bluuebunny/crossref_metadata_2025 huggingface dataset:
On an application of a generalization of the discrete Fourier transform to short time series
Authors: Grindlay J
Published: April 2011

A generalization of the discrete Fourier transform (DFT) is discussed. This generalization or GDFT provides a smooth interpolation between the points of the DFT. The GDFT of a sinusoidal function in a finite time window is (a) described in detail and (b) shown to coincide (aside from a simple scaling constant) with the corresponding Fourier transform, provided that certain conditions are satisfied by the sinusoidal parameters. The sinusoidal GDFT is proposed as a tool to investigate, (independently of any Fourier transform connection) the sinusoidal nature of time series. The method is applied successfully to the case of a specific trajectory of the Hénon and Heiles model.

PACS Nos.: 02.30, 05.45
Electromagnetic (self-) interactions in relativistic Schrödinger theory
Authors: Mattes M , Rupp S , Sorg M
Published: April 2011

The Relativistic Schrödinger Theory (RST) is applied to a system of N particles with electromagnetic interactions. The gauge group is U(1) × U(1)... × U(1). By exploiting the mathematical structure of fibre bundles, the energy-momentum content of the gauge field can be defined in such a way that no infinite self-energy of point charges can arise. However, the picture of classical point particles becomes insufficient in any case in view of the exchange and overlap effects occurring in RST. The presence of overlap currents seems to be necessary to remedy certain pathological features of the classical point-particle theories.

PACS Nos.: 03.65Pm, 03.65Ge, 03.65Ta
Breit-Pauli energy levels and transition rates for the carbonlike sequence
Authors: Tachiev G , Fischer C Froese
Published: April 2011

BreitPauli results for energy levels, lifetimes, and some transition data are reported for all levels up to 2s22p3d 1PJo of the C-like spectrum for 7 [Formula: see text] Z [Formula: see text] 15. For all but the lowest members of the sequence, these include all the states of the 2s22p2, 2s2p3, 2p4, 2s22p3s, 2s22p3p, and 2s22p3d configurations. For carbon, only the states for the 2s22p2, 2s2p3, and 2s22p3s configurations are included. A simultaneous optimization scheme was applied so that a radial basis could be determined for a set of terms that mix in the BreitPauli approximation. All results have been posted at a Web site. In this paper, lifetimes are reported and, in addition, results for N II, O III, and Si IX are critically evaluated. Energy levels are compared with experiment and adjusted transition rates, along with uncertainty estimates are presented. Selected results are compared with other theory and experiment.

PACS Nos.: 31.25Jf, 32.30Jc, 32.70Cs
Interpretation of the spectrum of Pb(II). Theoretical transition probabilities and lifetimes
Authors: Colón C , Alonso-Medina A
Published: April 2011

Radiative transition probabilities for 190 lines arising from the ns 2S1/2, np 2P1/2,3/2, nd 2D3/2,5/2, nf 2F5/2,7/2, and 6p2 (4P1/2,3/2,5/2, 2D3/2,5/2, 2P1/2,3/2, and 2S1/2) levels of Pb(II) have been calculated. Lifetimes of the above mentioned levels have been determined from the present transition probabilities. These values were obtained in intermediate coupling (IC) and using ab initio relativistic Hartree-Fock calculations. For the IC calculations, we use the standard method of least-square fitting of experimental energy levels by means of computer codes from Cowan. The results of calculations for radiative transition probabilities and excited states lifetimes are presented and compared with the experimental results present in the literature and with other theoretical values. There is generally good agreement between our values and the experimental data available. Analysis of the interaction shows that the level 4P5/2 of the 6s6p2 configuration presents a large contribution to the 2D5/2 level of the 6s26d configuration. This result explains the good agreement between our result and the experimental values obtained to the observed as the 6s6p2 4P5/2  6s 25f2F7/2 dipole-forbidden transition.

PACS Nos.: 32.70^*, 32.70Fw, 32.70Cs
Supersymmetric models on AdS2
Authors: McKeon D.G.C. , Sherry T N
Published: April 2011

Models with N = 1 and N = 2 supersymmetry on AdS2 are formulated using generators of the symmetry group on this space. The effective action to one-loop order is considered.

PACS No.: 12.60Jv
Energy transfer between the 2S and 2D states in alkalis: experiments and theory
Authors: Ekers A , Glodz M , Grushevsky V , Klavins J , Szonert J
Published: April 2011

Collisional energy transfer (ET) between the 2S and 2D states of alkali atoms is reviewed. Recent experimental results on the ET in homonuclear collisions in Na, K, and Rb vapours upon cw (continuous wave) and pulsed laser excitation, as well as theoretical calculations of the respective cross sections are discussed. The mechanisms of these processes are considered in an attempt to clarify the role of the dipoledipole interaction.

PACS No.: 34.50Fa
Thermoluminescence recorded in a hyperbolic heating profile
Authors: Bhattacharya M
Published: April 2011

Thermoluminescence (TL) glow curves corresponding to a hyperbolic heating profile are computed, for the first time, by solving a system of coupled differential equations using the fourth-order RungeKutta method taking into account the presence of thermally disconnected traps. The variations of the peak temperature and the symmetry factor with the change of the fractional-filling ratio have been studied, not only for the TL peaks obtained as a result of the solution of the coupled differential equations but also for TL peaks obeying RandallWilkins and GarlickGibson equations in a hyperbolic heating program. Finally, the validity of the plateau test has also been considered.

PACS No.: 78.60Kn
Polarization dependence of optical harmonic generation from solid targets at high intensities: Role of Faraday rotation
Authors: Wu S , Zhan R -J , Chen J
Published: April 2011

In this letter, we show that the Faraday rotation effect of the strong spontaneous magnetic field generated by the focus of a short-pulse, high-power laser interacting with a solid target may blur out the distinction between the s and p polarization of the incident laser. This in effect leads to the result that the harmonic yield ratio between p and s polarization is not as large as a PIC (particle-in-cell) simulation predicted. An approximate calculation of the harmonic yield ratio versus the magnetic field is carried out and the result is in relatively good agreement with the observations by Norreys et al.

PACS Nos.: 42.90, 78.90
Measurement of radiative lifetimes in Nd II
Authors: Pinciuc C M , Rivest R C , Izawa M R , Holt R A , Rosner S D , Scholl T J
Published: April 2011

We have measured radiative lifetimes of 35 levels of Nd II using the collinear beam-laser method. The levels studied had term energies up to ~30 000 cm1 and lifetimes of 10 to 100 ns. Experimental accuracy was in the range 1.514%. These measurements are a first step to providing new and updated oscillator strengths needed for abundance determinations from stellar spectra.

PACS No.: 32.70Cs
Ground state of an Ising-type spin-1/2 chain with competing interactions
Authors: Tonegawa T , Matsumoto H , Hikihara T , Kaburagi M
Published: April 2011

The ground state of an Ising-type spin-1/2 chain with ferromagnetic bond-alternating nearest-neighbor and anti-ferromagnetic uniform next-nearest-neighbor interactions is studied by using the exact-diagonalization method and the density-matrix renormalization-group method. The Hamiltonian describing the system is expressed as H =  Σi h2i1,2i  J1 Σi h2i,2i+1 + J2 Σi hi,i+2 with hi,i' = γ(Six Si'x + Siy Si'y) + Siz Si'z, where J1 [Formula: see text] 0, J2 [Formula: see text] 0, and 1 > γ [Formula: see text] 0. Special attention is paid to the ground-state phase diagram on the J1 versus J2 plane for a given value of γ. The phase diagram is composed of the ferromagnetic, intermediate, and up-up-down-down phases, the intermediate phase being characterized by its magnetization, which takes finite but unsaturated values. The phase diagram obtained for γ = 0.5 shows that the region of the intermediate phase for a given value of J1 is widest when J1 = 1.0 and becomes narrower rather rapidly as J1 decreases or increases from 1.0. The J2-dependence of the ground-state magnetization for γ = 0.5 and J1 = 0.85 is also discussed.

PACS Nos.: 75.10Jm, 75.40Mg
Is there a phase transition in the isotropic Heisenberg anti-ferromagnet on the triangular lattice?
Authors: Stephan W , Southern B W
Published: April 2011

The phase diagram of the classical anisotropic (XXZ) Heisenberg model on the two-dimensional triangular lattice is investigated using Monte Carlo methods. In the easy-axis limit, two finite-temperature vortex-unbinding transitions have been observed. In the easy-plane limit, there also appear to be two distinct finite-temperature phase transitions that are very close in temperature. The upper transition corresponds to an Ising-like chirality ordering and the lower temperature transition corresponds to a KosterlitzThouless vortex-unbinding transition. These phase-transition lines all meet at the Heisenberg point and provide strong evidence that the isotropic model undergoes a novel finite-temperature phase transition.

PACS Nos.: 75.10Hk, 75.40Mg
Millimetre-wave ESR (electron-spin resonance) measurements of frustrated system ZnCr2xGa22xO4
Authors: Ohta H , Okubo S , Kikuchi H , Ono S
Published: April 2011

The magnetic properties of a three-dimensional topological frustrated system ZnCr2xGa2-2xO4, which is an anti-ferromagnet with a spinel structure, have been investigated by our millimetre-wave ESR (electron-spin resonance) measurements using the pulsed magnetic field up to 16 T in the temperature region from 1.8 to 265 K. In the high-temperature region, typical Cr3+ EPR (electron-paramagnetic resonance) with the g-value of 1.95 was observed. For the x = 1 sample, AFMR (anti-ferromagnetic resonance) with the easy-plane-type magnetic anisotropy was observed below TN. It turned out that the anti-ferromagnetic gap opens up just below TN suggesting that the transition is of the first order. The x dependences of ESR were also observed and their temperature dependences of the g-value and the linewidth will be discussed in connection with those of other frustrated systems such as Kagome lattice substance. PACS Nos.: 75.50, 76.30-v, 75.40-s
Alteration of the stacked 2π/3 magnetic structure in the triangular lattice anti-ferromagnet LiCrS2
Authors: Lafond A , Henggeler W , Mutka H , Ouladdiaf B
Published: April 2011

LiCrS2 has magnetic Cr ions with spin S = 3/2 on a triangular lattice. Other researchers (J. Solid State Chem. 3, 590, 1971) concluded that this compound has an anti-ferromagnetic order with a stacked 2π/3 structure below a transition temperature of the order of TN = 50 K. We have re-examined this system with neutron scattering methods on powder samples, paying attention to the temperature dependence of the magnetic scattering. The overall characteristics of the magnetic ordering are in agreement with the earlier study but we have observed significant modifications of the stacked 2π/3 structure well below the critical temperature. The main new features observed on cooling from T = 25 K down to T = 1.5 K are (i) the gradual decrease from 2.5 µB to 2.3 µB of the ordered moment attributed to the 2π/3 structure, (ii) the appearance of new correlations corresponding to a multiplication of the magnetic unit cell, and (iii) the growth of a diffuse elastic scattering component that can be ascribed to a frozen disorder. These observation are not explained in the framework of the standard theoretical treatments concerning the stacked triangular anti-ferromagnet with Heisenberg or slightly anisotropic interactions.

PACS Nos.: 75.10Nr, 75.25+z, 75.40Gb
Conventional and unconventional orderings in the jarosites
Authors: Wills A S
Published: April 2011

The jarosites make up the most studied family of Kagome anti-ferromagnets. The flexibility of the structure to substitution of the A and B ions allows a wide range of compositions to be synthesized with the general formula AB3(SO4)2(OH)6 (A = Na+, K+, Ag+, Rb+, H3O+, NH4+, 1/2Ba2+, and 1/2Pb2+; B = Fe3+, Cr3+, and V3+). Additional chemical tuning of the exchange between layers is also possible by substitution of the (SO4)2 groups by (SeO4)2 or (CrO4)2. Thus, a variety of S = 5/2, 3/2, and 1 systems can be engineered to allow study of the effects of frustration in both the classical and more quantum limits. Within this family both conventional long-ranged magnetic order and more exotic unconventional orderings have been found. This article reviews the different types of magnetic orderings that occur and examines some of the parameters that are their cause.

PACS Nos.: 75.25+z, 75.30Et, 75.30Gw, 75.50Ee, 75.50Lk
Triangular-lattice Heisenberg anti-ferromagnets: A Schwinger-boson study
Authors: Manuel L O , Ceccatto H A
Published: April 2011

We study, within the Schwinger-boson approach, the ground-state structure of two Heisenberg anti-ferromagnets on the triangular lattice: the J1  J2 model, which includes a next-nearest-neighbor coupling J2, and the spatially-anisotropic J1  J'1 model, in which the nearest-neighbor coupling takes a different value J'1 along one of the bond directions. For both models, the inclusion of one-loop corrections to saddle-point results leads to the prediction of nonmagnetic phases for particular values of the parameters J1/J2 and J'1/J1. In the case of the J1  J2 model we shed light on the existence of such a disordered quantum state, a question which is controversial in the literature. For the J1  J'1 model our results nicely agree with series-expansions predictions.

PACS No.: 75.10Jm
Effective Hamiltonians and dilution effects in Kagome and related anti-ferromagnets
Authors: Henley C L
Published: April 2011

What is the zero-temperature ordering pattern of a Heisenberg anti-ferromagnet with large spin length S (and possibly small dilution), on the Kagome lattice, or others built from corner-sharing triangles and tetrahedra? First, I summarize the uses of effective Hamiltonians to resolve the large ground-state degeneracy, leading to long-range order of the usual kind. Secondly, I discuss the effects of dilution, in particular that the classical ground states become nonfrustrated, in that every simplex of spins is optimally satisfied. Of three explanations for this, the most satisfactory is the MoessnerChalker constraint enumeration. Quantum zero-point energy may compete with classical exchange energy in a diluted system, creating frustration and enabling a spin-glass state. I suggest that the regime of over 97% occupation is qualitatively different from the more strongly diluted regime.

PACS Nos.: 75.10N, 75.50Ee, 75.40, 75.25+z
Origin of spin-ice behavior in Ising pyrochlore magnets with long-range dipole interactions: an insight from mean-field theory
Authors: Gingras M JP , den Hertog B C
Published: April 2011

Recent experiments suggest that the Ising pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7 display qualitative properties of the ferromagnetic nearest-neighbor spin-ice model proposed by Harris et al. Phys. Rev. Lett. 79, 2554 (1997). The manifestation of spin-ice behavior in these systems despite the energetic constraints introduced by the strength and the long-range nature of dipoledipole interactions, remains difficult to understand. We report here results from a mean-field analysis that shed some light on the origin of spin-ice behavior in (111) Ising pyrochlores. Specifically, we find that there exist a large frustrating effect of the dipolar interactions beyond the nearest neighbor, and that the degeneracy established by effective ferromagnetic nearest-neighbor interactions is only very weakly lifted by the long-range interactions. Such behavior only appears beyond a cut-off distance corresponding to O(102) nearest neighbor. Our mean-field analysis shows that truncation of dipolar interactions leads to spurious ordering phenomena that change with the truncation cut-off distance.

PACS Nos.: 75.10-b, 75.10Hk, 75.20-g, 75.30-m
Quantum tetrahedral mean-field theory of the pyrochlore lattice
Authors: García-Adeva A J , Huber D L
Published: April 2011

A quantum mean-field theory of the pyrochlore lattice is presented. The starting point is not the individual magnetic ions, as in the usual Curie-Weiss mean-field theory, but a set of interacting corner-sharing tetrahedra. We check the consistency of the model against magnetic susceptibility data and find a good agreement between the theoretical predictions and the experimental data. Implications of the model and future extensions are also discussed.

PACS Nos.: 75.10Jm, 75.30Cr, 75.40Cx
Spin-liquid phase in the pyrochlore anti-ferromagnet
Authors: Canals B , Garanin D A
Published: April 2011

Correlation functions (CFs) of the classical Heisenberg anti-ferromagnet on the pyrochlore lattice are studied by solving exactly the infinite-component spin-vector model. As in many fully frustrated lattices, the constraint due to the minimization of the energy and the particular structure based on corner-sharing tetrahedra both contribute to the creation of local degrees of freedom. The resulting degeneracy destroys any magnetic order at all temperatures and we obtain no sign of criticality, even at T = 0. Calculated neutron-scattering cross sections have their maxima beyond the first Brillouin zone and reproduce experimental results obtained on Y(Sc)Mn2 and CsCrNiF6 as well as theoretical predictions previously obtained by classical Monte Carlo simulations. Evidences for thermal and spatial decoupling of the magnetic modes are found so that the magnetic fluctuations in this system can be approximated by S(q,T) [Formula: see text] f(q) h(T).

PACS Nos.: 75.10Hk, 75.50Ee, 75.40Cx, 75.40-s
Muon-spin relaxation measurements of geometrically frustrated magnets
Authors: Kojima K M
Published: April 2011

Muon-spin relaxation (µSR) has been applied to investigations of slow dynamics and quasi-static features of geometrically frustrated spin systems. We take an example in the Kagome-lattice anti-ferromagnets, and briefly review µSR works on S = 1, 3/2, and 5/2 Kagome compounds.

PACS No.: 75.30
High-resolution neutron study of the effects of magnetic dilution in the strongly frustrated system SrCrxGa12xO19
Authors: Mondelli C , Mutka H , Payen C
Published: April 2011

We have pursued the neutron examination of SrCrxGa12xO19, with special emphasis on the role of magnetic dilution in the spin dynamics and freezing. We have examined samples with different levels of magnetic dilution, ranging from 7.0 < x < 8.8, characterized by neutron powder diffraction with Rietveld refinements and bulk susceptibility. The elastic magnetic response examined by high-resolution neutron scattering (µeV range) has confirmed the trend on increasing dilution: the decrease of the freezing temperature as well as of the frozen moment/magnetic site. However, the least diluted sample that we have produced with x = 8.8, deviates from this trend, with a smaller than expected freezing temperature and frozen moment. This suggests that the freezing might be suppressed at the clean limit.

PACS Nos.: 75.10Nr, 75.25+z, 75.40Cx, 75.40Gb
Comparison of several tetrahedra-based lattices
Authors: Elhajal M , Canals B , Lacroix C
Published: April 2011

A comparison of the quantum Heisenberg anti-ferromagnetic model on the pyrochlore lattice, the checkerboard lattice, and the square lattice with crossing interactions is performed. The three lattices are constructed with the same tetrahedral unit cell and this property is used to describe the low-energy spectrum by means of an effective Hamiltonian restricted to the singlet sector. We analyze the structure of the effective Hamiltonian and solve it within a mean-field approximation for the three lattices.

PACS No.: 75.10Jm
Anomalous behavior in a three-dimensional frustrated itinerant electron magnet
Authors: Isoda M , Mori S
Published: April 2011

We present a simple microscopic theory for the magnetic and electronic properties of a three-dimensional frustrated itinerant electron magnet. Based on the single-band Hubbard model, it is investigated in the weak-correlation limit at a half-filling on the pyrochlore lattice. A doubly-degenerate flat band in the bare spectrum emerges as a character of the fully frustrated geometry. The random-phase-approximation dynamical susceptibility reproduces some characters in the low-frequency regime that were found in the neutron inelastic-scattering experiment of the cubic Laves compound Y(Sc)Mn2, especially in the spectral intensity distribution in the reciprocal space and in the almost irrelevant feature of the distribution to frequency. The quasi-particle self-energy shows a peculiarity, resulting from an anomalous frequency dependence in the non-interacting dynamical susceptibility, and then it leads to the breakdown of the Fermi-liquid picture.

PACS No.: 75.25+z
7Li NMR studies in magnetically frustrated LiV2O4: Evidence for a spin-liquid ground state?
Authors: Büttgen N , Kaps H , Trinkl W , Loidl A , Klemm M , Horn S
Published: April 2011

7Li NMR measurements were performed in the metallic spinel LiV2O4. The temperature dependence of the spin-lattice relaxation rate is documented in the temperature range 100 mK < T < 280 K. A comparison with the spin-glass behavior of Li1xZnxV2O4 for small concentrations of x is given. For low temperatures T < 1 K we observe a maximum for the spin-lattice relaxation rate in LiV2O4. The frequency dependence of this maximum is indicative for a slowing down of spin fluctuations. The NMR results can be explained by a spin-liquid behavior and the opening of a spin gap of the order 1 K.

PACS Nos.: 75.20Hr, 75.50Lk, 76.60Es, 76.60-k
Geometric frustration in the RMn2 Laves phase compounds
Authors: Ballou R
Published: April 2011

An overview of neutron-scattering investigations of the geometrically frustrated Mn itinerant-electron magnetism in the RMn2 Laves phase compounds is given. Magnetic structures of magnetically ordered compounds are briefly described, in particular the mixed phases where magnetic and nonmagnetic Mn coexist. Magnetic correlations in the paramagnetic phase of YMn2 and in (Y0.97Sc0.03)Mn2, where the substitution of Sc for Y inhibits the magnetic order down to the lowest temperatures, are then discussed. An unusual neutron-scattering function S(Q, ω) is measured, which appear to arise from an itinerant-electron spin liquid.

PACS Nos.: 71.27+a, 75.40Gb, 75.50Ee
Magnetic ordering and excitation in triangulated anti-ferromagnet Cu9Cl2(cpa)6·nH2O
Authors: Mekata M , Abdulla M , Kubota M , Oohara Y
Published: April 2011

The Cu2+ ions in Cu9Cl2(cpa)6 · nH2O (cpa is the anion of 2-carboxy pentonic acid) form a slightly deformed Kagome lattice with a smaller triangle plaquette in each triangle of a Kagome lattice showing strong frustration. The anomalous features of magnetism are the reduction of the Curie constant below 50 K, fractional saturation even in a field of 38 T, and nonlinear magnetic susceptibility below 5 K. We performed inelastic neutron scattering measurements on powder samples and observed dispersionless scattering around 6.5 meV with a full width of about 8 meV indicating a single-site excitation with E/kB [Formula: see text] 70 K. The scattering is less conspicuous above 50 K. These results are interpreted in terms of the plaquette-ordering model that assumes a 120° arrangement of three moments on each triangular plaquette and a random freezing of the remaining paramagnetic moments below 5 K.

PACS No.: 75.10Hk
Magnetic-ordering process in SrCr9(Ga-In)3O19
Authors: Mekata M , Yamada Y
Published: April 2011

To investigate the anomalous magnetic properties of SrCr9xGa3+xO19, we synthesized SrCr9x(Ga0.95In0.05)3+xO19 compounds including the x = 0 compounds and carried out magnetic and µSR measurements. The results show clearly the insignificant role of the defects in the magnetic Cr lattice. Based on the results, a classical Heisenberg spin model, the plaquette-ordering model, is presented. Below 60 K, seven moments on a bi-tetrahedron plaquette correlate anti-ferromagnetically to give one moment, so that the Curie constant decreases to 1/9 at low temperatures. The surviving moments forming a triangular lattice do not exhibit long-range order due to frustration but the c-components of the moments are frozen randomly below Tf. The muoniums formed in the compound combine with the oxygen ions connecting Cr3+ ions and are subject to transferred hyperfine fields from Cr moments. This field is shielded by the electrons of the muonium so as to be hardly decoupled by external fields.

PACS Nos.: 75.40Cx, 75.50Ee
Magnets with strong geometric frustration
Authors: Moessner R
Published: April 2011

A nontechnical introduction to the theory of magnets with strong geometric frustration is given, concentrating on magnets on corner-sharing (Kagome, pyrochlore, SCGO, and GGG) lattices. Their rich behaviour is traced back to a large ground-state degeneracy in model systems, which renders them highly unstable towards perturbations. A systematic classification according to properties of their ground states is discussed. Other topics addressed in this overview article include a general theoretical framework for thermal order-by-disorder, the dynamics of how the vast regions of phase space accessible at low temperature are explored, the origin of the featureless magnetic susceptibility fingerprint of geometric frustration, the role of perturbations, and spin ice. The rich field of quantum frustrated magnets is also touched on.

PACS No.: 75.50-y
Dependence on crystallographic orientation of trapping properties in a polished MgO single crystal
Authors: Dammak N , Kallel A , Fakhfakh Z , Tréheux D
Published: April 2011

It is well known that the presence of space charges in an insulator is correlated with electric breakdown. Many studies have been carried out on the experimental characterization of space charges and on phenomenological models of trapping and detrapping. In this paper, we outline the dependence on crystallographic orientations of the charge-trapping phenomenon in polished MgO. The charging phenomenon was characterized during and after electron injection by using a scanning electron microscope (SEM). It was shown that the trapping ability depends on the dislocation network of different crystallographic orientations.

PACS No.: 72.20Jv
Antiprotonic helium and kaonic helium – A tale of two exotic helium atomsThis 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: Hayano R. S.
Published: April 2011

Recent progress on the precision laser spectroscopy of antiprotonic helium atoms, as well as on the X-ray spectroscopy of kaonic helium atoms, are presented. These two may appear to be unrelated topics (except that both involve exotic helium atoms), but in fact a past study of kaonic helium system led to the serendipitous discovery of antiprotonic helium. Some historical background connecting these two exotic helium atoms, as well as future prospects, are discussed.
Fundamental constants and tests of theory in Rydberg states of hydrogenlike ionsThis 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: Jentschura Ulrich D. , Mohr Peter J. , Tan Joseph N. , Wundt Benedikt J.
Published: April 2011

A comparison of precision frequency measurements to quantum electrodynamic (QED) theoretical predictions can be used to test theory and to obtain information regarding fundamental constants. We find that for Rydberg states, theoretical uncertainties due to the problematic nuclear size correction are very small. With the help of QED calculations, the largest remaining source of uncertainty can be eliminated. Theoretical predictions, taking advantage of the latest theoretical results, in combination with planned experiments, can lead to an improved value for the Rydberg constant.
The BMV project: Search for photon oscillations into massive particlesThis 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: Robilliard C. , Pinto Da Souza B. , Bielsa F. , Mauchain J. , Nardone M. , Bailly G. , Fouché M. , Battesti R. , Rizzo C.
Published: April 2011

In this contribution to PSAS08 we report on the research activities developed in our Toulouse group in the framework of the BMV project, concerning the search for photon oscillations into massive particles, such as axion-like particles, in the presence of a strong transverse magnetic field. We recall our main result obtained in collaboration with LULI at École Polytechnique (Palaiseau, France). We also present the very preliminary results obtained with the BMV experiment which is set up at LNCMI (Toulouse, France).
Antihydrogen Physics at ALPHA/CERNThis 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: Cesar C. L. , Andresen G. B. , Bertsche W. , Bowe P. D. , Bray C. C. , Butler E. , Chapman S. , Charlton M. , Fajans J. , Fujiwara M. C. , Funakoshi R. , Gill D. R. , Hangst J. S. , Hardy W. N. , Hayano R. S. , Hayden M. E. , Humphries A. J. , Hydomako R. , Jenkins M. J. , Jørgensen L. V. , Kurchaninov L. , Lambo R. , Madsen N. , Nolan P. , Olchanski K. , Olin A. , Page R. D. , Povilus A. , Pusa P. , Robicheaux F. , Sarid E. , El Nasr S. Seif , Silveira D. M. , Storey J. W. , Thompson R. I. , van der Werf D. P. , Wurtele J. S. , Yamazaki Y.
Published: April 2011

Cold antihydrogen has been produced at CERN (Amoretti et al. (Nature, 419, 456 (2002)), Gabrielse et al. (Phys. Rev. Lett. 89, 213401 (2002))), with the aim of performing a high-precision spectroscopic comparison with hydrogen as a test of the CPT symmetry. Hydrogen, a unique system used for the development of quantum mechanics and quantum electrodynamics, has been continuously used to produce high-precision tests of theories and measurements of fundamental constants and can lead to a very sensitive search for CPT violation. After the initial production of cold antihydrogen atoms by the ATHENA group, the ALPHA Collaboration ( http://alpha.web.cern.ch/ ) has set forth on an experiment to trap and perform high-resolution laser spectroscopy on the 1S-2S transition of both atoms. In this contribution, we will review the motivations, goals, techniques, and recent developments towards this fundamental physics test. We present new discussion on predicted lineshapes for the 1S-2S spectroscopy of trapped atoms in a regime not discussed before.
Towards a precision test of time dilation at high velocityThis 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: Novotny C. , Bernhardt B. , Bing D. , Ewald G. , Geppert C. , Gwinner G. , Huber G. , Karpuk S. , Kluge H.-J. , Kühl T. , Nörtershäuser W. , Reinhardt S. , Saathoff G. , Schwalm D. , Stöhlker T. , Wolf A.
Published: April 2011

We report on first measurements towards an Ives–Stilwell test of time dilation at velocities around 0.3c. In Ives–Stilwell type experiments, fast atomic ions containing a well-known transition are used as moving clocks, and time dilation as well as the velocity can be derived from the simultaneous laser-spectroscopic measurements of the Doppler shifts with and against the direction of motion. To accurately measure these Doppler shifts, the Doppler broadening caused by the ions velocity distribution needs to be overcome. We performed first feasibility studies for laser spectroscopy on 7Li+ ions in the 2s3S21 metastable ground state at the Gesellschaft für Schwerinonenforschung (GSI) in Darmstadt. The ions were stored in the Experimental Storage Ring (ESR) at a velocity of 0.338c, and optical–optical double-resonance spectroscopy on a closed Λ-type three level system was performed with two lasers propagating antiparallel to the ions motion. We found that Doppler shift measurements on a narrow subclass of the ions velocity distribution with sufficient signal-to-noise ratio are possible if the ion beam is electron-cooled and bunched. Together with the control of systematic error sources developed in our previous experiments on slower beams, the ESR experiment promises an improvement of previously achieved sensitivities to time dilation by about an order of magnitude.
A new trap loading mechanism for hydrogenThis 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: Crivelli P. , Cesar C. L. , Lambo R.
Published: April 2011

In this paper, we report on our recent advances on a new trap loading mechanism for neutral atoms. The idea is based on our recently published results for chromium spectroscopy of atoms released from a solid neon matrix at cryogenic temperatures. The proposed trap loading mechanism consists of magnetically capturing the low-energy fraction of paramagnetic atoms being released from the matrix, while the host Ne atoms stick to the walls. Two different designs are described: one with a superconducting magnet producing a trap depth of 3 T and another with a superconducting dynamically switched magnet that generates a trap depth of about 1 T. Some preliminary results are presented.
Higher order nonlinearities in a non-Doppler free geometryThis 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: Narayanan Andal , Sharma Archana , Preethi T. M. , Abheera H. , Ramachandran Hema
Published: April 2011

Multi-level gaseous atomic systems showing electromagnetically induced transparency (EIT) phenomenon also exhibit low light intensity nonlinear optical phenomena. This is primarily due to the supression of linear susceptibility for the probe light during EIT. Therefore under EIT, nonlinear interactions become appreciable even at very low light intensities. In particular, Kerr nonlinearity in N systems irradiated by three fields has been both experimentally and theoretically investigated. In this paper, we report an all optical observation of an absorptive three-photon resonance feature, of subnatural width, in a N level scheme of gaseous rubidium, at room temperature, in a novel geometry of three independent beams. The non-Doppler free configuration of the beam in which the absorption is seen is the first such feature reported in a beam that is not directly taking part in the transparency effect. We have demonstrated the velocity selective nature of this absorption and studied the contrast dependence on detuning from the fourth level. Density matrix calculations have been carried out for this geometry, the results of which are in qualitative agreement with the experiment.
Frequency-comb-based measurements of lithium and beryllium isotopes for nuclear structure studiesThis 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: Sánchez R. , Žáková M. , Geppert Ch. , Krämer J. , Krieger A. , Tiedemann D. , Nörtershäuser W.
Published: April 2011

We report on the measurement of the 2s-3s transition frequencies in the stable lithium isotopes and 2s-2p isotope shift measurements of 7,9,10,11Be, using a femtosecond frequency comb. For the beryllium isotopes, we extract the changes in the mean-square nuclear charge radius along the isotope chain by comparison with high-precision atomic mass shift calculations. The 2s-3s transition frequency is compared with theoretical calculations, and possibilities to extract an absolute value for the nuclear charge radius of lithium isotopes are discussed.
Non-spherical proton shape and hydrogen hyperfine splittingThis 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: Buchmann A. J.
Published: April 2011

We show that the non-spherical charge distribution of the proton manifests itself in hydrogen hyperfine splitting as an increase (in absolute value) of the proton Zemach radius and polarization contributions.
THE ABSORPTION OF MICROWAVES IN EXCITED HYDROGEN
Authors: Reesor G. E.
Published: April 2011

Direct absorption measurements were made upon excited atomic hydrogen in a discharge tube placed inside a wave guide. Two ranges of wave lengths in the 3 cm. region were investigated. The results can be satisfactorily explained by absorption due to free electrons. Although the 2s[Formula: see text] to 2p[Formula: see text] transition of atomic hydrogen is in this region, no selective absorption was observed.
METEOROLOGICAL EFFECTS ON COSMIC RAY INTENSITY AND THE MESON SPECTRUM
Authors: Rose D. C.
Published: April 2011

Continuous recording of the intensity of the hard component of cosmic rays has been carried out at Ottawa (Geomagnetic Lat. 56.8) and at Resolute (Geomagnetic Lat. 83) in the Canadian Arctic for over a year. Two counter telescopes with different amounts of lead shielding are used at each station. The results have been analyzed for barometer effect in four series of observations each extending over three months. When averaged, they show a barometer coefficient of –1.75% per cm. of mercury for mesons with momenta above 350 Mev./c and –2.13% per cm. of mercury for those with momenta above 630 Mev./c.A calculation has been made of the temperature and barometer effects. It was based on the variations in the probability of decay of mesons in the atmosphere, under varying atmospheric conditions. The calculations of the temperature effect do not yield results comparable with measurement; those of the barometer effect show that considerable information can be obtained about the meson spectrum from measurements of the barometer coefficients. The results favor a spectrum in agreement with parts of spectra measured by other authors. They suggest the possibility of a second maximum in the production spectrum of mesons.
ENERGY SPECTRUM OF NEUTRONS FROM A THORIUM ACTIVE DEPOSIT – BERYLLIUM SOURCE
Authors: Bromley D. A.
Published: April 2011

The energy spectrum of the neutrons emitted when beryllium is bombarded with alpha particles from Th (C + C′) has been determined by measuring the ranges and directions of recoil of protons produced in a cloud chamber by the neutrons. The maximum energy of the neutrons was found to be about 15.5 Mev., within experimental error of the calculated maximum, 14.4 Mev. Many neutrons were found with energy of about 2.15 Mev. and the structure in the remainder of the spectrum can be attributed to the existence of energy levels in C12 at about 7.1 and 4.5 Mev. The angular distribution of the protons scattered by the neutrons from this source was isotropic to within experimental error.
PULSER FOR CYCLOTRON OSCILLATOR
Authors: Henry W. H. , Keys J. D.
Published: April 2011

A pulser for the R.F. oscillator of the McGill synchrocyclotron is described. This pulser is triggered at a selected precise frequency and controls the oscillator for selected pulses or for predetermined exact periods of continuous operation.
THE CALIBRATION OF PLATINUM RESISTANCE THERMOMETERS IN THE TEMPERATURE RANGE 11° TO 90°K
Authors: Los J. M. , Morrison J. A.
Published: April 2011

A set of six platinum resistance thermometers of a form suitable for low temperature calorimetry has been made and calibrated in the region 11° to 90°K. by intercomparison with a similar thermometer which had been calibrated at the National Bureau of Standards. Above 90°K. calibration has been made on the International Temperature Scale.Using the intercomparison data, it has been possible to derive a method whereby for these thermometers the scale for the region 20° to 90°K. may be found to within 0.002°C. by means of fixed points. The method applies a 'Z function' of the type used at the National Bureau of Standards (13), plus a corrective term which depends upon the resistance of the thermometer at the boiling point of hydrogen and upon the normal constants which are determined for the International Temperature Scale above 90°K.
THE RAMAN SPECTRUM OF FLUORINE
Authors: Andrychuk D.
Published: April 2011

The rotational and vibrational Raman spectra of gaseous fluorine at 1 atm. pressure were obtained. From these spectra the constants of the molecule in the electronic ground state were determined to be:[Formula: see text]The intensity alternation in the rotational spectrum shows that the nuclear spin of fluorine is [Formula: see text] and that the F19 nuclei follow Fermi statistics.
EFFECT OF VARIABLE MASS OF THE ELECTRON ON THE SPACE-CHARGE LIMITED CURRENT IN A DIODE
Authors: Visvanathan S.
Published: April 2011

The change in the current-potential distribution due to the relativistic variation of the mass of the electron has been calculated by suitable series expansions in the case of a plane parallel diode and has been shown to be considerable in the case of large power tubes.
ROTATIONAL ANALYSIS OF THE γ BAND SYSTEM OF THE NS MOLECULE
Authors: Zeeman P. B.
Published: April 2011

The band heads of the NS spectrum discovered in 1932 by Fowler and Bakker have been remeasured on plates taken on a large quartz spectrograph and on first order grating plates. The (0,0) and (0,1) γ bands have been photographed in the 6th, 8th, and 9th orders of a 21 ft. concave grating, and a rotational analysis of these bands has been carried out. For the ground state (2II) it was found that [Formula: see text] = 0.77364 cm−1, [Formula: see text] = 0.00612, and A = 223.03 cm.−1 For the upper state the value [Formula: see text] = 0.82670 was obtained.
SUR LA CORRELATION ENTRE LES DISCONTINUITIÉS DANS LA VALLÉE DES MASSES ET LES ENVELOPPES NUCLÉAIRES. APPLICATION À L'ÉTUDE DE LA SYSTÉMATIQUE α
Authors: Broniewski A.
Published: April 2011

not available
NUCLEAR MAGNETIC MOMENT OF SCANDIUM OF MASS 45
Authors: Hunten D. M.
Published: April 2011

By the method of nuclear magnetic resonance, the magnetic moment of Sc45 (without diamagnetic correction) is found to be 4.74916 ± 0.00012. The correction is +0.00717 with unknown and possibly large error. The equipment designed to search for magnetic resonance by varying the field of the magnet is described, with special emphasis on the magnet current regulator.
A FUNDAMENTAL THEORY OF THE MAGNETISM OF MASSIVE ROTATING BODIES
Authors: Luchak George
Published: April 2011

A phenomenological theory, based on a relativistically covariant generalization of Maxwell's equations to include gravitational fields, is developed to account for the magnetic fields of massive rotating bodies. The equations yield the Wilson–Blackett expression for the magnetic moment of the earth and stars but give no magnetic field for mass-bodies moving without rotation in their own gravitational fields. They indicate that the magnetic field due to the motion of the earth in its orbit is negligibly small compared to the field due to its rotational motion, and they provide a possible explanation for the variable magnetic fields of light-variable stars.
ELECTROMAGNETIC CASCADES IN PHOTOGRAPHIC EMULSIONS
Authors: Hooper J. E. , King D. T. , Morrish A. H.
Published: April 2011

Photographic emulsion techniques are described for observation and identification of electromagnetic processes which occur in the soft component of the cosmic radiation. Several cascade showers are illustrated and measurements on these are discussed in the light of theoretical predictions.
A 200 kv. HIGH TENSION SET FOR THE ACCELERATION OF H3 AND He3
Authors: Allen K. W. , Almqvist E. , Dewan J. T. , Pepper T. P.
Published: April 2011

A 200 kv. high tension set suitable for the acceleration of H3 and He3 is described. Special features incorporated in the accelerator include a radio-frequency type ion source capable of giving large beam currents with low gas consumption, a differential pumping system for recovering the gas used by the ion source, and an electronic stabilizer which reduces voltage fluctuations to a negligible value.
THE MAGNETIC DIPOLE OVER THE HORIZONTALLY STRATIFIED EARTH
Authors: Wait James R.
Published: April 2011

The behavior of a small current-carrying wire loop over a horizontally stratified earth is investigated. The layers are considered to have a contrast in conductivity and dielectric constant only. Both harmonic steady-state and step-function current sources are considered.
ELECTRON MICROSCOPE STUDIES OF EVAPORATED CADMIUM AND ZINC
Authors: Sennett R. S. , McLauchlan T. A. , Scott G. D.
Published: April 2011

Employing a technique, previously described, whereby evaporations are carried out within the specimen chamber of an electron microscope, continuous observations have been made on the formation of evaporated deposits of cadmium and zinc. The particles first seen appear suddenly, have a regular crystalline shape, and are often relatively large (200 Å). At first they remain regular while increasing in size, but later develop irregular spurs, secondary crystallites, or link together with their neighbors. This behavior is quite different from that of silver and gold in which the aggregates appear irregular at all stages.
THE LOW ENERGY SPECTRUM OF COSMIC-RAY MESONS AT SEA LEVEL AT HIGH GEOMAGNETIC LATITUDES
Authors: Rose D. C. , Voisin A. G.
Published: April 2011

The differential range spectrum of cosmic-ray mesons has been measured by three different methods the first of which was used at two northern geomagnetic latitudes 56.8 (Ottawa) and 83.0 (Resolute in the Canadian Arctic). In the first method the integral spectrum was measured by absorption, and after various corrections the differential spectrum was derived. In the second method the number of particles stopped in a block of lead was measured by a coincidence–anticoincidence arrangement of counters. In the third method the delayed coincidence method was used, the meson being identified by its decay electron. Over the range studied (ranges in lead up to 700 gm∙per cm∙2) the results of the three methods are in general agreement and agree with others in that the smoothed data show only a small variation in intensity over the range studied. Some of the results suggest that a more detailed study of the spectrum might show some irregularities in the intensity variation with range. As would be expected no significant difference was found in the shape of the curves at the two stations.