bluuebunny/crossref_metadata_2025 huggingface dataset:
Corner-Expansion Flow of Ionized Argon
Authors: Igra O. , Glass I. I.
Published: April 2011

The recombination rate constant for ionized argon as a function of temperature was determined by using dual-frequency laser interferometry to measure total density and electron number density in a 15° corner-expansion flow. The flow was induced by a normal shock wave in a 4 in. × 7 in. (10.2 cm × 17.8 cm) hypervelocity shock tube over a range of initial shock Mach numbers [Formula: see text] and pressures [Formula: see text] Torr at room temperature T1 ~ 300 °K, with impurity levels less than 150 parts per million.
E2/M1 Mixing Ratios of the 22+ → 21+ Gamma Transitions in 132Xe and 132Ba
Authors: Taylor H. W. , Singh B.
Published: April 2011

The E2/M1 mixing ratios for the 22+ → 21+ transitions of the 629.8–667.5 keV cascade in 132Xe and the 567.0–464.5 keV cascade in 132Ba have been determined with a Ge(Li)–NaI(Tl) directional correlation spectrometer. The δ values are[Formula: see text]The corresponding E2% admixtures are [Formula: see text] for the 629.8 keV transition and [Formula: see text] for the 567.0 keV transition.
Spin of the 4.057 MeV Level in 25Mg
Authors: Kean D. C. , Ollerhead R. W.
Published: April 2011

A gamma-ray polarization measurement has shown that the 4.057 MeV level of 25Mg has spin–parity Jπ = 9/2+ in agreement with previous speculations regarding the structure of this state. This experiment illustrates that in selected cases a single-crystal Ge(Li) polarimeter is capable of giving useful polarization information for gamma-ray energies as high as 4 MeV.
On Constructing Massive Particles out of Massless Particles in the Nambu Model
Authors: Esch Robert J.
Published: April 2011

It is possible to construct massive particles from a generalized biparticle state of massless particles in the center of momentum using the Nambu interaction. The spectrum generated is fitted to the η0+ spectrum which uniquely determines the coupling constant and a cutoff. One of the renormalized masses of the fermion field is then shown to be approximately the physical mass of the muon.
Measurement of the Intermittency Factor in Diffuser-Flow
Authors: Azad R. S. , Hummel R. H.
Published: April 2011

The intermittency factor in a thick axisymmetric boundary layer with positive pressure gradient (diffuser-flow) was evaluated with hot-wire anemometers and a multi-channel analyzer. The probability density of the signal S(t) (a space–time derivative of the streamwise velocity) is evaluated and then decomposed into three separate curves representing fluids in the turbulent, the transition, and the non-turbulent states respectively. Different values of the intermittency factor γ are calculated by taking different fractions of fluid in the transition state with the turbulent fluid. A model of flow in a conical diffuser is suggested.
Semi-Empirical Approach for Fission Fragment Energy Degradation in any Elementary Medium
Authors: Hakim M. , Shafrir N. H.
Published: April 2011

A semi-empirical equation for the electronic energy loss of fission fragments has been derived by fitting the theoretical approach of Bohr, specifically developed for heavy stopping materials, to experimental data in gases and solids in a wide range of atomic numbers. The fitting procedure was performed by choosing a different expression for the number of electrons of the medium taking part in the stopping process, which includes empirical parameters obtained by fitting to experiment.The equation enables the energy loss of fission fragments in substances of any Z2, regardless of their physical state, to be predicted to a good degree of accuracy down to energies of approximately 20 MeV.
Electron-Impact Excitation of 3s3p6nl States of Ar
Authors: Bolduc E. , Quéméner J. J. , Marmet P.
Published: April 2011

Clearly resolved structures are reported for the first time in the ionization curve of Ar between 24 and 29.5 eV. We have found the energy and the shape of the excitation cross section for several states. The negative-ion state Ar− (3s3p64s2) has also been detected.
Electron Spin Resonance of Mn2+ Impurities in Blodite
Authors: Kiggins B. , Manoogian A.
Published: April 2011

The electron spin resonance of Mn2+ impurities in natural crystals of blodite, 2(Na2Mg(SO4)2∙4H2O), was studied at ~9.2 GHz and at ~290 °K. Two differently oriented, but otherwise equivalent, magnetic complexes of Mn2+ were found. The complexes are related to each other by two-fold symmetry about the crystallographic b axis. The resonance line positions were fitted to a spin Hamiltonian of rhombic symmetry and the following parameters were determined: g = 1.9993 ± 0.0005, b20°= 334.0 ± 1.5, b22 = 260.0 ± 1.5, b40 = 1.2 ± 0.2, A = 89.0 ± 1.0, and B = 86.4 ± 0.5. The values of bnm, A, and B are in units of 104 cm−1. The magnitudes of the A and B hyperfine parameters were used to calculate covalency in crystals containing Mn2+ coordinated by mixed types of ligands. The covalency analysis was extended to crystals which contain two different sites with the same type of ligands. This analysis enabled us to determine which of the Mn2+ magnetic complexes reported for diopside belong to a Ca or a Mg site.
ρ-Dominance Electromagnetic Pion Form Factor with Vacuum-Polarization Insertions
Authors: Buchl R. A. , Nigam B. P.
Published: April 2011

The ρ-meson propagator is modified by insertions of the vacuum-polarization tensor due to charged pion pairs. The sum of all such contributing graphs via the Duffin–Kemmer formalism is seen to give a Breit–Wigner-type expression for the electromagnetic pion form factor. The width of the ρ meson is associated with the absorptive part of the pion form factor and at t = mρ2 we estimate fρππ2/4π = 2.5 using the experimental width Γρ = 125 ± 20 MeV.
Critical Examination of a Proposed Charged-Particle Stern–Gerlach Experiment
Authors: Knott Thomas F.
Published: April 2011

It has been proposed by Enga and Bloom that combined electric and magnetic helical quadrupole fields may be used to perform a Stern–Gerlach experiment on charged particles. A detailed investigation shows that the longitudinal Lorentz force due to coupling of the transverse velocity of the particles to the transverse magnetic field produces an additional focusing effect which masks the Stern–Gerlach force in large regions of initial phase space. Consideration of uncompensated magnetic fields, produced by small random variations in conductor dimensions and location, shows that the tolerances required to preserve spin separation in the useful range of initial conditions are several orders of magnitude higher than can be achieved at this time.
Spectrum of the Airglow between 3 and 4 Microns
Authors: Bunn F. E. , Gush H. P.
Published: April 2011

The spectrum of the airglow in the region of 3 to 4 microns wavelength has been measured through morning and evening twilight. A sudden drop in intensity of the Δν = 1 sequence of OH bands occurs at sunrise, with a slow recovery taking place during the day. A relatively smaller change occurs at evening twilight.
Observation of the Influence of Centrifugal Distortion of the Methane Molecule on Nuclear Spin Relaxation in the Gas
Authors: Beckmann P. A. , Bloom M. , Burnell E. E.
Published: April 2011

The spin–lattice relaxation time T1 was measured in gaseous CH4 as a function of density at room temperature between 0.006 and 7.0 amagats. T1 was found to pass through a minimum near 0.04 amagats in agreement with previous, less precise measurements. The spin–rotation interaction is the dominant relaxation mechanism in gaseous CH4. Since the spin–rotation constants are accurately known for CH4, the relaxation experiments provide a check on the theory of spin–lattice relaxation for spherical top molecules. In the conventional theory, it is assumed that the correlation function of the spin–rotation interaction is a simple exponential function of time. These experiments show that this assumption is not true for CH4 gas. The observed fine structure in the plot of relaxation rate versus density is attributed to the influence of centrifugal distortion of the CH4 molecule, which removes the degeneracy of rotational states having the same value of the quantum number J by an amount somewhat greater than the nuclear Larmor frequency of 30 MHz.
Zero Field Level Crossing in Excited States of Molecular Hydrogen
Authors: van der Linde J. , Dalby F. W.
Published: April 2011

Zero field level crossing effects have been observed in the lines emitted from the J = 1, 2, and 3 rotational levels of the [Formula: see text] state of molecular hydrogen excited in an r.f. discharge. The polarization of the R(0), R(1), and R(2) lines of the 3d1Σ → 2p1Σ(0 → 0) band as a function of magnetic field was observed to be Lorentzian, and using the Landé g factors measured by Dieke et al. yields radiative lifetimes of 2.66 × 10−8 s, 3.83 × 10−8 s, and 3.93 × 10−8 s for J = 1,2, and 3 respectively. The half-width of the level crossing curves was observed to vary linearly with pressure in the range 15 m Torr to 90 m Torr and yield collision cross sections of [Formula: see text] for all three states. The source of the discrepancy between the first and the latter two lifetimes is discussed. The lifetime of the J = 21, 3d1Π state has also been measured with less precision and yields 3.84 × 10−8 s.
On the Electronic Polarization Effect on Excitons in Insulators
Authors: Mahutte C. K. , Matsuura M. , Wang S.
Published: April 2011

The electronic polaron model and a rapidly convergent expansion in second-order perturbation theory are used to study the effect of electronic polarization on the states of excitons in insulators. The effective interaction obtained consists of two parts: a direct interaction, which contains the usual self-energy, mass correction, and Lamb shift; and an exchange (screening) interaction, the leading terms of which are closely related to the Haken–Schottky potential and a term obtained by Shindo. Our results are applied (a) to calculate exciton binding energies and (b) to investigate the electronic polarization effect on excitons for rare gas solids, making use of a variational technique. As expected, deep levels are affected less by polarization effects than the shallower levels.
Electromagnetic Wave Scattering from a Layer with a Plane Interface in Front and a Rough Interface in Back (Kirchhoff Method)
Authors: Krishen Kumar
Published: April 2011

Mathematical expressions have been developed for the average electric field and the average power density associated with an electromagnetic wave scattered from a rough layer. Furthermore, the scattering cross sections of the rough layer have been calculated upon using these expressions. The special cases of back-scattering and scattering in the plane of incidence have been treated in detail.
Quantum-Field Theoretic Analysis of Paramagnetic Spin–Lattice Relaxation
Authors: Hernández R. , Walker M. B.
Published: April 2011

The theory of the spin–lattice relaxation of dilute concentrations of paramagnetic ions (having non-degenerate energy levels) in both harmonic and anharmonic insulating crystals is formulated in terms of Green functions, and the Abrikosov diagram technique for spins is used to analyze these Green functions. A set of rate equations for the populations of the spin energy levels of a spin subjected to a low-frequency longitudinal, external magnetic field is derived using intuitive arguments, and the result of the Green function analysis is shown to be in agreement with these equations. Expressions for the transition probabilities are derived which are correct to all orders in the spin–phonon coupling, and to second order in the three-phonon anharmonic coupling. The transition probabilities for the direct process, the Orbach process, the first- and second-order Raman processes, and the anharmonic Raman process are among those obtained. The perturbation series for the transition probability is shown to be an expansion in powers of the parameters [Formula: see text] and [Formula: see text]where f′ and f″ are spin–phonon coupling constants (having dimensions of energy), εD is the Debye energy, [Formula: see text] is the mean square atomic displacement, and a0 is the lattice constant. The diagrammatic method used here has three major advantages over the decoupling procedures previously used to analyze spin–phonon Green functions. (1) Approximations are made by expanding in powers of a small parameter, (2) contact is made with an intuitive formulation of the rate equations, and (3) formulas valid to all orders in the spin–phonon interaction are obtained. An appendix is added which clarifies some existing ideas concerning the Orbach process.
Propagation of Ion Acoustic Waves from and to a Spherical or Cylindrical Conductor
Authors: Schott L.
Published: April 2011

Analytic expressions for the spatial variation of the phase velocity and amplitude of ion acoustic waves propagating radially through the plasma boundary layer at a conducting sphere or cylinder are derived using the two-fluid model. The Debye length is assumed to be small compared with any relevant dimension of the problem and the wavelength small compared with the radius of the conductor. The limits of ion mean free paths small and large compared with the radius of the sphere are considered. In the cylindrical case only the collisionless limit has a self-consistent solution. It is found that both the converging and the diverging waves are damped and that the phase velocity of the wave is approximately equal to the sum of the ion acoustic velocity in a homogeneous plasma and the ion drift velocity. The contribution of Landau damping to the total damping is estimated.
Transition Probabilities of the 35.5, 428, and 463 keV Transitions in 125Te
Authors: Satyanarayana G. , Lakshminarayana V. , Murty D. S.
Published: April 2011

The lifetimes of the 35.5 and 463 keV states in 125Te, populated in the beta decay of 125Sb, are determined employing a time-to-pulse-height-converter arrangement. The half-life of the 35.5 keV state, determined by the slope method, yielded a value 1.51 ± 0.05 ns. The mean life of the 463 keV state, determined by the centroid-shift technique, yielded a value (3.8 ± 1.1) × 10−11 s. This value is in complete disagreement with the previous delayed-coincidence results and is in agreement with the recent Coulomb-excitation experiments. The present experimental values are employed to estimate the M1 and E2 transition probabilities of the 35.5, 428, and 463 keV transitions, and are compared with the values obtained from the single-particle estimates. De-Shalit's core-excitation model is found to be not applicable for the present case. The theoretical values estimated using the wave functions of Kisslinger and Sorensen are found to be unsuitable for the estimation of the transition probabilities. The experimental values are therefore employed to obtain phenomenological wave functions for the ground, 35.5 keV, and 463 keV states. The resultant wave functions show sizable parts of the 5/2+ phonon contribution in both the ground and 35.5 (3/2+) keV states, while the 463 keV state contains a dominant 3/2+ phonon contribution.
Fluctuations in Drift Velocity of High-Field Domains in n-GaAs
Authors: Hart L. G.
Published: April 2011

A source of frequency-modulation (FM) noise in a free-running Gunn diode, due to fluctuations in valley population in the accumulation layer, is investigated using the results of recent Monte-Carlo high-field transport studies.
New Electronic Transitions of SiO
Authors: Cornet R. , Dubois I.
Published: April 2011

A new 3Πi–a3Πr transition of SiO is observed in the region 3700–3950 Å. The vibrational and rotational analysis gives the following constants for the upper 3Πi state (in cm−1)[Formula: see text]Another transition is also observed at about 2950 Å, which could be identified as a 3Σ+–a3Πr transition. Electron configurations are discussed.
Spin-Wave Excitations in Manganese Carbonate
Authors: Holden T. M. , Svensson E. C. , Martel P.
Published: April 2011

The dispersion curves for spin waves propagating along the [0, 0, ζ], [ζ, ζ, ζ, 0], [ζ, ζ, ζ], [–ζ, –ζ, 2ζ], and [ζ, ζ, 1.5–2ζ] directions in MnCO3 at 4.6 °K have been determined by neutron inelastic scattering. The maximum spin-wave frequency is 0.95 ± 0.02 THz. Theoretical expressions for the spin-wave frequencies in MnCO3 are developed, and the interatomic exchange interactions determined by least-squares analysis. The dominant exchange interaction is the nearest-neighbor intersublattice interaction, J1 = −0.0290 ± 0.0011 THz. The next-nearest-neighbor intersublattice interaction, J2 = −0.0029 ± 0.0004 THz, and the nearest-neighbor intrasublattice interaction, [Formula: see text], are almost an order of magnitude smaller, and other interactions are negligible within experimental error.
On the Role of N Mixing in Nuclear Problems using Nilsson's Model
Authors: Trainor L. E. H. , Turner R. J. , Tam Genevieve , Rosen L.
Published: April 2011

The importance of major shell mixing in Nilsson's model is discussed with reference to calculations using Nilsson wave functions as a basis set. In particular it is shown that the N-mixing terms play an essential role in shaping the density distribution and are of paramount importance in determining electric quadrupole moments. Our calculations also suggest that for each choice of deformation parameter there is an associated characteristic "shell structure".
Spatially Resolved Gain Measurements in a CO2 Amplifier
Authors: McQuillan A. K. , Carswell A. I. , Jammu K. S.
Published: April 2011

Spatially resolved gain measurements at 10.6 μm have been made transverse to the discharge in an axially flowing CO2 laser amplifier. The composition of the amplifier medium has been varied to include initially pure CO2, binary mixtures of CO2:CO, CO2:He, and CO2:N2, and triple mixtures of CO2:N2:He. Strong spatial variations of gain are observed which depend on the gas mixture, flow rate, temperature, pressure, and current. Corresponding spatial intensity profiles of the sidelight emission of CO2 at 4.3 μm are shown.
Anisotropy in the Dicke Narrowing of Rotational Raman Lines (A New Measure of the Nonsphericity of Intermolecular Forces)
Authors: Gupta B. K. , Hess S. , May A. D.
Published: April 2011

The diffusion coefficient characterizing the Dicke narrowing of the rotational Raman lines, in general, depends on the polarizations of the incident and scattered light and on the scattering angle. Experimental results for the anisotropic diffusion coefficient are presented for 90° scattering and vv and vh polarizations of the S0(1) line in gaseous hydrogen. The physical interpretation of the observed anisotropy is given with the help of a simple collision model.
Soft-Photon Cross Sections for π−d → nnγ
Authors: Picciotto Charles
Published: April 2011

A phenomenological calculation of cross sections for the reaction π−d → nnγ for pion lab energies of 150–300 MeV is presented.
Second-Order Raman Spectra of Fluorites. I. Critical Point Analysis
Authors: Krishnamurthy N. , Soots V.
Published: April 2011

With the use of a high-powered Ar+ laser and conventional photon counting techniques it has been possible to observe the second-order Raman spectra of single crystals of CaF2, SrF2, BaF2, and PbF2. The symmetries of the various parts of the spectra of the latter two were determined by using oriented single crystals of these two fluorides. The main features of the observed spectra have been analyzed, with the aid of group-theoretical selection rules, in terms of calculated phonon frequencies at the critical points of the Brillouin zone of these crystals.
Complete Electron Spin–Spin Contact Interaction in Atoms with fn Configurations
Authors: Saxena K. M. S. , Lo B. W. N. , Fraga S.
Published: April 2011

The total electron spin–spin contact interaction, including both the inter and intrashell contributions, has been evaluated from existing numerical Hartree–Fock functions, for the ground states of the neutral atoms and doubly and triply charged positive ions from La to Yb.
Analysis of Wire Antennas in the Presence of a Conducting Half-Space. Part I. The Vertical Antenna in Free Space
Authors: Miller E. K. , Poggio A. J. , Burke G. J. , Selden E. S.
Published: April 2011

An integral equation method (based upon the electric field) for the analysis of a vertical antenna located in free space near the interface with a lossy half-space is presented. Two methods are considered to account for the influence of the interface-reflected fields upon the antenna current distribution: (1) the rigorous Sommerfeld integral approach and (2) a plane-wave reflection coefficient approximation. Numerical results for antenna impedance from the two methods are compared. It is found that for the parameter variations studied, the reflection coefficient approximation provides results within 10% of those obtained from the rigorous approach at approximately 1% of the computer time. The reflection coefficient technique has the further advantage of being readily extended to arbitrary antenna geometries and orientations.
A Dielectric Loss Model Based on Interfacial Electron Tunneling
Authors: Wilcox P.
Published: April 2011

A dielectric loss model based on the tunneling of electrons from metal electrodes into traps in the insulator near the interface is described. The temperature dependence of the losses is controlled primarily by the energy distribution of the traps and the frequency dependence is controlled by their spatial distribution. Traps distributed uniformly in both energy and space result in essentially temperature- and frequency-independent losses. The model predicts an inverse dependence of losses on sample thickness. The step-response currents for the tunnel mechanism become nonlinear at high applied fields; however, the detailed behavior is very sensitive to the trap distribution assumed. For a particular trap distribution it is possible to have a polarity-dependent, irreversible step response.
Acoustic Diffraction of a Plane Wave by Two Coplanar Parallel Perfectly Soft or Rigid Strips
Authors: Jain D. L. , Kanwal R. P.
Published: April 2011

The problem of diffraction of a normally incident plane acoustic wave by two parallel and coplanar infinite strips is considered. The assumed boundary conditions on the strips are the vanishing of either the total wave function or its normal derivative. Expressions are obtained for the first few terms of the series for the far-field amplitude and the scattering cross section when the wavelength is much larger than the distance between the outer edges of the strips. The corresponding results for two parallel and coplanar infinite slits in a soft or a rigid screen follow by applying Babinet's principle. This analysis also gives the transmission coefficients for the case of two infinite parallel slits in a thin conducting screen when the electric or magnetic field vectors of the incident plane monochromatic waves are polarized parallel to the edges of the slits.
Fluctuating Properties of Gaussian Light Beams in an Atmosphere
Authors: Imai Masaaki
Published: April 2011

Fluctuations of a Gaussian light beam propagating through an atmosphere, whose refractive index inhomogeneities are assumed to obey the Kolmogorov's law, are discussed statistically from the viewpoint of mode conversion. The results obtained here are concerned with the dependence of the mode conversion on beam shape parameters (beam spot size and radius of wave front curvature), propagation distance, and medium turbulence features. The mode conversion increases proportionally to the propagation distance z in the near-field region of a transmitting aperture and then to 8/3 powers of z in the far-field region. The mode conversion also increases according to 5/3 powers of the beam spot size s at a short distance, while it decreases for a large spot size at a long distance. Studies on wave front curvature are also done. Near the focal point of a focused beam, the reduction effect of the mode conversion appears.
Ray Tracing over a Transequatorial Path
Authors: Gerson N. C.
Published: April 2011

Ray tracing procedures including the magnetic field were employed in an attempt to explain the mechanism of transequatorial propagation. The analysis was based upon (a) 41 MHz backscatter soundings south from Mayaguez, Puerto Rico and (b) vertical-incidence observations from the ionosonde chain near 75 °W. The latter were converted into electron density versus true height profiles. Data from both sources obtained during the same month were utilized.The computed ray tracings show the expected effects for refraction from the F layer: skip and horizon focusing, predawn blackout (0200–0600 LST), escape of all rays launched above 18° irrespective of time of day, diurnal variation in one-hop propagation distances, etc. Some calculated rays attain TE distances (6000–11 000 km without intervening ground reflections) at 0800 LST, 1600–2000 LST and 2400 LST. Others are trapped to distances exceeding 11 000 km at 0800 LST and 1400–2400 LST. Fair agreement is found between TE observations and TE calculated ray paths. Specific hours and distances showed some correlation. Qualitatively the general features of TE seem clarified. The calculations imply that rays launched within 9° of the horizon southward across the (magnetic) equator are responsible for TE propagation. These rays are injected into an ionospheric trapped mode by a strong electron density gradient. For a ray launched at the ground to propagate to TE distances, two requirements must be satisfied: (a) vertical refractivity gradients propitious for radiowave trapping, and (b) horizontal refractivity gradients allowing injection and ejection of the ray into and out of the duct. TE concurrences near 0800 LST may arise because of the rapid strengthening of the postsunrise electron density gradient near 20° geomagnetic. This strong horizontal gradient then disappears, possibly because of an atmospheric expansion, and does not reappear until late afternoon. The trapping conditions, however, remain from about sunrise to midnight.The results imply that at the same or a higher frequency more TE would be observed if more energy was emitted at lower launch angles.
On the Theory of Transient Electromagnetic Sounding over a Stratified Earth
Authors: Wait James R.
Published: April 2011

Electromagnetic transient coupling between two small ungrounded loops is considered for the case where the earth is a two-layer conducting half-space. The formal solution for the impulse response is approximated with special attention to the initial stages of the time function. Various limiting cases are also considered. It is shown that the most convenient scheme for interpretation is when the two loops are raised above the earth's surface.
Rotational Analysis of the A1Σ+ → X1Σ+ and B1Π → X1Σ+ Systems of 24MgH+, 25MgH+, and 26MgH+
Authors: Balfour W. J.
Published: April 2011

Previous analyses of the A1Σ+–X1Σ+ and B1Π–X1Σ+ systems of 24MgH+ have been extended. Dunham coefficients and RKR potential energy curves have been determined for the A and X states. Franck–Condon calculations based upon these curves show improved agreement between theory and experiment for the A–X transition. Measurements on the stronger bands of 25MgH+ and 26MgH+ are also reported.
EPR Spectrometer Sensitivity Calculations
Authors: Buckmaster H. A. , Skirrow J. D.
Published: April 2011

The physical basis for the definition of noise performance is reexamined with the object of providing an unambiguous derivation of the system noise figure for a reflection-cavity EPR spectrometer incorporating a preamplifier when the sample cavity is at an arbitrary temperature.
Mössbauer Study of the Ferrimagnetic Spinel FeCr2S4
Authors: Spender M. R. , Morrish A. H.
Published: April 2011

The normal spinel Fe[Cr2]S4 has been studied using the Mössbauer effect. Spectra have been collected over the temperature range 2–500 °K. Results are presented for the quantity [Formula: see text], the hyperfine field, and the isomer shift. We find that the magnetically split spectra can be fitted using a zero value of the asymmetry parameter over the temperature range 7–170 °K. But for [Formula: see text] an asymmetry parameter is required to fit the spectrum. Experiments in applied fields at 7 and 81 °K show that the quadrupole interaction is not produced by a crystallographic distortion. Attention is drawn to features of the spectra which suggest the presence of relaxation effects in the compound. The isomer shift shows deviations from the Debye model behavior. A model, which allows explanations of the observations, is proposed.
Surface Tension of Helium II Films
Authors: Chan S. L.
Published: April 2011

The contribution from surface wave modes to the temperature behavior of the surface tension of both saturated and unsaturated helium II films has been considered. It is found that in saturated films the surface tension has a T2dependence and this comes solely from capillary wave modes. The result holds in the approximate temperature range 10−6 °K < T < 0.8 °K. For [Formula: see text] and for very thick saturated films, Atkins' expression for the surface tension of bulk helium II is obtained. In thin unsaturated films the surface tension varies as T2 at relatively high temperatures when capillary modes still dominate the surface excitations and when the normal component is totally locked to the substrate. Below a certain temperature, which depends on the film thickness, third sound waves become predominant and the surface tension varies as T3.
Photoalpha Reactions in the Region Z = 22 – 30
Authors: Keller N. A. , McConnell D. B.
Published: April 2011

The yields and angular distributions of photoalphas from seven elements in the region Z = 22–30 were investigated experimentally. Strong anisotropies in the angular distributions from the even–even nuclei were observed. Improved statistical model calculations using the known spins and parities of the low lying levels of the even–even daughters give good agreement with the experimental results.
Low-Lying Structure and Inelastic Scattering of Cu Isotopes in a Unified Model
Authors: Castel B. , Johnstone I. P. , Singh B. P. , Stewart K. W. C.
Published: April 2011

The odd-Cu isotopes are examined in a model which couples quasi-particle states to anharmonic vibrations of neighboring Ni cores. The f7/2, f5/2, p3/2, and p1/2 orbitals are available and the core properties are taken directly from the experimental spectrum of the Ni isotopes. The results are compared with experimental estimates as well as with a recent shell model calculation. The inelastic scattering cross sections for protons on 65Cu are also discussed within the framework of this model.
Resonant Cavities that are Frequency Insensitive to Axial Elongation
Authors: Aboul-Atta O. A. , Tomchuk E.
Published: April 2011

Microwave power is used to accelerate particles by allowing them to pass through a structure of coupled cavity resonators (standing wave linear accelerators). To accelerate the particles to high velocities over a short length, these accelerators must have a nonperiodic structure because the cell length ought to vary gradually according to the particle velocity. As the resonance frequency of all cells must be the same, the search for those particular cells that are frequency insensitive to axial elongation is of considerable importance. This phenomenon is found in some cylindrically symmetric cavities which are also symmetric about a middle plane perpendicular to the axis of symmetry (meridian of symmetry). They can be stretched axially by an additive cylindrical (tube) section in the middle without need for retuning provided that the average electromagnetic energy is perfectly balanced at that middle plane. Also the work presented here yields the theoretical answers to both the justification of the frequency insensitive phenomenon and the existence of such resonant cavities. As the mathematical conditions are related to the balance of the electromagnetic energy density at the meridian of symmetry, they are concurrently interpreted physically.
Diagonal and Off-Diagonal Hyperfine Structure in the Ground Multiplets of Boron and Aluminum by the Atomic Beam Method; Magnetic Dipole Radial Parameters
Authors: Harvey J. S. M. , Evans L. , Lew H.
Published: April 2011

The magnetic resonance spectra of the ground 2P multiplets of 11B and 27Al have been remeasured by the method of atomic beams and the coupling constants A3/2, B3/2, and gJ(2P3/2) and gJ(2P1/2) for 11B, and A1/2 for 27Al, have been redetermined to higher precision. Measurements have also been made, by the triple resonance method, of two ΔMJ = 0, ΔMI = ± 1 transitions in both 11B and27 Al and from these the off-diagonal magnetic dipole coupling constants A3/2,1/2 have been determined.These measurements have enabled us to evaluate the magnetic dipole radial parameters [Formula: see text], [Formula: see text], and [Formula: see text] for both boron and aluminum. The departures of [Formula: see text] and the ratio [Formula: see text] from their restricted Hartree–Fock values are plotted as functions of the occupation number N for all elements with (2p)N and (3p)N ground configuration for which data are available. The trends are briefly discussed.
Properties of Superconducting Alloys Containing Paramagnetic Impurities with Local States within the Gap
Authors: Chaba A. N. , Nagi A. D. Singh
Published: April 2011

Using the Green's function given by Shiba or Rusinov, we have calculated several properties of superconducting alloys containing paramagnetic impurities and having local states within the gap. At temperatures equal to zero, near zero, and near Tc, the analytic expressions for the order parameter and various thermal properties are given. For various values of ε0 (the normalized position of a local state with a single impurity), the dependence of the zero temperature order parameter and the zero temperature critical field on the inverse spin-flip collision time are computed. Further, for various values of ε0, the impurity-concentration dependence of the zero temperature order parameter, the transition temperature, the zero temperature critical field, and the jump in specific heat at Tc are computed. Some of our results would also apply to superconducting Kondo systems.
Performance and Limitations of Shock Tubes with Imploding Detonation Drivers
Authors: Redfern P. , Ahlborn B.
Published: April 2011

Strong shock waves have been generated in a diaphragm shock tube using an imploding detonation driver of conical geometry. In comparing the performance of the conical driver to a Chapman–Jouguet detonation driver we have found that the conical driver provides comparable Mach numbers at considerably smaller ratios of driver to test gas filling pressures. For example Mach 10 was reached at a pressure ratio of 25 in the conical driver while a ratio of 100 is required to produce Mach 10 in a Chapman–Jouguet driver. In theory the Mach number available from a conical driver is expected to increase without bounds as the ratio of driver cone base to test tube diameter. A simplified model for this scaling is discussed and compared with experimental data. In addition an investigation of Mach number and shock attenuation versus cone slant angle is carried out in order to optimize the driver geometry.
Drift Instability in Plasmas with Nonuniform Macroscopic Rotation Profiles
Authors: Caplan M. , Capjack C. E. , James C. R.
Published: April 2011

The drift instability is examined in a collisionless low β plasma in the presence of nonuniform radial electric fields in the limit where charge neutrality cannot be assumed. A numerical solution and a Weber–Hermite approximation for the resulting differential equation describing the drift instability are presented.
Quadrupole Interaction of 181Ta in Hafnium Oxychloride
Authors: Zmora H. , Lowe L. M. , Prestwich W. V.
Published: April 2011

The static electric quadrupole interaction of 181Ta in HfOCl2∙8H2O and HfOCl2∙4H2O, incorporating the perturbed angular correlation of the 133–482 keV γ-rays cascade, has been measured. The quadrupole interaction frequencies obtained were ω1 = (1356 ± 65) mrad/s for HfOCl2∙8H2O, and ω1 = (858 ± 40) mrad/s, η = 0.58 ± 0.01 for HfOCl2∙4H2O. Comparison with other measurements is given.
The Fundamental Infrared Absorption Band of Ortho-Enriched Solid Hydrogen
Authors: Boggs S. A. , Clouter M. J. , Welsh H. L.
Published: April 2011

Spectra of the infrared fundamental band of solid hydrogen with orthohydrogen concentrations in the range 75 to ~99% were recorded at 1.05 and ~5 K, i.e. below and above the order–disorder phase transition which occurs at 2.8 K for pure o-H2. The effect of "impurity" para molecules in the o-H2 lattice could thus be studied with and without orientational ordering of the o-H2 molecules. The zero-phonon Q1, S1(0), and S1(1) features are of particular interest, and are interpreted in terms of travelling vibrational, rotational, and orientational excitations (vibrons, rotons, and librons). The Q branch for ~100% o-H2 in the ordered state shows a structured side band, shifted by ~6–26 cm−1 from the Q1(1) frequency and due to one- and two-libron excitations; in the disordered state this becomes a Boltzmann-modified band of half-width 12 cm−1, centered at the Q1(1) frequency, and due to predominantly low-energy orientational transitions of interacting o-H2 molecules. The S1(0) group of maxima in the ordered state is interpreted as the superposition of the transitions, Q1(1) + S0(0) and Q1(1) + S0(0) + libron, where Q1(1) is an o-H2 vibron and S0(0) is the localized rotational transition of an impurity p-H2 molecule, the J = 2 level of which is split into three sublevels by the C3i field of the Pa3 crystal structure.
On Conformally Covariant Spinor Field Equations
Authors: Drew Mark S.
Published: April 2011

Conformally covariant equations for free spinor fields are determined uniquely by carrying out a descent to Minkowski space from the most general first-order rotationally covariant spinor equations in a six-dimensional flat space. It is found that the introduction of the concept of the "conformally invariant mass" is not possible for spinor fields even if the fields are defined not only on the null hyperquadric but over the entire manifold of coordinates in six-dimensional space.
The (ν1, 2ν2) Vibron–Phonon Infrared Absorption Band of Solid CO2
Authors: Mannik L. , Allin Elizabeth J.
Published: April 2011

The infrared absorption spectrum of thick samples of solid CO2 (~4 mm path length) has been investigated in the frequency range 1100–1600 cm−1 at temperatures from 88 to 160 K. The (ν1, 2ν2) Fermi doublet is inactive because of the crystal symmetry but absorption is observed with maxima at the frequencies ν1 ± ai, 2ν2 ± ai(i = 1, 2, 3, 4). At 88 K the values of ai are 60, 75, 95, and 108 cm−1; at lower temperatures the maxima are sharper and the ai greater. These four frequencies correspond to maxima in the phonon frequency distribution. The agreement with existing theoretical calculations is not good; there is better agreement with the zone boundary frequencies determined for two symmetry directions by inelastic neutron scattering experiments. The present results are consistent with previously observed combinations with the allowed ν2 and ν3 internal modes.
The Lifetimes of the 3/2+, 975 keV Level in 25Mg and the 3/2+, 945 keV Level in 25Al
Authors: Alexander T. K. , Häusser O. , McDonald A. B. , Ewan G. T.
Published: April 2011

The 3/2+, 975 keV level in 25Mg and the 945 keV level in 25Al were populated in the 2H(24Mg,pγ)25Mg and 2H(24Mg,nγ)25Al reactions respectively and their mean lifetimes for gamma-ray decay were measured by the recoil-distance method. The mean lifetime of the 975 keV level in 25Mg is 14.6 ± 1.5 ps and that of the 945 keV level in 25Al is 6.2 ± 1.6 ps. Using previously measured branching and mixing ratios, the absolute M1 and E2 transition probabilities have been obtained and are compared with predictions of the unified model.
Nonlinear Boundary-Value Problem for a Conducting Source Flow in an Inhomogeneous Magnetic Field
Authors: Wilhelm H. E.
Published: April 2011

A closed form solution in terms of elliptic functions is given for a nonlinear boundary-value problem describing a conducting viscous fluid, which flows between plane divergent walls across an azimuthal magnetic field. The conducting fluid is injected through an inner circular section (source) and removed downstream through an outer circular section (sink). The magnetic field has its sources in an external current flowing parallel to the line at which the extended walls would intersect. It is shown that the flow exhibits regions of forward and backward fluid motion in the general case. The separation of the boundary layer occurs if the angle of inclination of the walls is larger than a critical value, which depends on the source or sink strengths of the flow and the magnetic field current. Separation is inhibited by the magnetic field at sufficiently large Hartmann numbers.
The Magnetic Moment of 59Fe
Authors: Daly P. W. , Gorling R. L. A. , Martin P. W. , Turrell B. G.
Published: April 2011

We have attempted to measure γ-ray anisotropies from 59Fe nuclei oriented in pure iron. The negative result allows us to put a limit of 0.9 n.m. on the magnetic moment.
Fast Neutron Cross Sections in the 2S–1D Shell
Authors: Norman G. R. , Prestwich W. V. , Kennett T. J.
Published: April 2011

Total neutron cross sections for six elements in the 2S–1D shell have been measured in the energy region 0.8–3.0 MeV using a new method. The experiment utilizes the fast neutron flux from a nuclear reactor with the neutron energies being determined by a measurement of their time of flight.From the present results the resonance parameters for aluminum have been determined and examined in the context of earlier low energy results for this element. The observed widths, which range to greater than 100 keV, are found to be consistent with compound nucleus formation when the reduced widths are compared with the corresponding low energy data. It is concluded that the observation of resonances with large widths is not sufficient to discount compound nucleus formation.
Beam–Foil Studies of Oxygen Below 2000 Å
Authors: Lin C. C. , Irwin D. J. G. , Kernahan J. A. , Livingston A. E. , Pinnington E. H.
Published: April 2011

Oxygen spectra between 1050 and 1800 Å were studied by the beam–foil technique. Mean lives were obtained for 22 levels in OI–OV. Some amended mean lives from studies below 650 Å are also given.
Flow Stress and Yield Point Observations on Normal and Superconducting Indium and Lead
Authors: Hutchison T. S. , McBride S. L.
Published: April 2011

Measurements of the plastic flow stress and 30 MHz ultrasonic attenuation in normal and superconducting 99.9999% pure In and Pb are presented. For both In and Pb, with a strain rate of 10−5 s−1, the attenuation change Δαsn takes about 3 s while the related flow stress change Δσsn takes about 30 s. In indium Δαns and Δσns are completed in about 40 s; in Pb the corresponding times are about 3 s or less. Experimental evidence is presented which shows unequivocally that the dislocation arrangements in the normal and superconducting states are different.
Phonon Dispersion in ZnSe
Authors: Irwin J. C. , LaCombe J.
Published: April 2011

Second-order Raman spectra have been obtained from oriented single crystals of ZnSe. The spectra have been interpreted and the results have been used to determine the zone boundary frequencies at the critical points X, L, and W. The resulting set of frequencies are consistent with known polarization selection rules and with a theoretical model. The frequencies in turn serve to determine the parameters in the theoretical model and the resulting model has been used to calculate the phonon dispersion throughout the Brillouin zone, the density of states, and the specific heat. The results are compared to the small amount of experimental data that is available.
Analysis of Wire Antennas in the Presence of a Conducting Half-Space. Part II. The Horizontal Antenna in Free Space
Authors: Miller E. K. , Poggio A. J. , Burke G. J. , Selden E. S.
Published: April 2011

An integral equation approach for the analysis of a horizontal wire antenna(s) located in free space near a lossy half-space is described. Two methods, a rigorous one based upon the Sommerfeld formulation and an approximation technique involving the Fresnel plane-wave reflection coefficients, are used to account for the influence of the interface-reflected field upon the antenna current distribution. A moment method (subsectional collocation) solution procedure is used to obtain numerical results for antenna impedance and radiation patterns. The reflection coefficient approach is found to agree well (generally within 10%) with those due to the rigorous method at a fraction (approximately 1%) of the computer cost.
Levels in 89Rb Populated by the Beta Decay of 89Kr
Authors: Poehlman W. F. S. , Singh B. , Johns M. W.
Published: April 2011

The decay of 3.2 min 89Kr has been investigated with small and large volume Ge(Li) detectors used singly and in a dual parameter coincidence arrangement. A total of 162 gamma rays are identified with the decay of this isotope, 120 of which are placed in a level scheme on the basis of gamma–gamma coincidence evidence and the energy differences between established levels. Levels at 220.9, 497.7, 577.3, 586.1, 930.7, 931.5, 997.6, 1195.5, 1324.6, 1530.1, 1533.6, 1694.1, 1822.1, 1998.9, 2160.5, 2401.5, 2598.5, 2867.2, 3099.7, 3329.9, 3363.1, 3372.1, 3534.1, 3719.3, 4145.1, 4217.4, 4340.9, and 4487.5 keV are well established by coincidence data and many energy sums. The levels proposed at 2783.4, 3429.7, 3456.6, 3978.4, 4058.4, and 4406.5 keV are less securely established. The most probable spins of the ground state and the first two excited states arc 3/2−. 5/2− and 1/2− respectively. Improved energies and intensities of the gamma rays from the decay of 15 min 89Rb have also been determined.
Multi-Modal Transient Excitation Effects in an Infinite, Parallel-Plate Wave Guide
Authors: Dudley D. G. , Quintenz J. P.
Published: April 2011

An analysis of higher-order mode effects in a parallel-plate wave guide is presented. Green's functions for the wave guide are derived in the frequency domain which can be inverted analytically to give the step function response for the TM modes and the delta function response for the TE modes. Plots of the responses are given for different excitation functions and the results are interpreted physically at various locations in the structure.
On the Geometry of the Insulating Barrier in Thin Film Tunnel Junctions
Authors: Adler J. G. , Kreuzer H. J.
Published: April 2011

We discuss an experiment to obtain information about the geometry of the insulator in tunneling junctions.
Backscattering of Electromagnetic Waves from a Rough Surface Model
Authors: O'Kelly P. D. , Kharadly M. M. Z.
Published: April 2011

A model of a rough surface, perfectly conducting identical hemispherical humps on a perfectly conducting plane, was constructed and tested through scanning the surface with a 35 GHz microwave beam. The surface statistics were controlled in accordance with a specially developed coordinate distribution function that gave a good approximation to a uniform distribution and took into account the finite size of the scattering objects. The results of a statistical analysis of experimental data were compared with similar results from a Monte-Carlo simulation and sources of errors in both cases were discussed.
Development of the Asymptotic Action Principle
Authors: Pugh Robert E.
Published: April 2011

The action principle for asymptotic quantum field theory is discussed in greater detail. A corollary is derived and an interpolating generator is developed.
A Test of Scaling Theory on the Critical Isotherm
Authors: Betts D. D. , Filipow L.
Published: April 2011

Using recently extended data of Sykes et al. on the high field expansion of the free energy of the two-dimensional spin-1/2 Ising model the critical behavior of the magnetization and its first six temperature derivatives are examined on the critical isotherm. The estimates of the critical exponents and the critical amplitude ratios are found to be in reasonable to excellent agreement with scaling theories.