bluuebunny/crossref_metadata_2025 huggingface dataset:
An Alternative Method of Obtaining Approximate Solutions to the Dirac Equation. I
Authors: Moore R. A.
Published: April 2011

An alternative method of obtaining approximate solutions to the Dirac equation is presented. The method takes advantage of the fact that the wave functions can be written as an ordered series in powers of the fine structure constant, α, and that the Hamiltonian can be separated into two parts such that one part connects adjacent orders of the wave function. Energy calculations to order α2, requiring only the solution to the lowest order equation, are considered in this article. The procedure is tested by applying it to the hydrogen atom. It is seen that the lowest order equations are similar to and no more difficult to solve than the nonrelativistic equations for all systems of physical interest. The simplicity and accuracy of the method implies that full relativistic calculations are unnecessary for most situations. The inclusion of electric and magnetic fields and the solution to the first order equation will be considered in later articles.
Kinetic Theory of Molecular Gases I: Models of the Linear Waldmann–Snider Collision Operator
Authors: Tenti G. , Desai Rashmi C.
Published: April 2011

Using a method closely akin to the Gross–Jackson–Sirovich procedure, we present a modeling theory of the linear Waldmann–Snider collision operator. The resulting model kinetic equations are applicable to all regions of wavelength and frequency consistent with the original equation itself. The theory is made parameter free by relating the matrix elements of the collision operator to measured transport properties. It is sophisticated enough to afford a study of both scalar and tensorial phenomena and can be applied to the analysis of a variety of initial and boundary value problems.
Effect of Many Particle, Many Hole States in 16O on Positive Pion Photoproduction
Authors: Rao K. Srinivasa
Published: April 2011

The 1p–1h odd parity T = 1 states of 16N (2−, 0−, 3−, 1−) are amended to include the 3p–3h configuration admixtures consistent with the choice of a 16O ground state containing 2p–2h correlations. Estimates indicate that these 3p–3h admixtures result in a nonnegligible increase or decrease of the cross sections depending upon the amount of 2p–2h correlations in the ground state of 16O.
Rotational Analysis of the A2Π–X2Σ+ Band System of the BeBr Molecule
Authors: Carleer M. , Herman M. , Colin R.
Published: April 2011

A rotational analysis has been performed on the 0–0 band of the A2Π–X2Σ+ transition of the BeBr molecule photographed at high resolution in emission from a beryllium hollow cathode in the presence of bromine vapor. The following principal molecular constants have been determined:[Formula: see text]
Transport Properties of n Type Cd3−xZnxAs2 Alloys
Authors: Aubin M. J.
Published: April 2011

Measurements of the Hall and magneto-Seebeck effects were performed on polycrystalline Cd3−xZnxAs2 alloys at room temperature. The range of x considered here (0 to 1) is characterized by samples which are normally n type. Analysis of the data with Kane's model gives a minimum of the matrix element P at x = 0.6 which is interpreted as the manifestation of the band crossover suggested by Wagner et at. The scattering parameter also exhibits a minimum but at x ~ 0.2. A possible explanation may involve the manner in which the zinc atoms occupy the lattice vacancies.
L Subshell Fluorescence Yields and Coster–Kronig Transitions at Z = 70
Authors: McNelles L. A. , Campbell J. L. , Geiger J. S. , Graham R. L. , Merritt J. S.
Published: April 2011

The nine L subshell radiative and nonradiative de-excitation probabilities, ωi and fij, have been determined for the atom Yb (Z = 70) by conversion electron–X-ray coincidence measurements. The results are in good agreement with theoretical values calculated by McGuire using a simple approximation to the Herman–Skillman potential.
CO2 Laser Induced Breakdown and Heating of Hydrogen in a Magnetic Mirror Field Geometry
Authors: Offenberger A. A. , Burnett N. H.
Published: April 2011

A 1 GW, 125 J CO2 laser pulse focussed by a 10 cm f.l. parabolic mirror has been used to induce breakdown and heating in 15 Torr hydrogen along the axis of a short 50 kG magnetic mirror field. Evolution of the breakdown plasma thus produced has been studied by high speed photography, ruby laser Thomson scattering, and a Mach–Zehnder interferometer. Results indicate an efficient radial confinement of plasma by the mirror field with an electron temperature much enhanced over that resulting from a fieldfree breakdown. Interferometric measurements show that breakdown results in a cylindrical plasma with an electron density minimum on axis in both cases. A monitor of the transmitted CO2 laser pulse indicates very incomplete coupling of laser radiation into the plasma column with the field applied, presumably due to refraction losses at the entrance boundary of the breakdown.
A Study of Fluid Argon via the Constant Volume Specific Heat, the Isothermal Compressibility, and the Speed of Sound and their Extremum Properties along Isotherms
Authors: Stephenson John
Published: April 2011

The properties of fluid argon are investigated via the maxima and minima along isotherms of selected thermodynamic functions, the isothermal compressibility, χT, the constant volume specific heat, CV, and the speed of sound, W. Calculations are based on an equation of state due to Gosman, McCarty, and Hust and on speed of sound data compiled by Thoen, Vangeel, and Van Dael. The calculation of CV in the dense liquid region, from the equation of state and from the speed of sound, is discussed in detail. Also, the linear dependence of W on the density in the liquid region is reconciled with the behaviour of W at temperatures above critical to obtain a unified description of the variation of W along isotherms.
The Lifetime of the 72.6 keV Level in 138La
Authors: Wender S. A. , Islam A. , Summers-Gill R. G.
Published: April 2011

By means of a 138Ba(p,nγ) delayed coincidence experiment, the first excited state of 138La has been found to have a half-life of 116 ± 5 ns. We conclude that the transition is electric quadrupole and that the state has Jπ = 3+.
Threshold Photoneutron Angular Distributions and an M1 Giant Resonance in 208Pb
Authors: Haacke L. C. , McNeill K. G.
Published: April 2011

Threshold photoneutron time-of-flight spectra from the 208Pb(γ,n)207Pb reaction have been measured at five angles to the incident photons. Angular distributions obtained for 14 resonances within 850 keV of the 208Pb(γ,n) threshold have led to assignments of M1 strength totalling 67.5 ± 12 eV. The total M1 strength available from spin-flip transitions from the i13/2 neutron shell and the h11/2 proton shell has been calculated to be 100 eV (Weiss). Thus, the data confirm the existence of an M1 giant resonance just above threshold in 208Pb.
The Ground State and A2Π Excited State of Magnesium Deuteride
Authors: Balfour Walter J. , Cartwright Hugh M.
Published: April 2011

The visible emission spectrum of MgD has been reexamined at high resolution. Published analyses of the A2Π → X2Σ+ system have been extended and the data have been combined with observations in the B′2Σ+ → X2Σ+ system to provide information on the ground state levels ν = 3, 4, 5, and 6 for the first time. The following molecular constants (in cm−1) have been determined—for the A2Π state: ωc = 1154.75, ωcxc = 16.675, Bc = 3.2190, Dc = 9.64 × 10−5 and for the X2Σ+ state: ωc = 1077.71, ωcxc = 15.92, Bc = 3.0306, and Dc = 9.39 × 10−5. The dissociation energies in the A2Π and X2Σ+ states have been estimated to be ~ 15 500 cm−1 and ~ 11 500 cm−1 respectively. The MgH/MgD isotope effect and the Λ doubling in the A2Π state are discussed.
Lifetime of the 8543 keV (6+) State of 28Si
Authors: Dixon W. R. , Storey R. S. , Carter A. L. , Pai H. L.
Published: April 2011

The 25Mg(α,nγ)28Si reaction has been used to populate the 8543 keV, 6+ state of 28Si and the mean lifetime has been determined from the attenuated Doppler shift of the 8543 → 4617, 6+ → 4+ transition. The result is 19 ± 8 fs, in good agreement with results from the (p,γ) reaction but not with an earlier measurement using the (α,nγ) reaction.
Equation radiale de Schrödinger et complétude du système {H, L2, Lz}
Authors: Dormale Bernard M. de , Gautrin Henri-François
Published: April 2011

This paper gives the relationship between the spectral analysis of the Hamiltonian in quantum mechanics and the Schrödinger radial equation, using for this a generalization of the Riesz–Lorch lemma (Riesz and Lorch; Riesz and Sz.-Nagy). The results obtained are then used to study the completion of set of operators {H, L2, Lz} (de Dormale and Gautrin).
Three Photon Ionization of Alkali Atoms at the Ruby Laser Wavelength
Authors: Cervenan M. R. , Chan R. H. C. , Isenor N. R.
Published: April 2011

Single mode ruby laser radiation (694 nm) and an atomic beam apparatus have been used in the study of the three photon ionization of Na, K, Rb, and Cs atoms. The process in all cases is nonresonant, the observations being consistent with a rate given by W3F3 where F is the photon flux. The values obtained for W3l (linear polarization) and W3C (circular polarization) and the ratio W3c/W3l are discussed in relation to recently calculated results and the few other experimental results available. Discrepancies well beyond the assigned errors exist between experimental and calculated results.
Proton NMR Study of Molecular Motions in the Solid Phase of a Smectic A Liquid Crystal
Authors: Dong Ronald Y. , Wiszniewska M. , Tomchuk E. , Bock E.
Published: April 2011

Proton T1, T1ρ, and T1D were studied in the solid phase of diethylazoxybenzoate from 105 K to the melting point. The activation energies for the threefold reorientation of methyl groups and for the molecular self-diffusion were determined to be about 3.3 and 11 kcal/mole respectively. Between 170 and 240 K, a new slow molecular motion with an estimated activation energy of 3.7 kcal/mole was detected via the T1ρ data.
The 16O(p, γ)17F Direct Capture Cross Section with an Extrapolation to Astrophysical Energies
Authors: Chow H. C. , Griffiths G. M. , Hall T. H.
Published: April 2011

The cross section for the direct radiative capture of protons by 16O has been measured relative to the proton elastic scattering cross section for energies from 800 to 2400 keV (CM). The elastic scattering cross section was normalized to the Rutherford scattering cross section at 385.5 keV. The capture cross section for the reaction 16O(p,γ)17F, which plays a role in hydrogen burning stars, has been extrapolated to stellar energies using a theoretical model which gives a good fit to the measured cross sections. The model involves calculation of electromagnetic matrix elements between initial and final state wave functions evaluated for Saxon–Woods potentials with parameters adjusted to fit both elastic scattering data and binding energies for the ground and first excited states of 17F. Cross sections for capture to the 5/2+ ground and 1/2+ first excited states of 17F in terms of astrophysical S factors valid for energies ≤ 100 keV have been found to be: S5/2+ = (0.317 + 0.0002E) keV b (± 8%); S1/2+ = (8.552 − 0.353E + 0.00013E2) keV b (± 5%).
The Nuclear Three Body Problem with Phase Equivalent Separable Interactions
Authors: McGurk N. J. , Fiedeldey H.
Published: April 2011

The triton ground state energy and the neutron–deuteron doublet scattering length have been calculated with two families of phase equivalent separable interactions in the 1S0 and 3S1–3D1 states of the nucleon–nucleon interaction. Generating the interactions from a solution of the inverse scattering problem, a separable representation of the nucleon–nucleon interaction is fully exploited to fit the scattering and bound state data as well as possible. Off shell constraints on the interactions are then discussed. Results for the three nucleon quantities are compared to those obtained with realistic local and one boson exchange potentials. It is shown that all results for potentials obeying the known off shell constraints lie on the Phillips band, which appears to be independent of the potential model employed. This is a consequence of the fact that the triton binding energy and doublet scattering length are only sensitive to the broad detail of the nucleon–nucleon S matrix in the 1S0 and 3S1–3D1 states and to certain global features of the residues at the singlet deuteron and deuteron poles. Relatively large off shell variations in the triton binding energy and doublet scattering length along this Phillips band are possible and the plausibility that the experimental values could be fitted is discussed.
Collision Induced Absorption in N2, CO2, and H2 at 2.3 cm−1
Authors: Dagg I. R. , Reesor G. E. , Urbaniak J. L.
Published: April 2011

Collision induced microwave absorption is reported in pure N2, CO2, and H2 in the region of 2.3 cm−1. For N2 the results are taken at temperatures ranging from 208 to 333 K and at densities ranging from 50 to 300 amagat. The parts of the loss factor which are proportional to the square and the cube of the density are found to depend respectively on T−1.55±0.12 and T−2.56±0.44. These results are well explained by the theory which relates the virial coefficients and relaxation times to the loss factor. Both the two and three body relaxation times, τ2 and τ3 follow very closely a T−0.5 dependence. The ratio of τ2/τ3 is found to be 0.83. For CO2 the results are taken at temperatures ranging from 273 to 363 K and at densities ranging from 8 to 80 amagat. The parts of the loss factor which are proportional to the square and cube of the density depend respectively on T−3.08±0.05 and T−5.4±0.059. These results together with existing infrared results show that τ2 is nearly proportional to T−0.5 and the ratio τ2/τ3 is 0.91 at 296 K. An initial measurement is reported for collision induced absorption in H2. The results for all three gases have been compared to previously reported results in the low frequency region.
First Observation of the BeXe+ Molecule: The A2Π–X2Σ Band System in Emission
Authors: Coxon J. A. , Jones W. E. , Subbaram K. V.
Published: April 2011

Twenty-three new violet degraded bands in the region λ 4100–4700 Å have been observed in emission from a microwave discharge through beryllium chloride and flowing xenon at total pressures near 200 Torr. The band system is attributed to the A2Π–X2Σ+ transition of the new molecule BeXe+. Approximate molecular constants are reported from the vibrational analysis. The observation and assignment of this spectrum of BeXe+ confirm our recent results on the BeAr+ and BeKr+ molecules, for which it was proposed that the ion-induced dipole interaction was largely responsible for the ground state binding energies.
Theoretical Confinement Times in Electromagnetic Traps
Authors: Dolan T. J. , Larsen J. M. , Stansfield B. L.
Published: April 2011

An approximate theory has been developed for the calculation of particle confinement times in 'electromagnetic traps' (electrostatically plugged, minimum B plasma confinement devices). Thermalization losses and cross field diffusion losses are taken into account. Results are presented for characteristic machines, corresponding roughly to present experiments, the next generation of electromagnetic traps, and a fusion reactor.
Positron Scattering and Annihilation in Neon Gas
Authors: Mao A. C. , Paul D. A. L.
Published: April 2011

The lifetimes of positrons have been measured in pure neon gas with and without the application of an electric field and in neon–nitrogen mixtures. The results for pure neon are complicated by not quite pure exponential decays and internal consistency arguments have been used to set minimum values upon the equilibrium (or thermal) value of Zeff and upon the thermalization time. Annihilation in neon–nitrogen mixtures provides an extrapolated Zeff for thermal positrons of 6.02 ± 0.16. This result is consistent with the results for pure neon and enables the thermalization time to be set at a minimum value of 2700 ns amagat. Comparison with the theory of Montgomery and LaBahn and also with the phase shifts of Jaduszliwer and Paul suggests that the true thermalization time in pure neon may be more than twice this value, the possible discrepancy being explainable on the basis of one to two parts per million polyatomic impurity in the neon gas. The Zeff of Montgomery and LaBahn in the '2p → d and 2s → p norm.' approximation is 20% higher than the experimental value. Results under electric field show no unexpected features up to 31.9 V cm−1 amagat−1.
A Mössbauer Study of the β Phase of Iron–Germanium
Authors: Daniels J. M. , Moore F. E. , Panda S. K.
Published: April 2011

Measurements have been made of the Mössbauer spectra of 5 samples of the β phase of iron–germanium, covering the full range of composition, Fel+yGe (1/2 ≤ y ≤ 1), of this phase. Spectra were taken for both randomly oriented powders and also powders with the grains oriented with an easy direction of magnetization perpendicular to the plane of the absorber. The spectra resolved into 3 six-line patterns, indicating 3 inequivalent Fe sites. The occupation numbers and canting angles of each site were measured and the spins localized on each site were deduced to be 1/2, 2, and 2. The structure of this phase is discussed in the light of these observations.
Propriétés des niveaux de l'37Ar entre 2.7 et 3.8 MeV d'énergie d'excitation
Authors: Vaillancourt R. , Haas B. , Taras P.
Published: April 2011

The properties of seven levels in 37Ar were studied via the 34S(α,n)37Ar reaction at Eα = 10.5 MeV. The simultaneous measurement of the linear polarization and the angular distribution of the decay γ rays, in coincidence with the neutrons emitted along the beam axis, provided values of the branching and mixing ratios of these γ rays. From these measurements the spin–parity values for the following levels were established, excitation energy in keV: Ex(Jπ) = 2797(5/2+), 3170(5/2+), 3185(9/2−), 3274(5/2−), 3527(7/2−), 3605(3/2+), 3706(7/2−). The Jπ values of the 3706 keV level are in disagreement with the results of Gadeken et al.
The Percus–Yevick Equation of State for the Sticky Hard Rod Gas
Authors: Tago Yoshio , Katsura Shigetoshi
Published: April 2011

The Percus–Yevick (PY) equation is solved exactly for the sticky hard rod gas. The isotherms obtained from the virial, compressibility, and energy equations are compared with the exact one. The PY energy equation of state is shown to be exact.
Note on Interference Effects in Two-Step Reaction Processes
Authors: Cejpek J. , Dobeš J.
Published: April 2011

The reaction processes in which a one-step transition is forbidden are analyzed from the point of view of the first order perturbation theory. The interference between two competing two-step reaction paths is found to be always constructive. A qualitative explanation of the experimentally observed reaction intensities is presented.
Radio-frequency Echoes from Metal Powders
Authors: Kupca S. , Searle C. W.
Published: April 2011

Echoes, following an rf pulse sequence, which originate from excitation and refocusing of elastic modes in powders of various metals were observed in a 10–100 MHz frequency range. The echoes from ferromagnetic and normal metals have many identical properties; differences between them are due to different excitation mechanisms. The experimental evidence suggests that in all cases the echo is formed by refocusing of single particle resonance modes.
The 7/2− Doublet in 55Fe
Authors: Robertson B. C. , Micklinghoff M. , Castel B.
Published: April 2011

An investigation of the Jπ = 7/2− states at 1316 and 1408 keV excitation in 55Fe is presented as a test of the coexistence of particle and hole states in that nucleus. The lifetimes were measured using the solid stopper Doppler shift attenuation technique, yielding values of [Formula: see text] and τ > 4 ps for the 1316 and 1408 keV levels respectively. The 1408 → 1316 keV branch was determined to be 2.5 ± 0.5%. The results are compared with other available experimental information and with the predictions of a quasiparticle–core coupling calculation. The model analysis indicates very limited mixing of particle and hole configurations.
Neutron Optical Activity Through Spin–Orbit Interaction
Authors: Kabir P. K. , Karl Gabriel , Obryk Edward
Published: April 2011

A theoretical estimate is made of the natural rotation of neutron spin arising through spin–orbit interaction when a polarized neutron beam passes through an assembly of handed molecules. The rotatory power first appears in third order for fixed molecular orientation but only in fourth order for an assembly of randomly oriented molecules. For a favorable case, the magnitudes are expected to be of order 10−9 cm−1 and 10−13 cm−1 respectively.
Observation of particles delayed long times after extensive air showers
Authors: Smith Gary R. , Standil S.
Published: April 2011

A large aperture, five element cosmic ray telescope was operated in conjunction with an air shower array in a search for long lived particles, delayed between 1 and 45 μs after extensive air showers. After sampling ~ 29 000 air showers with an energy greater than ~ 1014 eV, over a period of 9 months, an excess of 11 such events were observed with time delays in the interval of 1 to 6 μs following the showers. The events in the remainder of the 45 μs interval were consistent with background random coincidences. We estimate that only 1 of the 11 excess events might be attributable to afterpulsing in our telescope photomultiplier tubes. All the excess 'trailing particle' events can be explained as being due to electrons resulting from shower associated muons that stop and decay in the vicinity of the cosmic ray telescope.
Zeeman effects in the band System of sulfur dioxide
Authors: Brand J. C. D. , Hardwick J. L. , Humphrey D. R. , Hamada Y. , Merer A. J.
Published: April 2011

Bands of the [Formula: see text] system of sulfur dioxide appear as structured absorption superimposed on an apparent continuum. A portion of this System between 3250 and 3000 Å has been recorded in a magnetic field and is found to exhibit a strong Zeeman effect, contrary to expectation for a singlet-singlet transition between bent states of an asymmetric rotor. Line shift and broadening is observed in relatively low fields (< 3 kG), and the spectra become diffuse in fields of ~ 10 kG. The possibility is considered that the magnetic moment in the Ã state results from rotational coupling of singlet electronic states but it appears unlikely that the angular momentum so developed is sufficient to account for the observations. The most probable explanation of the magnetic sensitivity is that the Ã state couples with a background of interacting vibrational levels of the ground state and low lying states of the triplet manifold.
Nitrogen implanted SiC: Correlation of channeling and electrical studies
Authors: Thompson D. A. , Chan M. C. , Campbell A. B.
Published: April 2011

A study has been made of silicon carbide implanted with nitrogen at an elevated temperature (450 °C) using channeling techniques and electrical (C–V) measurements. Results indicate the formation of a PIN structure after high temperature anneals. The buried insulating region is related to a buried damaged layer, both of which decrease in thickness with increasing anneal temperature. In a thin (~ 100 Å) surface layer, 20–30% of the implanted nitrogen atoms became electrically active. This is shown to be in reasonable agreement with a measured average 'substitutional' percentage of 50% throughout the implanted layer.
Absorption oscillator strengths to autoionizing states in Li, N, and F and their isoelectronic sequences
Authors: Beck Donald R. , Nicolaides Cleanthes A.
Published: April 2011

We have calculated the photoabsorption oscillator strengths of the one and two-electron transitions Li 1s22s2S → 2s22p2P0, NI 2s22p32P0 → 2s2p42D, NI 2s22p32D0 → 2s2p42D, and FI 2s22p52P0 → 2s2p62S, whose upper states are autoionizing, according to a new first order theory of oscillator strengths (FOTOS). These oscillator strengths are often very small and are sensitive to the details of electron–electron interactions. Also computed are the f values for ions in the N and F isoelectronic sequences. Comparison of our theory with three very recent beam-foil values in OII, FIII, and NeII shows excellent agreement.
Cyclotron masses in ReO3 measured by the de Haas–van Alphen effect
Authors: Razavi F. S. , Datars W. R.
Published: April 2011

Cyclotron masses in ReO3 have been determined from the temperature dependence of the de Haas–van Alphen (dHvA) amplitude. Three frequency branches for magnetic field directions in the (110) plane were investigated. The dHvA effect was detected by the low-frequency field-modulation technique using magnetic fields between 35 and 55 kOe at temperatures below 2.172 K. Measured cyclotron mass values are in reasonable agreement with the theoretical predictions of Mattheiss calculated by the augmented plane wave (APW) method. A small frequency branch in the region of the [110] direction with a frequency of 72.0 MG and a cyclotron mass of 1.07 m0 at [110] was detected in addition to the six frequency branches in the (110) plane which were reported previously. The new branch is attributed to an electron orbit resulting from magnetic breakdown between the β and γ APW Fermi surface sheets.
Nuclear spin–lattice relaxation of 3He on neon surfaces
Authors: Chapman R. , Bloom M.
Published: April 2011

Measurements have been made of the NMR wall relaxation time, T1W, of a system of 3He gas in contact with a strongly relaxing untreated pyrex surface and also a weakly relaxing neon-coated pyrex cell. The experiments were performed at temperatures in the range 2.6 K < T < 20 K and at fields between 0.5 and 9.3 kG. The field dependence of TIW for the weakly relaxing neon surfaces can be understood in terms of a model of a surface layer of adsorbed 3He atoms. A theory of relaxation governed by the two-dimensional diffusion of 3He atoms is presented and found to give a satisfactory fit to the data. The experiments suggest that measurements of the gas phase 3He relaxation times T1 are an effective and useful probe of the adsorbed phase of 3He.
High resolution studies of magnetic optical activity in the 3A2–lA1 system of formaldehyde
Authors: Brown J. M. , Buckingham A. D. , Ramsay D. A.
Published: April 2011

Magnetic rotation spectra of the 3A2–1A1 system of formaldehyde have been photographed with high resolving power; the 1+–0 band has been studied in detail throughout its rotational fine structure. The magnetic circular dichroism (MCD) and birefringence (MCB) of this band have also been recorded. The results have been interpreted using the theory of Buckingham and Stephens and satisfactory agreement found. The magnetic optical activity arises primarily from A terms although some features which can be attributed to B terms have been identified.
Spectre du radical P2+ : Etude des transitions C2Π – X2Π et D2Π–X2Π
Authors: Malicet J. , Brion J. , Guenebaut H.
Published: April 2011

The emission spectrum of the P2+ molecular ion has been obtained with a high frequency discharge through a mixture of helium and phosphorus vapour. Both the C2Π–X2Π and D2Π–X2Π systems have been photographed under high dispersion and their rotational structure analysed.The previously known C2Π–X2Π system has been completed by analysing 21 new bands. The D2Π(inv)–X2Π system has not been observed previously. For the three states, involved in these two transitions, the vibrational and rotational constants have been calculated or refined. The p constants for the Λ-doubling for each state have been evaluated. Finally the interpretation of the data of the C2Π state requires a centrifugal distortion term AD in the spin–orbit coupling constant A.
Efficient computation of one-electron two-centre exchange integrals in ion–atom collisions
Authors: Msezane Alfred
Published: April 2011

A scheme is presented for the reduction to one-dimensional integrals of any one-electron two-centre exchange matrix elements which incorporate the momentum associated with the translational motion of the electron. These elements are of the types occurring in close coupling-based treatments of ion–atom collisions. It is shown in a six state approximation, by coupling both eigenstates and pseudostates for the asymmetric He2+–H collision process, that computing time for the evaluation of the matrix elements is determined mainly by the number of different exponents in the matrix elements. The coupling of additional states with the same principal quantum number as the already coupled ones alters computing time insignificantly.
Charge density fluctuations and the softening of phonons in electron–phonon systems
Authors: Kurihara Yasunari
Published: April 2011

The theory of charge–density fluctuations and phonon-softening is formulated exactly using the diagrammatic method for simple electron–phonon systems without many band effects and Umklapp processes. These electron–phonon systems are classified to three cases according to the strength of the electron–electron interaction and the electron–phonon interaction. The criteria for occurrence of the charge-density wave state and periodic lattice distortion are discussed in each case. They are given using the partial summation of diagrams. Here the phase transition is assumed to be of second order.
Representations of sl(3, IR) with half-integral spin bands
Authors: Rosensteel G. , Rowe D. J.
Published: April 2011

A series of irreducible representations of sl(3,IR) is constructed with half-integral spin bands which parallels the principal series of SL(3,IR). While the principal series for SL(3,IR) was shown by Weaver and Biedenharn to be applicable to even–even deformed nuclei, the series constructed here applies to odd mass nuclei. It is shown how parity is included in an SL(3,IR) algebraic model. A second (cuspidal parabolic) series of representations of SL(3,IR) is constructed, which is required for the harmonic analysis of wave functions on SL(3,IR), a necessary preliminary to the application of the results of the SL(3,IR) model in a full microscopic treatment of deformed nuclei. It is shown that the cuspidal parabolic series has undesirable properties for the description of collective states in rare-earth nuclei.
Effect of magnetic fields on the anomalous shear ultrasonic attenuation peak in Ho
Authors: Simpson A. M. , Jericho M. H. , Jain M. C.
Published: April 2011

The magnetic field dependence of the anomalous attenuation peak for ultrasonic shear waves propagating along the c axis in Ho single crystals near 90 K has been studied. We find that a magnetic field has a pronounced effect on the attenuation peak and that for certain field orientations the attenuation anomaly disappears altogether. For some field orientations the attenuation showed hysteresis effects when the field was cycled. We have also found evidence for considerable rotation of the plane of polarization of the sound waves when the field was near the c axis or the basal plane. It is hoped that the results will contribute to the understanding of the nature of the attenuation anomaly.
Tensor interactions of conduction electrons in simple metals
Authors: Sy H. K.
Published: April 2011

Recent experiments by Lubzens, Shanabarger, and Schultz on aluminum have stimulated considerable theoretical works. In one of these, a tensor interaction between conduction electrons was proposed (Walker). We present here the first calculation of this interaction due to the spin–orbit contribution to the electron–phonon matrix element. Single orthogonalized plane waves (OPW) and realistic potentials are used. The spin–lattice relaxation due to the same mechanism is also computed. The tensor and spin–lattice contributions to conduction electron spin resonance (CESR) line width for Na and Al are compared with experiments. Although the calculations are crude, they demonstrate that the tensor interaction gives a contribution to the effective g tensor which is comparable in magnitude to the one-electron contribution and cannot be neglected.
The electronic (yellow and violet) emission spectra of zirconium nitride
Authors: Bates John K. , Dunn T. M.
Published: April 2011

Two emission systems of ZrN have been obtained under high resolution at 5700 and 4050 Å. They are the A2Π → X2Σ and B2Σ → X2Σ systems analogous to those previously known for the isoelectronic molecules ScO and TiN.Analysis of the B2Σ → X2Σ system of the 90Zr14N species yields the values B0 = 0.4587 cm−1 and B0 = 0.4830 cm−1 for the B and X states respectively, while for the A2Π state (which is severely perturbed at low J for the 90Zr14N species) the90Zr15N species gives B0 = 0.4523 cm−1 and this yields a (calculated) value for the A state of the 90Zr14N species of 0.4799 cm−1.There are four perturbations in the 2Π3/2 state of both the Zr14N and Zr15N species.
Spin waves in a model of commensurate chromium alloys
Authors: Walker M. B.
Published: April 2011

The wave vector and frequency dependent transverse magnetic susceptibility is evaluated at long wavelengths, low frequencies, and low temperatures for a rigid band model describing the commensurate phase of chromium alloys. The results, including the value of the spin wave velocity, are found to be independent of alloy concentration in the stable commensurate phase. The magnetization density is separated into intraband and interband parts, the former giving rise to a spin wave pole in the susceptibility of intensity proportional to ωq (the spin wave energy) in the neighborhood of nuclear Bragg reflections, and the latter giving rise to a spin wave pole of intensity proportional to ωq−1 in the neighborhood of magnetic superlattice reflections. The introduction of an appropriate notation renders the results identical to those for a Heisenberg antiferromagnet. Some results for a metastable commensurate phase are also given.
A study of levels in 155Dy using the (d,t) and (3He,α) reactions
Authors: Straume O. , Burke D. G. , Thorsteinsen T. F.
Published: April 2011

The (d,t) and (3He, α) reactions on a target of 156Dy have been used to study the nuclear structure of 155Dy. Beams of 15 MeV deuterons and 24 MeV 3He were obtained from the McMaster University FN tandem Van de Graaff accelerator. The reaction products were analyzed with an Enge-type magnetic spectrograph and detected in photographic emulsions. The (d,t) reaction was studied at 15 angles with typical peak widths (FWHM) of ~ 6 keV and (3He,α) exposures were made at 5 angles with peak widths of ~ 18 keV. The (d,t) angular distributions and ratios of the (3He,α) and (d,t) cross sections were used to determine l values for a number of transitions. It is found that the positive parity states can be described in terms of the Nilsson model when Coriolis coupling is included while for the negative parity states only the gross features are well-described this way.
Superoperator methods for calculating cross sections: I. Correlation functions and the Born approximation
Authors: Turner R. E. , Snider R. F.
Published: April 2011

Quantum mechanical scattering theory has recently been formulated exclusively in terms of density operators. The present work interprets the resulting generalized collision cross sections as integrals overtime correlation functions of relative coordinate, two body operators. It is shown that a straight line trajectory approximation to these time correlation functions is identical to the Born approximation. A phase space representation of the quantum collision dynamics is formulated. In these terms, the quantum cross section can be reduced in a natural way to the corresponding classical cross section provided there is no 'singular' behaviour. It would appear that this formulation would be very appropriate for making semiclassical approximations for the differential cross sections.
Precise measurement of the ground state (2P1/2–2P3/2) splitting of atomic chlorine by CO2 laser Zeeman spectroscopy
Authors: Dagenais M. , Johns J. W. C. , McKellar A. R. W.
Published: April 2011

The 2P1/2–2P3/2 transition within the 2P ground state of atomic chlorine has been studied by the technique of laser Zeeman spectroscopy using a 13C16O2 laser line at 882.288 cm−1. The 2P1/2–2P3/2 splitting is measured to be 882.3519 ± 0.0012 cm−1 (weighted mean for the 35Cl and 37Cl isotopes), and this splitting is determined to be 28.2 ± 2 MHz larger for 37Cl than for 35Cl.
Z-dependence of correlation effects and f values in the sodium iso-electronic sequence
Authors: Fischer Charlotte Froese
Published: April 2011

An accurate theoretical study of ionization potentials and f values in the sodium iso-electronic sequence has been performed using a frozen core, multi-configuration Hartree-Fock procedure.The Z-dependence of core-polarization and its effect on the transition integral are investigated. The initial increase in both these quantities as Z increases is explained in terms of a relative collapse in the size of the atom. Analytic expressions are derived for 3s–3p, 3s–4p, 3p–4s, and 4s–4p transition integrals.Core-polarization has reduced the f values for the 3s–3p transitions somewhat, but still leaves a discrepancy of up to 25% between theory and recent beam–foil results.
Nouvelle approche dans la mesure de la largeur d'une fente
Authors: Brochu M. , Delisle C.
Published: April 2011

A method to measure the width of a slit which is based on the phenomenon of fringes of equal chromatic order is described. The use of spectral fringes for this application is new and differs totally from the method normally used in industrial metrology laboratories. In the latter case, one uses a high quality instrument to measure with precision the distance a slit has to move in order for the operator to bring a carefully adjusted microscopic reticle from coincidence with one edge of the slit to coincidence with the other. In the proposed method, we measure the alternating component of the luminous flux through the slit when a cosinusoidaly modulated light distribution is moved in front of the slit. A null alternating component indicates equality between the width of the slit and the spacing of the fringes. This approach, although requiring more complex instrumentation, introduces a new dimension in industrial metrology related to the measure of the width of a slit.[Journal translation]
Investigations of metal ion – rare gas pairs by optical spectroscopy: High resolution analysis of the A2Πr–X2Σ+ system of BeAr+
Authors: Subbaram K. V. , Coxon J. A. , Jones W. E.
Published: April 2011

Rotational analyses have been performed for the 1–0, 0–0, 0–1, 0–2, 0–3, and 0–4 bands of the A2Πr–X2Σ+ system of BeAr+ near 4000 Å. Molecular constants have been obtained by direct least squares fits of the line frequencies to model Hamiltonians. The Λ-type doubling in the A state is compared with that found for other nine valence-electron systems. RKR curves are calculated for both states, and provide an estimate of Dc″ = 4100 ± 200 cm−1 for the X2Σ+ state. Franck–Condon factors and r-centroids for the transition are also reported.
Eighth spectrum of selenium: Se VIII
Authors: Joshi Y. N. , vanKleef Th. A. M. , Benschop H.
Published: April 2011

The spectrum of selenium was photographed in the region 90 Å – 600 Å on a 10.7 m grazing incidence spectrograph at the National Bureau of Standards Laboratory, Washington, D.C. The source used was a triggered vacuum spark. On the basis of our measurements the Se VIII spectrum has been revised and extended. The parametric calculations of the energy levels and the intensity calculations of the observed transitions confirm the analysis. Forty-five lines are now classified in this spectrum. Resonance lines of Se VII spectrum were also measured accurately.
Doppler spectrum of 42 MHz CW auroral backscatter
Authors: Haldoupis Christos , Sofko George
Published: April 2011

Spectral studies of 42 MHz CW auroral backscatter indicate the existence of two general categories of spectra, discrete and diffuse, that correspond to radio echoes from auroral irregularities produced by different mechanisms. The discrete spectra are of two types, narrow and broad, probably caused by longitudinal plasma waves. The narrow discrete spectra are almost certainly due to two-stream generated ion-acoustic plasma waves. The diffuse spectra constitute about 70–75% of the total observations and appear to be due to a random assembly of electron irregularities, possibly caused by plasma turbulence, whose mean drift motion changes from being strongly southward to weakly northward as time proceeds from the midnight to dawn sector. These echoes disappear when the mean velocity crosses zero, which implies that the same parameter may be responsible for both the mean drift and generation of the irregularities. It is argued that this parameter is probably the east–west electric field and that the motions observed are E×B Hall-drift motions.
Spin isomer conversion and orientational ordering in solid methane: I. The nuclear susceptibility
Authors: Piott J. E. , McCormick W. D.
Published: April 2011

The mechanisms responsible for spin isomer con version in CH4 and some of the ramifications of such a conversion are investigated. The approach to equilibrium of an unstable mixture of spin isomers suggests possible transitions responsible for the conversion. Transitions between the lowest states belonging to spin isomers as well as transitions between excited, nearly degenerate, states occur. The temperature dependence of the mean square nuclear spin determines the hindered rotational energy levels whose energies are below 18 K. Previously published data agree with the specific heat and entropy calculated from the rearrangement of the molecules among these hindered rotational energy levels.
Density and lifetime measurements in the KEMP II electromagnetic trap
Authors: Stansfield B. L. , Larsen J. M. , Bergevin B. , Couture P. , Gregory B. C.
Published: April 2011

The temporal evolution of the electron density in a repetitively-pulsed electromagnetic trap has been measured. The plasma is produced by ionization of a background gas by a pulsed electron beam. The plasma density is measured by a microwave interferometer (8 GHz), and the particle lifetime by the density decay after the interruption of the beam pulse. These measurements show that reasonably dense plasmas (~4 × 1011 cm−3 cm−3) can be confined for the order of a millisecond. Apparently the effect of residual ionization becomes important in the decay phase, due to the high electron energies (~2000 eV).
Intermediate-field effects and electron motion in an axial plane in cadmium
Authors: Alderson J. E. A. , Hurd C. M. , McAlister S. P.
Published: April 2011

The Hall resistivity ρ21(B,T) observed in Cd when B lies in the basal plane has been measured in fields B = 0.1–2.4 T and at temperatures T = 1.7–560 K. The behaviour of ρ21(B,T) in the intermediate-field condition is analysed first qualitatively in terms of contributions arising from features such as intersheet scattering, magnetic breakdown, open and saddle-point orbits, as well as closed electron and hole orbits. These qualitative conclusions are supported by a path integral calculation of the magnetoresistive tensor that is produced by model orbits chosen to imitate the principal contributors to conduction in an axial plane. The results provide an explanation of the origins of the principal features seen in the behaviour of ρ21(B,T) when [Formula: see text].
Resonance dipole–Raman scattering at the forbidden yellow exciton in Cu2O
Authors: Choudhury Gayatri Bhattacharya , Jain K. P.
Published: April 2011

It has been observed by Yu, Shen, Petroff, and Falicov that there is a strong resonance enhancement in the 220 cm−1 Raman line of Cu2O at the Γ12− phonon-assisted absorption threshold of the forbidden 1s yellow exciton. In this paper we present a more complete theory to explain their experimental results over the entire spectral range. The theory includes both the continuum and discrete scattering. It has been shown that away from the resonance the continuum part plays a dominant role. The kinetic energy of the 1s yellow exciton is incorporated into the theory by introducing an energy-dependent lifetime broadening parameter Γ(ω). In the absence of detailed knowledge of the contribution of various phonons to the exciton lifetimes over the entire energy range, we have chosen to work with a phenomenological Γ(ω).
Etats Rydberg de NS. Etude du domaine spectral 2400–1750 Å
Authors: Vervloet Michel , Jenouvrier Alain
Published: April 2011

Five electronic transitions, C2Σ+–X2Π, I2Σ+–X2Π, E2Π–X2Π, J2Σ+–X2Π, and F2Δ–X2Π of NS have been observed in the region 1750–2400 Å. The complete analysis of these transitions has been carried out. The molecular constants of the C2Σ+, E2Π, J2Σ+, and F2Δ Rydberg states are given. Many perturbations in the rotational structures (ν = 1 and 2 of C2Σ+, ν = 0 of E2Π) and predissociations in the levels ν = 0 J2Σ+ and F2Δ are observed. The perturbation in the level ν = 0 of the E2Π state is described, the perturbing level being ν = 11 of the H2Π valence state.The most important results are given in the tables of constants. An energy level diagram and potential curves show the relative position of the different states. All the observed states of NS are finally compared with those of PO.
The 3-D distribution of sources of optical scattering computed from complex-amplitude far-field data
Authors: Lam D. K. , Schmidt-Weinmar H. G. , Wouk A.
Published: April 2011

We present a fast computer algorithm to solve the scalar inverse scattering problem numerically by inverting a linear transformation which maps a 3-D distribution of scattering sources into the angular distribution of the resultant scattered far field. We show how an approximate solution to the problem can be found in discrete form which leads to non-singular systems of linear equations of a type whose matrix can be inverted readily by fast algorithms.The method uses Born's first approximation and is valid for a slowly varying refractive index: the resultant numerical problem can be solved by a fast algorithm which reduces computing time by ~10−7, storage requirement by ~10−5, as compared with Gaussian elimination applied to 125 000 sample points. With this algorithm, computerized 3-D reconstruction becomes feasible.
Fock approximation to the large polaron in a magnetic field
Authors: Lepine Y. , Matz D.
Published: April 2011

We study the large polaron ground state energy in the presence of a constant and uniform magnetic field within the Fock approximation. By use of a new trial spectrum we find a new upper bound to the ground state energy for all magnetic fields and electron–phonon coupling constants. The trial spectrum has the novel feature of keeping cylindrical symmetry for certain values of coupling, even in the absence of magnetic field.
The closed-shell effect on fission barriers at Z = 82 and N = 126
Authors: Pai H. L. , Andrews D. G.
Published: April 2011

A method is suggested for the separation of the overlapping proton and neutron closed-shell effects on experimental fission barriers at Z = 82 and N = 126.