined in detail for wave propagation along and perpendicular to the magnetic field.
Interaction of plane electromagnetic waves with a moving compressible plasma fluid
Authors: Fujioka H. , Nihei F. , Kumagai N.
Published: April 2011

The problem of reflection and transmission of plane electromagnetic waves by a semi-infinite compressible plasma fluid moving parallel to its own interface with vacuum is investigated. Solutions are obtained for both incident E wave and H wave. It is found that (i) for the case of incident E wave which excites only two distinct magnetoacoustic waves, the reflection and transmission coefficients add to unity; however, (ii) for the incident H wave which excites only the transverse magnetohydrodynamic wave, both coefficients do not add to unity in general, because of the interaction of the electric field of the transmitted wave with surface charge density at the moving interface. Other interesting features due to the movement of the medium are discussed, and a few numerical examples are given.
Trapping and quenching of potassium resonance radiation
Authors: Copley G. , Krause L.
Published: April 2011

The effects of imprisonment of resonance radiation in potassium vapor and of collisions between excited potassium atoms and N2, H2, HD, and D2 molecules, on the measured lifetimes of the 42P states, have been investigated by the method of delayed coincidences. The potassium atoms were excited with short pulses of resonance radiation, and the delays between the exciting and fluorescent pulses were measured with a time-to-amplitude converter. At pure potassium densities below 1010 atoms/cm3, the measured lifetimes approach the constant values 27.8 ± 0.8 and 27.6 ± 0.8 ns, corresponding to the natural lifetimes of the 42P1/2 and 42P3/2 states, respectively. At higher densities the effective lifetimes are in satisfactory agreement with the predictions of Holstein's theory. The decrease in the measured decay rates observed upon addition of the diatomic gases yielded cross sections for quenching collisions with N2, H2, HD, and D2 which equal 34.0 ± 2.0 Å2, 9.4 ± 1.3 Å2, 11.9 ± 1.5 Å2, and 8.0 ± 2.0 Å2, respectively.
Precision measurement of the half-life of 113Inm
Authors: Berg H. van den , McDonnell M. , Ramaswamy M. K.
Published: April 2011

The half-life of the isomeric state of 113In has been variously reported. We have made a precision determination on the chemically separated daughter of the [Formula: see text] reaction and obtain for the half-life of 113Inm a value of 99.2 ± 0.6 min or 1.65 ± 0.01 h.
Slater–Condon parameters for the atoms gallium to krypton, 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 Ga to Kr have been evaluated from analytical Hartree–Fock functions.
Cesium diffusion at a tungsten surface
Authors: Love H. M. , Wiederick H. D.
Published: April 2011

The diffusion of cesium at the surface of tungsten ribbons has been measured under ultrahigh vacuum conditions. A photoelectric method was used to determine the cesium surface concentrations which were in the range from about 5 × 10−4 to 2 × 10−2 monolayers. The measured changes in concentration with time and temperature were consistent, for a polycrystalline ribbon, with two bulk diffusion processes with activation energies of 1.7 ± 0.3 eV and 0.17 ± 0.03 eV. For a single crystal, it was found that limited bulk diffusion occurred with an activation energy of 0.21 ± 0.02 eV. The mean surface diffusion coefficient for cesium on a (110) tungsten surface over the temperature range from 550 °K to 850 °K was given by D = (0.23 ± 0.10 cm2 s−1) exp [−(0.57 ± 0.02 eV)/kT].
Collision broadening in the 3P1 state of Zn
Authors: Cook D. W. , Timsit R. S. , May A. D.
Published: April 2011

A study of the broadening of the "double resonance" line of zinc in the4 3P1 state has been carried out. The cross sections for alignment depolarization by He, Ne, Ar, Kr, and Xe are found to be larger than the values predicted by the theory of Byron and Foley. An empirical formula which describes exactly both the observed shapes and intensities of the resonance curve is proposed.
Study of moving striations in plasmas. V. A study of the saturation process in large amplitude moving striations
Authors: Bolton Richard , Šícha Miloš , Drouet Michel G.
Published: April 2011

Measurements made near the Pupp current limit for the existence of moving striations in neon illustrate the process of saturation of moving striations as the column amplification increases. The measurements show that the nature of the striations changes from the characterization of Pekárek for small amplitude to that of Nedospasov for large amplitude as the plasma potential variation in the striation approaches the potential drop of the external electric field per striation wavelength. Measurements of the relative phases of electron temperature, plasma potential, and luminous intensity for striations near the Pupp current limit are presented.
Application of coordinate transformation to two-dimensional scattering and diffraction problems
Authors: Shafai L.
Published: April 2011

The two-dimensional problem of determining the electromagnetic field scattered by a cylinder of arbitrary cross section is reduced to the solution of first-order, coupled differential equations. The procedure for finding the surface currents, scattered field, and the scattering cross section for a perfectly-conducting cylinder is given in detail. A brief study of the scattering by a polygonal cylinder and n identical strips equally spaced azimuthally around the z axis is used to examine the behavior of the differential equations.
Magnetic field dependence of the thermoelectric power at low temperatures for very dilute alloys of Fe in Au
Authors: Huntley D. J. , Walker C. W. E.
Published: April 2011

Fe–Fe interactions are shown to be responsible for an increase in thermoelectric power with applied magnetic field. A simple model, with Kondo's theory, accounts qualitatively for the observations. Observation only of effects of isolated Fe atoms requires concentrations < 1 p.p.m.
Theoretical ionization energies and oscillator strengths for the sodium isoelectronic sequence
Authors: McEachran R. P. , Tull C. E. , Cohen M.
Published: April 2011

Orbital wave functions for a number of 2S, 2P0, 2D, and 2F0 states of Na, Mg+, and Al2+ have been calculated by means of the frozen core approximation. The oscillator strengths of all allowed dipole transitions have been determined using both length and velocity formulations for the transition matrix element; these results agree with each other to within a few percent.
The half-life of the first metastable state in 90Nb
Authors: Geiger J. S. , Graham R. L. , Johns M. W.
Published: April 2011

A delayed γ activity, Eγ = 122.2 ± 0.2 keV, t1/2 = 18.82 ± 0.09 s, is observed following 10 MeV proton bombardment of targets of natural Zr and of natural Hf in which Zr is present as a contaminant. The present results taken together with other recently published data show that this activity arises from 90Zr(p,n)90Nbm. The tentative assignment of this 122 keV γ activity to 179Ta, which we proposed in an earlier publication, is withdrawn.
Electrical resistivity of binary chromium alloys with vanadium, niobium, and tantalum
Authors: Arajs Sigurds
Published: April 2011

Electrical resistivity of binary chromium alloys containing 1.02, 2.04, and 3.06 at. % vanadium; 0.33, 0.57, and 1.13 at. % niobium; and 0.14, 0.30, and 0.58 at. % tantalum have been measured as a function of temperature between 4 and 325 °K. These studies show that the Néel temperature, TN, decreases with increasing solute concentration in such a manner that ln T plots are linear with respect to the solute content. The curve of TN vs. solute concentration for tantalum, within the solubility limit, overlaps that for vanadium. The corresponding curve for niobium is slightly above the curve associated with vanadium and tantalum. This behavior cannot be explained simply from the viewpoint of the localization of d-wave functions using the model of Fedders and Martin. The increase in the residual electrical resistivity at 4.2 °K due to 1 at. % vanadium, niobium, and tantalum has been found to be 0.45, 2.7, and 3.6 μΩ cm, respectively. The residual resistivity vs. vanadium concentration curve shows an anomaly at about 3 at. % due to the changes in the Fermi surfaces, because of the disappearance of the antiferromagnetic state. None of the binary chromium alloys exhibit the Kim effect at low temperatures found in certain chromium alloys.
Hydromagnetic waves in a finitely conducting fluid mass immersed in a nonuniform magnetic field
Authors: Bajwa G. S. , Srivastava K. M.
Published: April 2011

We have studied the propagation of hydromagnetic waves in a finitely conducting, nonviscous fluid mass of constant density. It is immersed in a time-independent inhomogeneous magnetic field. Due to the nonuniformity of the magnetic field the lines of force are not in general straight lines, and we have made use of a general curvilinear coordinate system. The lines of force of the magneticfield are taken as the coordinate lines and the propagation of hydromagnetic waves is explored. In the discussion we have chosen symmetry with respect to the binormal to the osculating plane containing lines of force, and the lines of force are assumed to be torsionless which make the curvilinear coordinate system orthogonal. By taking binormal as the z axis of the Cartesian coordinate system we conclude that Alfven waves propagate along the field lines and the local inhomogeneity of the magnetic field causes damping of the waves.
A covariant treatment of relativistic plasma oscillations in the presence of an external magnetic field
Authors: Tam Kwok-Kee , O'hanlon John
Published: April 2011

A covariant theory of plasma oscillations for a many-component plasma in the presence of an external magnetic field is formulated.
On the interaction of acoustic surface waves with thermal phonons at low temperatures
Authors: McBride S. L.
Published: April 2011

The attenuation of surface waves by thermal phonons may be treated using the existing theory for the attenuation of bulk waves by thermal phonons, by identifying the interacting modes and suitably generalizing the parameter which describes the coupling between the acoustic mode and the thermal phonons.
An experimental determination of the dipole moments of the X(1Σ) and A(1Π) states of the BH molecule
Authors: Thomson Ritchie , Dalby F. W.
Published: April 2011

The optical emission spectrum of the BH radical produced in a discharge tube designed to give high electric fields shows Stark effects. From these, the dipole moments of the X(1Σ+) and A(1Π) states are determined to be (1.27 ± 0.21) D and (0.58 ± 0.04) D, respectively.
Observation of stimulated radiative emission from normal to superconducting metal junctions
Authors: Gregory W. D. , Leopold L. , Repici D.
Published: April 2011

Approximately 10−7 W of radiation at the energy-gap frequency of Ta (3 mm wavelength at 4.26 °K) has been observed traveling through free space from specially formed Ta–Al point contacts. This radiation appears discontinuously at a threshold current density of about 105 A/cm2, disappears as the sample is warmed above Tc, and appears to be tunable by changing the energy gap with temperature. These results are consistent with our predictions of stimulated emission from normal–superconductor contacts.
Origin shifts in divergent Feynman integrals
Authors: Pugh Robert E.
Published: April 2011

The surface terms arising from a shift of origin in divergent Feynman integrals are considered. Sum rules and recursion relations between these terms are derived for an arbitrary degree of divergence and tensor rank. These relations are explicitly solved for linear, quadratic, cubic, and quartic divergences.
Transient response of the penumbral currents for plane wave diffraction by a cylinder
Authors: Wait James R.
Published: April 2011

Diffraction of plane electromagnetic waves by a perfectly conducting cylinder is considered. Following a discussion of the alternate representations for the time harmonic problem, the transient solution is obtained for impulsive excitation. A convergent expansion for the transient response of the currents in the penumbral region is developed. It is shown that the latter is consistent with an operational approach used earlier for step-function excitation.
Nuclear spin relaxation in hydrogen gas
Authors: Lalita Krovvidi , Bloom Myer , Noble John D.
Published: April 2011

The proton spin–lattice relaxation time T1 in normal H2 gas has been measured as a function of temperature between 293 °K and 738 °K and pressure between 7 and 135 atm. These data and previous measurements at lower temperatures are analyzed in terms of a generalized theory which takes into account the influence of collisions which change the rotational quantum number J as well as those which only change MJ. It is concluded that collisions which change J play an important role even at temperatures as low as 200 °K. The relative importance of different types of inelastic collisions which give rise to changes in J is discussed. Some preliminary results of the radial dependence of the anisotropic H2–H2 interaction are given, but more accurate measurements of T1 as a function of ortho-H2 below room temperature are required to make a definitive interpretation.
Relative yields of stable tin isotopes in neutron-induced fission
Authors: Laeter J. R. de , Thode H. G.
Published: April 2011

A tandem mass spectrometer of high sensitivity has been used to measure the relative yields of the six stable isotopes of tin (117Sn, 118Sn, 119Sn, 120Sn, 122Sn, and 124Sn) and the long-lived isotope 126Sn, produced in the thermal- and fast-neutron fission of 233U and in a reactor fuel rod of natural uranium. Samples of the order of 10−9 g of tin were extracted and analyzed to give a range of yields in the region of symmetric fission. The results show that the mass yield curves in the region of symmetric fission covered by the stable tin isotopes are almost identical for the three irradiations. Furthermore, a smooth curve can be drawn through the yield points for the seven isotopes of tin and there is no evidence of "fine structure" or sharp depression in the curves in this region as has been predicted.
Variational approximations to nonspherical particle-like solutions of ΔΦ = Φ – Φ3
Authors: Darewych J. W. , Schiff H.
Published: April 2011

Variational approximations to nonspherical neutral particle-like eigensolutions of ΔΦ = Φ – Φ3 are obtained. Trial functions of the type [Formula: see text] (cos θ) are used for axially symmetrical solutions. The coupled Euler–Lagrange equations, obtained by extremizing the associated energy–momentum tensor component with respect to the Rl's, are solved numerically for N = 1, 2, and 3 when the Rl's are nodeless and for N = 1 and 2 when they have a single node each. Integrals are computed which, for exact solutions, are equal to the extremized energy, but which are not generally simultaneously extremized by the variational approximations. The results are compared with variational calculations of Betts, Schiff, and Strickfadden, who made use of trial functions with adjustable constant parameters rather than functions. Results indicate that no axially symmetric single-particle solution exists which is asymptotically proportional to P1(cos θ).
Spin–lattice relaxation of Fe3+ in rutile for X- and F-band transitions
Authors: Lichtenberger G. J.
Published: April 2011

Detailed measurements of the angular and temperature dependence (1.6 °K to 4.2 °K) of the dominant spin–lattice relaxation rates of Fe3+ in rutile have been carried out for a number of strong transitions at 9.4 Gc and 121 Gc using the pulse saturation method. At 9.4 Gc, two relaxation time components were observed, ranging from 0.5 to 1.2 ms and 1.6 to 4.0 ms, respectively, at 4.2 °K. Assuming a relationship of the form log(relaxation time) = −n∙log(temperature), the temperature dependence factor n was found to be between 0.4 and 1.0. The single relaxation time resolved at F band had values from 0.7 to 1.0 ms at 4.2 °K, and n between 0.1 and 0.6. The corresponding relative relaxation rates were calculated from the direct process spin–phonon transition probabilities, assuming Debye elastic isotropy for rutile. Using a cubic spin–lattice coupling tensor, [Formula: see text] was found to be 0.5 and the rate equations for the six-level system were solved. The calculated effective relaxation times were successfully identified with the slower dominant relaxation component of the experimental data.
Rotational analysis of the A–X bands of AsO+
Authors: Shanker Rama , Singh I. S. , Singh O. N.
Published: April 2011

The (1,0) and (2,0) bands of the A–X system of the AsO+ molecule have been recorded in the third order of a 35-ft concave grating spectrograph. The rotational analysis has been carried out and the transition has been found to be 1Π–1Σ. The rotational constants are given.
Properties of the 9.699 MeV level in 28Si
Authors: Anyas-Weiss N. , Charlesworth A. M. , Carlson L. E. , Jackson K. P. , Azuma R. E.
Published: April 2011

The decay of the 9.699 MeV level in 28Si has been studied using the reaction 27Al(p,γ)28Si at Ep = 1724 keV. Gamma rays from the decay of the 9.699 MeV level were observed with large-volume Ge(Li) detectors. Branching ratios for the decay of the 9.699 MeV level have been obtained and a lower limit for the lifetime of this level has been measured to be [Formula: see text] using the Doppler-shift attenuation method.
Electronic spectrum of ethylene. I. The 1744 Å Rydberg transition
Authors: Merer A. J. , Schoonveld L.
Published: April 2011

The vibrational structures of the 1744 Å Rydberg transitions of C2H4 and C2D4 have been examined in detail. For both isotopes the relative intensities of the principal bands have been measured, and various 'hot' bands appearing in high temperature spectra have been assigned. Vibrational analysis has shown that the ethylene molecule is non-planar at equilibrium in the 1B3(u) upper electronic state, being twisted by 25° ± 1°, with a potential barrier of 290 ± 20 cm−1 to inversion through the planar configuration. The C–C bond length in the upper state is 1.41 ± 0.01 Å and the hydrogen atoms lie 0.03 Å further from the axis of least moment of inertia (through the C–C bond) than they do in the ground state. It is concluded that C2H4 in its higher Rydberg states and the C2H4+ ion in its ground state are also twisted at equilibrium.The correct form for the torsional potential function for the 1B3(u) electronic state (which becomes one component of a degenerate 1E state when the molecule is twisted by 90°) has been considered; it is found that although the 1E state suffers a comparatively large static Jahn–Teller distortion, there are no observable effects resulting from coupling of the electronic and torsional motions (dynamic Jahn–Teller effect).
Range of implanted boron, phosphorus, and arsenic in silicon
Authors: Davies D. Eirug
Published: April 2011

Experimental range data for boron, phosphorus, and arsenic implanted into silicon are presented over the energy region from 0.15 to 1.8 MeV, 0.5 to 1.7 MeV, and 1.0 to 1.7 MeV respectively. The range energy dependence at these energies shows the expected predominance of electronic stopping in the case of boron and the increased importance of nuclear stopping for the two heavier ions.
Electron spin–lattice relaxation of Ni2+
Authors: Lee K. P. , Walsh D.
Published: April 2011

The electron spin–lattice relaxation rate by the direct process for Ni2+ in lanthanum magnesium nitrate is surprisingly fast (5 × 103 s−1 at 1.55 °K). Ni2+ is a non-Kramers ion, however, and consequently is strongly coupled to the lattice in most cases. The effective spin triplet and the absence of both hyperfine structure and phonon bottleneck are optimum requirements for a maser material.
Experimental evidence for the absence of a long-lived K–Xe complex in 42P1/2–42P3/2 mixing in potassium induced by collisions with xenon atoms
Authors: Copley G. H. , Krause L.
Published: April 2011

An experimental investigation of the delay in the sensitized fluorescence in potassium, induced by collisions with xenon atoms, has been carried out using the delayed coincidence method in a search for a long-lived molecular collision complex. Potassium atoms, present at low densities in mixtures with xenon, were excited with 50 ns pulses of potassium resonance radiation of wavelength 7665 Å. The delay in the appearance of the sensitized fluorescence, of wavelength 7699 Å, was monitored in relation to xenon pressure. The results indicate that 2P1/2–2P3/2 mixing in potassium proceeds mainly by a prompt reaction and does not involve a long-lived intermediate state.
Absorption spectrum of SiH in the vacuum ultraviolet
Authors: Herzberg G. , Lagerqvist A. , McKenzie B. J.
Published: April 2011

A new electronic transition of SiH has been observed in absorption near 1907 Å in flash discharges through mixtures of SiH4 and H2. The rotational analysis shows this transition to be of the type 2Σ+−2Π. The corresponding transition of SiD has also been observed and analyzed. The D2Δ−X2Π transition near 2058 Å which was observed and analyzed by Verma in SiD has been measured here for SiH, where the lines are much broader on account of predissociation. The predissociation phenomena in SiH and SiD and the electron configurations are briefly discussed, and the presently known molecular constants of these molecules are summarized.
Spectroscopic analysis of single-particle transfer reactions in the SU3 scheme
Authors: Stewart K. W. C. , Castel B.
Published: April 2011

Spectroscopic factors for single-particle exchange reactions are calculated in the SU3 model. As a first approximation, each state is described by only one SU3 representation. Agreement with experiment is found to be as good as for the more complicated versions of the Nilsson and shell models.
Resonance strengths and decay schemes in 23Na(p,γ)24Mg
Authors: Baxter A. M. , Cassell K. J. , Kuehner J. A.
Published: April 2011

Six resonances in the reaction 23Na(p,γ)24Mg have been studied using a 40 cm3 Ge(Li) detector. These resonances occur at proton energies of 512, 987, 1020, 1174, 1318, and 1416 keV. Decay schemes and branching ratios for the levels in 24Mg corresponding to the resonances have been established and a number of discrepancies between this and previous work have been found. Resonance strengths and hence γ-decay widths for the resonances at 987, 1020, 1174, and 1318 keV have been obtained in terms of the known width of the 512 keV resonance. The observation of a weak transition from the 1416 keV resonance to the 9.46 MeV level in 24Mg plus a Doppler-shift measurement on the decay of the 9.46 MeV level have permitted the spin and parity of the 9.46 MeV level to be restricted to 3+ or 4− with the former favored.
Stationary properties of approximate wave functions
Authors: Ruffa A. R.
Published: April 2011

The accuracy of quantum mechanical wave functions is examined in terms of certain stationary properties. The most elementary of these, namely that displayed by the class of wave functions which yields a stationary value for the total energy of the system, is demonstrated to necessarily require few other stationary properties, and none of these appear to be particularly useful. However, the class of wave functions which yields both stationary energies and charge densities has very important stationary properties. A theorem is proven which states that any wave function in this class yields a stationary expectation value for any operator which can be expressed as a sum of one-particle operators. Since the Hartree–Fock wave function is known to possess these same stationary properties, this theorem demonstrates that the Hartree–Fock wave function is one of the infinitely many wave functions of the class. Methods for generating other wave functions in this class by modifying the Hartree–Fock wave function without changing its stationary properties are applied to the calculation of wave functions for the helium atom.
Etude quantitative de l'énergie libre de PbZrO3 pur et dopé avec Nb2O5
Authors: Benguigui L. , Hervet H.
Published: April 2011

Pure and Nb2O5 doped PbZrO3 exhibit the following phases: antiferroelectric, ferroelectric, and paraelectric. By means of measurements of heat transition, dielectric constant in paraelectric phase, determination of electrical field – temperature phase diagrams, we calculate the free energy of each phase. Given that the free energy can be developed in powers of the polarization, we show the coefficients of the ferroelectric phase are slightly modified by the addition of Nb2O5, while those of the antiferroelectric phase vary by a factor greater than two.
Nuclear interaction matrix elements in a phase-shift approximation
Authors: Srivastava M. K. , Jopko A. M. , Sprung Donald W. L.
Published: April 2011

A method suggested by Elliott for calculating nuclear interaction matrix elements directly from phase shifts is developed into a practical scheme applicable to all partial waves. Matrix elements are constructed from experimental phase shifts and compared to several other calculations. A shell-model calculation of 58Ni based on these matrix elements gives results comparable to those of Kuo.
Relaxation of the uniform Knudsen gas coupled to a thermal bath
Authors: Grmela M. , Kyncl J.
Published: April 2011

The possibility of a reduced macroscopic description of the Knudsen gas coupled to a thermal bath (by analogy with the hydrodynamical description of an isolated rarefied gas) is discussed.A study of the relaxation of the Knudsen gas coupled to a thermal bath with time-varying characteristics (e.g. with time-varying temperature) is made.
The binding energies of s-shell nuclei
Authors: Law J. , Bhaduri R. K.
Published: April 2011

We have calculated the binding energies of 4He and 3H with soft- and hard-core nucleon–nucleon potentials. With central forces, using harmonic-oscillator wave functions, we find that accurate results can be obtained by taking only the long-range part of the potential and its second-order perturbative term. When tensor forces are present, the long-range interference term is also included in the calculation. In this case, the method is not accurate and underbinds these nuclei by about 1 MeV per particle. Ignoring Coulomb forces, our method yields a value of 18.5 MeV for the binding energy of 4He with the Hamada–Johnston potential.
Octupole transitions in 19F and other s–d shell nuclei
Authors: Cusson R. Y.
Published: April 2011

The deformed Nilsson model is first applied to the study of the E3 transition from the 1.347 MeV state (Jπ = 5/2−) in 19F to the ground state (Jπ = 1/2+). The value 0.56 W.u. is obtained while the experimental one is 7.6 ± 1.3 W.u. A deformed schematic RPA calculation is then performed to describe a Q3,0 octupole oscillation. An enhanced value of 2 W.u. is obtained without changing excessively the Nilsson configuration of the excited band head. Octupole sum rules are derived and evaluated for 16O, 19F, and 20Ne. A study is made of the interplay between permanent quadrupole deformations and octupole vibrations.
Effect of Hall current on the stability of an anisotropic plasma
Authors: Kalra G. L. , Talwar S. P.
Published: April 2011

The magneto–gravitational instability of an unbounded tenuous plasma, subject to the influence of a uniform magnetic field which results in a tensorial plasma pressure, is investigated. The Chew, Goldberger, and Low equations for a collisionless plasma and a generalized Ohm's law, which includes the effects due to Hall current and electron inertia, are used. Criteria of instability in terms of plasma pressure, parallel and perpendicular to the magnetic field, and the Hall current parameter are derived for the special cases of parallel and perpendicular propagation vectors. It is found that the Hall effect has a stabilizing influence, although it does not produce stability for all wavelength perturbations. The monotonic instability is replaced by a growing wave instability (overstability). The presence of electron inertia, however, destabilizes a certain range of wavelengths which are stabilized by Hall current.
Inelastic electron scattering from the 13 MeV region in oxygen-16
Authors: Kim J. C. , Singhal R. P. , Caplan H. S.
Published: April 2011

The cross section for the inelastic scattering of electrons from 16O was measured at excitation energies between 11.5 and 13.25 MeV and momentum transfers between 0.45 and 0.9 fm−1. This momentum transfer range bridges the gap between the previous high momentum transfer data of Bishop et al. and the low momentum transfer data of Stroetzel. The odd parity states are compared with the particle–hole predictions generated from Gillet's wave functions. The generalized Helm model fits the 11.5 MeV (2+) level fairly well. An upper limit is set on the excitation of the magnetic monopole (0−) level at 12.70 MeV.
Theory of conduction-electron spin resonance
Authors: Walker M. B.
Published: April 2011

The influence of the conduction-electron magnetization density, induced in a metallic slab by an incident microwave electromagnetic field, on the power absorbed from the microwave field, and on the field transmitted through the slab, is studied theoretically. The motion of the magnetization density is described by a Bloch equation, modified to include diffusion; this approach is equivalent to, but simpler than, that of Dyson. For classical skin effect conditions, exact formulas for the amplitudes of the transmitted fields and for the surface impedance are obtained for symmetric excitation, for antisymmetric excitation, and for one-sided excitation. In performing the calculations, it is found to be convenient to separate the magnetization density into two parts, a forced part and a free part; the forced part is the more important in the slow-diffusion limit, while the free part is the more important in the rapid-diffusion limit. A calculation of the amplitude of the transmitted field, valid under anomalous skin effect conditions, is given for the limiting cases where the diffusion is either very rapid or very slow. Also, the dependence of the polarization of the transmitted fields on the angle which the static applied magnetic field makes with the normal to the slab is discussed.
Dielectric constants and indices of refraction of Xe, Kr, and Ar
Authors: Marcoux Jules
Published: April 2011

Dielectric constants of Xe, Kr, and Ar have been measured at the boiling point, the melting point, and in the solid phase. They are compared, using Maxwell's relation, with the indices of refraction measured at these points by the same author.
Spectroscopic identification of the SiH+ molecule: The A1Π–X1Σ+ system
Authors: Douglas A. E. , Lutz Barry L.
Published: April 2011

The A1II–X1Σ+ transition of the SiH+ molecule has been observed in the emission spectrum of a hollow-cathode discharge through helium containing a trace of silane. The analysis of five bands yields the molecular constants Bc″ = 7.6603 cm−1, ΔG″(1/2) = 2088.69 cm−1, Bc′ = 4.9125 cm−1, ΔG′(1/2) = 390.17 cm−1, and v(0–0) = 25 025.20 cm−1. Because of the shallowness of the upper-state potential curve, a good estimate of the dissociation limit is obtained: D00(SiH+) = 3.20 ± 0.08 eV. This dissociation limit leads to an ionization potential of 8.01 ± 0.08 eV of SiH. The SiH+ molecule is tentatively identified in the solar spectrum and the possibility of detecting interstellar SiH+ is briefly discussed.