bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Yields of Stable Cadmium Isotopes in Neutron Induced Fission
Authors: Laeter J. R. De , Thode H. G.
Published: April 2011

The relative fission yields of the five stable isotopes of cadmium (111Cd, 112Cd, 113Cd, 114Cd, and 116Cd) produced in the thermal and epicadmium fission of 233U and 235U and the epicadmium fission of 238U have been measured by solid source mass spectrometry. Nanogram sized samples of fission product cadmium were analyzed to give a range of yields on the low mass side of symmetric fission. The results indicate that the mass yield distribution for thermal induced fission is relatively flat within five mass units of the valley of symmetry. The epicadmium induced fission results show enhanced yields at mass 111, the degree of enrichment depending on the mass of the fissioning nucleus. The only significant fine structure occurs at mass 113 for the epicadmium induced fission of 235U. Although less certain, there is also a suggestion of a depressed yield at mass 113 for thermal neutron induced fission of 235U as well. No evidence of a symmetric peak was observed in any of the data. The absence of significant fine structure in this mass range suggests that the average number of neutrons emitted per fission event varies fairly smoothly with mass.
Isotope Shifts and Rotational Analysis of the As32S+A1Π–X1Σ Band System
Authors: Shimauchi Midori , Karasawa Shiro
Published: April 2011

The emission spectrum of As32S+ and As34S+ has been excited in a quartz discharge tube by a 27 MHz oscillator. Vibrational isotope shifts have verified the vibrational quantum numbers of the upper and lower states. The 2–0, 1–0, 1–1, 0–1, 2–1, and 1–2 bands were chosen for the first rotational analysis of the As32S+ spectrum. The analysis has established that the transition is 1Π–1Σ. The principal molecular constants are as follows:[Formula: see text]Calculated dissociation energies based on the above constants and observed Tc suggest that X1Σ and A1Π have a common dissociation limit, As+(3P) + S(3P). In the upper state several perturbations have been found.
On the Field Distribution in Rectangular Apertures Using Surface Patch Modeling
Authors: Spiegel R. J. , Young D. E.
Published: April 2011

In this paper the H integral equation is investigated for the problem of plane wave diffraction by a rectangular aperture cut into an infinite, perfectly conducting screen. The field distribution in the aperture is calculated by the application of the method of moments with point matching and pulse expansion functions. Various sized apertures are considered and the numerical stability of the solution is discussed.
Scattering from Many Centers in One Dimension
Authors: Bajaj K. K. , Nogami Y.
Published: April 2011

The accuracies of the fixed scatterer approximation (FSA) and the Glauber approximation (GA) are examined for an exactly soluble, one dimensional model which simulates nucleon–nucleus scattering. These approximations are found to work well at unexpectedly low energies. For example, the errors in the FSA and GA for the 'nucleon–deuteron' forward scattering cross section at 10 MeV (laboratory system) are only 5 and 7% respectively. The reason for this success is examined.
Upper Limits on Fluxes of Low Energy Interstellar Cosmic Rays and Nuclear Gamma Rays
Authors: Yoshimori M.
Published: April 2011

The upper limits on an interstellar flux of low energy cosmic rays are derived from interpretations of the γ ray spectral feature at 473 ± 30 keV, the enhancement in the flux of galactic diffuse γ rays, the ionization rate of interstellar hydrogen, and the abundance ratios of stellar light elements. The derived upper limits are compared with the observed flux and the demodulated flux. Nuclear γ rays are emitted from excited nuclei which are produced by inelastic collisions between low energy cosmic rays and the interstellar gas. Fluxes of nuclear γ rays emitted from [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] are evaluated and found to be of the order of 10−6 to 10−8 photons cm−2 s−1.
Segmented Random Walks and Correlation Factors in Solid State Diffusion
Authors: Kidson G. V.
Published: April 2011

Hart's discussion of the measured diffusion coefficient D, for systems in which atom transport occurs via both the vacancy mechanism and along dislocation pipes, has been generalized to include any number of contributing mechanisms. The treatment introduces the concept of uncorrelated segments and shows that the correlation factor associated with each contributing mechanism contains a time independent parameter [Formula: see text] associated with the average number of jumps per segment. The analysis shows that the usual expression for the correlation factors obtained by assuming [Formula: see text] can be corrected for finite values of [Formula: see text]. The error involved in a typical case is less than 1% if [Formula: see text].
The Electronic Spectrum of HF+
Authors: Gewurtz S. , Lew H. , Flainek P.
Published: April 2011

The A2Σ+–X2Π emission spectrum of HF+, between 3580 and 4830 Å, has been photographed at high resolution and measurements on eight bands are reported. The analysis yields rotational and vibrational constants of the X state for ν = 0 to 2 and of the A state for ν = 0 to 3. A predissociation by rotation in the A2Σ+ state is observed and yields a dissociation energy of 3203 ± 50 cm−1 above the ν = 0, N = 0 level of this state. It is shown that this corresponds to a dissociation into H+(1S) + F(2P1/2). A detailed comparison with previous results obtained from photoelectron and photoionization experiments and from recent theoretical calculations is given.
The Inversion Problem for Two Fold Photoelectron Counting Statistics
Authors: Blake Julian , Barakat Richard
Published: April 2011

The extraction of spectral information from measurements of the full or clipped photoelectron correlation function is treated. Unlike previous treatments, the discussion here is not limited to counting times short compared to the coherence time of the light. The method of singular value decomposition is applied to the case where there is no prior knowledge of the spectrum. Parameter estimation is applied when the general structure of the spectrum is known.
The Field Gradient Tensor at the Metal Site in Hafnium Acetylacetonate
Authors: Lowe L. M. , Prestwich W. V. , Zmora H.
Published: April 2011

Time differential perturbed angular correlation measurements (TDPAC) were performed on 181Ta in hafnium acetylacetonate, Hf(acac)4. The asymmetry parameter, quadrupole interaction frequency, and frequency distribution spread of sources of synthetic and irradiated Hf(acac)4 were measured. Evidence for the existence of two sites with different asymmetry parameters (Beraud et al.) was not found.
Elastic and Plastic Anisotropy of Indium
Authors: Wicks L. R. , Tyson W. R.
Published: April 2011

The elastic anisotropy of face centered tetragonal indium has been examined with reference to the ratios between selected moduli, Young's modulus, and shear modulus. Elastic energies and lattice friction stresses have been calculated for the likely slip systems and dissociation reactions have been considered. Slip on {111} is favored, being in agreement with experiment.
Current Limitation in an Argon Discharge
Authors: Stangeby P. C. , Daoud M. A.
Published: April 2011

Upper and lower limits to the current which can be carried by an electrical discharge have been predicted by recent theories and substantiated by experiments employing Hg vapor. Poor agreement appeared to obtain for other gases, raising uncertainties about the validity of the theoretical model. New experiments have been undertaken with argon for which theoretical–experimental discrepancy was greatest and the new results are found to be in agreement with theory. Possible reasons for the earlier disagreement are considered.
Disorientation of K(42P1/2) Atoms, Induced in Collisions with Noble Gases
Authors: Niewitecka B. , Krause L.
Published: April 2011

The cross sections for disorientation of 42P1/2 potassium atoms, induced in collisions with noble gas atoms, have been determined in zero magnetic field by studying the depolarization of K(7699 Å) resonance fluorescence in relation to noble gas pressures. Potassium vapor at low density, mixed with a noble gas in a fluorescence vessel, was irradiated with circularly polarized 7699 Å potassium resonance radiation and the resulting resonance fluorescence, observed in an approximately backward direction, was analyzed with respect to circular polarization. The variation of the degree of polarization with gas pressure was interpreted on the basis of a 'J randomization' model for the collisions and yielded the following disorientation cross sections which are appropriately corrected for the effect of nuclear spin: K–He, 24 ± 4 Å2; K–Ne, 21 ± 3 Å2; K–Ar, 37 ± 5 Å2; K–Kr, 51 ± 7 Å2; K–Xe, 69 ± 9 Å2. The cross sections are significantly smaller than values obtained previously in kilogauss fields.
On the Particle Interpretation for the Quantized Fields in External Field Problems
Authors: Labonté Gilles
Published: April 2011

We review the main recent results concerning the capacity of the quantized field system in the presence of an external field to represent physical particles at all times. We deal more particularly with the Dirac spin 1/2 equation since it is known to be trouble free at the c number level. As this had not been done explicitly before, we present a proof, valid for a wide class of potentials, which shows that at each time a Fock basis for individual energy quanta (the physical particles) exists in the same Hilbert space, i.e. the system can be completely described in terms of these.
Dipole Moment of CS2 in its ã3A2 State
Authors: Larzillière M. , Ramsay D. A.
Published: April 2011

The Stark effect on the [Formula: see text] system of 12C32S2 has been investigated. The most pronounced effects involve the 270,27 and 261,26 rotational levels of the 140 vibrational state and the 290,29 and 281,28 rotational levels of the 050 vibrational state. These pairs of levels are nearly degenerate and are coupled by an off-diagonal matrix element in the presence of an electric field. An analysis of the Stark shifts and the shapes of the Stark broadened lines yields[Formula: see text]Comparison of these energy separations with values calculated from measurements in the near ultraviolet spectrum and lower state term values based primarily on infrared data reveals a systematic discrepancy of 0.022 cm−1.
The Scattering Equations for Charged Particles Colliding with Many Body Systems
Authors: Bui T. D. , Stauffer A. D.
Published: April 2011

We have derived the total wave function of a many body system scattering by a charged particle by using a first order perturbation technique (the polarized orbital method). The derivation is based on an adiabatic approximation for the incoming particle. Particular cases of electrons colliding with the alkali atoms are shown. S, P, and D wave phase shifts and the total elastic cross sections for electron–sodium atom scattering are calculated using this method for the energy range 0 to 4 eV.
Quantum Mechanical Calculations for the Electron Impact Broadening and Shift of some Lines of Neutral Helium in a Hot Plasma
Authors: Bassalo J. M. , Cattani M.
Published: April 2011

In this paper we apply the quantum mechanical formalism developed by Bassalo and Cattani to calculate the broadening and shift produced by electronic collisions of some lines (5876, 5048, 5015, 4713, 3964, and 3889 Å) of neutral helium in a plasma. The effect of the ions are also taken into account. Our theoretical predictions are compared with the experimental results of Bötticher et al. and with the semiclassical estimates of Griem et al.
Scattering of Optical Photons by an Electron in a Microwave Field
Authors: Guccione-Gush R. , Gush H. P.
Published: April 2011

The problem of optical photon scattering by an electron in a microwave field is studied in the context of Schrödinger theory, neglecting spin. A strong dependence of the spectrum of the scattered radiation on the microwave intensity is found; however, the total scattering cross section is only weakly affected. The calculation includes the derivation of the exact Green function for the electron in a classical electromagnetic field.
Elastic Photon Scattering Cross Section for the H− Ion in the Asymptotic Approximation
Authors: King Frederick W.
Published: April 2011

A comparison is made between the calculation of the elastic photon scattering differential cross section for the H− ion in the asymptotic approximation, employing both the dipole length and dipole velocity formulations. The divergence of the cross section using the dipole velocity formulation is discussed.
Induced Torque in Potassium
Authors: Holroyd F. W. , Datars W. R.
Published: April 2011

Torque induced in potassium samples prepared in a variety of ways has been studied as a function of the magnitude and direction of magnetic field. The twofold anisotropy in the induced torque reported previously by Schaefer and Marcus was observed in some samples and was absent in others. The effect depended on the method of sample preparation and the presence of oil on the sample during the experiment. The conditions existing in previous experiments showing both isotropic and anisotropic torque are shown in the present experiment. The magnetic field dependence is linear at torque minima and faster than linear at torque maxima. Possible causes of the anisotropy and magnetic field dependence are considered.
Effect of Initial Nuclear State on Penetrability Through Two-Peaked Fission Barriers
Authors: Sharma R. C. , Leboeuf J. N.
Published: April 2011

Fission penetrability is computed for a fission barrier of Strutinsky type where the initial state of a nucleus and a nonzero reflection coefficient at the last well of the barrier are taken into account. Some effects of initial nuclear state on fission penetrability are explored and the model is then applied to the specific case of Pu240. The results compare favorably with the ones already existing for this nucleus.
Some thermodynamic and stability properties of a fluid with gradient dependent free energy
Authors: de Sobrino Luis
Published: April 2011

A thermodynamic theory for a fluid continuum whose free energy depends on the density gradient is developed. Such a theory is, perhaps, the simplest approximation to a nonlocal theory, necessary to account for the dynamics of the liquid–vapor transition. Relations between the thermodynamic quantities and an expression for the entropy production are found. It is shown that asymptotic dynamic stability of the equilibrium, in the sense of Lyapunov, is equivalent to classical thermostatic stability. The theory predicts that homogeneous equilibrium solutions of negative compressibility may be stable if the fluid is enclosed in a sufficiently small constant volume container.
Electron spin resonance studies of 53Cr3+ and VO2+ ions in AlCl3∙6H2O
Authors: Pack K. , Manoogian A.
Published: April 2011

The electron-nuclear double resonance (ENDOR) of 53Cr3+ ions and the electron spin resonance (ESR) of VO2+ ions are studied in single crystals of AlCl3∙6H2O. The ENDOR measurements are done at 4.2 K while the resonance of VO2+ is studied at room temperature. The sign of the Cr3+ spin Hamiltonian zero field splitting parameter D is found to be negative while the anisotropic hyperfine parameter has the relation A < B. It is concluded that the octahedron of waters surrounding the chromium ion is trigonally compressed. The value of the 53Cr3+ quadrupole interaction parameter Q′ is nearly the same as that found previously in the cesium alums even though the D value is considerably smaller in AlCl3∙6H2O. This indicates that Q′ is independent of D at 4.2 K in these salts and the expected proportionality [Formula: see text], which is based on a purely static distortion for the octahedron of waters surrounding the Cr3+ ion, does not hold. The resonance results for VO2+ show the nature of the two inequivalent but otherwise similar Al∙6H2O complexes in the unit cell. The VO2+∙5H2O complexes associated with the two types of aluminum sites are found to be rotated relative to each other by an angle of 33 ± 3° in the plane perpendicular to the crystal c axis. A comparison of the spin Hamiltonian parameters of VO2+ and 53Cr3+ in AlCl3∙6H2O with those obtained previously in CsAl alum indicates that the Al∙6H2O complexes in CsAl alum are more susceptible to distortion upon impurity doping than are those in AlCl3∙6H2O.
Steady transverse MHD viscous flows
Authors: Chandna O. P. , Garg M. R.
Published: April 2011

Steady plane flows of viscous incompressible fluids of finite electrical conductivity in the presence of a transverse magnetic field are studied. The only flows with straight streamline pattern are shown to be those with parallel or concurrent streamlines and if the streamlines are involutes of a curve, then they are concentric circles. It is also established that if the natural net is isometric, then the streamlines are restricted to parallel lines, concurrent lines, concentric circles, or logarithmic spirals.
Activation energy barrier for intersystem crossing in platinum phthalocyanine
Authors: Huang Tzer-Hsiang , Rieckhoff Klaus E. , Voigt Eva-Maria
Published: April 2011

Phosphorescence quantum yields and lifetimes of platinum phthalocyanine in α-chloronaphthalene solution are reported for temperatures from 1.3 K to 300 K. Activation energies of intersystem crossing are deduced and found to be Ea = 17 ± 3 cm−1 for crossing from the first excited singlet state to the lowest lying triplet state and Eap = 8 ± 1 cm−1 for crossing from the lowest lying triplet state to the singlet ground state.
On the computation of dipole transitions in the HD molecule. Part II
Authors: Wolniewicz L.
Published: April 2011

The nonadiabatic coupling with Πu states in the electronic ground state of the HD molecule is discussed. Formulas are given that facilitate the evaluation of Πu contributions to the energies and transition moments. Numerical computations are performed for all ν ≤ 4 vibrational and J ≤ 4 rotational levels yielding the Πu and Σu nonadiabatic corrections. The variational wave functions are employed to compute the transition moments for the 0–ν bands with ν ≤ 4. The results are in good agreement with experimental data except in the case of the 0–ν band where the theoretical results are larger than the mean experimental moment by a factor of about 1.4.
On the enhanced confinement of cylindrically confined gas discharge plasma due to external r.f. signals
Authors: Chiplonkar V. T. , Sapre A. V.
Published: April 2011

Enhanced confinement of a cylindrical plasma produced by externally applied r.f. signals has been shown to involve not only the incremental change in the d.c. floating potential of the probe, in contact with the plasma, but also the leakage current through the container dielectric wall and its impedance.
The magnetic field at chromium nuclei in iron and nickel
Authors: Wender S. A. , Keszthelyi L. , Cameron J. A.
Published: April 2011

The integral rotation of the angular distribution of γ rays from the 749 keV level of 51 Cr excited by the (α,n) reaction in Ti5Fe95 and Ti5Ni95 targets has been used to measure the hyperfine magnetic fields at Cr nuclei in these alloys at liquid nitrogen temperature. The values are[Formula: see text]
Etalonnage du sextant
Authors: Bouillon Gratien , Delisle Claude , Pichard François
Published: April 2011

A procedure for the calibration of the sextant is given in which the only instruments required are: two autocollimators, a plane mirror, and a surface plate of good quality.
The electromagnetic decay of the T = 3/2 states in19F
Authors: Rogers D. W. O. , Carter A. L. , Symons T. J. M. , Dolan S. P. , Anyas-Weiss N. , Allen K. W.
Published: April 2011

The gamma-decay modes of the first two T = 3/2 levels in 19F at Ex = 7538 ± 2 and 7659 ± 2 keV have been studied at resonances in the 15N(α, γ)19F reaction at Eα = 4.465 and 4.618 MeV. Several weak decay branches have been seen: 7.54 → 5.11 MeV, 1.7 ± 0.4%; 7.54 → 1.35 MeV, 1.2 ± 0.4%; 7.66 → 4.55 MeV, 5.1 ± 0.3%; 7.66 → 5.11 MeV, 5.9 ± 0.5%. Comparison with (sd)3 shell model calculations indicate that the 4.55 and 5.11 MeV levels can be associated with the second and third calculated 5/2+ states. Using the DSAM, upper limits have been set on several lifetimes: 4377 ± 1 keV, < 22 fs; 4548 ± 2 keV, < 50 fs; 5105 ± 2 keV, < 30 fs.
Far-infrared absorption in cubic ZnS
Authors: Kwasniewski E. A. , Koteles E. S. , Datars W. R.
Published: April 2011

Far-infrared absorption in cubic ZnS due to single-phonon and two-phonon processes was measured with a high resolution, far-infrared Fourier transform spectrometer. A 14-parameter lattice dynamical shell model was fitted to phonon dispersion curves measured by Vagelatos et al. The two-phonon density-of-states calculated with these parameters was compared with the absorption spectrum. Two-phonon combinations and their locations in the Brillouin zone were identified with features of the absorption spectrum. Critical points were found on or near the zone boundary and not only at high symmetry points as suggested previously.
On the longitudinal momentum distributions of particles produced in high energy nucleon–nucleus collisions
Authors: Ahmad I. , Zafar M. , Irfan M. , Shafi M.
Published: April 2011

Experimental results on longitudinal momentum distributions of pions, protons, deuterons, tritons, and 3He produced in the interactions of 24 GeV/c protons with the Ag and Br nuclei of nuclear emulsion are presented. The variation of [Formula: see text] with the shower multiplicity, the angle of emission, and the mass of the particles has been studied. Many characteristics of pions have been found to be similar to those produced in hadron–hadron collisions. The results on pions suggest that perhaps the multiparticle production in nucleon–nucleus collisions takes place via a two-step mechanism.
Magnetoacoustic oscillations and the stress dependence of the Fermi surface of tungsten
Authors: Stanley D. J. , Perz J. M. , Au H. -P.
Published: April 2011

The absolute amplitudes of quantum oscillations in magnetostriction and the elastic constant, c11, have been measured simultaneously, for the first time, in a single crystal sample of tungsten. They are combined to give the strain dependence of the Fermi surface cross sections normal to [100] of the ball and ellipsoid surfaces. Comparison with values measured in another type of uniaxial experiment and with pressure derivatives indicates that the results are consistent, and that the method is feasible, although less convenient than other possible measurements giving the same information.
The Kerr–Newman metric in the nonsymmetric unified field theory
Authors: Boal D. H.
Published: April 2011

The method introduced by Newman and Janis for obtaining the metric of a rotating, charged particle in the Einstein–Maxwell theory of gravitation and electromagnetism is examined in the context of the nonsymmetric unified field theory. It is found that a transformation very similar to theirs, when applied to the antisymmetric part of the tensor gμv, will generate the required electromagnetic field associated with the Kerr–Newman metric.
On the constant temperature level density formula
Authors: Pai H. L.
Published: April 2011

The paper is to show that the constant temperature level density formula is the direct consequence of the Boltzmann distribution which is especially good for the description of evaporation of nucleons, and is expected to work both for the high and the low excitation. For other compound nucleus phenomena other than nuclear evaporation, it would be considered as the mathematical equivalence of the Fermi gas model under higher excitation.
Influence des paramètres du milieu sur la réduction des modèles d'atomes fortement ionisés
Authors: Noëns J. C. , Rozelot J. P.
Published: April 2011

In a previous paper (Rozelot et Noëns), a method for reducing models of highly ionized atoms was presented. An application was made, in the case of stationary statistical equilibrium, to the calculation of relative level populations for the fundamental configuration of the Fe XI ion in the coronal plasma, with particular values for the physical parameters of the medium. In order to generalize the conclusions established in that previous work, the calculations are now extended to an important range of values of the parameters. The analysis of the results obtained justify the conclusion that the proposed reduction can be used, within the limits indicated, for any physical conditions of the medium in which the ion is placed.[Journal translation]
Numerical solution of the transient gain equations for stimulated backward scattering in absorbing fluids
Authors: Rangnekar S. S. , Enns R. H.
Published: April 2011

The transient gain equations for stimulated backward scattering in absorbing fluids are solved numerically by the method of characteristics for an amplifier setup. In addition to the 'spiking' of the signal pulse previously noted by Maier, Kaiser, and Giordmaine, the existence of a characteristic dip in the amplification of the signal pulse in nonabsorbing fluids when the interaction region ceases to increase is reported. The effect of increasing absorption is to wipe out both the spike and the dip.
Analyse vibrationnelle et rotationnelle de la transition A2Σ+–X2Πi de la molécule 63Cu80Se
Authors: Lefebvre Y. , Bocquet J. L.
Published: April 2011

High dispersion vibrational and rotational analysis of a 63Cu80Se visible band system has been performed.The presence of a splitting proportional to [Formula: see text] in each observed subsystem indicates that these bands arise from a transition from a 2Σ state (with γ-type doubling) to a 2Π state. This hypothesis allows us to derive specific molecular constants of these two states.
Proton spin relaxation in dilute methane gas: A symmetrized theory and its experimental verification
Authors: Beckmann P. A. , Bloom M. , Ozier I.
Published: April 2011

Nuclear spin relaxation in low density methane gas is investigated theoretically and experimentally. A theory is developed in which full account is taken of the tetrahedral symmetry of the molecule. For a nuclear Larmor frequency of 30 MHz, the time evolution of the nonequilibrium magnetization is measured as a function of density between approximately 0.005 and 17 amagats at temperatures of 110, 150, and 295 K. In all cases, exponential relaxation is observed. By using the theory in conjunction with the known spin rotation constants and rotational energy levels of CH4, the measured values of the relaxation rate R1 have been fit very well at each temperature, both for the maximum value of R1 which contains no adjustable parameters and for the density dependence of R1 which contains a single parameter taken to be the collision cross section for molecular reorientation. The centrifugal distortion splittings of the rotational levels are shown to have an important influence on the observed values of R1 at 30 MHz and. more generally on the dependence of the time evolution of the nonequilibrium magnetization on density and frequency. On the basis of the theory, a new type of 'relaxation rate spectroscopy' is proposed. Non-exponential relaxation is predicted to occur at low densities when the nuclear Larmor frequency is tuned to a centrifugal distortion splitting.
Phonon broadening of bound exciton luminescence in silicon
Authors: Thewalt M. L. W. , Kirczenow G. , Parsons R. R. , Barrie R.
Published: April 2011

We report accurate measurements of the broadening of the phonon replica luminescence lines of excitons bound to P, B, Ga, As, and Bi impurities in silicon and formulate a theory of the lineshapes. The broadenings were obtained experimentally from a comparison of the phonon replica lineshapes with the no-phonon lineshape. We explain these broadenings by a new mechanism in which the spread in recombination wave vectors of the localized electron and hole leads to a spread in energy of the photons emitted since the energy of the momentum-conserving phonon is wave vector dependent. We give an expression for the donor luminescence lineshape in terms of the impurity state wave functions and the phonon dispersion. It is not necessary to invoke phonon lifetime broadening to explain our data. We find that the broadening of the TA and TO bound exciton phonon replica lines is considerably smaller than the phonon lifetime broadenings previously invoked to explain the free exciton lineshapes in silicon. We feel that the 'broadening' which has been observed for the free exciton lineshapes can be accounted for by the splitting of the free exciton ground state and the associated nonparabolicity of the free exciton bands.
Measurement of total cross sections (e+, Ne) and (e+, Ar)
Authors: Tsai J-S. , Lebow L. , Paul D. A. L.
Published: April 2011

The total cross sections for positrons on neon and argon atoms have been measured in the energy ranges 15 eV to 272.5 eV and 25 eV to 300 eV respectively. The cross sections indicate clearly that Born values will not be reached until at least 3 KeV. Interpolating between the measured and the valid Born regions has allowed an application of the sum rule which connects scattering length. Born forward scattering amplitude, and the momentum-integral over the total cross section. This procedure gives scattering lengths as = −0.53 ± 0.15 Bohr radii for neon and as = −2.8 ± 0.7 Bohr radii for argon; the errors include maximum credible uncertainties in the interpolations.
Spin isomer conversion and orientational ordering in solid methane: II. The second moment
Authors: Piott J. E. , McCormick W. D.
Published: April 2011

The various contributions to the second moment in methane, CH4, are investigated. A general expression for the intermolecular second moment is obtained. Using this, the intramolecular second moment was measured using a series of observations during spin isomer conversion. The value found, near 1.5 G2, suggests restricted motion of a preferred axis of reorientation. A search for the onset of the intramolecular second moment shows that it occurs in the same region as the onset of birefringence.
Quantum transitions in the double-hole SQUID
Authors: Vrba J. , Fife A. A. , Macura V. , Burbank M. B. , Lomnes R.
Published: April 2011

A generalized theory of the double-hole SQUID is developed and the importance of the mutual inductive coupling between the SQUID holes is demonstrated. The basic flux periodicity Φeff is found to depend on this inductive coupling and is shown to be within the limits Φ0 ≤ Φeff ≤ 2Φ0 for coupling constant k in the range 1 ≥ k ≥ 0.
The and band systems of the CS2+ ion
Authors: Balfour Walter J.
Published: April 2011

The [Formula: see text] and [Formula: see text] emission systems of the CS2+ ion have been photographed at medium resolution following controlled electron excitation of CS2 gas. Vibrational analyses have been performed for both systems. The (0010)–(0010) transitions of the [Formula: see text] and [Formula: see text] subsystems lie at 21 107 and 20 843 cm−1, respectively. Evidence is presented for Fermi resonance interactions between (100) and (020) levels in the [Formula: see text] and [Formula: see text] electronic states. The rotational structures of six partially resolved subbands of the [Formula: see text] system have been studied and a value of 1.615 Å obtained for the C—S bond length of CS2+ in the [Formula: see text] state.
K-shell autoionization in the beta decay of 95Nb
Authors: Jurčević M. , Ljubičić A. , Krečak Z. , Ilakovac K.
Published: April 2011

The X-ray–γ-ray coincidence method was applied to determine the probability of K-shell autoionization in the beta decay of 95Nb. A value of PK = (3.4 ± 0.4) × 10−4 was obtained. This result is in agreement with the recent theoretical result obtained by Law and Campbell.
Effect of surface layers on the dielectric properties of NaNO2 powders
Authors: Mansingh Abhai , Rai Gulshan
Published: April 2011

The dielectric constant of sodium nitrite powders as a function of particle size in the five ranges, > 151 μm, 151–124 μm, 124–104 μm, 104–75 μm, and < 75 μm, has been measured. The measurements have been made in the temperature range 30 °C to 180 °C and in the frequency range 1 kHz to 100 kHz. A dispersion possibly due to electrode polarization has been observed at temperatures higher than 60 °C. The dielectric constant is found to decrease with decreasing particle size at and near the transition temperature, while the room temperature dielectric constant values are found to be independent of particle size. The results can be qualitatively explained by assuming the formation of a surface layer with small thickness (~ 10−5 cm) and a low dielectric constant (~ 8).
Hot electron in a polar crystal. II. Loss to single phonon modes
Authors: Hede B. , McMullen T.
Published: April 2011

A quantum theory of momentum and energy loss of a fast electron based on the eikonal approximation but including quantum interference effects is applied to a hot electron in a polar crystal. The important interaction is assumed to be the electron–polar LO phonon coupling, and this is represented by the Fröhlich polaron model. Numerical results are presented for loss, as a function of time since injection of the hot electron, to phonon modes with wave vectors parallel to the initial injection velocity. A smaller average loss rate than predicted by the golden rule is found, and quantum oscillations are seen in the time dependence of the rate.
Electron spin fine structure constants of the ã3B1 state of SO2
Authors: Hallin K.-E. J. , Hamada Y. , Merer A. J.
Published: April 2011

Rotational analyses have been carried out for the (0,0) bands of the [Formula: see text] absorption systems of S16O2 and S18O2, from high dispersion plates taken with the gases at dry ice temperature. The rotational analysis of the (0,0) band of S16O2 given by Brand, Jones, and di Lauro is confirmed in general, but their values for the anisotropic electron spin fine structure constants are found to be in error. Our new values remove the discrepancy in the sign of the spin–spin interaction parameter β = E between the gas phase work and the solid state value given by Tinti. This discrepancy had been rationalized by Brand, Jones, and di Lauro in terms of a different choice of phases for the angular momentum operators, but this argument is shown to be incorrect. The spectrum of S18O2 confirms our new values for the spin constants in detail.
Compton profiles from numerical Hartree–Fock wave functions
Authors: Benesch Robert
Published: April 2011

Nonrelativistic Compton profiles, J(q)'s, calculated within the impulse approximation from numerical Hartree–Fock (HF) wave functions are reported for the neutral atoms As (Z = 33) through Yb (Z = 70). Comparison with results reported for relativistic HF wave functions indicates that the overall effect of using the relativistic functions is to produce total J(q)'s which are flatter at the centre than those computed from nonrelativistic HF wave functions.
One-component factorization of the Klein–Gordon equation
Authors: Brownstein K. R.
Published: April 2011

A one-component factorization of the Klein–Gordon operator is presented. The role of the factorizing matrices is played by certain (non-local) spatial reflection operators.
Nuclear spin relaxation by intramolecular interactions in gases of homonuclear diatomic molecules
Authors: Bloom Myer , Beckmann Peter , Sanctuary B. C.
Published: April 2011

The differential equations which describe the relaxation of macroscopic observables associated with nuclear spins in homonuclear diatomic molecules are derived using an expansion of the nuclear spin density matrix in terms of irreducible tensors. It is shown, using an intramolecular quadrupole mechanism, that the only difference between nuclear spin relaxation of the ortho- and para-species arises from the rotational states being restricted to odd and even values. This difference is vanishingly small at high temperatures so that the relaxation equations for nuclear magnetization become identical for both species. A previous paper predicting a difference even at high temperatures is shown to be in error and is corrected.
Perturbation of the static voltage breakdown mechanism in vacuum by a weak magnetic field
Authors: Watson Alan
Published: April 2011

The theory of static high voltage breakdown initiated by field emission defines a weak magnetic field as one with insufficient strength to deflect significantly the space charge beam associated with a virtual cathode. Experimental data with uniform field copper electrodes are presented, showing that the breakdown voltage is increased when weak magnetic fields below about 0.01 T are applied, but it is progressively reduced beyond this value. The functional variation is moreover dependent upon whether the cathode is pretreated by bakeout in hydrogen or vacuum. Magneto-transport of electrons through the surface layer of oxide is shown analytically to be capable of modifying the field emission from a protrusion and so to influence the Fowler–Nordheim equation. The effect is significantly influenced by the relative magnitude of the oxide work function and that of the inner potential barrier at the underlying metallic junction. Experimental data of the magnetic perturbation of the breakdown voltage are fitted to a corresponding family of analytical curves from which a value is derived for the electron density in the oxide layer. Consistency is achieved between theory and experiment, whilst the phenomena attendant upon pretreatment and conditioning are accounted for by shifting of the Fermi level.
A unified description of spectroscopic interferences in predissociation
Authors: Laplante Jean-Pierre , Bandrauk André D. , Carlone Cosmo
Published: April 2011

A general theory of spectroscopic interferences for predissociating systems is developed using scattering theory. The introduction of complex bound states with complex eigenvalues results in a simple method for the derivation of total absorption, predissociation, and photon scattering (Raman) cross sections. The validity of other formalisms for these interferences, including Fano lineshapes, is examined and cases of spectroscopic interest are pointed out.
Résistance de surface d'alliages Pb–Bi en régime de supraconductivité superficielle
Authors: Lyon M. , Zepp G.
Published: April 2011

The magnetic field dependence of the microwave surface resistance of superconducting alloys Pb–Bi has been studied. The experimental results and the theory are compared.
Spectre d'émission du radical P2 : Etude des perturbations dans les états c3Πu et C1Σu+
Authors: Brion J. , Malicet J. , Merienne-Lafore M. F.
Published: April 2011

The analysis of the c3Πu–b3Πg system of the radical P2, in particular of the 6–0, 6–1, and 2–3 bands of this system, shows the existence of perturbations in the upper levels ν′ = 2 and 6. These perturbations are shown to be caused by the ν = 2 and 5 levels of the state C1Σu+. The deperturbation is carried out, and the constants of the states c3Πu and b3Πg are calculated. The energetic positions of these states and of the state a3Σu+ are determined. More precise values are obtained for the vibrational constants of the states C1Σu+ and X1Σg+. Most of the perturbations by the ν = 0 to 13 levels of c3Πu observed in C1Σu+ are satisfactorily interpreted. [Journal translation]
A note on the perturbation theory and the triangular well potential
Authors: Wankhede P. C. , Swamy K. N.
Published: April 2011

The integrals which appear in the first order term and the macroscopic compressibility (mc) and the local compressibility (lc) approximation for the second order term in the Barker–Henderson (BH) perturbation theory of liquids are evaluated analytically for the triangular-well potential. The compressibility factors so calculated are compared with the Monte Carlo calculations.
Fluorescence yields of double-L vacancy states produced by KLL Auger emission in tantalum
Authors: Campbell J. L. , McNelles L. A. , Geiger J. S. , Merritt J. S. , Graham R. L.
Published: April 2011

Tantalum L X-ray spectra were recorded in coincidence with KLL Auger electrons emitted in the decay of 181W. The Chalk River [Formula: see text] spectrometer was used to select individual KLL peaks. The measured X-ray fluorescence yields for five different double-L vacancy states are in agreement with theoretical values derived on the assumption that for Ta, spectator vacancies have negligible effect on the de-excitation of their partners.
Transmission through nickel and Supermalloy at 24 GHz for parallel RF and static magnetic fields
Authors: Kurn Andrew , Cochran J. F. , Heinrich B.
Published: April 2011

Microwave transmission through a 40 μm thick Supermalloy foil (d/δ = 22.5) with RF and static magnetic fields parallel, and parallel to the sample surface, revealed a distorted replica of the usual FMAR transmission signal, but attenuated 600-fold in amplitude. Transmission through a 7.2 μm thick foil of nickel gave a field-independent signal at fields greater than approximately 1 kOe in agreement with the observations reported by Lieu and Alexandrakis. This background signal was found to be consistent in strength with the signal expected for the ordinary electromagnetic wave in a ferromagnetic metal when the RF and static fields are parallel. For both foils an extra transmission signal due to ferromagnetic domain walls was observed near zero static field.
Floquet theory of Bragg interactions in an active medium with index modulation
Authors: Seshadri S. R.
Published: April 2011

The exact dispersion relation deduced from the Floquet theory for a plane electromagnetic wave progressing parallel to the sinusoidally varying permittivity in an unbounded, active medium is analyzed by singular expansions. For the first four orders of Bragg regions, the wave characteristics are deduced with attention given to their physical explanations. Correct results are reproduced for the special cases of zero modulation and zero gain.
On the ionization energies of the hydrogen molecule ion in intense magnetic fields
Authors: Lai C. S.
Published: April 2011

The variational principle with a two-parameter trial wave function is used to determine the ionization energies and equilibrium internuclear separations of a hydrogen molecule ion situated in intense magnetic fields. The results for E1 obtained are improved significantly for fields less than 3 × 1010 G. and they approach the values predicted by de Melo, Ferreira, Brandi, and Miranda for very high fields.
Effects of hydrogen impurities on shock structure and stability in ionizing monatomic gases: 2. Krypton
Authors: Glass I. I. , Liu W. S. , Tang F. C.
Published: April 2011

At shock Mach numbers [Formula: see text] in pure krypton, at initial pressures p0 ~ 5 Torr, and final electron number densities ne ~ 1017 cm−3, the translational shock front in a 10 cm × 18 cm hypervelocity shock tube develops sinusoidal instabilities which affect the entire shock structure including the ionization relaxation region, the electron-cascade front and the final quasi-equilibrium state. By adding a small amount of hydrogen (~0.5% of the initial pressure), the entire flow is stabilized. However, the relaxation length for ionization is drastically reduced to about one half of its pure-gas value. Unlike argon the stability appears to diminish with the addition of hydrogen beyond about 0.5%. Using the familiar two-step collisional model coupled with radiation-energy loss and the appropriate chemical reactions, it was possible from dual-wavelength interferometric measurements to deduce a more precise value for the krypton–krypton collision excitation cross-section, S*Kr–Kr = 1.2 × 10−19 cm2/eV, with or without the presence of hydrogen impurities. The reason for the success of hydrogen, and not other gases, in bringing about stabilized Shock waves in argon and krypton is not clear. It was also found that the electron-cascade front approached closely to the translational-shock front with increasing proximity to the shock-tube wall. This effect appears independent of the wall material and is not affected by the evolution of adsorbed water vapour from the walls or by water added deliberately to the test gas. The sinusoidal instabilities investigated here may offer some important clues to the abatement of instabilities that lead to detonations and explosions.
Two discrete forms of the inverse scattering problem
Authors: Hron M. , Razavy M.
Published: April 2011

The inverse problem for a class of quantum mechanical systems with discrete spectra is studied. First, for the case of a particle moving in a large sphere and interacting with a separable potential, it is shown that the potential can be found from the analytic properties of the eigenvalues, if they are given as the roots of a transcendental equation. The same technique is also applied for the construction of the form factor from the eigenfunctions of a two channel Wigner–Weisskopf model, when the system is enclosed in a large sphere. Then a completely different method of inversion is developed for the determination of the matrix elements of a tri–diagonal shell-model Hamiltonian. In this case the input data are the energy eigenvalues and the reduced widths. This method utilizes the continued.J-fraction expansion of a quantity which is analogous to the R-matrix of the nuclear reaction theory. The same technique is also used to investigate the exact inversion of the scattering problem, when the phase shifts are calculated by solving the finite-difference approximate form of the Schrödinger equation.
Comparison of experimental and theoretical relative intensities of the rotational lines of the (0–0) O2+b4Σg−–a4ΠU band
Authors: Lambert A. M. , Goure J. P. , Albritton D. L.
Published: April 2011

The wavelengths and relative intensities of the rotational lines of the (0–0) band of the O2+b4Σg−–a4Πu first negative system have been recorded photoelectrically with a high-resolution grating spectrometer. The wavelengths compare within 0.02 Å to those established by earlier high-resolution photographic measurements. The relative intensities are compared line-by-line to rotational line strengths computed with 4Σ and 4Π Hamiltonians containing experimentally-obtained molecular constants. For pairs of non-superimposed branches that originate from the same upper levels, the measured and calculated ratios typically agree within 5%, which is well within the experimental uncertainties.
The use of nuclear reactions and ion channeling to study trapping of Cu self-interstitial atoms by Be solute atoms in a Cu – 0.25 at.% Be crystal
Authors: Swanson M. L. , Howe L. M. , Quenneville A. F.
Published: April 2011

In a Cu – 0.25 at.% Be crystal, the 9Be(d,α)7Li and 9Be(d,p)10Be nuclear reaction yields were compared with backscattering yields of 0.6 MeV deuterons from Cu atoms at 30 K to study the irradiation-induced displacement of Be atoms from lattice sites. From an analysis of yields for [Formula: see text], [Formula: see text], and [Formula: see text] channels it was concluded that Be atoms were displaced approximately 0.13 nm in [Formula: see text] directions by the trapping of Cu self-interstitial atoms. Thus the trapping configuration was the [Formula: see text] mixed dumbbell. The Be atoms had returned to lattice sites by the end of stage III recovery (at 250 K).
Three-body annihilations of and the quark rearrangement model
Authors: Logan Robert K. , Kogitz Stephan , Tanaka Seiichi
Published: April 2011

Aphenomenological study of the quark rearrangement model is made using the results of cross section measurements of a number of [Formula: see text] annihilation reactions. The experimental data is shown to be consistent with the quark rearrangement model and Zweig's rule, if we restricted ourselves in the three-meson final states.