bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of deuteration on the magnetic critical temperatures of hydrogen-bonded materials
Authors: Turrell B. G. , Yue C. L.
Published: April 2011

The change in the magnetic critical temperature caused by deuteration of the sample has been measured for two hydrated salts. For antiferromagnetic MnCl2∙4H2O, a shift in the Néel point of −2.3% was observed when 96% of the protons were replaced by deuterons. For ferromagnetic Cu(NH4)2Br4∙2H2O, the Curie point was shifted by +0.8% on deuteration. These results are compared with measurements on other materials and the results semiquantitatively explained by proposing an intimate relation between the superexchange interaction and the hydrogen bond strength.
Linear damping of a sinusoidal oscillation in a plasma
Authors: Pocobelli Gustavo
Published: April 2011

The linearized Vlasov equation for a plasma is solved by means of integration along the particle trajectories assuming an oscillatory electric field of variable amplitude. A procedure is established which gives exactly the Landau–Jackson dispersion equation, showing that if the assumption of the constancy of amplitude of the electric field is removed, then O'Neil's method of integration of the nonlinear Vlasov equation yields the correct result in the linear limit. A simple application of the present formalism allows a determination of the earliest time at which the Landau damping law becomes valid for an arbitrary stationary distribution (previous work is limited to the case of a Maxwellian distribution) and initial perturbation. The minimum value of this time as a function of wave number is calculated explicitly for a Maxwellian stationary distribution.
Observation of optical activity in Brillouin scattering experiments
Authors: Kharusi M. S. , Farnell G. W.
Published: April 2011

Analytical expressions have been developed for calculating the diffraction geometry for Brillouin scattering experiments in which the applied acoustic beam and the optical wave vectors lie in a plane containing the optic axis of uniaxial crystals. A computer program solves for the diffraction angles for the general cases where the choice of crystal, crystal face, direction of acoustic propagation, plane of optical incidence, and amount of optical activity are all arbitrary. It is shown that for acoustic propagation along the X axis in quartz, the optical activity produces easily detectable changes in the angles of the incident and diffracted light beams in the XZ plane when polarization change occurs on diffraction. Moreover for this case, the optical activity produces a cutoff acoustic frequency below which Brouillin scattering with polarization rotation does not occur. Experimental measurements verify the predicted angular changes to within the accuracy permitted by the finite acoustic beam width.
Spin–orbit splitting in 2Δ states of diatomic molecules
Authors: Lefebvre-Brion H. , Bessis N.
Published: April 2011

The origin of the splitting of the 2Δ states arising from the σπ2 configuration is studied. For light diatomic molecules, the splitting is shown to arise from the spin–other–orbit interaction which gives a small negative value for the spin–orbit coupling constant A. Non-empirical calculations of A for the 2Δ states of the CH, NH+, and NO molecules are in good agreement with experiment. In heavier molecules, the spin–other–orbit interaction becomes negligible and the second-order spin–orbit effect is dominant.
New electronic transitions of the C2 molecule in absorption in the vacuum ultraviolet region
Authors: Herzberg G. , Lagerqvist A. , Malmberg C.
Published: April 2011

Three new electronic transitions of the C2 molecule have been observed in absorption in the region 1300–1450 Å. The system of shortest wavelength is readily identified as a 1Πu–1Σg+ transition; the lower state is the ground state X1Σg+ of the molecule. The other two systems arise by absorption from the low-lying a3Πu state; the upper states are new 3Σg− and 3Δg states. Rotational and vibrational constants of the three new states have been determined. The new states are Rydberg states. Their correlation to the separated atoms is briefly discussed.
Photoconductivity of semi-insulating gallium arsenide in the presence of a magnetic field
Authors: Milner-Brown H. , Fortin E.
Published: April 2011

The effect of a magnetic field on the photoconductivity of GaAs has been investigated at 300 °K and 90 °K. The field deflects the photocarriers towards the surface or the volume of the sample, resulting in a decrease or an increase of the photocurrent. The effect is attributed to lifetime inhomogeneities across the sample thickness and has been studied as a function of temperature, surface treatment of the sample, and wavelength of excitation. The results can be expressed as the ratio R = ip+/ip−, where ip+ and ip− are the photocurrents when the carriers are deflected away or towards the sample surface respectively. For a sample mechanically polished, R = 10 at 300 °K and R = 40 at 90 °K while for a chemically polished sample R = 3.5 at 300 °K and R = 10 at 90 °K for B = 2.2 Wb/m2, V = 400 V, and λ excitation = 7500 Å. Independent measurements of the carrier mobilities and of their surface and bulk lifetimes have been performed to allow a direct comparison between experimental results and theoretical predictions based on a simple model.
Ion-acoustic waves in the auroral plasma
Authors: Hofstee J. , Forsyth P. A.
Published: April 2011

Two coherent bistatic radio systems were used to observe auroral radio reflections under geometrical conditions which would favor the detection of ion-acoustic waves in the auroral ionization. The displaced "line" spectrum, characteristic of scattering by ion-acoustic waves, was a prominent feature of some of the observations but the strength of the wave-scattered component varied widely relative to the non-wave-scattered components. It is concluded that ion-acoustic waves do indeed occur in the auroral plasma but that such waves cannot be the only source of radio-wave scattering in aurora.
Spin–other–orbit and spin–orbit splitting factors in f5 electron configurations
Authors: Saxena K. M. S. , Malli Gulzari
Published: April 2011

The expressions of the spin–other–orbit splitting factors (λ′) and spin–orbit splitting factors (λ) for all the states arising from f5 electron configurations are computed and tabulated for general usage. These are used to evaluate the Hartree–Fock values of λ′ and λ for Pm(4f5), Sm3+ (4f5), Tb(4f9), and Dy3+(4f9).
Measurement of the directional correlation of the 1038–605 keV gamma cascade in 134Ba
Authors: Taylor H. W. , Singh B. , Kukoč A. H. , King J. D.
Published: April 2011

The directional correlation of the 1038–605 keV gamma-ray cascade in 134Ba has been determined using the well-known 1365–605 keV gamma-ray cascade as a reference. The detection system was a conventional fast–slow coincidence system using a 9 cm3 cylindrical Ge(Li) counter and a 5 cm × 5 cm NaI(Tl) counter. The observed correlation coefficients were A2 = 0.285 ± 0.030, A4 = −0.002 ± 0.050. The most probable spin sequence for the 1038–605 cascade is 3 (1, 2) 2 (2) 0 with a quadrupole content of 35–49% for the 1038-keV transition.
The magnetic rotation spectrum of glyoxal
Authors: Goetz W. , McHugh A. J. , Ramsay D. A.
Published: April 2011

Twenty-one bands of the first triplet–singlet system of glyoxal (3Au–1Ag) have been photographed in absorption and in magnetic rotation using high resolving power. Analysis yields the following vibrational frequencies for the molecule in the 3Au state: v2 = 1458∙9 cm−1, v4 = 963∙4 cm−1,v5 = 502∙6 cm−1, v7 = 234∙3 cm−1, and v12 = 391∙9 cm−1. These frequencies are very similar to those for glyoxal in the corresponding 1Au excited state.
The interaction of electrons with ultrasonic shear waves in copper
Authors: Simpson A. M. , Jericho M. H.
Published: April 2011

Measurements of the electronic component of the acoustic attenuation of shear waves travelling in the [110] direction in copper are reported. The magnetic field dependence of the attenuation has also been investigated in fields up to 50 kG. The data have been compared with theory on the basis of a simple examination of the Fermi surface of copper. The results show strong polarization dependence of the attenuation and suggest that when [math], a detailed theoretical description will require consideration of electromagnetic as well as Fermi surface deformation interactions of sound waves with the conduction electrons.
Measurement of the reorientation effect in 24Mg
Authors: Häusser O. , Hooton B. W. , Pelte D. , Alexander T. K. , Evans H. C.
Published: April 2011

The reorientation effect in Coulomb excitation with 62 MeV 35Cl projectiles was used to measure the static quadrupole moment of the first excited state in 24Mg. From a comparison of the inelastic scattering cross sections at CM scattering angles of 123.1° and 72.8°, a static quadrupole moment of Q = −0.243 ± 0.035 b was deduced. The E2 matrix element connecting the ground state and first excited state was also measured and corresponds to 20.3 ± 1.4 W.u. for the 2+ → 0+ transition. The results are compared with predictions of the rotational model.
Lifetimes in 32S
Authors: Ollerhead R. W. , Alexander T. K. , Häusser O.
Published: April 2011

Lifetimes have been measured for five levels in 32S. The levels were populated by inelastic scattering of protons, and the gamma rays were detected at angles between 0° and 127° using a 40 cm3 Ge(Li) detector mounted inside a split annular NaI(Tl) crystal. The spectrometer was used simultaneously as both an escape-suppressed and a three-crystal pair spectrometer. Decay schemes and lifetimes have been determined using thick targets of PbS, MoS2, and sulfur cooled to 77 °K. Lifetime information was obtained both from analysis of the observed gamma-ray line shapes and from analysis of the Doppler shift attenuation in the different target materials. The two methods of analysis agree within the errors. A weak ground-state transition was observed from the J = 3 level at 5.012 MeV, establishing its parity as negative. Analysis of the line shape observed at 0° and the Doppler shift attenuation gave an average lifetime of 7.5 ± 0.5 × 10−13 s. The observed branching ratio (4 ± 0.4% to the ground state) implies an E3 enhancement of 20 ± 2.4 Weisskopf units (W.u.). A similar analysis gave a lifetime of 4.9 ± 0.9 × 10−13 s for the J = 1 level at 4.699 MeV, which implies that the dipole transition to the ground state is highly retarded. Lifetimes have also been measured for levels at 3.780 MeV [Formula: see text], 4.288 MeV (7.4 ± 0.6 × 10−14 s), and 5410 MeV (1.9 ± 0.2 × 10−13 s); the transition strengths are tabulated and discussed.
Field effect and the role of excitons in the photoconductivity of CdS
Authors: Colbow K. , Jmaeff A. , Yuen K.
Published: April 2011

For many crystals of cadmium sulfide, the photoconductivity spectrum contains a great deal of structure due to excitons. In particular, two types of spectra have been found: type I, wherein photoconductivity maxima correspond to absorption maxima, and type II, wherein photoconductivity minima correspond to absorption maxima. Various methods have been used to change one type of response into the other, among them, heat treatment, mechanical surface treatment, electron bombardment, and ultraviolet irradiation. The evidence presented in this paper supports the view that the common denominator in all these treatments is the change in the electric field near the surface. The surface field is a sensitive function of defect concentration, adsorbed oxygen, and free carrier concentration.
Phénomènes de pulvérisation et de distribution en profondeur. Partie IV. Pulvérisation cathodique des oxydes Nb2O5, Ta2O5 et WO3
Authors: Nghi L. Q. , Kelly Roger
Published: April 2011

Three different methods have been used to determine the sputtering yield (S) for 2–30 keV Kr ions on the amorphous anodic oxides Nb2O5, Ta2O5, and WO3. The methods were based on (a) the change of interference colors due to ion bombardment, (b) the perforation of a film of free oxide by an intense ion beam, and (c) the loss of weight of the target. Although S for Kr–WO3 was larger than expected, S for Kr–Nb2O5 and Kr–Ta2O5 was similar to what has been found for other oxides. For example, at 4 keV, S lies between 1.1 and 2.4 atoms/ion for Ar or Kr bombardment of Al2O3, Nb2O5, SiO2, Ta2O5, TiO2, and UO2, whereas it is 6.2 atoms/ion for WO3. The results were interpreted first with a modified form of the theory of Rol et al., in which S is equated to K′E/Rm, where K′ is a constant in Å/keV and Rm is the experimental median range. A good fit between experiment and theory was obtained for K′ equal to 25 for Nb2O5, 13 for Ta2O5, and 51 for WO3. The recently formulated theory of Sigmund, which is in principle completely analytical, was also considered. The observed values of S could be made compatible with the predictions of the theory by taking the following values for Eb, the surface binding energy (units of kcal/gram atom): 100–150 for Nb2O5, 200–250 for Ta2O5, and 45–60 for WO3, We would point out that these latter values are similar to the heats of atomization.
Infrared fundamental band of solid orthohydrogen in the ordered state
Authors: Clouter M. J. , Gush H. P. , Welsh H. L.
Published: April 2011

The structure of the zero-phonon branches [Q, S(0), S(1)] of the infrared fundamental band of solid orthohydrogen (99% pure) has been measured for the ordered state at 1.05 °K. The Q branch consists of a weak Q1(1) line, due to perturbation of the lattice symmetry by para-H2 impurities, and a more intense sideband with maxima shifted from Q1(1) by 8.8, 10.6, and 15.3 cm−1; the latter are discussed in terms of recent theoretical results on travelling orientational excitations (librons) in the ground state (J = 1) of solid orthohydrogen. The S(0) absorption of the impurity para molecules exhibits a fine structure which is interpreted as crystalline field splitting of the J = 2 rotational state. Structure is also observed in the S(1) absorption which is associated with the vibron + roton combination transition, Q1(1) + S0(1).
Mutual excitation and reorientation of target and projectile in Coulomb excitation
Authors: Häusser O. , Cusson R. Y.
Published: April 2011

In the usual treatment of Coulomb excitation, one of the interacting nuclei is considered as a point charge. In this paper we show, for the special case of E2 excitation, how multipoles of both target and projectile can be incorporated in a coupled-channels calculation. It is found that reorientation of the projectile ground state affects the results only if polarized beams are used.
The symmetrization of Maxwell's equations, and fractionally charged particles
Authors: Leiter Darryl
Published: April 2011

It is shown that Maxwell's equations can be consistently symmetrized by the introduction of an additional vector 4-current as the source of the dual of the generalized electromagnetic tensor. The additional 4-current is related to a second type of electric charge which we shall call "m-electric charge," as distinguished from the conventional electric charge (denoted as "e-electric" charge). A Lagrangian formulation of this theory for classical point charges is constructed, yielding the symmetrized Maxwell equations, in which each particle is assumed to carry both an "e-electric" charge and an "m-electric" charge. We show that if the m-electric to e-electric charge ratio is the same for all particles in the model universe, then the predictions of the symmetrized Maxwell equations are the same as that of the unsymmetrized, conventional Maxwell equations. However, if all particles in a detector carry the same m-electric to e-electric charge ratio, not equal to zero, then a detected particle with different m-electric to e-electric charge ratio (than that of the detector) could appear to have only a fractional e-electric charge. This implies that fractionally charged particles could be generated even if only integral multiples of e-charge and m-charge were allowed in the symmetrized theory. This means that it might be experimentally difficult to distinguish between a differently "m-charged" particle, and an SU3-type "quark," in purely electromagnetic interactions alone.
High-temperature specific heat series of the Ising model on the crystobalite lattice
Authors: Gibberd R. W.
Published: April 2011

Betts and Ditzian have recently published the first 11 coefficients of the exact high-temperature series for the specific heat of the spin 1/2 Ising model on a crystobalite lattice. In this paper the exact coefficients for the next 8 terms are derived by making use of an approximate transformation between the Ising partition function of the crystobalite and diamond lattices. The series is analyzed by using the ratio and Padé approximant methods, but a reliable estimate for α has not been obtained.
Mössbauer study of the Ni–Zn ferrite system
Authors: Daniels J. M. , Rosencwaig A.
Published: April 2011

Mössbauer spectra of 57Fe in the nickel–zinc ferrite system (ZnO)x(NiO)1−xFe2O3 have been obtained, at room temperature and at 77 °K, in zero magnetic field and also in a longitudinal magnetic field of 13.5 kG, covering the full range of zinc content. The dependence of the isomer shifts, line widths, quadrupole interactions, and nuclear magnetic fields of 57Fe3+ ions in both tetrahedral and octahedral sites has been determined. The principal results of this study are (a) the confirmation of the determination of the nuclear magnetic fields by Abe et al. using NMR, and the extension of these measurements to higher zinc concentrations, (b) an indication that the hypotheses of paramagnetic centers, proposed by Gilleo, and superparamagnetic clusters, proposed by Ishikawa, are not applicable to the nickel–zinc ferrites, (c) evidence of canted spin structures, first proposed by Yafet and Kittel, (d) various effects of chemical disorder in the nickel-zinc ferrites, and (e) an observation of the effect on the Mössbauer spectrum of relaxation in a magnetically ordered iron system.
Observation of the 2159-keV level in 60Ni following the beta decay of 60Co
Authors: Dixon W. R. , Storey R. S.
Published: April 2011

A search has been made with a Ge(Li) detector for weak gamma-ray transitions in 60Ni following the beta decay of 60Co. Observation of a gamma ray of energy 2158.8 ± 0.4 keV and intensity of about 10−5 per disintegration has confirmed that the 2159-keV level of 60Ni is populated in about 10−4 of the disintegrations. A much stronger peak at 822 keV has been shown to be the single-escape peak of the 1332-keV gamma ray rather than the (2159 → 1332) transition as claimed by Hansen and Spernol. The search for other weak gamma rays in 60Ni was inconclusive, and the mechanism for feeding the 2159-keV level is not clear. As a byproduct of this investigation, the energy of the first excited state of 64Ni is found to be 1345.9 ± 0.3 keV.
Theory of the interaction of the lattice vibrations with the vibrational excitations in solid hydrogen
Authors: Noolandi J. , Kranendonk J. Van
Published: April 2011

The theory of the interaction of the vibrational excitations (vibrons) with the lattice vibrations in solid hydrogen is developed. The phonons are treated in the self-consistent harmonic (SCH) approximation appropriate to quantum crystals. The vibron–phonon interaction is expanded in terms of the SCH phonon operators rather than in powers of the displacements of the molecules from their equilibrium positions. First- and second-order perturbation corrections to the vibron energies arising from the vibron–phonon coupling are calculated. The effect of the anharmonicity of the intramolecular vibrations in conjunction with the vibron–phonon coupling is also discussed.
Transferred hyperfine interactions in Co2P2O7
Authors: Atkinson R. J. , Fowlis D. C. , Stager C. V.
Published: April 2011

The transferred hyperfine interaction has been investigated in Co2P2O7 by means of the 31P nuclear magnetic resonance. The expectation values of the cobalt ion spins were determined from the electron spin resonance of Co++ ions in the isomorphous diamagnetic salt Mg2P2O7. The values were confirmed by comparison with bulk susceptibility measurements. The fraction of unpaired electron transferred per Co–O–P path is (0.057 ± 0.005)%. This value is anomalously small compared with previous results of the transferred hyperfine interaction in Mn2P2O7.
Relativistic contribution to the second-order crystal-field splitting in Eu2+:CaWO4
Authors: Harvey J. S. M.
Published: April 2011

When relativistic effects are taken into account, the second-order spherical component of the crystal field can cause a splitting in the 8S7/2 ground state of Eu2+ in low-order perturbation theory. This splitting is closely related to the free-ion quadrupole splitting. The contribution from this mechanism to the crystal-field parameter b20 for Eu2+ in CaWO4 is estimated from electron paramagnetic resonance and electron–nuclear double resonance measurements on the divalent europium ion. It is found that the remaining contributions to b20 do not have a simple dependence on lattice parameters or low-lying energy levels and may be influenced by dynamic processes.
Anharmonic broadening of localized vibrational modes in alkali halide crystals containing H− ions
Authors: Gethins T.
Published: April 2011

Calculations are presented of the anharmonic broadening of the high-frequency localized mode associated with H− ion impurities (U centers) in KI and KBr, and also of the gap mode which occurs in the KI:KH crystal. Expressions are obtained which give the half widths of the infrared absorption peaks induced by these modes in terms of matrix elements of the impurity Green function of Lifshitz. It is shown that by taking specific forms for the localized modes and for the anharmonic terms in the Hamiltonian, closed expressions result which may be evaluated taking into account the perturbation of the lattice by the impurity. The gap mode is assumed to be completely localized on the nearest neighbors of the impurity and the high-frequency localized mode on the impurity ion alone. Only anharmonic terms derived from the nearest-neighbor, short-range forces are considered. These forces are assumed to be of the Born–Mayer form and are described by anharmonic coefficients pertinent to the pure crystal, with the exception of the force between the impurity and its nearest neighbors. In this case the cubic coefficient deduced from the observed relative intensity of the U center sideband is used and the quartic coefficient estimated from this.The numerical results show that the high-temperature behavior of the half width of the gap mode peak in the KI:KH sideband is essentially determined by that of the high-frequency localized mode peak. At low temperatures the theoretical result is smaller than the experimental value by a factor close to two. This is probably a consequence of using an oversimplified anharmonic Hamiltonian. The half width of the HFLM peak is found to be determined essentially by decay processes at low temperatures, whereas at high temperatures the contribution of scattering processes is dominant, producing the expected T2 dependence. Comparison of theory and experiment is restricted to high temperatures by the available data. In this region the theoretical half widths are too small by a factor of the order of 10. It is shown that this discrepancy may result from the neglect, in calculating the contribution to the broadening of indirect scattering processes, of three-phonon interactions in which none of the interacting phonons is the high-frequency localized mode phonon. Additional processes which are possible when such interactions are included are briefly discussed.
The virial coefficients for the 6:12 potential using the Percus–Yevick theory
Authors: Henderson D. , Chen M.
Published: April 2011

The virial coefficients which result from the use of the energy equation and the Percus–Yevick pair-distribution function, g(R), are calculated for the 6:12 potential and are found to be superior to those obtained from the Percus–Yevick g(R) using either the pressure or compressibility equations.
Capture cross section of 242Pu
Authors: Durham R. W. , Molson F.
Published: April 2011

The neutron capture cross section of 242Pu has been measured by determining the 243Am product. Samples were irradiated in a neutron flux having essentially a Maxwellian distribution defined by the temperature (37.5 °C) of a water annulus around the sample tube. Plutonium and americium were separated from each other chemically and their concentrations and isotopic compositions obtained by low-geometry α counting and α spectrometry. A value for gσ0 of 18.7 ± 0.7 b was obtained where g represents the deviation from 1/v behavior.
Faraday-rotation studies of CaF2:Eu
Authors: Brodie D. E. , Coburn J. W. , Haering R. R.
Published: April 2011

The Faraday rotation associated with divalent Eu in Eu-doped CaF2 has been measured. The percentage of the total Eu concentration which is in divalent form depends on crystal-growth conditions and on the doping level. The concentration of Eu2+ cannot be altered substantially by X or γ irradiation and is increased only slightly by electrolysis because of the strong association between Eu3+ impurities and charge-compensating F− interstitials. This conclusion is consistent with a wide variety of independent measurements on CaF2:Eu crystals.
Scattering of 100-MeV protons by 11B and 16O
Authors: Houdayer A. J. , Li T. Y. , Mark S. K.
Published: April 2011

The scattering of 100-MeV protons from 11B and 16O has been studied. An optical-model analysis of the elastic scattering on these nuclei has been performed and a consistent set of optical potential parameters which gave a good fit to the experimental results was obtained. In the inelastic scattering on 11B, it has been found that the first and third excited states were weakly excited whereas the second excited state was fairly strongly excited. The results were explained in terms of the unified model.
Instability in a radio-frequency discharge in argon in the presence of a magnetic field
Authors: Brooks D. , Pépin H.
Published: April 2011

Some experimental results and their theoretical interpretation are presented on the plasma instabilities found in a radio-frequency discharge in argon in a magnetic field. The cylindrical plasma vessel has a conducting wall and a length-to-diameter ratio of less than one. No narrow-band sinusoidal oscillations are obtained except for within the approximate pressure range 0.1 to 1 Torr, where a low-frequency, high-mode-number oscillation is found. This latter is tentatively accounted for using hydrodynamic theory.
Diffusion in a magnetic field
Authors: Youdelis W. V. , Cahoon J. R.
Published: April 2011

The effect of a magnetic field on ambipolar diffusion is considered and it is shown that for a heterovalent metal alloy, significant diffusion inhibition should occur in a transverse magnetic field when ω2ceτ2e → μe/μi, where ωce and τe are the cyclotron frequency and relaxation time respectively for the diffusion transported electrons, and μe and μi, are respectively the electron and ion mobilities. Ambipolar diffusion becomes essentially electron motion controlled when [Formula: see text]. The magnetic field effect on diffusion in Al(rich)–Cu alloys (previously reported) is discussed in relation to the criteria developed.
Etude de la transcription de la quasi-particule dans l'espace idéal
Authors: Banville M. , Simard P. A.
Published: April 2011

The transcription of the quasi-particle in the ideal space has been studied in such a way that all terms in the Hamiltonian in the QTD approximation for the system of four quasi-particles can be found. It is found that an infinity of solutions exists which verify the commutator {α, α+} while yielding correct Hamiltonian matrix elements. Finally, particular solutions which do not verify this commutator are found. Their particular invariance properties under canonical transformations make them relatively easy to obtain. Nonphysical states are eliminated by these transcriptions and all the physical states appear properly antisymmetrized.
Use of perturbation theory and statistical concepts in nuclear structure studies with application to the ground state of 14N
Authors: Ullah Nazakat , Wong S. S. M. , Trainor L. E. H.
Published: April 2011

A statistical theory due to Ullah in which the dominant configuration of a nuclear state is identified, and the remainder treated statistically, is modified to include an energy weighting factor. When applied to the problem of 14N the modified theory predicts a 10–20% admixture of 2s–1d configurations in the ground state.
Measurement of potential variations in a dense oscillating plasma
Authors: Zakrzewski Z. , Beaudry C. , Cloutier G. G.
Published: April 2011

When temperature fluctuations are large in a plasma, the floating potential cannot be used to calculate electric fields. This note describes a method which allows the calculation of the plasma potential as a function of time from measured values of the electron temperature and the floating potential. An application of this technique to the evaluation of electric fields in a reflex discharge is briefly outlined.
An improved integral equation for the numerical solution of two-dimensional diffraction problems
Authors: Shafai Lotfollah
Published: April 2011

Using a conformal transformation, the singularities of electromagnetic fields near a sharp edge are related to the geometry of the scatterer. The results are then used to treat the singularities of the current in the integral equations for the current distribution. The properties of the improved integral equations and the procedure for their evaluation is discussed by considering two-dimensional scattering by a conducting square prism.
Singularities in general relativity
Authors: Pachner J.
Published: April 2011

The problem of singularities is examined from the standpoint of a local observer. A singularity is defined as a state with an infinite proper rest mass density. It is proved that any inhomogeneity and anisotropy in the distribution and motion of a nonrotating ideal fluid accelerates collapse. Collapse is also inevitable in a rotating fluid in the case of extremely high pressure when the relativistic limit of the equation of state must be applied. In order to investigate the influence of rotation on the existence of singularities in incoherent matter the Einstein equations together with their first integrals are written out for the points on a vortex filament. They show that rotation decelerates the contraction of space not only in the direction perpendicular to the vector of the angular velocity, but indirectly also along this vector and can prevent the occurrence of a singularity. This conclusion is confirmed by the numerical integration of the Einstein equations. The paper concludes with a discussion of some cosmological implications.
Anomalous line shapes in the internal conversion electron spectrum from 227Th
Authors: Gelletly W. , Geiger J. S. , Merritt J. S.
Published: April 2011

The conversion electron spectra of the 29.9 and 31.6 keV transitions in 223Ra which are excited by the α decay of 227Th have been studied using the Chalk River [Formula: see text] spectrometer. The shapes of the L and M subshell conversion lines of the 29.9 keV transition differ significantly from those of the corresponding lines of the 31.6 keV transition. This observation confirms the difference in line shapes first reported by Valadares, Walen, and Briancon. The conversion electron spectra which are coincident with α particles which penetrated normally through the source backing have also been measured. The coincidence arrangement selects the component of the conversion electron spectrum contributed by atoms recoiling freely into the spectrometer vacuum. The conversion lines of the 31.6 keV transition appear as single doppler-shifted components which are displaced toward higher momentum relative to the main peaks of the singles spectrum. The conversion lines of the 29.9 keV transition have a more complex structure. The doppler-shifted peak is less pronounced for these lines and 68 ± 10% of the intensity in these coincidence spectra appear in broad momentum distributions lying some hundreds of electron volts lower in energy than the doppler-shifted peak. These observations provide support for the explanation which Valadares, Walen, and Briancon have advanced to account for the anomalous appearance of the conversion lines of the 29.9 keV transition in their singles spectra. From the coincidence spectra measured in this work together with results from the charge state studies of Perrin and de Wieclawick, we infer that the LII, LIII, and MIII binding energies in 223Ra atoms of mean charge + 12 are 239 ± 32, 216 ± 25, and 212 ± 38 eV higher than the corresponding binding energies in 223Ra atoms of mean charge + 1.
Study of thermal neutron capture in potassium
Authors: Johnson L. V. , Kennett T. J.
Published: April 2011

The 39K(n,γ)40K reaction has been studied using a Ge(Li) and a Ge(Li)–Ge(Li) spectrometer. A total of 252 gamma-ray transitions has been observed and a gamma–gamma coincidence matrix involving 62 transitions has been established. A decay scheme based on the experimental results is deduced for 202 of the observed gamma-ray transitions. Spins and parities of some excited states have been estimated from the deduced branching ratios. The neutron separation energies of the 40K and 42K nuclei have been determined as 7800.5 ± 0.2 and 7535.2 ± 1.5 keV respectively.
Thermal wave propagation in single crystals of bismuth at 4 K
Authors: Brown C. R. , Matthews P. W.
Published: April 2011

We present preliminary results from continuous-wave experiments made on two single crystals of bismuth. The object of the experiments was the examination of the initial deviations from diffusive propagation with increasing thermal signal frequency. The thermal conductivity of bismuth is phonon-dominated at low temperatures and has a peak of the type found in good dielectric crystals. However, the observed initial deviations were not in quantitative agreement with results obtained by applying a simple theory of second sound in dielectric crystals.
Electric dipole moment of formaldehyde in the first 3A2 excited state
Authors: Buckingham A. D. , Ramsay D. A. , Tyrrell J.
Published: April 2011

The Stark effect on the rotational lines of the 1+–0 band of the 3A2–1A1 (π* ← n) transition of formaldehyde has been studied using field strengths up to 25 kV/cm. Measurements of the Stark splittings and shifts for the Q3(3, 3), R2(3, 3), Q2(3, 3), and Q2(5, 5) lines in parallel polarization lead to a value of 1.29 ± 0.03 D for the dipole moment of formaldehyde in its 3A2-excited state. This value is significantly smaller than the value (μ′ = 1.56 ± 0.07 D) obtained by Freeman and Klemperer for the corresponding 1A2-excited state. A few measurements on lines of the 0+–0 band of the 3A2–1A1 system show that the Stark splittings and shifts are closely similar (± 3%) to those for the 1+–0 band.The spin constants for the 3A2 state have been redetermined and are:[Formula: see text]The Stark splittings show conclusively that the line assigned in earlier work as R1(3, 3) is indeed a Q2(3, 3) line in agreement with the intensity formulas of Hougen.
Liquid helium and the properties of a Bose–Einstein gas. III. The density dependence of hard-core models
Authors: Goble D. F.
Published: April 2011

We have used the results of a previous paper by Goble and Trainor to compute the density dependence of the hard-core Bose–Einstein gas in the t-matrix ladder approximation, utilizing the coordinate-space method of Brueckner and Sawada as modified by Parry and ter Haar, and the pseudopotential treatment of the hard-core boundary condition presented by Liu and Wong. Various thermodynamic parameters of these model systems are compared with the properties of liquid helium four. The disagreements which are found are shown to be primarily related to differences in the magnitudes of the Landau parameters.
Dispersion of strong shock waves by radiative energy transfer
Authors: Ahlborn B. , Richter E.
Published: April 2011

A piston driven shock which is optically thick for ionizing radiation and sufficiently strong will generate a supersonic ionizing radiation front. This discontinuity preheats and pre-accelerates the gas ahead. It propagates faster than the shock itself, so that the distance between shock and radiation front will grow, although the Mach number of the shock is constant.
Difference frequency harmonic ion heating using Whistler modes
Authors: Capjack C. E. , James C. R.
Published: April 2011

The heating of ions in a magnetized plasma by the second-order electric fields generated through the nonlinear mixing of two Whistler modes is examined. The kinetic equations describing the mixing and heating process are solved using the method of orbit integrations. Two techniques are available for optimizing the energy absorbed by the ions. One is to allow the mixed wave to approach a natural mode in the plasma, resulting in a field resonance. A second method is to have the ions absorb energy through cyclotron damping. The latter technique and the combination of the two optimizing schemes will be investigated. The resulting sensitivities to fluctuations in frequency, density, static magnetic field, and the direction of propagation of the source waves will be given.
Final-state interaction in the 3H(t, α)2n reaction at 90 keV
Authors: Poutissou R. Larose , Jérémie H.
Published: April 2011

The neutron–neutron final-state interaction in the reaction 3H(t, α)2n has been studied at an incident energy of 90 keV. An evaluation of the observed events according to current final-state interaction theories yields a value of [Formula: see text] for ann.
An effective ion–ion potential for sodium
Authors: Basinski Z. S. , Duesbery M. S. , Pogany A. P. , Taylor Roger , Varshni Y. P.
Published: April 2011

The effective ion–ion interaction for sodium is calculated from a fundamental basis, using a one-orthogonalized plane wave (OPW) bare electron – ion matrix element, and the Geldart and Taylor electron gas screening function. Particular attention is paid to the form of the interaction for asymptotically large ion–ion separation, and it is shown that this interaction varies approximately as the fifth power of the ion–ion separation in the region in which the amplitude of the potential is appreciable. The elastic constants, cohesive energy, and the specific heats of body-centered cubic (b.c.c.) and close-packed sodium are shown to be in excellent agreement with experiment. The equilibrium and stability of the model sodium lattice described by the proposed potential are discussed, and it is concluded that the potential can be used tentatively in a fundamental calculation of atomic properties of defects.
Magnon scattering in the Raman spectrum of α-oxygen
Authors: Mathai P. M. , Allin Elizabeth J.
Published: April 2011

A previously Unobserved line at a displacement of 27.2 cm−1 in the Raman spectrum of the anti-ferromagnetic phase (α) of solid oxygen is reported. Its frequency, low intensity, small half-width, and variation of frequency with temperature are all consistent with its assignment to scattering by a k = 0 magnon mode.
Optical reflection from a shock front at grazing incidence
Authors: Pert G. J. , Smy P. R.
Published: April 2011

The reflection of light from a shock front at near grazing incidence is considered. It is found that under these conditions the calculated reflectivity may be significantly changed from the first-order approximation used by earlier workers, due to higher-order effects, namely attenuation, refraction, and multiple reflection. Asymptotic analytic expressions for the upper and lower bounds of the reflectivity are obtained.The error in the reflectivity introduced by deviation in the shock front from planarity is also calculated. Quantitative expressions valid in the grazing incidence limit, which may also be expected to give good order-of-magnitude results in the general case, are obtained.
Early free-fall afterglow of a cylindrical mercury vapor plasma
Authors: Gregory B. C.
Published: April 2011

The free-fall theory for the decay of average electron density and electron temperature in a mercury vapor discharge afterglow presented recently in a letter (Gregory) is improved by the addition of a pressure term for the ions in the second moment equation. The neglect of charge-transfer collisions is justified. The development of the theory is reviewed in detail and a complete series of comparison curves for the measured and calculated electron density decay is presented for four tubes of different diameter.
Theory of a phonon–exciton resonance in a molecular crystal
Authors: Zaidi H. R.
Published: April 2011

The theory of a coupled phonon–roton (rotational exciton) mode in a molecular crystal is developed using the propagator technique. The dispersion relation and the phonon density of states are calculated. The results are applied to the case of solid HD. The line-shape function for the one phonon branch, phonon–roton coupling, and the roton band frequencies are calculated for this case. Near the phonon–roton resonance, the one phonon branch shows strong influence of the interaction with the roton band.
Surface layers and their conductivity on high-resistance Cu2O
Authors: Kužel R. , Weichman F. L.
Published: April 2011

The surface and bulk conductivities of high-resistance Cu2O crystals were measured on natural and etched samples over a temperature range from 230 to −145 °C in vacuum and in air. The total conductivity measured from high temperatures in vacuum was found not to be influenced by the surface conductivity. The bulk conductivity followed the simple exponential temperature dependence with a single activation energy of about 0.61 eV over the entire range. Exposure to air caused the formation of conducting surface layers which changed over several days. The surface conductivity of samples could be detected by a change in activation energy at 20 °C. The elimination of surface layers was only possible by heat treatment in vacuum. The temperature behavior of the surface conductivity is explained on the assumption that absorption and desorption of oxygen and diffusion of copper ions take part in the formation of the surface layers.
Mesures de vies moyennes dans 12B, 14N et 16O
Authors: Gallmann A. , Haas F. , Balaux N. , Heusch B. , Toulemonde M.
Published: April 2011

Lifetimes of nuclear states have been measured by the Doppler-shift attenuation method. Gamma radiations from the 11B(d,pγ)12B, 19F(p,αγ)16O, and 12C(h,pγ)14N reactions were observed with a Ge(Li) detector at θγ = 7°, 90° and 173°. The following lifetimes were obtained:[Formula: see text]Upper limits have been set for very fast lifetimes, and transition energies were also determined. The partial widths of the radiative transitions from the 6.44 MeV state of 14N were compared with theoretical predictions. The amplitude of a (p3/2)−2 configuration in the wave function of this level was evaluated using the partial width of the 6.44 → 3.95 MeV transition determined in the present work.
A survey of new resonances in the 15N(α,γ)19F reaction
Authors: Aitken J. H. , Azuma R. E. , Litherland A. E. , Charlesworth A. M. , Rogers D. W. O. , Simpson J. J.
Published: April 2011

Thirteen new resonances in the 15N(α,γ)19F reaction have been discovered in the region Eα = 600–3150 keV. γ-Decay schemes and radiative yields are reported for several of them. Spins and parities for 10 levels in 19F are also reported.
Ground state photoneutron angular distributions in the giant resonance of 16O
Authors: Jury J. W. , Hewitt J. S. , McNeill K. G.
Published: April 2011

Photoneutron spectra for transitions to the ground state in the giant resonance of 16O were measured with high neutron energy resolution (ΔE ~ 60 keV) at angles of 50, 66, 82, 98, 114, 130, and 146 degrees relative to the direction of the incident bremsstrahlung beam. The spectra at the various angles were measured during successive experimental runs using a single 50 m time-of-flight spectrometer. The different angles were obtained by bending the electron beam relative to the direction of the flight path. Angular normalization was achieved by using a fast neutron monitor located at the end of a short flight path which was always normal to the reaction plane. Legendre coefficients for the angular distributions were extracted as functions of the excitation energy. From the energy dependence of the coefficients, interference effects are evident in the ground state (γ,n) cross section in the region from 17 to 30 MeV.
Independent yields of 80Br, 82Br, 128I, and 130I from the thermal neutron fission of 235U, 239Pu, 233U, and 238Np
Authors: Tracy B. L. , Thode H. G.
Published: April 2011

Absolute independent yields of the shielded nuclides 80Br, 82Br, 128I, and 130I produced in the thermal neutron fission of 235U, 239Pu, and 233U have been determined by careful mass spectrometric analyses of krypton and xenon fission products. In addition, a fractional independent yield of 130I from the thermal neutron fission of 238Np has been determined, and an upper limit has been set for the independent yield of 126I from 235U fission. All the yields from 235U fission except that of 128I are consistent with the Gaussian charge distribution described by Wahl. However, conventional theories of charge distribution in fission do not account for the irregular variation in iodine yields from one fissile nuclide to another. A mechanism based on differences in neutron emission probabilities from prompt fission fragments is proposed in order to explain this variation.
Some remarks on the role of neutrino processes in red giants
Authors: Chaudhuri Probhas Ray
Published: April 2011

It is shown that the plasma neutrino emission rate, when calculated according to the photon–neutrino weak coupling theory, has significant effects on the evolution of red giants.
Fresnel zone plate solved by the boundary-diffraction-wave theory
Authors: Lit J. W. Y. , Tremblay R.
Published: April 2011

The Fresnel zone plate is studied by the boundary-diffraction-wave theory (BDWT). Expressions are given for the fields in the transverse planes and along the axis; in particular, the wave amplitudes at the foci are considered in some detail. The BDWT provides a clear physical picture of the problem. The wave amplitude at any point is given by the sum of a finite number of rays determined by the number of zones in the plate. The foci are the points where the singly diffracted rays are in phase.
Transient fields for an electric dipole in a dissipative medium
Authors: Wait James R. , Spies Kenneth P.
Published: April 2011

Explicit expressions are presented for the electric and magnetic field components of a step-function excited electric dipole immersed in an infinite homogeneous medium with a specified conductivity and dielectric constant. It is shown that displacement currents influence only the early part of the waveform.
Ion-acoustic waves and radio aurora
Authors: McDiarmid D. R.
Published: April 2011

A previously proposed model of radio aurora is developed further and is used to relate and explain data obtained during an event described by Hofstee and Forsyth. The basis of the model is the two-stream, ion-acoustic wave instability. Although the model explains this particular event very well, attempts to apply it to certain other experimental situations have resulted in unresolved difficulties. These are discussed briefly.During the Hofstee and Forsyth event a geomagnetic bay was observed north of the scattering region. An explanation of this bay using the electric field deduced from the radio backscatter data required the assumption of a polarization field within the band of enhanced plasma associated with the visual aurora present at the same location (Boström's model 1).