bluuebunny/crossref_metadata_2025 huggingface dataset:
Joint effect of N-atom coherences, saturation broadening, and collisions on absorption profiles of two-level atoms
Authors: Schuller F. , Nienhuis G.
Published: April 2011

We consider the Dicke model for cooperative decay of N two-level atoms confined to a very small volume assuming moreover that this system is submitted to a strong monochromatic driving field. We study the influence of foreign-atom collisions on the corresponding absorption profile by taking into account the simultaneous action of collisions, multiatom coherence, and saturation effects. In the case of a two-atom system we calculate the profile exactly by especially avoiding the secular approximation introduced in previous work. In the N-atom case we discuss both the low-intensity and the large-detuning limit for which exact expressions can also be obtained. Finally, we present some numerical results for the two-atom case and compare these with a simple Karplus–Schwinger-type formula with coherence effects incorporated in the low-intensity profile.
Collision-induced absorption in nitrogen at low temperatures
Authors: Dagg I. R. , Anderson A. , Yan S. , Smith W. , Read L. A. A.
Published: April 2011

The collision-induced absorption (CIA) spectrum for nitrogen has been measured in the spectral region below 360 cm−1 at 126, 149, 179, and 212 K. The measurements have been obtained using Fourier transform infrared (FTIR) techniques, a far infrared (FIR) laser system operating at 84.2 and 15.1 cm−1, and microwave cavity techniques. The experimental line shapes have been compared with the theoretical predictions of Joslin, based on Mori theory, and of Joslin and Gray, based on information theory alone. The data have been used to determine the quadrupole moment employing various intermolecular potentials. One Lennard–Jones potential has resulted in a quadrupole moment of 1.51 B, the value that was used in generating the theoretical line shapes. These results, when combined with our forthcoming measurements on nitrogen mixed with methane and argon, may be helpful in determining the role of CIA in calculating the opacity of some planetary atmospheres.
Tachyon-trapping and Ernst space-times
Authors: Krori K. D. , Sarmah J. C.
Published: April 2011

We discover in this paper a physically significant feature of Ernst space-times. These space-times are capable of trapping tachyons, although Schwarzchild, Reissner–Nordstrom, Kerr, and Kerr–Newman fields fail to perform this job.
Nuclear-magnetic-resonance study of spin transfer to H in Rb2CuCl4∙2H2O and Rb2CuBr4∙2H2O
Authors: Moon Nam Doo , Lee Kyunghee , Choh Sung Ho
Published: April 2011

The nuclear magnetic resonance of 1H in Rb2CuCl4∙2H2O and isomorphic Rb2CuBr4∙2H2O has been measured at room temperature, near 165, and 77 K. The fractional spin transfer from the copper ion to hydrogen due to the transferred hyperfine interaction is analyzed: 0.22 ± 0.03% at 300 K, 0.25 ± 0.02% at 168 K, and 0.29 ± 0.02% at 77 K in Rb2CuCl4∙2H2O; and 0.22 ± 0.03% at 300 K, 0.28 ± 0.02% at 163 K, and 0.32 ± 0.02% at 77 K in Rb2CuBr4∙2H2O. The temperature-dependent spin transfers are discussed in terms of the molecular mass and the bond strength of the two compounds.
Réaction (3He, α) : validité du modèle optique dans la description de la voie 3He-noyau
Authors: Potvin L. , Roy R. , Bricault P. , Larue R. , Rioux C. , Slobodrian R. J.
Published: April 2011

The transfer reaction (3He, α) on 17O, 29Si and 53Cr nuclei has been studied at 14-MeV incident energy. Complete angular distributions were measured for ground-state transitions and described in the framework of the distorded-wave Born approximation. Parameters have been defined from analysis of the corresponding elastic scattering channels, but avoiding pronounced variations in their values from one nucleus to the other. In addition, the sum of the real depths V for 3He scattering and for the transferred neutron was taken approximately equal to that term in the alpha channel to validate the Born approximation.
Vibration–rotation spectra of nitrous acid, HONO
Authors: Deeley C. M. , Mills I. M. , Halonen L. O. , Kauppinen J.
Published: April 2011

High-resolution Fourier-transform infrared spectra have been recorded and analyzed for the ν4 ν5, and ν6 fundamental bands of trans-HONO, and for the ν4 fundamental of cis-HONO. The spectral resolution was better than 0.01 cm−1, and the rotational structure has been analyzed to give improved ground-state and excited-state rotational constants, with a standard deviation of the fit to the observed line positions of around 0.0006 cm−1. Two Coriolis interactions have been analyzed between the ν5 and ν6 bands of trans-HONO.
Comments on: Line broadening by focusing; Gas ionization by focused laser beams
Authors: Curzon F. L.
Published: April 2011

It is pointed out that the frequency spectrum of a laser beam is not broadened when the beam is focused by a normal lens. This assertion contradicts the conclusion reached by the authors of the articles cited in the title above.
A general iterative time-independent perturbation theory
Authors: Castaño F. , Laín L. , Sanchez M. N. , Torre A.
Published: April 2011

An iterative method for time-independent perturbation theory is presented. Lennard-Jones–Brillouin–Wigner (LBW) and Rayleigh–Schrödinger (RS) power series are shown to be particular cases of the iteration and the combined expansion–iteration. Improvements in convergence of the power series are suggested and analyzed.The iterative method gives considerable insight into the nature and relative convergence of the currently used time-independent perturbation methods.
Microwave and millimetre wave spectra of diazirine-d2: Rotational and hyperfine structure analysis and molecular structure
Authors: Verma Udai P. , Möller Klaus , Vogt Jürgen , Winnewisser Manfred , Christiansen Jørn Johs.
Published: April 2011

The rotational spectrum of diazirine-d2, [Formula: see text], has been recorded in the ranges 8–40 and 100–400 GHz. The hyperfine structure of the measured rotational lines has been analyzed. The analysis required the treatment of two pairs of equivalent nuclei, which is discussed in detail. The deduced deuterium nuclear-quadrupole coupling constants are[Formula: see text]The quadrupole coupling constants of the nitrogen nuclei[Formula: see text]are taken from the parent species, and the spin-rotation coupling constants are[Formula: see text]The rotational and centrifugal distortion constants have been obtained for the ground vibrational state from the analysis of the unperturbed line positions. The complete rs structure of diazirine has been determined using the rotational constants of all available isotopomers of diazirine. The internuclear distances are rs(C—N) = 148.13(24) pm, rs(C—H) = 108.03(29) pm, and rs(N—N) = 122.80(25) pm, and the bond angles are [Formula: see text] and [Formula: see text], with the HCH plane perpendicular to the NCN plane.
Ab initio self-consistent-field molecular-orbital calculations on AlO4 centres in alpha-quartz. II.
Authors: Mombourquette Michael J. , Weil John A.
Published: April 2011

In this paper, the second of a series devoted to developing quantitative understanding of defect species in silicates, we report ab initio self-consistent-field molecular-orbital calculations done on 10-atom and 22-atom clusters designed to simulate cation-compensated aluminum impurity centres [AlO4/M+]qt in alpha-quartz; here qt = 0 or + 1, and M = H, Li, or Na. The geometric configurations of the small models of these centres were optimized. The calculated values for total energies, various static structural parameters, electron-spin densities, net atomic charges, and orbital energies are compared with experimental data, especially those derived from electron-paramagnetic-resonance studies of hole centres and give good agreement. For example, the models predict that the holes will occur at opposite types of oxygen ions adjacent to Al3+, respectively, for uncompensated centres [AlO4]0 and for the centres [AlO4/M+]+, as is, in fact, observed. Some calculations for interstitial cations M+ and atomic hydrogen on clusters simulating large-channel c-axis oxygen sites of alpha-quartz are reported. Various reaction energies involving the aluminum centres and the interstitial species are listed.
Properties of dual parabolic cylindrical reflectors
Authors: Sanad M. S. A. , Shafai L.
Published: April 2011

Two parabolic cylinders having the focal line of one coincident with the directrix of the other form an optical system that focuses the focal line of the first reflector to a point at infinity. The operation principle of such a system is studied, and its far diffracted field is determined. The unit is assumed to be illuminated by a directional point source, simulating a feed horn, and a ray-tracing approach is used to obtain the reflected and main diffracted fields over its aperture. The far-field patterns in the vicinity of the main beam direction are then computed by an aperture-integration method. The effects of various system parameters, on the far-field patterns, are also determined.
The optical bandgap and band-edge positions of semiconducting p-type CuYO2
Authors: Benko F. A. , Koffyberg F. P.
Published: April 2011

CuYO2, doped with calcium, is a low-mobility p-type semiconductor. From photoelectrochemical measurements it is found that the valence band edge is 5.3 eV below the vacuum level, typical for oxides with a metal-3d valence band. The lowest bandgap is 1.20 eV and the transition is indirectly allowed. An optical transition at 3.60 eV indicates an oxygen-2p valence band at 7.7 eV below vacuum. The results are discussed with the help of a simplified band scheme.
Asymptotic behaviour of nonlocal effective potentials in two-cluster atomic scattering
Authors: Treml T. F.
Published: April 2011

Dilation and boost transformations are used to study the nonlocal effective potentials in two-cluster atomic scattering below the lowest three-cluster threshold, where the particles interact via two-body Coulomb potentials and at least one cluster is neutral. Boost analyticity is used to express the rotated potential in a form that displays explicitly its behaviour for large values of the cluster separation. When one cluster is neutral, the nonlocal effective potential falls off, in some sense, as r−4 for large values of r, where r is the distance between the centres of mass of the two clusters. When both clusters are neutral, the nonlocal potential can be shown to fall off as r−5 for large values of r.
Conformally invariant operator-product expansions of any number of operators of arbitrary spin
Authors: Lam C. S. , Tratnik M. V.
Published: April 2011

We derive operator-product expansions of any number of operators of arbitrary spin that are invariant under the collinear conformal group. The corresponding parton wave functions of hadrons are calculated. The result can be expressed in terms of the conformal polynomials or the dual-conformal polynomials, the properties of which are also discussed.
The equilibrium and time evolution of the parameters of the Tokamak de Varennes
Authors: Shoucri M. , Shkarofsky I. P. , Fuchs V. , Johnston T. W.
Published: April 2011

The equilibrium and time evolution of the density, current, and temperature profiles for a tokamak are numerically analyzed using the one-dimensional transport code VARTOK1. The numerical model contains the full neoclassical transport, with coefficients covering transitions between regimes, and includes the Ware pinch and bootstrap currents, empirical anomalous particle and electron heat transports based on Alcator scaling, neutral particle transport, oxygen impurity, and diffusion of the poloidal magnetic field. The solution uses a time- and space-centered Crank–Nicolson scheme. The equilibrium profiles are first determined for a constant current of 200 kA by running the code at constant current. Then the current is ramped down to zero in 20 ms, and the time evolution of the different parameters are followed.
Quantum-chromodynamics radiative corrections in quarkonia
Authors: Dentamaro Anthony V. , Goldstein Gary R.
Published: April 2011

The quantum chromodynamics radiative corrections to heavy quarkonium s-state parameters are studied using Stevenson's principle of minimal sensitivity to define the renormalization. We obtain good results using a nonrelativistic confining potential to generate wave functions to fit the experimental data for the hyperfine splittings as well as the leptonic widths.
Rotational analysis of the B1Σ+ → X1Σ+ system of H35Cl
Authors: Coxon J. A. , Roychowdhury U. K.
Published: April 2011

The B1Σ+ → X1Σ+ system of HCl has been recorded photographically at high resolution in the range 155–250 nm. Rotational assignments of the measured line positions have been made for 39 bands of H35Cl with 0 ≤ ν′ ≤ 6and7 ≤ ν" ≤ 17. Least squares parameter estimates from individual bands have been merged to obtain a set of single-valued parameters that reproduces most of the experimental data to within the measurement precision. First-order Rydberg–Klein–Rees (RKR) turning points for the B and X states are reported from a second set of parameters derived from a truncated data set. The reliability of the ground-state RKR potential is discussed in terms of the first-order approximation and Born–Oppenheimer breakdown. Transitions have been observed to quasi-bound states of several high-lying vibrational levels of the ground state.
Some imaging properties of volume reflection holography
Authors: Huang Yihe
Published: April 2011

Some imaging properties of a volume reflection hologram are studied as a special case of Bragg diffraction. A spherical reflector is shown to serve as a geometrical model for imaging properties.
Effects of the T-matrix center-of-mass approximation in the Brueckner–Sawada theory of liquid helium II
Authors: Bose S. K. , Goble D. F.
Published: April 2011

As a model for liquid helium II, we study the Bose–Einstein gas with a two-body interaction potential of the form ~δ(r − a), where r is the interparticle separation. Excitation spectra for various values of a are calculated using the Brueckner–Sawada approach based on the concept of the T matrix. However, unlike the work of Brueckner and Sawada and many other related works that followed, we take into account the dependence of the T matrix on the center-of-mass momentum of the interacting particles. Excitation spectra calculated with and without this dependence, using two different expressions for the two-particle propagator, indicate the validity of the Brueckner and Sawada center-of-mass approximation for physically interesting values of a. The difference between the two spectra is found to increase as a increases.
Remarks on the Z−1-expansion theory and the Z−1/3 expansion of the ground-state energy of a neutral atom
Authors: Lai C. S.
Published: April 2011

Using the fact that the second-order Z-expansion coefficient ε2 is approximately proportional to [Formula: see text], we calculate the first-and second-order Z-expansion coefficients ε1(Z) and ε2(Z) in terms of the Z−1/3-expansion coefficients Ck of the non relativistic binding energy E. The result obtained for various values of Z is in good agreement with the exact result. The accuracy of an energy model proposed by Tal and Levy predicting C6 = 0.4701 is also discussed. Our analysis tends to support the correctness of the Scott–Lieb–Schwinger value C6 = 0.5.
Metal–nonmetal transition in lanthanum hydrides
Authors: Mota Ronaldo
Published: April 2011

The dependence of the band structure of lanthanum hybrides on hydrogen concentration is investigated by considering an approximate model Hamiltonian that takes into account the hybridization of the d and hydrogen-derived s bands. A Green's function technique is used to obtain the hybrid bands in the Hartree–Fock approximation. The model is used to discuss the role of H concentration and the s–d interaction on the observed metal–semiconductor phase transition in LaHx.
Collision-induced absorption in a gaseous mixture of nitrogen and argon
Authors: Dagg I. R. , Anderson A. , Yan S. , Smith W. , Joslin C. G. , Read L. A. A.
Published: April 2011

The collision-induced absorption spectrum of a nitrogen–argon gas mixture is treated theoretically and the theory is applied to results obtained by us in the spectral region below 360 cm−1 at four temperatures, namely, 126, 149, 179, and 212 K. The measurements have involved the use of Fourier transform infrared and microwave techniques as well as a far-infrared laser system operating at 84.2 and 15.1 cm−1. The theoretical line shape is obtained from a convolution of a free rotation spectrum and a translational component. The spectra calculated from either information theory alone or combined with Mori theory both show good agreement with experimental results, especially above 30 cm−1. An important feature of the theoretical development is that no adjustable parameters need to be introduced.
Hydroxide-ion dynamics in cesium hydroxide: a deuteron nuclear magnetic resonance study
Authors: Amm David T. , Segel Stanley L. , Jeffrey Kenneth R.
Published: April 2011

CSOD exists in a number of solid phases that are distinguished by the different equilibrium positions and dynamics of the OD− ion. Deuteron nuclear magnetic resonance (NMR) was used as a probe because the observed quadrupolar split spectra provide a sensitive means of detecting changes in the symmetry properties of the unit cell and the motion of the O—D bond. Measurements are reported for the nuclear quadrupole coupling constant and the effective asymmetry parameter over the range from 100 to 500 K. The NMR data as well as differential thermal analysis confirm phase transitions from the cubic (Pm3m) to the high-temperature orthorhombic phase (Cmcm) at 497 K and a transition to a lower temperature phase at 247 K. The quadrupolar split spectra in the region from 497 to 247 K are consistent with a twofold reorientation of the O—D bond throughout this phase. The effective asymmetry parameter of the quadrupolar interaction increases rapidly with decreasing temperature, indicating a substantial change in the angle of reorientation. Below 247 K the spectra suggest that the motion of the OD− ion slows down on the time scale of the NMR line width (10−5 s).
Valence band structure of CuGa(S1−zSez)2 alloys
Authors: Quintero Miguel , Yoodee Kajornyod , Woolley John C.
Published: April 2011

Measurements of wavelength-modulated reflectance have been made in the temperature range 20–300 K on single-crystal samples of the alloy system CuGa(S1−zSez)2 and values of the valence to conduction band transition energies EA, EB and EC determined as a function of temperature. It has been shown that if the quasi-cubic model is used in the analysis of these data to determine values of spin-orbit and crystal-field splittings and their variation with temperature, the results are inconsistent with those from X-ray diffraction measurements of lattice parameters and tetragonal distortion. This is because the quasi-cubic model does not properly allow for the fractional d-character of the valence bands of these materials. The results have therefore been analyzed in terms of a recently developed theoretical model which takes into account the effects of p–d hybridization on both spin-orbit and crystal-field splittings. The analysis gives values of a dimensionless parameter M/E which is a measure of the interaction between the p and d states forming the valence bands and which determines the fractional d-like character [Formula: see text] of those bands. The variations of M/E and [Formula: see text] with both temperature and composition are considered in some detail.
Vibrational spectra of crystalline organic sulphides: dimethyl sulphide and diethyl sulphide
Authors: Cataliotti Rosario Sergio , Paliani Giulio , Santini Sergio
Published: April 2011

The vibrational spectra of crystalline dimethyl sulphide and diethyl sulphide have been measured at 77 K. The comparison with the liquid-state spectra has provided the correlation between the normal motions of the free molecules and those of the molecules in the Bravais unit.All Davydov components in the solid-state spectra have been assigned with the aid of polarized infrared radiation, and the analysis of the unit-cell symmetry of both molecules has been derived.
Effect of optical diffraction on laser heating of a field emitter
Authors: Robins E. S. , Lee M. J. G. , Langlois P.
Published: April 2011

The wavelength of the illuminating radiation used in studies of photofield emission is comparable to the diameter of the shank of the field emitter. Under these conditions, diffraction is expected to play an important role in determining the absorption of energy from the electromagnetic field. The complicated geometry of the field emitter has so far prevented an exact calculation of this effect. By considering the diffraction of a plane wave by an idealized model of a field emitter, we have calculated the absorption of energy from an incident focussed laser beam. Calculations based on the present results yield accurate predictions of the magnitude of the temperature rise and its dependence on the position of the focal spot and on the direction of polarization of the incident beam.
The cosmic microwave background radiation and galaxy formation
Authors: Silk Joseph
Published: April 2011

Observational limits on the microwave-background-radiation anisotropy on various angular scales are reviewed. Comparison is made with the predictions of the gravitational-instability theory of galaxy formation from primordial fluctuations in the very early universe. There is no entirely satisfactory theory that presently reconciles inflationary cosmology predictions of the flatness of the universe and of the scale-invariant primordial fluctuation spectrum with the limits on the amplitude of the anisotropy (δT/T), with the Virgo-cluster motion inferred from the dipole anisotropy, and with astronomical determinations of the cosmological density parameter.
An electric quadrupole transition: the emission system of oxygen
Authors: Fink E. H. , Kruse H. , Ramsay D. A. , Vervloet M.
Published: April 2011

The 0–0 band of the [Formula: see text] system of oxygen has been recorded in emission using a Bomem Fourier transform spectrometer. Five branches are observed with ΔJ = 0, ±1, ±2. The relative intensities of the branches agree with those calculated for an electric quadrupole transition.
Nuclear-magnetic-resonance determinations of fluorine content and relaxation times in bone powder
Authors: Ebifegha M. E. , Code R. F. , McNeill K. G. , Szyjkowski M.
Published: April 2011

The detection of trace amounts of fluoride ions from ground rat-bone samples using a 27-MHz solid-state single-coil pulsed nuclear-magnetic-resonance (NMR) spectrometer is described. The fluorine content in the bone samples as determined from the amplitudes of the free-induction-decay (FID) signals is in good agreement with analyses based on standard chemical and neutron-activation techniques. The value of the spin-lattice relaxation time T1 is 1.46 ± 0.07 s in dry rat-bone powder and is slightly longer in wet bone powder depending on the water content. The contribution of cross-relaxation processes to these results is discussed. The value of the spin–spin relaxation time T2 (as determined from the point where the 19F FID signal has decayed to 1/e of its maximum amplitude) is approximately 75 μs. The Hahn echo sequence [(π/2)0-τ-(π)0] applied to 7 g of bone powder with a fluorine concentration of 3 mg F/g bone in a relatively homogeneous region of the external magnetic field yields echoes that persist for times 2τ up to ~0.5 ms.
Effective thickness determination for volume transmission multiplex holograms
Authors: Couture Jean J. A. , Lessard R. A.
Published: April 2011

The effective thickness of absorption multiplex holograms are evaluated by a numerical analysis of angular-selectivity curves obtained by the reconstruction process. These transmission holograms were respectively recorded in sequential and incoherent superposition of 2, 10, or 21 volume-coupled gratings. The experimental effective thickness represents 50% of the nominal thickness associated with Kodak 649F plates for 21 recorded, coupled gratings. The many experimental unpublished curves presented in this paper for 10 and 21 gratings permit one to obtain interesting numerical values of the thickness and angular-selectivity bandwidth of resultant multiplex holograms.
Quasi-Riemannian Kaluza–Klein theory
Authors: Viswanathan K. S. , Wong Brenden
Published: April 2011

We review the quasi-Riemannian approach to d-dimensional gravity and its application to Kaluza–Klein theory.
The equation of state of the two-dimensional Lennard–Jones fluid
Authors: Reddy M. Rami , O'Shea Seamus F.
Published: April 2011

By combining pressure and energy data from the virial equation of state, through fifth virial coefficients, with the second and third virial coefficients themselves and the results of computer-simulation calculations, we have constructed an equation of state for the two-dimensional Lennard–Jones fluid for 0.45 ≤ T* ≤ 5 and 0.01 ≤ ρ* ≤ 0.8. The fitted data include some in the metastable region, and, therefore, the equation of state also describes "van der Waals loops" including unstable regions. The form used is a modified Benedict–Webb–Rubin equation having 33 parameters including one nonlinear one. The fitting was done using a nonlinear least squares algorithm based on a Levenberg–Marquardt method. A total of 211 simulation points, 97 reported here for the first time, were used in the fitting, and the overall standard deviation is less than 2% for both energy and pressure. Second and third virial coefficients derived from the fit in the supercritical region are in excellent agreement with exact values. The critical constants derived from the fit are in reasonable agreement with published estimates.
Tables of input impedance and directivity of long linear antennas
Authors: Saoudy S. , Hamid M.
Published: April 2011

Hurd's Wiener–Hopf solution for the input impedance of long dipoles of different lengths and radii is extended and compared with results based on other methods. Corresponding values of effective length and directivity are also tabulated.
High-resolution studies of the near-ultraviolet bands of oxygen: II: the system
Authors: Borrell P. M. , Borrell P. , Ramsay D. A.
Published: April 2011

Bands of the [Formula: see text] system of oxygen have been re-examined using longer absorption paths and higher resolution than in the early work of Herzberg (1952). More accurate values are given for the molecular constants v0, B, D, λ, and γ for levels with v′ = 0–11. The principal constants for the [Formula: see text] state are as follows:[Formula: see text]
Freestreaming mode excited by a pulse
Authors: Schott Ludwig
Published: April 2011

When a voltage pulse is applied to an exciter (probe or grid) immersed in a plasma, both an ion-acoustic wave and a freestreaming (ballistic) signal are excited. It is shown that the density perturbation produced by the freestreaming signal is independent of the shape of the applied-voltage pulse for times that are large compared with the temporal width of the pulse and at distances that are large compared with the size of the sheath at the exciter, but it depends on the second derivative of the zeroth-order velocity-distribution function. Analytic expressions that are valid for all times and positions are derived for a simple sheath model. Criteria are presented that enable the experimentalist to distinguish freestreaming modes from ion-acoustic waves.
Transport coefficients of the Lennard–Jones fluid by molecular dynamics
Authors: Heyes D. M.
Published: April 2011

New nonequilibrium molecular dynamics (MD) calculations of the shear viscosity, bulk viscosity, and thermal conductivity are presented. Together with the self-diffusion coefficients obtained from equilibrium MD, the success of the Dymond–Batchinski expressions for the density and temperature dependence of these transport coefficients is demonstrated.The shear viscosity and self-diffusion coefficients are very good probes for the approach point of the solid-to-liquid phase change. The bulk viscosity and thermal conductivity are less useful in this respect.
Hydrosulfide-ion dynamics in cesium and rubidium hydrosulfide: a deuteron nuclear magnetic resonance study
Authors: Jeffrey Kenneth R. , Wasylishen Roderick E.
Published: April 2011

RbSD and CsSD have a multiplicity of solid-state phase transitions involving changes in the degree of order of the SD− ion. Because the deuteron has a nuclear quadrupole moment, the observed NMR spectrum reflects any changes that take place in the deuteron-site symmetry as a result of a phase change. Furthermore, the magnitude of the observed nuclear quadrupole interaction depends on the time average of the electric-field gradient at the deuteron site; this, in general, is a function of any molecular motion in the crystal. The nuclear spin–lattice relaxation times provide information about the time scale of any molecular reorientation taking place in the crystal structure. Deuteron NMR spectra and relaxation times are presented for RbSD and CsSD over the temperature range from 100 to 400 K. The spin–lattice relaxation time data show that there is reorientation of the SD− ion in the tetragonal phase of CsSD and in the trigonal phase of RbSD. While the correlation time for the reorientation changes from being short compared with the reciprocal of the quadrupole interaction to being the same order of magnitude in the temperature range studied, the deuterium NMR line shapes do not change substantially. It is concluded that the observed reorientation of the SD− ion in both RbSD and CsSD in the low-temperature noncubic phases is end-for-end flipping of the SD− ion since only reorientation by 180° leaves the static quadrupole splitting unchanged.
Variational thermodynamic calculations for some liquid sd metals: II
Authors: Li D. H. , Moore R. A. , Wang S.
Published: April 2011

A procedure employing a generalized, nonlocal, model-pseudopotential theory for the calculation of the total valence-electron energy in liquid metals was presented earlier and shown to be suitable for use in a variational calculation of the Helmholtz free energy, and hence also for other properties, of sd and the early 3d transition metals. In the first part of this paper we show that the same procedure also works well for the first four of the 4d transition metals. However, the accuracy of the calculations decreases with increasing number of d-like valence electrons. This is attributed to narrow valence d bands. Thus, in the second part of this paper we revise and generalize the earlier procedure to consider explicitly the localization of some of the d-like valence electrons on the ions. The validity of the revisions is shown by calculating a number of the properties of liquid metallic Cr, Mn, and Fe.
Core-polarization effects in the alkali atoms: oscillator-strength calculations
Authors: Martin Inmaculada , Barrientos Carmen
Published: April 2011

Oscillator strengths for the alkali group of elements have been computed through the quantum defect orbital (QDO) formalism. Three forms of the dipole transition moment have been employed, two of them accounting for core–valence polarization. Clear improvement is obtained over the nonpolarized calculations for the lighter elements, whereas for K, Rb, and Cs, the additional inclusion of spin–orbit effects is shown to be required.
Zero-temperature properties of quantum spin models on a triangular lattice I: the ferromagnet
Authors: Fujiki S. , Betts D. D.
Published: April 2011

The calculation of two- and four-spin correlations of the [Formula: see text] ferromagnet has been extended to an N = 21 site triangular lattice. By fitting a quadratic in 1/N to the nearest neighbour transverse pair correlations, we have estimated the ground-state energy per bond on the infinite lattice to be E0/3NJ = −0.5326 ± 0.003. We conjecture that the square of the magnetization per site vanishes very sharply as N−0.06. The nearest neighbour longitudinal correlation per bond [Formula: see text] for all two-dimensional lattices.
Charged matter and a one-parameter group of conformal motions: I
Authors: Krori K. D. , Borgohain P. , Das Kanika , Sarma Arunima
Published: April 2011

A study of charged matter under a one-parameter group of conformal motions has been presented in this paper. First we have worked out some general results and then we have derived some exact solutions for charged-matter distributions of spherical symmetry.
The basic physics of laser fusion
Authors: Evans R. G.
Published: April 2011

The essential features of a laser-fusion pellet are shown to be a high-density, high-pressure core with a central hot spot. The pressure in this core is produced by amplification of the laser ablation pressure during the spherical implosion. A high degree of symmetry in the implosion is required and the related subjects of symmetry and hydrodynamic stability are briefly discussed. The laser–plasma interaction process is important in producing high-absorption efficiency without preheating the core by fast electrons.
Magnetic-field generation in laser fusion and hot-electron transport
Authors: Haines M. G.
Published: April 2011

The many sources of generation of magnetic field are derived from a generalized Ohm's law. These sources include the [Formula: see text] effect, anisotropic pressure, as well as the effect of the quiver velocity associated with the incident laser beam. The magnetic field can be generated either through some imposed lack of spherical symmetry or through an instability. Among the latter, the collisional Weibel instability appears to be the most important. Convection and amplification can occur through the Nernst effect, and the resulting magnetic-field structure can inhibit fast-electron transport. Dynamo action and diffusion processes are also included in this review.
Hot-electron generation and transport in high-intensity laser interaction
Authors: Burnett N. H. , Enright G. D.
Published: April 2011

Experience has shown that at sufficiently high intensity, laser–target interaction is dominated by long mean-free-path electrons generated by resonance absorption. Experimental observations relating to the generation and target coupling of these hot electrons are reviewed with particular emphasis on results obtained in CO2 laser interaction experiments at the National Research Council of Canada. Possible applications of laser-generated hot electrons as a direct driver for inertial-confinement fusion are discussed.
Thermal electron transport in direct-drive laser fusion
Authors: Delettrez J.
Published: April 2011

The experimental and theoretical aspects of electron thermal transport in direct-drive laser-fusion are reviewed. The Fokker–Planck equation and the flux-limited diffusion model, which is widely used in laser-fusion simulation codes, are described. After a discussion on the limitation of planar-target transport experiments, results of spherical experiments are surveyed. Solutions of the Fokker–Planck equations for cathode problems and for cases with stationary and moving ion density profiles are presented. Limitations of the flux-limited diffusion model are discussed in light of the Fokker–Planck results. Comparisons between experimental and theoretical results lead to the conclusion that the modeling of electron thermal transport in uniform spherical geometry does not require the existence of magnetic fields or anomalous plasma effects.
Raman scattering
Authors: Simon Albert
Published: April 2011

Observations of Raman scattered light from inhomogeneous laser-produced plasma have shown characteristics quite different from the simple predictions for the stimulated Raman scattering instability. An alternative explanation in terms of enhanced scattering, produced by bursts of hot electrons arising at the quarter-critical or critical surface, is described. Comparison is made between the predictions of this theory and four experiments.
The anomalous analyzing power for the 11B(d,n)12C reaction to the 2+ state at 4.44 MeV
Authors: Foot P. B. , Shute G. G. , Spicer B. M.
Published: April 2011

Exact finite-range calculations for the 11B(d,n)12C reaction at 79 MeV reproduce the measured analyzing powers satisfactorily for the 0.00-, 9.64-, 12.71-, and 15.11-MeV states in 12C. However, in the case of the 4.44-MeV state in 12C, there is a striking disagreement between theory and experiment. Various unsuccessful attempts have been made to find a solution to this discrepancy.
Partial-wave analysis of lepton-pair annihilation into two photons
Authors: Roberts Winston
Published: April 2011

The partial-wave (Jp) composition of the process ℓ+ℓ− → γγ is analyzed in lowest order quantum electrodynamics. The results for low-momentum leptons are as expected, the partial wave with Jp = 0− being dominant. At high energies, the partial wave with Jp = 2+ has the largest single partial cross section. At all energies, it is found that lepton pairs in the triplet state give rise exclusively to positive-parity final states, whereas pairs in the singlet state give rise to negative-parity final states.Some features of the differential cross section are also explained in terms of the spin state of the annihilating lepton pair. Possible implications for e+e− → γγ → hadrons and [Formula: see text] hadrons are briefly discussed.
On the linear response of Bardeen–Cooper–Schrieffer superconductors I. clean superconductors
Authors: Cleary Robert
Published: April 2011

We calculate the linear response of a Bardeen–Cooper–Schrieffer superconductor to transverse and longitudinal electromagnetic radiation. Oscillations in the pair potential are also investigated. The order parameter and electric field of a point charge imbedded in a superconductor are also calculated. We assume a reasonable bare potential for the point charge. Finally, the linear response to the order parameter and magnetic vector potential is calculated for a reasonable model of a magnetic point dipole, again employing a more accurate model for the spin impurity than the usual delta-function approximation.
Waves with harmonic structure below and above the lower hybrid resonance observed on the CENTAUR 35.001 and 35.002 rockets
Authors: Neubert T. , Holmgren G. , Ungstrup E. , Melgård K.
Published: April 2011

Measurements obtained from the 0- to 10-kHz electric-wave experiment and the 0- to 4.2-kHz electron-density fluctuation experiment on the CENTAUR 35.001 and 35.002 rockets launched in December 1981 are presented. The observations include (i) spectacular narrow-banded signals with harmonic structure related to the proton gyrofrequency. The bands are observed both below and above the lower hybrid frequency, from 2 to 10 kHz, and are modulated in frequency during a rocket spin, typically by 2 kHz. The character of the signals indicate that they are generated by the presence of the payload in the plasma. The source of free energy remains unidentified; we suggest, however, a perpendicular ion beam emitted by or created by the presence of the payload, generating flute-mode ion cyclotron harmonic waves. (ii) Bursts of harmonic waves are received primarily below 2 kHz. The fundamental frequency of these emissions varies over a large range, from 47 to 700 Hz, and is rarely at any of the characteristic frequencies of the plasma. (iii) Waves with a clear lower cutoff at the lower hybrid frequency are also observed. The lower hybrid frequency estimated from magnetic field and density measurements and from the wave measurements agree within 6% (500 Hz).
Particle precipitation and ionospheric convection morphology in dayside aurora
Authors: Yau A. W. , Whalen B. A. , Steele T. G.
Published: April 2011

We present particle precipitation and ionospheric ion measurements from the Black Brant rocket IVB-38, which was launched from Cape Parry, Northwest Territories, Canada, on December 10, 1981, at 2314:58.5 UT as part of Project CENTAUR. The payload reached an apogee of 603 km and crossed two regions of electron precipitation. In both precipitation regions, the energetic-electron spectra were soft, with peak intensities of ≈1010 cm−2∙s−1∙keV−1 at 200 eV. The 100-eV electrons were anisotropic in the downcoming hemisphere (field aligned). The spectra varied with the electron pitch angle. They had larger characteristic energy at small pitch angles and revealed appreciable atmospheric degradation (and hence predicted optical auroral emissions) in the 300-km altitude region. No proton precipitation was observed. The topology of the ionospheric convection was found to be correlated with both the location and the drift motion of the aurora.
Note on the ν11 and ν10 fundamentals of cyclopropane
Authors: Pliva Josef , Johns J. W. C.
Published: April 2011

Previous measurements on the ν11 and ν10 fundamentals of cyclopropane have been refitted using a corrected Hamiltonian. For the most part, changes in the resulting parameters are less than their confidence limits.
Stability of trajectories in Ernst space–time
Authors: Krori K. D. , Choudhury Ranjana , Sarmah J. C.
Published: April 2011

In this paper we show that stable trajectories of charged particles, neutral particles, photons, and tachyons occur in the equatorial plane of the Ernst space–time. We also present typical bound trajectories of these particles in the equatorial plane (θ = π/2) as well as on an r = constant surface.
Triple differential cross sections for fast electron-impact ionization of helium
Authors: Baliyan K. S. , Sharma Sadhana , Srivastava M. K.
Published: April 2011

The recent absolute data of Jung et al. for the ionization of helium in a coplanar asymmetric geometry at an incident electron energy of 600 eV are analyzed by using a product of two Coulomb wave functions in the final state. This model leads to an improvement in the binary-peak to recoil-peak ratio and in the location of the binary peak compared with the first Born approximation.
Acceleration of electrons in vacuum by two laser beams
Authors: Laberge M. , Bélanger P. A.
Published: April 2011

A method of acceleration is proposed in which electrons gain energy at the intersection of two laser beams. The interaction takes place in vacuum far away from any conductor or dielectric, avoiding the usual breakdown problems. An acceleration gradient of more than 1 GeV/m is produced for a CO2 laser of 1014 W/cm2.
Study of relativistic heavy-ion interactions and antiproton annihilation data: search for shock waves
Authors: Ghosh Dipak , Roy Jaya , Sengupta Ranjan
Published: April 2011

The characteristics of 12C–AgBr interaction at 4.5-GeV∙c−1∙nucleon−1 incident momentum are studied by means of the photoemulsion technique, to search for shock-wave phenomena. The angular distributions indicate an anisotropic process in the nuclear matter. The results are compared with the antiproton–AgBr reaction observations of Breivik et al. (1983) at 1.4 GeV∙c−1.
Two-particle potential in field theory
Authors: Rogers Duncan , Kovarik Mitchel D. , Darewych Jurij W.
Published: April 2011

The many-particle binding energy in the model [Formula: see text] in 1 + 1 dimensions is obtained using simple nonrelativistic quantum mechanics. We determine an effective two-particle potential from approximate field-theoretical solutions of the two-particle bound state and use it to obtain the many-particle binding energy. The results agree reasonably well with numerical calculations of the three- and four-particle binding energy in the field theory for weak coupling, λ. We also use this nonrelativistic potential to calculate the two-particle scattering amplitude.
Les intensités des raies rotationnelles du système b1Σ+ – X3Σ− de la molécule NF
Authors: Vervloet M. , Watson J. K. G.
Published: April 2011

The 0–0 band of the b1Σ+ – X3Σ− system of the NF molecule has been measured in emission using a Fourier-transform spectrometer. The line assignments of Douglas and Jones are confirmed, but their statement regarding the relative size of the parallel and perpendicular transition moments is incorrect. From a least squares fit of the line intensities, we determine the value μ1/μ0 = 0.261 for the ratio of the perpendicular (μ1) and parallel (μ0) transition moments. This value lies between two recent ab initio estimates, 0.96 and 0.049.
Excitation of O(1D) atoms in aurorae and emission of the [OI] 6300-Å line
Authors: Rees M. H. , Roble R. G.
Published: April 2011

The electron aurora leads to six processes capable of exciting the O(1D2) metastable state of the atomic-oxygen ground-state configuration, the parent state of the 6300-Å red line. Altitude profiles of the volume emission rate resulting from each process are computed for Maxwellian electron spectra with characteristic energies between 0.1 and 2.0 keV. Since each process peaks at a different altitude, the sum or total volume emission rate extends over a wide altitude range. Measurements of 6300-Å emission obtained by rocket and satellite-borne instruments are summarized, and it is shown that the chemical reaction of N(2D) with O2 is the major source of O(1D) atoms in the electron aurora. New calculations of the 6300-Å:4728-Å column emission-rate ratio are presented for a range of characteristic energies in an assumed Maxwellian electron spectrum. An approximate equation for the red-line emission per unit energy input is given as a function of electron-spectrum characteristic energy.
Excitation of vibrational emission bands in aurora and airglow
Authors: Gordiets B. F.
Published: April 2011

The major results of the theoretical study of infrared radiation in the vibrational–rotational bands of minor molecular constituents in the terrestrial thermosphere are reviewed. Various mechanisms of vibrational excitation of radiating molecules are discussed for both quiet and disturbed conditions (e.g., aurorally enhanced electric fields, etc.). Intensities of infrared emissions and correlations between some of them and emissions in other spectral regions are analyzed, as well as the role that infrared radiation plays in the thermospheric energetics.
Flow induced by the rotation of a curved tube and a coaxial rigid core
Authors: Karahalios G. T.
Published: April 2011

When an incompressible viscous fluid is contained between a curved tube and a coaxial rigid core, the relative motion of the boundaries sets the fluid in motion. The fluid motion from the effects of rotation of the tube and core is the subject of this paper.
Pure rotational spectrum of 13CD4 and isotope effects on the tensorial centrifugal-distortion constants of methane
Authors: Kreiner W. A. , Müller P. , Jörissen L. , Oldani M. , Bauder A.
Published: April 2011

Infrared-laser – radio-frequency double-resonance experiments and pulsed-microwave Fourier-transform measurements have been performed with 13CD4. From 25 observed ΔJ = 0 transitions in the vibronic ground state, the tensorial centrifugal-distortion constants Dt = 32.6600(12) kHz, H4t = −2.0302(61) Hz, H6t = 1.1692(29) Hz, L4t = 1.201(77) × 10−4 Hz, L6t = −1.353(63) × 10−4 Hz, and L8t = −1.466(46) × 10−4 Hz have been determined. Experimental carbon-13 and deuterium isotope effects on the tensorial centrifugal-distortion constants of methane have been compared with theoretical predictions.