bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionization-detected opticaloptical double resonance spectroscopic studies of moderate energy Rydberg states of calcium monofluoride
Authors: Gittins C M , Harris N A , Hui M , Field R W
Published: April 2011

This paper describes a systematic investigation of quasi-bound Rydberg states of calcium monofluoride (CaF) existing between the molecule's υ+ = 0 and 1 ionization thresholds. Experiments utilized ionization-detected opticaloptical double resonance spectroscopy to assign states as belonging to one of the six core-penetrating ([Formula: see text] [Formula: see text] 2) or to a core-nonpenetrating ([Formula: see text] [Formula: see text] 3) Rydberg series. Most states observed had effective principal quantum number, ν, between 12 and 18 and one quantum of vibrational excitation in the CaF+ ion-core, although lower ν, υ [Formula: see text] = 2 states were also identified. Core-nonpenetrating states were observed both directly and through avoided crossings with core-penetrating states. Five of the seven [Formula: see text] components in the f-complexes derived from Ca+, 13f and n = 14f, have been identified. We present a detailed analysis of the CaF electronic structure for 12.5 [Formula: see text] ν [Formula: see text] 14.6, υ = 1 using an effective Hamiltonian model to describe CaF+ ion-core-induced [Formula: see text]-mixing between [Formula: see text] [Formula: see text] 3 (s,p, d, and f) Ca+ atomic orbitals. An observed avoided crossing between the 14.19 2Σ+, υ = 1 and 14f ([Formula: see text] = 3), υ = 1 states implies that the previously identified 0.19 Σ+ core-penetrating series has 2030% f 2υ+-character. The effective Hamiltonian approach accounts for much of the data, however, a complete accounting requires the use of multichannel quantum defect theory (MQDT). An MQDT analysis of the data presented here is provided in a companion paper by Jungen and Roche in this issue. The effective Hamiltonian model enabled derivation of electrostatic properties of the CaF+ core as well as the 0.14Δ series quantum defect derivative, [dδ/dR]Re+, which governs the exchange of energy between the Rydberg electron and the CaF+ ion-core. The CaF+ electric quadrupole moment, defined with the coordinate origin at the center-of-charge, is 11.3 ± 0.5 a.u. PACS Nos.: 33.40+f, 33.80Eh, 33.15Ry, 33.15Ta
Soft-X-ray spectra of highly charged Au ions in an electron-beam ion trap
Authors: Träbert E , Beiersdorfer P , Fournier K B , Utter S B , Wong K L
Published: April 2011

Systematic variation of the electron-beam energy in an electron-beam ion trap has been employed to produce soft-X-ray spectra (20 to 60 Å) of Au with well-defined maximum charge states ranging from Br- to Co-like ions. Guided by large-scale relativistic atomic structure calculations, the strongest Δn = 0 (n = 4 to n' = 4) transitions in Rb- to Cu-like ions (Au42+  Au50+) have been identified. PACS Nos.: 32.30Rj, 39.30+w, 31.50+w, 32.20R
Fourier transform spectra and inverted torsional structure for a CH3-bending fundamental of CH3OH
Authors: Lees R M , Xu L -H , Kristoffersen A K , Lock M , Winnewisser B P , Johns J WC
Published: April 2011

The high-resolution Fourier transform spectrum of CH3OH has been investigated in the 14001650 cm1 CH3-bending region, and perpendicular Δ K = 1 subbands forming a consistent pattern have been identified with origins from 1490 to 1570 cm1. The location of the subbands as the only significant spectral features towards the upper edge of the CH3-bending absorption favours their assignment to the ν4 in-plane A' asymmetric CH3-bending mode. The upper state term values have been fitted to J(J + 1) power-series expansions to obtain substate origins and effective B-values. The origins exhibit a linear K-dependence as well as the normal variation with K2. The mean effective B-value of 0.82 cm1 is higher than that of the ground state, consistent with a bending vibration. The pattern of K-reduced torsionvibration energies is anomalous. It appears to be inverted relative to the customary picture for n = 0 torsional levels, in agreement with a recent prediction, but has unusual periodicity significantly different from the ground state. A simple Fourier cosine series model for the energy curves gives a vibrational band origin of 1477.6 cm1 for this CH3-bending mode, close to the best current calculated value for ν4. PACS Nos.: 33.20E, 33.80B
Rate coefficients for rotationally inelastic collisions of CO with H2
Authors: Mengel M , De Lucia F C , Herbst E
Published: April 2011

We have performed quantum-scattering calculations to determine inelastic rate coefficients of the astrophysically important collision system COH2. We have used a modified version of the most recent potential-energy surface by Jankowski and Szalewicz (J. Chem. Phys. 108, 3554 (1998)), which has been proven to be superior to a previous potential surface by comparison with experimental pressure broadening data. In contrast to previous studies we find that inelastic rates with Δ J = 2 for CO are smaller than those with Δ J = 1. PACS No.: 34.50Ez
Millimetre-wave spectrum of HC17O+. Experimental and theoretical determination of the quadrupole coupling constant of the 17O nucleus
Authors: Dore L , Puzzarini C , Cazzoli G
Published: April 2011

The millimetre-wave spectrum of HC17O+ has been analyzed up to 348.2 GHz by recording the J = 2 [Formula: see text] 1 and J = 4 [Formula: see text] 3 rotational transitions. Present measurements and the previous detection of the J = 1 [Formula: see text] 0 transition carried out in this laboratory allowed us to determine accurate values of the rotational and centrifugal distortion constants, and of the nuclear quadrupole coupling (χ) and spin-rotation constants. Moreover, χ has been evaluated from the electric field gradient at the oxygen nucleus calculated by using the multiconfiguration self-consistent field approach plus subsequent multireference configuration interaction computation, employing basis sets of quadruple zeta quality. Excellent agreement with experiment has been obtained. In addition, the molecular dipole moment has been calculated at the same level of accuracy. PACS No.: 33.20Bx
Refined potential-energy surfaces for the 2A" and Ã 2A' electronic states of the HO2 molecule
Authors: Jensen P , Buenker R J , Gu J -P , Osmann G , Bunker P R
Published: April 2011

In a previous paper (G. Osmann et al. J. Mol. Spectrosc. 197, 262 (1999)) we calculated ab initio the potential-energy surfaces of the ground [Formula: see text]2A" and excited Ã2A' electronic states of the HO2 molecule; these two states correlate with a 2Π state at linearity and participate in a Renner effect interaction. In that paper, we also calculated the electric- and magnetic-dipole moment and transition-moment surfaces, and the spin-orbit coupling constant; we then simulated the Ã ® [Formula: see text] emission band system including both electric-dipole and magnetic-dipole transitions. We now calculate more points on the surfaces to cover a wider range of bending geometries, and then refine the surfaces by fitting to rovibronic term values for both electronic states simultaneously. In the fitting we include levels having J values up to 9/2 and term values up to about 8000 cm1. In our calculation of the energy levels we allow for the Renner effect and spin-orbit coupling by using our variational computer program RENNER. A good fitting to the data is obtained and as a result we obtain an accurate representation of these two potential surfaces over an energy range of more than 1 eV. We tabulate the vibronic energies up to 1 eV for both HO2 and DO2. We can explain the origin of a perturbation observed in the F1 spin component levels of the Ã(0, 0, 0) vibronic state for J values around 51/2; this is caused by a spin-orbit interaction satisfying Δ N = ± 1 with the F2 spin component levels of the [Formula: see text](1,1,2) vibronic state. Using the new rovibronic energies and wave functions, with our ab initio electric dipole moment and transition moment surfaces, we calculate Stark coefficients and compare them with experiment for some ground vibronic state levels. PACS Nos.: 31.20D, 31.50, 33.10, 33.20E, 35.20D, 35.20J
Spectroscopy of the C2 molecule: Valence and Rydberg states in the 710 eV region. An ab initio study
Authors: Bruna P J , Grein F
Published: April 2011

The potential curves of selected valence and Rydberg states of C2 lying in the 710 eV region are reported for the first time. The states studied, using MRCI wave funtions, include (25)3,1Πu, (13)3Σ+g, (25)3Σg, (13)3Δg, and relevant quintet states. The f 3Σg, g3Δg, and F1Πu states observed in absorption from 8.88 to 9.25 eV by Herzberg et al. have originally been assumed to be πu ® 3s Rydberg states, with respect to a 3Πu(13Πu) for the triplets and to X1Σg+ for the singlet. Our calculations partially support such assignments: f 3 Σg corresponding to 33Σg has mixed valence σuσgπu 3πg and Rydberg σu 2σgπu 23s character, g 3Δg corresponding to 23 Δg has a valence σuσgπu 3πg structure, while F 1 Πu(21Πu) is confirmed to be a σu 2πu 33s state. The calculated f00-values for these bands are 0.027 for f¬ a, 0.051 for g ¬ a, and 0.098 for F ¬ X. The singletsinglet transition F ¬ X constitutes the strongest absorption band reported so far for C2. Our theoretical value agrees with f00(F¬X) = 0.10 ± 0.01 derived indirectly from interstellar data collected by the Hubble Space Telescope. The 13Σg+ (σuσgπu 3πg) state at Te = 7.57 eV lies much higher than expected by experimentalists. PACS Nos.: 31.20T, 31.50, 33.20N, 33.70.

PACS Nos.: 31.20T, 31.50, 33.20N, 33.70.
Multiple vs. single scattering in low energy electron holography
Authors: Shegelski M MR , Whitwick M B , Holenstein R
Published: April 2011

The theory of the low energy electron point source (LEEPS) microscope is presented in matrix form to account for multiple scattering. An iterative method is used to solve the matrix equation for the structure factor. An algorithm is developed for the storage and use of only the dominant elements of the structure matrix; this allows for the study of considerably large clusters. Examples of large clusters of atoms are studied to compare single scattering (SS) and multiple scattering (MS). A Kirchhoff-Helmholtz transform is used for the reconstruction. We report results where SS and MS give essentially the same reconstructions, and other results where SS and MS reconstructions are in severe disagreement. We find, for example, that SS and MS give virtually the same reconstruction along the optical axis for clusters that are "short" lateral to, but "long" in the direction of, the optical axis. In contrast, we also find that SS and MS give vastly different reconstructions lateral to the optical axis for clusters that are "wide" lateral to, and "thin" in the direction of, the optical axis. Some other results are also reported. Implications for further theoretical work, and for experimental LEEPS microscopy, are discussed. PACS No.: 61.14Nm
The electronic band structure of polydiacetylenes with second- and third-neighbor hopping interaction
Authors: Hu H F , Li Y B , Yao K L
Published: April 2011

We have studied the energy band structure of polydiacetylenes (PDAs) using the extensional Hückel Hamiltonian that includes the nonnearest-neighbor hopping interactions. The results show that with increase in the nonnearest-neighbor hopping interaction parameters ρ1 and ρ2, (i) the energy band symmetry is broken and the energy gap 2Δ has changed, (ii) the locations and the widths of energy bands have changed and their shifts depend mainly on ρ1 (next-neighbor hopping interactions), and (iii) the energy gap 2Δ depends mainly on ρ2 (third-neighbor hopping interactions), the effects of the nonnearest-neighbor hopping interaction on the band structure are discussed. PACS No.: 31.15Ct
Multicouches magnétiques Au/Co/Au : Étude structurale et magnétique
Authors: Belhi R , Jomni S , Mliki N , Abdelmoula K , Ayadi M , Clugnet G , Charai A , Leroux C , Nihoul G
Published: April 2011

Systematic structural studies by transmission electronic microscopy and magnetooptic measures on layered structure Au(111)/Co(00.1)/Au(111), obtained through ultrahigh vacuum vaporization, have clarified some correlations between the crystallographic structure of the cobalt layer and its magnetic properties and allowed us to put forward answers concerning some of these properties. Indeed, these studies provide information concerning the magnetic properties of this magnetic material in such structures. The presence of the gold atoms causes the elementary hexagonal cell of the Co to expand. A simple calculation based on this expansion describes well the anisotropic magnetic behavior of these layers as a function of their thickness. [Journal translation]
Investigation on dielectric properties of the polyetherketone nanocomposite with lead titanate ultrafines
Authors: Shi W , Fang C , Guo S , Ren Q , Pan Q , Gu Q , Xu D , Wei H , Yu J
Published: April 2011

The dielectric properties of polymer composites with inorganic nanoparticles were investigated. In the demonstration of the dielectric constant expression of the nanocomposite polymer, the dielectric contributions of the displacement polarization, the orientation polarization, and the space polarization in the nanocomposite polymer were all considered. In the demonstration, two dielectric relaxation models were used, that of Debye for inorganic nanoparticles and the HavriliakNegami function model for polymers. Then the expression of the complex dielectric constant of the nanocomposite polymer was obtained by using Onsager's local field theory. Furthermore, the nanocomposite polymer thin films that consist of PbTiO3 nanoparticles and polyetherketone were prepared. The real parts of the dielectric constants were measured and calculated, respectively. It was found that our calculated results are in good agreement with our measured results. PACS Nos.: 77.20, 77.55, 81.20T
Nonresonant multiphoton excitation spectra of atomic 7Li
Authors: Ballard M K , Bernheim R A , Bicchi P
Published: April 2011

The nonresonant multiphoton laser-induced fluorescence excitation spectrum of isotopically purified 7Li was obtained with a tunable, pulsed, nanosecond laser scanned between 13 600 and 14 500 cm1. The measured Rydberg series include n 2P [Formula: see text] 2 2S, n 2F [Formula: see text] 2 2S, n 2P [Formula: see text]2 2P, and n 2F [Formula: see text] 2 2P, and term values up to 14 2P and 28 2F were determined. Features due to the ac Stark effect become prominent for the high Rydberg states, but can be eliminated by using circular instead of plane-polarized radiation. Quantum defect values for the n 2P, n 2D, and n 2F levels were determined. Those for the n 2F states cover a range of principal quantum numbers not previously investigated.

PACS Nos.: 32.80Rm, 32.30Jc, 32.70Jz
Modelling the far wings of collision-induced translational spectral profiles
Authors: Glaz W , Tabisz G C
Published: April 2011

By comparing three model spectral profiles to precise line shapes obtained from quantum calculations, we assess the suitability of the various models for describing the far wings of translational collision-induced spectra. A profile obtained based on a generalized Langevin approach can give a better fit to the quantum shape than the widely used BirnbaumCohen model; the fit given by the six-parameter extended BirnbaumCohen profile proves to be the best of all three functions.

PACS No.: 32.70Jz
The pion cut and the negative-energy behaviour of neutronproton effective-range functions near threshold
Authors: Dijk W van , Kermode M W
Published: April 2011

We study the effect of the pion cut on the negative-energy effective-range parameters of the 3S1  3D1 neutronproton interaction. Utilizing an approach involving one-pion-exchange potentials truncated at large distances, we demonstrate that the mixing parameter at negative energies between zero and the deuteron energy is practically independent of presence or absence of the pion cut. At the same time, the analysis gives some interesting insight into the behaviour of the mixing parameter and other effective-range functions at more negative energies. This work complements our earlier result that the positive-energy mixing parameter is independent of the pioncut.

PACS Nos.: 0.3.80+r, 11.55Bq, 13.75C, 21.30-x
Convective heat transfer past a continuously moving plate embedded in a non-Darcian porous medium in the presence of a magnetic field
Authors: Abo-Eldahab E M , El Gendy M S
Published: April 2011

In the present study, free-convection and heat-transfer behavior of an electrically conducting fluid is investigated near a stretching sheet embedded in a non-Darcian medium. The temperature of the stretching sheet is varied. The sheet is stretched linearly with variable velocity and temperature. Boundary-layer equations are derived. The resulting approximate nonlinear ordinary differential equations are solved numerically. Velocity and temperature profiles as well as the local Nusselt number and skin-friction coefficient are computed for various values of the magnetic field, the Prandtl number, the free convective parameter, and the inertia parameter.

PACS No.: 44.30+v
WKB quantization rules for three-dimensional confinement
Authors: Sinha A , Roychoudhury R , Varshni Y P
Published: April 2011

Confined quantum systems have been studied by various authors over the past decades, by using various mathematical techniques. In this work, we derive the WKB quantization rules for quantum systems confined in an impenetrable spherical box of radius r0. We apply the proposed method to two systems explicitly, viz., the confined harmonic oscillator and the confined hydrogen atom. The results are found to be in reasonable agreement with those obtained by other methods.

PACS No.: 03.65
Origins of the energy distribution structure in coherent pion production at intermediate energies
Authors: Deutchman P A
Published: April 2011

New calculations have been done that now cover the intermediate energy range from 100 MeV/nucleon to 2.0 GeV/nucleon incident energy for the reaction 12C + 12C [Formula: see text] 12C + 12C (15.11 MeV) +π0, where constructive, coherent Δ-hole states are excited in either nucleus while the companion nucleus is excited to a coherent nucleonhole state describing the spinisospin, giant resonant state at 15.11 MeV. The Δ (1232 MeV) isobar then decays to a nucleon and pion. Theoretical pion energy distributions are calculated and, for the first time, results above 400 MeV/nucleon are shown. A theoretical basis for understanding how the shapes of the pion distributions change as a function of incident energy is described. The fundamental shape of the Δ-production amplitude as a function of momentum transfer is discussed and the effects of the energy-dependent nuclear width are examined. Furthermore, the connection between the origins of the pion distribution to the final pion shapes is made and the importance of the giant resonance in providing an important signature is pointed out. By pushing the calculations above 400 MeV/nucleon, it was discovered that sliding kinematics and kinematic turnarounds occur due to the two-to-three-body sequential nature of the reactions and these effects determine the final structure of the pion distributions at higher incident energies.

PACS Nos.: 24.10Cn, 24.30Cz, 25.70-z, 25.80-e
About the Dunham coefficients Y20 and Y11 for diatomic molecules
Authors: Sharma A K , Chandra S
Published: April 2011

For a diatomic molecule, when the Dunham coefficient Y20 is negative, all features of the potential-energy curve can be reproduced. When Y20 is positive, it is not possible to reproduce all features of the potential-energy curve. However, the turning points for some lower vibrational states can be obtained.

PACS No.: 33.15Mt
Exact vs. quasi-classical tunneling times for idealized potentials
Authors: Shegelski M R.A. , Reid M , Holenstein R
Published: April 2011

We compare the exact tunneling time with the quasi-classical tunneling time for idealized potentials. We examine three one-dimensional cases where the potential is chosen to have a simple form. In each case, the exact tunneling time and the quasi-classical time differ significantly. In one case, the two differ in magnitude by a factor of about ten. In another case, the two differ not only quantitatively, but qualitatively as well. A discussion is given as to why the two times are significantly different, and suggestions for further inquiries are made.

PACS Nos.: 03.65Xp, 03.65-w
Examination of the perturbative expansion parameter for piezo-electric coupling in CdS
Authors: Lee J H , Yi S N , Jo S G , Choi S D
Published: April 2011

A perturbative expansion parameter ε is introduced for reformulating the continued-fraction representation of the magneto-optical absorption linewidth function into a power-series expansion. The parameterε is calculated for cadmium sulfide, in which the piezoelectric coupling is dominant, by fitting the theory into the available experiment. The temperature dependence in the quantum limit is shown to be ε T2=1.8, where T is the temperature given in kelvins, or the parameter decreases monotonously as the temperature increases. This is thought to be due to our choice of the continued fraction, which involves the flux variables along with the projectors. We guess that for other piezoelectric materials, the magneto-optical absorption data will have a similar temperature dependence. It is to be regretted that the dependence cannot be checked for the other materials due to lack of experimental data.

PACS Nos.: 76.20+q, 76.40+b, 78.20Ls
Modeling the spectral line shapes with speed-dependent broadening and Dicke narrowing
Authors: Shapiro D A , Ciurylo R , Jaworski R , May A D
Published: April 2011

Shapes of pressure- and Doppler-broadened spectral lines are obtained by solving exactly a three-dimension transport and (or) relaxation equation. The speed dependence of collisional broadening and shifting caused by dephasing collisions and Dicke narrowing caused by velocity-changing collisions are taken into account within the impact approximation. The RautianSobelman and KeilsonStorer models are used to describe velocity-changing collisions. We show in the high density or hydrodynamic limit that both models lead to a profile that is the weighted sum of Lorentz profiles if the collisional broadening is much greater than the frequency of velocity-changing collisions and to the ordinary Lorentz profile in the opposite case. This shows that the relative size of the optical and kinetic cross section is important in determining the shape of absorption curves. The analytical solutions may be useful in modeling absorption profiles for remote sensing of the atmosphere.

PACS No.: 32.70Jz
Ga-NMR local susceptibility of the Kagome-based magnet SrCr9p Ga129pO19: A high-temperature study
Authors: Limot L , Mendels P , Collin G , Mondelli C , Mutka H , Blanchard N
Published: April 2011

We report a high-T GaNMR study in the Kagome-based anti-ferromagnetic compound SrCr9pGa129pO19 (0.81 [Formula: see text] p [Formula: see text] 0.96), and present a refined mean-field analysis of the local NMR susceptibility of Cr-frustrated moments. We find that the intralayer Kagome coupling is J = 86(6) K, and the interlayer coupling to non-Kagome Cr moments is J' = 69(7) K. The J' / J = 0.80(1) ratio confirms the common belief that the frustrated entity is a pyrochlore slab.

PACS Nos.:75.30Cr, 75.50Lk, 76.60-k
Structural and magnetic characterization of Ho3SbO7 and Dy3SbO7
Authors: Fennell T , Bramwell S T , Green M A
Published: April 2011

We present an experimental investigation of the structural and magnetic properties of Ho3SbO7 and Dy3SbO7. These compounds adopt the Y3TaO7 structure, space group C2221. The magnetic rare-earth ions occupy an intricate lattice related to the pyrochlore lattice that occurs in Ho2Ti2O7 and Dy2Ti2O7. The crystal structure of Ho3SbO7 is determined by Rietveld refinement of the powder X-ray diffraction pattern at ambient temperature, and that of the Dy analogue is inferred to be similar. Magnetic susceptibility measurements show that Ho3SbO7 and Dy3SbO7 have negative CurieWeiss temperatures: 8.4 K (Ho) and 9.2 K (Dy). Magnetic transitions have been detected at 2.0 K (Ho) and 3.0 K (Dy). We discuss the results in terms of the ``dipolar spin ice model'' that has been used to describe Ho2Ti2O7 and Dy2Ti2O7.

PACS Nos.: 75.25+z, 75.50Ee, 61.10Nz
Spin- and chirality-orderings of frustrated magnets  stacked-triangular anti-ferromagnets and spin glasses
Authors: Kawamura H
Published: April 2011

"Chirality" is a multispin quantity representing the sense or the handedness of the noncollinear spin structures induced by spin frustration. Recent studies have revealed that the chirality often plays an important role in the ordering of certain frustrated magnets. Here I take up two such examples, stacked-triangular anti-ferromagnets and spin glasses, where the inherent chiral degree of freedom affects underlying physics and might lead to novel ordering phenomena. The first topic is the criticality of the magnetic-phase transition of vector (i.e., XY or Heisenberg) anti-ferromagnets on the three-dimensional stacked-triangular lattice. The second topic is the nature of the spin-glass ordering. I will review the recent theoretical and experimental works on these topics, with particular emphasis on the important role played by the chirality.

PACS Nos.: 67.70+n, 67.57Lm
First-order transition in frustrated Yb2Ti2O7 without long-range order
Authors: Hodges J A , Bonville P , Forget A , André G
Published: April 2011

We have examined the pyrochlore lattice compound Yb2Ti2O7 using 170Yb Mössbauer spectroscopy and neutron diffraction. The Yb3+ ion has a well-isolated S' = 1/2 ground state with planar anisotropy and the net interaction is ferromagnetic. The Mössbauer measurements show that short-range correlations develop below about 2 K and at 0.2 K, where specific heat data evidence a λ-transition (Blöte et al. Physica, 43, 549 (1969)), there is a first-order transition to a state where the Yb3+ moments become blocked on the Mössbauer time scale (108 s) with well-defined directions. The neutron diffraction measurements show that below 0.2 K there is no long-range magnetic order.

PACS Nos.: 75.40-s, 76.80+y, 75.50Dd
Magnetization plateaux and bound states of the ShastrySutherland model for SrCu2(BO3)2
Authors: Momoi T , Totsuka K
Published: April 2011

In this paper, we briefly review our recent studies of the Heisenberg anti-ferromagnet on the ShastrySutherland lattice for SrCu2(BO3)2 under magnetic fields. Treating magnetic excitations promoted by the field as Bose particles and using a strong-coupling expansion, we derived an effective Hamiltonian for the magnetic particles. Anisotropic repulsive interactions between particles induce "insulating" states with a stripe spin-density wave structure at magnetization m/msat = 1/3 and with a checkerboard structure at 1/2, and thereby form magnetization plateaux. We also demonstrated how the unique geometry of the ShastrySutherland lattice affects dynamical properties and makes a novel type of quintuplet (S = 2) bound states condense for very small magnetization.

PACS Nos.: 75.50-y, 75.60Ej, 75.10Jm
The mechanisms of antihydrogen formationThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at University of Windsor, Windsor, Ontario, Canada on 21–26 July 2008.
Authors: Rizzini E. Lodi , Venturelli L. , Zurlo N.
Published: April 2011

Some years have passed since the report of the first production of cold antihydrogen by the Athena Collaboration and the Atrap Collaboration at CERN, but no clear answer has been given about the roles of the two mechanisms responsible for antihydrogen formation. A new preliminary analysis of the data acquired by the Athena Collaboration in different experimental conditions seems to suggest that three-body recombination mechanism is dominant in the first tens of seconds of the overlapping of the injected antiproton cloud with the positron plasma in the nested Penning trap, while radiative capture starts to become dominant afterwards.
AN ATTEMPT TO DETECT THE REACTION C14(n, γ)C15
Authors: Yaffe L. , Stevens W. H.
Published: April 2011

A search has been made for the reaction C14(n, γ) C15. We have been unable to find any activity ascribable to C15. If the β-ray energy of C15 is greater than 3 Mev. and the half life lies between 1 sec. and 1 min., the capture cross section for the above reaction is less than 1 microbarn.
CONSERVATION LAWS IN FEYNMAN'S MODIFIED ELECTRODYNAMICS
Authors: Daykin P. N.
Published: April 2011

In Feynman's treatment of the self-energy problem, the divergence is eliminated by introducing a convergence factor into the integral over the virtual photon momentum space. Feynman has remarked that his choice of convergence factor is inconsistent with the conservation of energy for the radiation field of an atom. This problem is examined in a more general way. The modification of the Maxwell equations caused by the convergence factor is deduced. The modified field equations belong to the generalized electrodynamics described by Podolsky. The modified energy-momentum tensor is shown to satisfy the conservation law for the field with source.
TEMPERATURE–PRESSURE HYPOTHESIS AND THE EARTH'S INTERIOR
Authors: Jacobs J. A.
Published: April 2011

Bullen and Ramsey have shown that the reciprocal of the compressibility is a linear function of the pressure both in the Earth's core and in the mantle below 1000 km. In view of this result, it seems reasonable to suppose that a similar relationship exists between the reciprocal of the volume coefficient of thermal expansion and pressure. Support for this hypothesis is obtained by two independent methods (a) using Uffen's results based on the theory of solids, (b) using Murnaghan's theory of finite strain. Assuming the validity of the hypothesis, an estimate is made of the adiabatic gradient throughout the Earth. Taking the temperature at 1000 km. to be 3600° K., values of the temperature at greater depths are estimated. In particular it is found that the temperature at the boundary of the core is 4350°K., and at the center of the Earth a little over 4800°K. These results have considerable interest and bearing on Bullard's theory of the transfer of heat from the core.
THEORY OF THE ELECTROMAGNETIC VACUUM (PRELIMINARY REPORT)
Authors: Kaempffer F. A.
Published: April 2011

It is shown that, if one assumes Dirac's electrodynamics to be the correct description of the electromagnetic field at the absolute zero of temperature, the electromagnetic vacuum ("the Dirac sea") can be considered as a nonviscous fluid, in which pressure waves ("sound") travel with velocity c, and in which with rising temperature excitations appear as particles analogous to the excitations ("phonons" and "rotons") in ordinary nonviscous fluids at low temperatures. It is suggested that photons be considered as vortex-free excitations and charged particles as vortex excitations of the fluid representing the electromagnetic vacuum. Some evidence which supports this suggestion is given.
THE PHYSICAL MEANING OF AUXILIARY CONDITIONS IN THE THEORY OF GRAVITATIONAL WAVES
Authors: Kaempffer F. A.
Published: April 2011

The conditions are examined which are necessary to reduce the gravitational field equations in first approximation to a set of ordinary wave equations. These conditions are evaluated for the case of the gravitational field produced by an accelerated particle, and it is shown that they restrict the consideration to observers whose radius vector towards the source of the field is perpendicular to the vector of acceleration of the particle at the retarded time.
WAVE GUIDE ARRAYS WITH SYMMETRICAL CONDUCTANCE FUNCTIONS
Authors: Griffiths H. D.
Published: April 2011

Design formulae for nonresonant slotted wave guide arrays with a symmetrical conductance function are given. Methods are outlined for the calculation of the patterns from the asymmetrical near-field distributions produced by symmetrical arrays.
NOTE ON THE RESONANCE METHOD OF MEASURING THE RATIO OF THE SPECIFIC HEATS OF A GAS, Cp/Cv
Authors: Woolley Harold W.
Published: April 2011

Experimental results of Clark and Katz and of Katz, Leverton, and Woods obtained in a resonance method for determining the ratio of specific heats Cp/Cv have been recomputed with an improved formula for the mass effect of the gas. Improved agreement with values based on spectroscopic and PVT data is obtained for nitrogen, argon, carbon dioxide, nitrous oxide, and sulphur dioxide.
THE PHOTOELECTRIC CONSTANTS OF IODINE
Authors: West D. C.
Published: April 2011

The retarding-potential method of photoelectric measurement has been applied to the determination of the work function and energy gap of a typical molecular crystal. Three allotropic forms of solid iodine, believed to be amorphous, monoclinic, and rhombic, have work functions of 6.8, 5.4, and 2.8 ev. respectively, and photoelectric thresholds of 1880, 2050, and 2360 Å. The energy gaps of the crystalline modifications are 0.6 and 2.5 ev.
METEOROLOGICAL VARIATIONS IN THE QUANTITY OF ATMOSPHERIC OZONE OVER EDMONTON (Lat. 53° 34′ N. Long. 113° 31′ W.)
Authors: Gowan E. H. , Leppard R. E.
Published: April 2011

Ozone observations have been made at Edmonton, Lat. 53° 34′ N. Long. 113° 31′ W. from August 2nd, 1950, to December 31st, 1952. The expected seasonal variation occurs, along with large short-term fluctuations. High values in all seasons are associated with relatively low temperatures, and low ozone values are accompanied by relatively higher temperatures. It is not yet possible to judge the degree to which the transport mechanism is responsible for ozone change, but it seems to play a large part over central Alberta.
PHOTO-ALPHA REACTIONS IN NUCLEAR EMULSIONS
Authors: Millar C. H. , Cameron A. G. W.
Published: April 2011

In experiments to search for new photonuclear reactions involving the emission of heavy particles [Formula: see text], Ilford E1 emulsions were exposed to 240 roentgens of X radiation from the University of Saskatchewan betatron operating at energies up to 27 Mev. The plates were developed by a special "grain-gradation" technique which suppressed proton tracks and X-ray fog. The ejection of single α particles was observed from C13, N14, O16, Ag, and Br. Multiple-pronged stars were observed due to the photodisintegration of C12, N14, O16, and probably Ag or Br. Interpretations of these events were deduced, and cross section versus energy curves for many of them were obtained. Range–energy relationships were obtained for Be9, B10, and C12 particles in E1 emulsions.
THE DECAY OF THE POPULATIONS OF NEON ATOMS IN THE 2p53s LEVELS
Authors: Eckl Donald J.
Published: April 2011

Improved apparatus has been designed to determine the rate of decay after excitation of the populations of the four states in the 1s22s22p53s configuration of neon. An absorption method is employed. Measurements show that the population of the 3P2 state decays exponentially. The decay curves for the 3P1 and 3P0 states may be expressed as the sum of two exponential rates of decay. Atoms in the 1P1 state disappear very rapidly making measurements difficult; the decay is assumed to be exponential. Curves of mean life as obtained from these exponentials are plotted against pressure for all four states. The initial populations of the four states, determined from initial absorption, are of the order of 109 atoms per cc. and are plotted as a function of pressure. Within the limits of error the populations so calculated are the same for different absorption lines.
AN ATOMIC MASS STUDY OF NUCLEAR SHELL STRUCTURE IN THE REGION AND
Authors: Hogg Benjamin G. , Duckworth Henry E.
Published: April 2011

New mass spectrographic masses are reported for some of the isotopes of gallium, germanium, arsenic, and selenium. These results are combined with previously reported atomic mass data in order to study atomic mass trends in the region [Formula: see text] and [Formula: see text]. The only pronounced mass effects which occur in this region are those associated with 28 and 50 nucleons. We have found no extra stability which can be associated with the filling of the f5/2, p3/2 and p1/2 subshells. A list of mass values used in this study is included.
NEUTRON CAPTURE γ-RAYS FROM HEAVY ODD-CHARGE NUCLEI
Authors: Bartholomew G. A. , Kinsey B. B.
Published: April 2011

The neutron capture γ-ray spectra of arsenic, niobium, rhodium, silver, indium, antimony, praseodymium, tantalum, gold, and thallium are described. The energies and intensities of the strongest high energy γ-rays are given for each element.
NEUTRON CAPTURE γ-RAYS FROM HEAVY EVEN-CHARGE NUCLEI
Authors: Kinsey B. B. , Bartholomew G. A.
Published: April 2011

The neutron capture γ-ray spectra of the elements selenium, strontium, zirconium, molybdenum, cadmium, tin, barium, samarium, gadolinium, wolfram, platinum, and mercury are described. The energies and intensities of the strongest high energy γ-rays are given for each element.
METEOR ECHO DURATION AND RADIO WAVE LENGTH
Authors: McKinley D. W. R.
Published: April 2011

The durations of radar echoes from meteors have been observed simultaneously on 9.22 m. and 5.35 m., and also on 9.22 m. and 2.83 m. The ratio of durations on two wave lengths decreases with increasing duration by a factor of two over the observed range, deviating significantly from the accepted square law of wave length. Plotting the log of the ratio against the log of the duration yields two straight lines of different slopes, one in the short-duration range and the other applying to the longer echoes. General empirical formulae are developed to predict the echo duration on one radio equipment in terms of the duration of the same echo recorded by another apparatus of different sensitivity and wave length.
THE SURFACE TENSION OF LIQUID HELIUM
Authors: Atkins K. R.
Published: April 2011

Following a suggestion due to Frenkel, the normal modes of a liquid helium surface are taken to be surface tension waves. The free energy associated with these modes is estimated and is found to give a major contribution to the temperature dependence of the surface tension of liquid helium II. The zero-point energy of the modes is shown to be an appreciable fraction of the total surface energy at 0°K.
UN OBJECTIF SPECIAL A GRANDE OUVERTURE NUMERIQUE
Authors: Lefaivre Par Jean
Published: April 2011

A dry objective of numerical aperture 0.84 has been computed for special purposes. It is a catadioptric objective of the centered type, after the terminology of Bouwers. It is not achromatic.
SCATTERING OF A PLANE WAVE FROM A CIRCULAR DIELECTRIC CYLINDER AT OBLIQUE INCIDENCE
Authors: Wait James R.
Published: April 2011

A solution is given for the problem of a plane wave incident obliquely on a circular cylinder of infinite length. The electric properties of the cylinder are taken to be homogeneous and isotropic but otherwise arbitrary. It is shown that in the general case the scattered field contains a significant cross-polarized component which vanishes at normal incidence. While the solution is derived for the magnetic vector of the incident wave transverse to the axis of the cylinder, the corresponding result for the other polarization can be obtained from symmetry.
VERTICAL EXTENT OF AURORAL ARCS AND BANDS
Authors: Currie B. W. , Weaver J. T.
Published: April 2011

Measurements of the vertical extent of quiet arcs and bands from 181 auroral photographs, taken at Chesterfield (63.3 °N., 90.7 °W.), Coppermine (67.8 °N., 115.2 °W.), and Saskatoon (52.1 °N., 106.6 °W.), indicate that these forms are confined to a narrow layer of the atmosphere immediately above the 100-km. level. The most frequent thickness of this layer is between 20 and 40 km. Values in excess of 50 km. rarely occur. The percentage of auroral time that the luminosity is restricted to this layer is uncertain. The ratio of the number of arcs and bands to the total number of observed forms suggests a value exceeding 50%. When the occurrence of each form is weighted according to the angular field covered by it, a value as high as 60% is indicated.
GAUGE-INVARIANT FORMULATION OF QUANTUM ELECTRODYNAMICS
Authors: Dirac P. A. M.
Published: April 2011

Electrodynamics is formulated so as to be manifestly invariant under general gauge transformations, through being built up entirely in terms of gauge-invariant dynamical variables. The quantization of the theory can be carried out by the usual rules and meets with the usual difficulties.It is found that the gauge-invariant operation of creation of an electron involves the simultaneous creation of an electron and of the Coulomb field around it. The requirement of manifest gauge invariance prevents one from using the concept of an electron separated from its Coulomb field.
NOTE ON THE USE OF NON-ORTHOGONAL WAVE FUNCTIONS IN PERTURBATION CALCULATIONS
Authors: Dirac P. A. M.
Published: April 2011

A method of first approximation is proposed for handling collision problems involving a chemical or ionic change, so that the interaction energy function is different at the beginning and end of the collision.
ON EQUATIONS OF MOTION IN GENERAL RELATIVITY
Authors: Tauber G. E.
Published: April 2011

It has been shown that both the equations of motion of a charged particle in a gravitational field and the field equations can be obtained from one variational principle by suitably generalizing Dirac's classical theory of electrons.
GAMMA RAYS FROM THE DEUTERON BOMBARDMENT OF BORON 10
Authors: Sample J. T. , Neilson G. C. , Chadwick G. B. , Warren J. B.
Published: April 2011

Bombardment of B10 with 1.4 Mev. deuterons has been found to produce gamma rays of energy 4.46 ±.04, 4.75 ±.03, 5.03 ±.09, 5.35 ±.05, 6.52 ±.04, 6.78 ±.07, 7.29 ±.04, 8.27 ±.09, and 8.87 ±.02 Mev., as measured with a three-crystal pair spectrometer. Tentative assignments to transitions in B11 and C11 agree well in most cases with the known energy level schemes. No gamma rays of very high energy were observed, even with a single-crystal spectrometer; consequently an upper limit of 10−31 cm.2 has been placed on the cross-section of B10(d, γ)C12 at 0.95 Mev. bombarding energy.
SMALL-ANGLE SCATTERING OF FAST POLARIZED NEUTRONS BY HEAVY NUCLEI
Authors: Sample J. T.
Published: April 2011

Detailed calculations have been carried out which indicate that the small-angle scattering of fast neutrons by lead depends on the polarization, or spin orientation, of the neutrons. When the scattering of neutrons whose spin vectors point upward is observed in the horizontal plane, more neutrons should be found scattered to the right than to the left. For completely polarized 3.1 Mev. neutrons, the theory predicts a maximum "right to left" intensity ratio of 14.5:1 at a scattering angle of 0.5°, the ratio decreasing to 1.6:1 at 5°, and approaching unity rapidly as the scattering angle increases.
AN EXAMINATION OF VERWEY'S MODEL FOR THE LATTICE STRUCTURE OF THE FREE SURFACE OF ALKALI HALIDE CRYSTALS
Authors: Benson G. C. , Schreiber H. P. , Patterson D.
Published: April 2011

The Verwey model for the free surface structure of alkali halide crystals at 0° K. has been used to estimate the effect of surface distortion on the surface energy of these crystals. It appears that the contributions from distortion are considerably larger than previously reported. In the case of some lithium salts the corrected surface energy becomes negative; the mechanical stability of the solid is considered in the light of this. Several aspects of the Verwey model have been examined. These include the effect of various repulsive potentials and forms of distortion.
SOME RESULTS OF THE HIGH DISPERSION ELECTRONIC EMISSION SPECTRUM OF FORMALDEHYDE
Authors: Robinson G. Wilse
Published: April 2011

It has been possible to obtain the emission spectrum in the near ultraviolet region of formaldehyde in a discharge tube at sufficiently high resolution and purity so that the rotational structure can be studied. Some preliminary results of the analysis are discussed, especially with regard to the vibrational assignment of the emission and absorption systems and to the nature of the upper electronic state. An examination of the data rather strongly indicates a non-planar equilibrium configuration in the excited electronic state. Some of the previous interpretations are shown to be in disagreement with the experimental findings. A long path length absorption study of the gas revealed a number of new bands, some of which may belong to a second electronic transition.
THE EFFECT OF INCIDENT ATOMIC VELOCITY ON THE STRUCTURE OF EVAPORATED SILVER FILMS
Authors: Aziz R. A. , Scott G. D.
Published: April 2011

The influence of the incident atomic velocity on the structure of evaporated films has been studied for silver films in the thickness range from 50 to 500 Å. The thermal velocities of the evaporated atoms were reduced (i) by "reflection" from a teflon surface at room temperature, and (ii) by "diffusion" through nitrogen gas at 3.0 μ. Films formed by these two methods are compared with "normal" high vacuum films for the same rates of deposition, which were relatively slow (0.4 to 4 Å of thickness per second). The results of both resistivity measurements and electron microscopy show that "diffusion" films are less aggregated, i.e. more continuous, than "normal" high vacuum films. "Reflected" films have a structure intermediate between the other two. A qualitative explanation of the observed effects is given in terms of the formation of nuclei and the growth of aggregates.
CROSS SECTIONS OF (p, xn) REACTIONS IN THE ISOTOPE OF LEAD AND BISMUTH
Authors: Bell R. E. , Skarsgard H. M.
Published: April 2011

Measurements have been made by the activation method of cross sections of (p, xn) reactions in Bi209, Pb206, Pb207, and Pb208. The present results cover x = 3 to 7 in Bi209, 2 to 6 in Pb206, 2 to 4 in Pb207, and 3 and 4 in Pb208, over a total proton energy range from 12 to 85 Mev. The absolute accuracy is about 15%. Each cross section plotted as a function of proton energy rises above its threshold to a peak whose height is of the order of one barn, and then falls again to a low and fairly constant value. The results from x = 3 to 7 are consistent with a compound nucleus plus prompt nucleon–nucleon cascade model using reasonable nuclear parameters, but the experimental (p, 2n) cross section appears to be almost double the value so predicted. Since (p, xn) reactions are dominant in the energy range 10 to 40 Mev., their sum approximates the total reaction cross section; the experimental sum fluctuates around the smooth curve computed for the compound nucleus model with r0 = 1.3 × 10−13 cm. The fluctuations are similar to, but more marked than, those in the total neutron cross section of heavy elements in the same energy range. A more detailed theoretical discussion of these results is given by Jackson in the paper immediately following.
A METHOD TO DETECT THE PRESENCE OF IONIZED HYDROGEN IN THE OUTER ATMOSPHERE
Authors: Storey L. R. O.
Published: April 2011

The method proposed for the detection of ionized hydrogen in the outer atmosphere relies on the influence of the positive ions on the propagation of whistlers. If ionized hydrogen is the chief constituent of the atmosphere at great heights above the earth, then the relation between frequency and time in a whistler should depart at low audio frequencies from the form observed at higher frequencies. The departure is likely to be most marked in whistlers occurring at low magnetic latitudes. At magnetic latitude 45° the effect of the hydrogen ions should be detectable at frequencies below about 2 kc./sec.