bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of pressure on magnetic phase transitions of europium chalcogenides: EuO, EuS, and EuSe
Authors: Srivastava V. C. , Stevenson R.
Published: April 2011

The effect of pressure on magnetic transitions of EuS and EuSe is reported up to 10 kbars. The compressibilities of EuO, EuS, and EuSe have been measured at 4.2, 82, and 300 °K for the same pressure range. The shift in the transition temperature of these materials has been measured through the mutual inductance of an astatic coil assembly containing the sample. Values of dTc/dP = +0.20 × 10−3 °K/bar for EuS and of dTN/dP = +0.16 × 10−3 °K/bar for EuSe have been obtained. Combining the compressibility measurements with dTc−N/dP the values of dTc−N/da = −290, −102, −68 °K/Å are obtained for EuO, EuS, and EuSe respectively, where a is the lattice parameter. These values of dTc/da for EuO and EuS are about three and two times the values derived from the plot of paramagnetic Curie temperature versus lattice parameter given by McGuire and Shafer. This difference is thought to be due to variations in covalency in going from oxide to selenide. For EuSe the value of dTN/da is in rough agreement with the value obtained by McGuire and Shafer. It is observed that volume dependence of magnetic exchange interactions in these solids deviates strongly from that of common superexchange materials; the magnetic Grüneisen constant is measured to be[Formula: see text]for EuO, EuS, and EuSe respectively. On the basis of recent theoretical models proposed for these materials, it is suggested that for EuS and EuSe the magnetic expansivity αmc should be proportional to the magnetic specific heat cm near the transition temperature according to the relation dTc/dP = 3TcVαmc/cm. The ratio αme/cm is estimated from the present measurements.
High-altitude observations of a luminous wake behind two Black Brant II rockets
Authors: Wallis D. D. , Anger C. D.
Published: April 2011

Measurements of a luminous region following two Black Brant II rockets are presented. This luminous region or wake appears as a circular cone of half angle 4° and length less than 1 km lying along the trajectory of the rocket, with vertex near the rocket. The wake was observed between 80 and 115 km at 4278 Å, but was not observed at 5577 Å.
Isobaric splitting of 1− levels in nuclei
Authors: Bergeron J. , Goulard B. , Venter R. H.
Published: April 2011

Isospin fragmentation of the dipole excitations of nuclei with neutron excess is discussed. Simple expressions are derived for the energy splitting and for the sharing of dipole strength between the two isospin components. The effect of relaxing some assumptions is investigated. The case of 90Zr is taken as an illustration.
Lifetimes and decay of the 2.07 MeV triplet in 26Al
Authors: Häusser O. , Anyas-Weiss N.
Published: April 2011

Gamma rays from resonances at Ep = 956, 1199, 1287, and 1701 keV in the reaction 25Mg(p,γ)26Al have been studied using 40 cm3 and 25 cm3 Ge(Li) detectors. Accurate γ-ray energy determinations and Doppler shift measurements indicate the existence of three levels at excitation energies of 2068.7, 2069.5, and 2071.7 keV. The level at 2068.7 keV has a mean lifetime of [Formula: see text] and decays 29% to the ground state, and 71% to the 416.6 keV level. The 2069.5 keV level has a mean lifetime of (1.3 ± 0.5) × 10−14 s and decays 5% to the 228.2, 22% to the 416.6, and 73% to the 1057.7 keV levels. The level at 2071.7 keV has a lifetime of [Formula: see text] and decays to the 228.2 keV (> 65%) and the 1057.7 keV (< 35%) levels. An upper limit of τ < 10−14 s has been placed on the lifetime of the 3159.4 keV level and the mean lifetime of the 1850.8 keV level has been measured to be (1.6 ± 0.7) × 10−14 s.
Infinite cylindrical antenna in a uniaxial compressible plasma
Authors: Miller Edmund K.
Published: April 2011

Numerical values are given for the admittance of an infinite cylindrical antenna in a uniaxial plasma, taking into account both plasma compressibility and a vacuum sheath. The susceptance is found to exhibit no significant sheath or compressibility dependence above the plasma frequency (ƒp) and only a slight dependence on these factors below ƒp. The conductance behavior shows no significant influence of compressibility or sheath in the range centered about ƒp, in which it is relatively constant in value except for a slight minimum at ƒp.
Effects of the interaction between 3d8 4p and 3d9 configurations of the Cu2+ ion under Td symmetry
Authors: Chatterjee R.
Published: April 2011

The admixture of the 3d8 4p configuration into the ground state 3d9(2D, Γ3 and Γ5) of the Cu2+ ion under Td symmetry has been calculated by using Racah formalism. The shift in the Γ3 and the Γ5 energy levels due to this configuration interaction effect has also been evaluated.
Dielectric properties of normal, reduced, and specially reduced rutile (TiO2) single crystals at room temperature
Authors: Lal H. B. , Srivastava K. G.
Published: April 2011

The variation of the dielectric constant (ε′) and the dielectric loss (ε″) have been studied as a function of frequency (102 to 1010 c.p.s.) for normal (as grown), reduced (heated in vacuum), and specially reduced (heated in vacuum in presence of an asymmetric d.c. field) rutile single crystals parallel to c-axis at room temperature. Dispersions in ε′ have been observed in the frequency ranges 102 to 103 and 107 to 109 c.p.s. for all the samples with absorption peaks in ε″ at 2 × 102 and 6 × 107 c.p.s. Also an extra absorption peak in ε″ has been found at 2 × 104 c.p.s. for the specially reduced sample. The absorption peak at 2 × 102 c.p.s. has been observed by many workers and is typical for interfacial polarization. The peak at 6 × 107 c.p.s. appears to be due to a dipole rotation process with a single relaxation time and is identified as due to relaxation of dipoles formed between Ti3+ and a neighboring oxygen vacancy. The possible mechanism of relaxation for the 2 × 104 c.p.s. absorption peak is also discussed.
Distribution of absorbed beta energy in solid media
Authors: Cross William G.
Published: April 2011

Distributions of absorbed beta energy around a point source in Al and C19H21 plastic have been measured, with an extrapolation chamber, for seven emitters with endpoint energies from 0.16 to 3.55 MeV. In contrast with previous measurements made with plane solid absorbers, the shapes of the distributions at short distances are quite different for low- and high-energy emitters and the distributions for low-energy emitters are in agreement with those measured in gases. Dose distributions in Al and C19H21 have the same shapes. The distance scaling factors relating these distributions to that in air are 1.04 ±.01 for C19H21 and 1.00 ±.01 for Al, and are independent of beta energy to within 1%. All of these results agree with calculations based on the theory of Spencer.
Twilight observations of upper atmospheric sodium, potassium, and lithium
Authors: Gault W. A. , Rundle H. N.
Published: April 2011

Twilight resonance emissions due to atmospheric sodium, lithium, and potassium have been measured for over one year. The existence of the potassium resonance line was verified by using an absorption cell.Several problems of measuring the emissions and of subsequently calculating a density distribution are discussed. The widths of about 13 km and the topside scale heights of about 4.5 km obtained for the sodium layer are significantly less than obtained at Saskatoon in previous measurements. Atmospheric transmission functions have been recalculated with the results that the sodium and lithium layers are both at about the same height of around 90 km. A lower height of about 85 km was obtained for the potassium layer.The seasonal variations of sodium and lithium twilight abundances are shown to be similar with additional sharp enhancements of lithium abundances thought to be due to natural and man-made injections of lithium. Any seasonal variations of the potassium abundances in the lower layer were masked by large day-to-day fluctuations.
Limit cycle solutions of a scalar model nonlinear field theory and the Hartree quantum levels
Authors: Leiter Darryl
Published: April 2011

A scalar model nonlinear field theory is constructed from an action principle so that the inherent "limit cycle solutions" of the theory correspond to the eigensolutions of the conventional Hartree equation for helium. The properties of the "limit cycle transition" solutions are discussed and offer an alternative method, for solving the nonlinear Hartree eigenvalue equation, which has the distinct advantage of not requiring the spherical averaging approximation inherent in the conventional "self-consistent field" calculations. The elements which control the speed of convergence of a limit cycle transition solution into a limit cycle solution are analyzed; a method of speeding up the process in order to make it competitive, in terms of computer time, with the conventional self-consistent field calculation is discussed.
Evaluation of perturbation theory terms in nuclear matter
Authors: Ko Che-Ming , Sprung Donald W. L.
Published: April 2011

The second-order perturbation term in nuclear matter is reduced, for the most general nonlocal potential, to a triple quadrature. A kinematic function of three variables which includes all kinematic effects of the Pauli principle is defined and evaluated analytically. An improved angle average approximation for nuclear matter calculations is derived and found to be very accurate for evaluating the Pauli correction in the reference spectrum method.
Interaction of a highly relativistic helical electron stream and a cold magnetoactive plasma
Authors: Fung P. C. W.
Published: April 2011

When a nearly monoenergetic relativistic electron stream is gyrating along a cold magnetoactive plasma with general pitch angle Φ (defined as the angle between the static magnetic field of the plasma and the momentum of a particle in the stream), the system is shown to be radiatively unstable with respect to synchrotron radiation. Using the classical kinetic approach, the temporal growth rate is derived for general wave-normal angle θ (defined as the angle between the static magnetic field and wave vector k). Deducing the spatial amplification rate from the temporal growth rate, the result obtained here is shown to be identical with that obtained from the Einstein-coefficients approach deduced by Fung earlier.
Origin of solar type IV meter-wave storms
Authors: Fung P. C. W.
Published: April 2011

The features of cyclotron radiation from electrons gyrating in the possible source regions of both "moving" and "stationary" solar type IV meter-wave storms are investigated. Assuming some models of spot magnetic field configuration and electron density distribution in the possible source regions, it is found that the majority of the important observed characteristics of type IV meter-wave storms can be well accounted for by the cyclotron mechanism. If we specify the magnetoactive plasma of the possible source region by the quantity A = fP2/fH2 (where fP = electron plasma frequency and fH = electron gyrofrequency), both the solar type I noise storm (Fung and Yip 1966a, b) and the second phase of type IV meter-wave storm are considered to be generated by cyclotron radiation from electrons in the o-mode, but in ambient magnetoactive plasmas of slightly different values of A. From our present investigation, cyclotron radiation in the x-mode from electrons trapped in "frozen-in" magnetic fields in a source region where A ≈ 0.1 can be applied to explain the main features of the type IV meter-wave first phase emission.
High resolution study of the 5515 Å band of s-tetrazine
Authors: Brown John M.
Published: April 2011

A high resolution study of the type C(0–0) band of s-tetrazine, C2H2N4, at 5515 Å has revealed regular fine structure in the central qQ branches. The nature of this fine structure is explained using a formula appropriate to high J, low Ka asymmetric top levels and it is shown to be dependent on the change in the rotational constant C between the two states involved. It is suggested that such rotational structure should occur quite frequently in type C bands of larger molecules.
On the operators for time of motion and delay time induced by scattering
Authors: Gien Tran Trong
Published: April 2011

Recently, Lippmann showed that a time operator might exist in quantum theory and that its explicit form is i ∂/∂E in the energy representation. In this paper, we wish to stress that i ∂/∂E actually represents only the time which the particle used to move from the scattering center to a certain point at the outside. (Later on, we shall call this time the "time of motion.") We also show that, although it is possible to define an operator for the "time of motion" of the particle in the energy representation, it is necessary to introduce a new conjugate representation of the energy representation, the "time representation," to overcome difficulties which may arise in the evaluation of the mean time of motion [Formula: see text]. If the position representation is used for the calculation instead, we shall meet these difficulties. The reason is that time of motion T, position x, and energy E are not two-by-two compatible variables. Bearing in mind that i ∂/∂E only represents the time of motion of the particle, we can then deduce the explicit form of the delay time operator Q in terms of the scattering matrix S directly from the time of motion operator by simple reasoning. This form is Q = −i(∂S/∂E)·S† as was found previously. Some interesting features of the delay time operator will also be sketched at the end of the paper.
Statistical behavior of fingering in a displacement process in heterogeneous porous medium with capillary pressure
Authors: Verma A. P.
Published: April 2011

The stabilization of fingers in a specific oil–water displacement process with capillary pressure has been statistically discussed for a given heterogeneous porous medium. The equation of motion has been solved by a perturbation method. It is shown that the perturbation solution does produce "stable" fingers in one special case corresponding to the investigated problem.
New X-ray diagram lines in the L spectrum of 65Tb
Authors: Deodhar G. B. , Varma P. P. , Singh R. B.
Published: April 2011

Investigating the L emission spectrum of terbium 65 experimentally, the existence of the quadrupole lines λλ1711.99, 1552.87 x.u. corresponding to the transitions LIIINIII and LIINIII respectively, the nonquadrupole line λ1427.12 x.u. corresponding to the transition LIIMV and the octupole line λ1765.13 x.u. due to the transition LIIMV has been established for the first time. Also, the dipole lines LIIOI (γ8), LIIOIV (γ6), and LIIIOIV,V(β5) and the quadrupole line due to the transition LIOIV,V reported so far only by Sakellaridis have been confirmed. However, the line LIIMI(η) also reported by Sakellaridis could not be confirmed.
Observation of the O2(1Δg–3Σg−)0,1 band in the day airglow
Authors: Gattinger R. L.
Published: April 2011

The O2(Δg–3Σg−)0,1 band at a wavelength of 1.58 μ has been observed in the day airglow with a ground-based scanning grating spectrometer. The observations were made near local noon in March, 1968, at 45.2 °N., 75.5° W. with the line of sight of the spectrometer directed towards the zenith. A spectrum with a resolution of 2 Å was obtained by employing signal averaging techniques. The brightness of the 0,1 band was approximately 630 kR.
Decay of 103Ag
Authors: Bakhru H. , Morse R. I. , Preiss I. L.
Published: April 2011

The reaction 14N + 11B forming a silver compound nucleus and the direct interaction of 107Ag + 14N were utilized to produce the isotope 103Ag. In both instances the 103Ag results from the subsequent evaporation of nucleons from either the Ag compound nucleus or from the 105Ag* reaction intermediate in the case of the direct process. The decay of this isotope was studied using Ge(Li) detectors as well as with standard scintillation counters. The beta- and gamma-ray measurements confirm three beta groups of maximum energies 1.31 ± 0.05 MeV (60%), 1.03 ± 0.05 (30%), and 0.500 ± 0.1 MeV (10%) and gamma rays of energies 0.118, 0.148, 0.235, 0.268, 0.420, 0.540, 0.555, 0.585, 0.655, 0.740, 1.002, 1.1, 1.14, 1.27, 1.36, and 1.56 MeV all decaying with a half-life 1.1 h. Coincidence studies show that the 0.118 MeV gamma ray is in coincidence with 0.148, 0.511, 0.555, 0.740, 1.0, and 1.1 MeV gamma rays; the 0.148 MeV gamma ray with the 0.118, 0.511, 0.555, 0.740, 1.0, and 1.1 MeV gamma rays; the 0.235 MeV gamma ray with the 0.420, 0.511, 0.585, 0.740, 1.04, and 1.13 MeV gamma rays; the 0.540 MeV gamma ray with the 0.511 and 0.820 MeV gamma rays; and the 0.820 MeV gamma ray with the 0.511 and 0.740 MeV gamma rays only. Two beta groups of maximum energies 1.03 and 0.5 MeV are observed to be in coincidence with the 0.148 and 0.268 MeV transitions and with the 0.555 and 0.820 MeV gamma rays as a gate, only the beta group of energy 0.5 ± 0.1 MeV appears. Based on the above observation, a decay scheme of 103Ag is proposed and the results are discussed. The half-life of 118 keV level is measured by delayed coincidence and found to be (1.9 ± 0.4) × 10−9 s indicating an M1 multipolarity for this transition. The mass difference between the ground state of 103Ag and 103Pd is found to be 2.32 MeV.
A facility for charged photoparticle experiments
Authors: Keller N. K. , Lee J. K. P. , McConnell D. B.
Published: April 2011

A low-background experimental arrangement for (γ, charged particle) reactions is described. Studies on the nature and sources of the background indicated that best results could be obtained through complete shielding, a paraffin lining in the scattering chamber, and the use of permanent magnets for electron sweeping. To demonstrate the capability of the system, a photoproton spectrum at 90° is presented for the 16O(γ, p)15N reaction.
Lifetimes and branching ratios of energy levels of 28Si. I
Authors: Litherland A. E. , Smulders P. J. M. , Alexander T. K.
Published: April 2011

The gamma rays from the 25Mg(α,nγ)28Si reaction have been studied using alpha particles with energies ranging from 4.8 to 6.0 MeV. A 25 cm3 Ge(Li) gamma-ray counter was used to observe the complex high energy gamma-ray spectra at angles between 0° and 130° to the alpha-particle beam. Estimates of the nuclear lifetimes of the energy levels excited were obtained from Doppler shift attenuation measurements. The de-excitation branching ratios of the levels were also measured. The existence of a new level in 28Si at 6695 keV was confirmed. The recently reported 3− level at either 6880 keV or 6889 keV was observed and found to be the 6880-keV member of the doublet. The enhancement of the octupole transition to the ground level of 28Si was found to be 13 Weisskopf units.
Application of many-fermion techniques to lattice statistical problems
Authors: Gibberd R. W.
Published: April 2011

The partition functions of many lattice statistical problems, such as the Ising models, the dimer model, and the ferroelectric model, have been written in the following general form:[Formula: see text]For models that can be solved by the pfaffian technique, H(j) is a quadratic function of fermion operators, but otherwise H(j) also contains quartic functions of fermion operators, making the above expression intractable to exact evaluation. General field theoretical perturbation methods, such as the Green's function techniques and the diagonalization (by a Fourier transformation) of the Hamiltonian, Ho(j), are developed in relation to the above expression. It is shown that the partition function for unsolved problems can be expressed in terms of an "irreducible vertex part" for which low-order approximations can be obtained. This general formalism is applied to the next-nearest neighbor two-dimensional Ising lattice. A first-order approximation is obtained for the irreducible vertex part, and the critical properties are obtained. For the equivalent-neighbor model, the critical temperature obtained is in excellent agreement with the series expansion results, being only 0.4 % higher.
Absorption spectrum in the vacuum ultraviolet and visible emission spectrum of the NO molecule. The 4d complex
Authors: Suter R.
Published: April 2011

The structure of the 4d Rydberg term complex of the nitric oxide molecule has been studied by rotational analyses of the following bands photographed with spectrographs of high resolving power: (i) the weak band 4d–X2Π observed at 1470 Å in the absorption spectrum, (ii) the group 4d–3p of Rydberg–Rydberg bands observed as 4d–C2Π (6400 Å) and 4d–D2Σ+ (6800 Å) bands in the emission spectrum of a discharge. A type of l uncoupling of the Rydberg electron of the molecule is found very similar to the case already known for the 3d complex of NO. Constants characterizing the d complexes are calculated, and a comparison of the 3d and 4d complex is made.
A spectroscopic study of HCP, the phosphorus analogue of hydrocyanic acid
Authors: Johns J. W. C. , Shurvell H. F. , Tyler J. K.
Published: April 2011

The ultraviolet absorption spectrum of HCP has been observed from 4100 Å to about 2350 Å, and seven electronic transitions have been identified. Three of these transitions involve excited singlet states and four of them involve excited triplet states. The symmetries, energies, and equilibrium conformations of these states are listed below:[Formula: see text]Some observations have also been made on the vibration–rotation energy levels of the ground electronic state, [Formula: see text], of HCP. The fundamental vibration frequencies (in cm−1) are ν1 = 3216.9, ν2 = 674.7, and ν3 = 1278.4.
Polar cap sporadic E
Authors: Gerson N. C.
Published: April 2011

Backscatter probings (at 28 MHz) of the arctic ionosphere were made at Alert, Canada, for almost two years. A skewed distribution around the site was found with (a) maximum occurrences constrained to the northeast within ±30° of the great circle through Alert and the principal northern magnetic dip pole, (b) a secondary maximum to the south, and (c) a marked dearth of observations as a tongue from the west (250°–280°) to about 800 km in the east. The annual pattern was almost identical with the summer and winter patterns. Equinoctial distributions were distinct. The maximum broadened to include the sector in the northeast within the great circles passing through Alert and the dip pole, and Alert and the geomagnetic pole. The secondary maximum and the tongue from the west of very low occurrences vanished.Seasonally, a pronounced maximum was found in the period June–August, and a weak secondary maximum during the equinoctial months. Diurnally, activity was present from 0700–1900 LST with a single peak near 1300 LST. Slight deviations from this pattern were noted in winter and summer. In the equinoxes, a plateau or double peak seemed present in the afternoon.Returns from the azimuth of Thule correlated with vertical-incidence sporadic E frequencies from Thule multiplied by the secant factor. No correlation with similar data from Resolute Bay was present. Indications of direct backscatter from field-aligned irregularities were found despite the large angles off perpendicularity. Es occurrences, after a lag of 1–2 days, seemed to be associated with appreciable increases in the daily value of ap. None of the results were predicted by standard maximum usable frequency prediction procedures.Two mechanisms seem possible for clarifying the results: (a) for the summer maximum, the Es layer tilted upwards to the principal northern dip pole; and (b) for the secondary equinoctial maximum, the daily swing of the auroral oval through the antenna beamwidth.
Spectrum of SO: Analysis of the B3Σ−–X3Σ− and A3 Π–X3Σ− band systems
Authors: Colin R.
Published: April 2011

The absorption spectrum of SO radicals produced by flash photolysis of a mixture of COS + O2 + Ar is investigated. A partial rotational analysis of the previously known bands of the B3Σ−–X3Σ− transition which lie in the region of 1900 to 2400 Å is presented, and the predissociations and perturbations of the B3Σ−state are discussed. A complex red-degraded band system near 2500 Å, previously observed in emission and attributed to SO2, is shown to be due to a 3Π–X3Σ− transition of the SO molecule. Effective rotational constants of the 3Π state are derived from the analysis of these bands photographed at high resolution. In order to obtain the vibrational numbering of the 3Π–X3Σ− bands, these were also photographed in emission from a microwave discharge through a mixture of S18O2 + S16O2. A general discussion of the currently known states of the SO molecule is given.
An investigation of hydrodynamic waves with a cylindrical microwave resonator. III. The influence of an axial magnetic field
Authors: Curzon F. L. , Pike R. L.
Published: April 2011

A microwave resonator has been employed to study the damping of a surface wave on mercury in the presence of a vertical magnetic field. The conditions of the experiment satisfy the linearity requirements of the theory and confirm the expected dependence of the damping frequency on magnetic field strength, fluid depth, and radius.
A nuclear quadrupole resonance investigation of the effect of pressure on molecular rotation in K2PtCl6
Authors: Armstrong R. L. , Jeffrey K. R.
Published: April 2011

The pressure dependences of the 35Cl quadrupolar relaxation rate and nuclear quadrupole resonance frequency in K2PtCl6 are measured for hydrostatic pressures up to 5000 kg cm−2 at six temperatures. The temperatures were selected so that the effects of pressure on the rotation of PtCl6 groups could be investigated. The relaxation resulting from the molecular rotation is discussed in terms of the simple classical model of an activated process. An activation volume ΔV* = 25.6 cm3 mole−1 for the rotation is deduced. The effect of the onset of the rotation on the nuclear quadrupole resonance frequency is noted. The results are shown to be consistent with earlier measurements on the 14N resonance in (CH2)6N4. The activation energy ΔE* for the rotation is shown to have a value between 12.6 and 18.8 kcal mole−1.
Eigenvalues of the axially symmetrical electromagnetic waves along an infinitely long and conductive circular cylinder in a homogeneous magnetoionic medium
Authors: Aoki K.
Published: April 2011

This paper discusses eigenvalues of the electromagnetic field along an infinitely long and conductive circular cylinder imbedded in a magnetoionic medium under assumptions that the medium is lossless and the field frequency is not equal to the cyclotron frequency. It is shown that they are classified into two kinds: (i) k1 and k2 are pure imaginary and (ii) k22 = (complex conjugate of k12), where k1 and k2 are the radial propagation constants and that no eigenvalues exist in the region bounded by [Formula: see text] where ωp and ωc are the plasma and cyclotron frequencies normalized to the field frequency. Some numerical results in the case of (radius of the cylinder/wavelength) [Formula: see text] are also shown.
Nuclear spin–lattice relaxation in solid methane and its deuterated modifications
Authors: Wit G. A. de , Bloom Myer
Published: April 2011

The proton and deuteron spin–lattice relaxation time T1 has been measured in CH4, CD4, CHD3, CH3D, and CH4–CD4 mixtures and CH4–krypton mixtures as a function of temperature between 1.2 °K and 60 °K. The aim of this study was to obtain information on the two low-temperature phase transitions characteristic of methane. Discontinuities in the plot of T1 versus temperature were observed for all the systems studied at the upper phase transition, and also for CHD3 and CH3D at the lower phase transition, but not for CH4 and CD4 at the lower phase transition. Analysis of the data revealed that the strong temperature dependence of T1 is associated with molecular reorientation, but the classical theory of molecular reorientation proved to be inadequate to explain the numerical values of T1 obtained for all the systems studied. It is suggested that a more complete analysis of the data requires a much more detailed theory of solid methane. In particular, more quantitative theoretical calculations of the energy levels of methane in the crystal field are required, and the role of the lattice vibrations in causing molecular reorientations must be elucidated before the data presented in this paper can be properly interpreted.
Formation of vacancy clusters by the dechanneling of channeled keV gold ions in gold
Authors: Schober T. , Balluffi R. W.
Published: April 2011

Thin silver–gold single-crystal sandwich specimens consisting of a silver layer 700 ± 50 Å thick and a gold layer 850 ± 50 Å thick were bombarded along [001] at normal incidence to the silver layer with 40 keV gold ions at room temperature. A significant number of the gold ions became channeled along [001] and were able to reach the gold layer where they produced radiation damage in the form of "black-spot" defects visible by transmission electron microscopy. (The silver layer therefore acted as a filter which allowed only channeled gold ions to enter the gold layer.) A stereo analysis of black–white contrast from the defects in the gold layer revealed that they were all vacancy type. Further measurements and observations indicated that the vacancy defects were formed in situ at displacement cascades initiated by the dechanneling of the channeled gold ions at thermally displaced atoms. It is concluded that the stopping of channeled gold ions in gold at room temperature by dechanneling at thermally displaced atoms is a major stopping mechanism in the energy range where nuclear stopping becomes important.
A search for galactic H2+
Authors: Shuter W. L. H. , Sloan D. S.
Published: April 2011

An attempt was made to detect a radio-frequency spectral line from orthohydrogen ions in two galactic regions. An upper limit to the brightness temperature of [Formula: see text] was established.
The 3300 Å band system of cyclobutanone
Authors: Moule D. C.
Published: April 2011

The ultraviolet spectrum of cyclobutanone vapor has been recorded under conditions of high resolution. The oxygen wagging vibrational levels have been found to be strongly anharmonic in the 1A2 electronic state and have been fitted to a double minimum potential function.
Theory of excitation transfer in collisions between alkali atoms. I. Identical partners
Authors: Dashevskaya E. I. , Voronin A. I. , Nikitin E. E.
Published: April 2011

A mechanism is derived for nonresonant transfer of electronic excitation energy, induced in the process M*(2P3/2) + M(2S1/2) → M*(2P1/2) + M(2S1/2), where M and M* are identical alkali atoms in the ground and first excited states, respectively. Various types of interactions, responsible for the nonadiabatic combination of electronic states of the quasi molecule M2*, were considered, and their respective contributions to the cross section for excitation transfer were determined.
A direct measurement of the thermal neutron conversion ratio of natural uranium
Authors: Bigham C. B. , Durham R. W. , Ungrin J.
Published: April 2011

A direct method for measuring the thermal neutron conversion ratio of natural uranium (capture in 238U)/(destruction of 235U), gives 0.5655 ± 0.0025 (20 °C Maxwellian) in good agreement with 0.565 ± 0.009 from the separately measured cross sections. The corresponding value for the 2200 m/s absorption cross section of 238U is 2.721 ± 0.016 b. The method is based on the use of a sample of 243Am, which α-decays to 239Np, for correlating the efficiencies of the fission counter and γ counter used to measure the number of fissions and the amount of 239Np produced during an irradiation of a natural uranium sample.
The effect of wind shear on the decay constant of meteor echoes
Authors: McIntosh B. A.
Published: April 2011

For a meteor trail, rotational motion caused by wind gradients leads to errors in the decay constant of the radar echo. Two cases are assessed. In the first, large wind shears produce gross motion of the reflection point along a trail in which the electron density varies exponentially. Secondly, smaller motions on a short, finite trail are examined. These models cannot account for all of the observed scatter in decay-time measurements.
Gravitational stability of cylinders in an aligned magnetic field
Authors: Wentzell R. A.
Published: April 2011

An examination has been made of the gravitational instability of an infinite, perfectly-conducting cylinder, maintained by its intrinsic gravitational force, with an axial magnetic field, and surrounded.by fluid of a different density. The magnetic field will suppress any axisymmetric instability due to axial flow if the Alfvén velocity is greater than the streaming velocity.
Lifetime of the 8.543-MeV level of 28Si
Authors: Lam S. T. , Litherland A. E. , Alexander T. K.
Published: April 2011

The 25Mg(α,nγ)28Si reaction has been used in a measurement of the lifetime of the (6+), 8.543-MeV level in 28Si. The incident α-particle energy was chosen to be close to the threshold energy of the reaction, so that the directions of the recoiling nuclei were confined to a narrow cone. The 0°–90° attenuated Doppler shift of the 3.926-MeV gamma ray from the 8.543-MeV to the 4+, 4.167-MeV level was measured with two Ge(Li) counters. The lifetime of the 8.543-MeV level was measured to be 58 ± 12 fs.
Some observations of twilight He (1.083) emission
Authors: Harrison A. W.
Published: April 2011

The 1.083 μ resonance line of Hel has been observed in the evening twilight airglow spectrum over the period February 1968 to February 1969. A winter maximum of ~1.0 kR and a summer minimum of ~0.4 kR is found for the absolute brightness of the Hel line for a zenith angle of observation = 80° in the solar azimuth and for a solar depression angle = 15°. An analysis of several winter twilight decays showed that the decay pattern is not constant. Comparison of the observed brightness and shadow height variations with solar depression angle indicates a maximum volume emission rate in the height range 400–600 km.
Nuclear spin relaxation in compressed nitrogen gas
Authors: Speight Patricia A. , Armstrong Robin L.
Published: April 2011

Measurements of the 14N spin relaxation in compressed nitrogen gas are presented for temperatures of 145, 200, 293, and 380 °K and for pressures spanning the range from 50 to 1700 atm. In all cases the recovery of the nuclear magnetization following saturation is describable by a single time constant, T1. The corresponding dependence of T1 on the gas density ρ is deduced and, to first order, a linear relation is found with a temperature dependence given by [Formula: see text]. Applying the semiclassical theory of nuclear relaxation of Gordon, the effective cross section for molecular reorientation during a collision due to the intramolecular electric quadrupole interaction is deduced. The result is shown to be in reasonable agreement with the values deduced from studies of depolarized Rayleigh scattering and the Sentfleben-viscosity effect. The data is also discussed in terms of the Bloom theory of nuclear relaxation. It is assumed that the rotational correlation function can be written as the product of a free-molecule correlation function and a reduced correlation function that decays exponentially with time constant τ2. A theoretical expression for the dependence of T1 on τ2 is obtained. From a comparison of the equation with the data it is seen that, to a first approximation, [Formula: see text], where the τ2 values are of the order of 10−12 s.
Scattering by a long imperfectly conducting wire
Authors: VanKoughnett A. L.
Published: April 2011

A solution is obtained for the field scattered by a long imperfectly conducting wire when illuminated by a plane time harmonic electromagnetic wave. The problem is formulated in terms of the current induced in the wire and the longitudinal component of electric field on the infinite cylindrical surface containing the scatterer. A Fourier transform of an integral equation relating these variables is taken and the unknown transform of the induced current is eliminated by applying the Wiener–Hopf technique. An integral equation for the transform of the electric field is obtained and solved approximately for long wires. The transform of the induced current and hence the scattered fields are then easily derived. The results presented indicate that the solution is useful for wires as short as 0.4 wavelengths.
Urbach's rule in impurity absorption
Authors: Dunn Dennis
Published: April 2011

We have investigated theoretically the shape of the long-wavelength edge of the impurity absorption spectrum in an insulator (or semiconductor) by means of a Green's function technique. The absorption process is assumed to be the excitation of a valence electron into a previously unoccupied impurity state. We have shown that Urbach's rule is obeyed, that is the absorption coefficient depends exponentially upon the photon energy, if either the valence electron or the impurity state electron is coupled strongly to monoenergetic phonons.
Reanalysis of the A3Πi–X3Σ− systems of OH+ and OD+
Authors: Merer A. J. , Achter E. K. , Horani M. , Rostas J.
Published: April 2011

Preliminary results from rotational analysis of new high-resolution spectra of the A3Π–X3Σ− transition of OH+ and OD+ are reported. The line assignments for low rotational quantum numbers given by previous authors have been found to be in error by up to 10 cm−1. Various irregularities in the Λ doubling of the A3Π state can probably be explained by strong interaction between the b1Σ+ and A3Π states. An analysis of rotational perturbations in the bands of OH+ suggests that the b1Σ+ electronic state lies about 1200 ± 50 cm−1 above the A3Π state.
Vibronic side bands of Sm2+ in alkali halides
Authors: Buchanan M. , Woll Jr. E. J.
Published: April 2011

The calculation of vibronic side bands of defects in crystals is discussed. A model for the deformation of the lattice about a Sm2+ defect in alkali halides and side-band calculations on this model for KBr and KCl containing Sm2+ are compared with experimentally observed side bands. Improvements, particularly in the low frequency region, are found over the calculations assuming no deformation.
The decay of 73As
Authors: Douglas D. G.
Published: April 2011

The relative intensities of the gamma and X rays of 73As have been measured with a Si(Li) spectrometer and the information used for the calculation of conversion coefficients. These are compared with theoretical values.Sufficiently precise gamma energy measurements have been made to remove an ambiguity in the ordering of two close energy levels.
Spin–orbit and spin–other–orbit interactions for f4 electron configuration
Authors: Saxena K. M. S. , Malli Gulzari
Published: April 2011

General expressions for the reduced matrix elements of spin–orbit and spin–other–orbit interactions are evaluated for all the states arising from f4 electron configuration. These are used to calculate the Hartree–Fock values of the matrix elements of the above-mentioned interactions for Nd(4f4), Dy(4f10), and Ho3+ (4f10) atomic systems.
Orbit–orbit interaction inn fN electron configurations
Authors: Saxena K. M. S. , Malli G.
Published: April 2011

The expressions of the matrix elements of the orbit–orbit interaction for various fN electron configurations are computed and tabulated for general usage. These expressions are used to evaluate the Hartree–Fock values of the orbit–orbit interaction in all the states for a large number of fN electron atomic systems.
Rocket measurements of plasma densities and temperatures in visual aurora
Authors: McNamara A. G.
Published: April 2011

Direct measurements in active visual auroral forms using electrostatic plasma probes are described. On-board probes and an ejected Langmuir probe were used to provide maximum accuracy of measurement and freedom from perturbations. An electron density of 9.5 × 105 electrons/cm3 was found within a visual band, with a background density of 1.5 × 105 electrons/cm3 outside the band. The ionization maximum occurred at 107 km altitude, with a half-density vertical thickness of 7 km. The temperature of the thermal electrons over the interval 100 km to 168 km was found to range from 500 °K to 1400 °K. A hyperthermal electron component was also observed. A rocket-borne photometer determined the height of the optical emission region, and an array of optical, radio, and magnetic ground-based instruments were used to provide supporting geophysical data, and to define the position and variations of the auroral forms.
Spectrum of the hydroxyl radical
Authors: Carlone C. , Dalby F. W.
Published: April 2011

The B2Σ+ → A2Σ+ and C2Σ+ → A2Σ+ systems of OH and OD were photographed at high resolution. The apparent dissociation energy D0(A2Σ+) is calculated to be (18 847 ± 15) cm−1 for OH and (19 263 ± 15) cm−1 for OD. An upper limit to D0(X2Π3/2) of OH is deduced to be (35 420 ± 15) cm−1. Evidence for a potential maximum in the B2Σ+ state, which is about 100 cm−1 larger than that in the A2Σ+ state, is presented.The broadening of the rotational lines in several bands of both systems has established a strong predissociation of the A2Σ+ state near ν = 5 in OH. The lifetime of these predissociated levels is ≈10−11 s. A definite identification of the predissociating state has not been possible.Newly-discovered vibrational levels in the C2Σ+ state have led to the following constants, in cm−1, of the OH radical in the C2Σ+ state:[Formula: see text]Rotational constants and spin splitting constants in the A2Σ+ and B2Σ+ states, more accurate than previously available, are presented.
Isotope shift in the second spectrum of cadmium
Authors: Contreras R. H. , Kelly F. M.
Published: April 2011

Measurement of isotope shifts have been made in the resonance line λ 2265 Å in the second spectrum of cadmium. The measurements are compared with those of other authors.
Equation of state of neutron gas and the critical mass of neutron stars
Authors: Binder M. , Pierce R. H. , Razavy M.
Published: April 2011

The equation of state of the neutron gas is calculated by a variational method, using the Hamada–Johnson potential for the two-nucleon interaction. The energy–density relation determined in this way is valid for low and moderate densities. This result is extrapolated to higher densities and is joined smoothly to the relativistic energy–density relation for free particles. The critical mass of neutron stars is obtained by integrating the general relativistic equations for hydrostatic equilibrium using the equation of state. The critical mass is found to be less than 0.7 of the mass of the Sun.
SU(4) polynomial bases
Authors: Jakimow G. , Sharp R. T.
Published: April 2011

Bases are derived for the irreducible representations of SU(4) as polynomials in the states of the three fundamental representations (100), (010), and (001) by forming first the bases (λ00), (0μ0), and (00ν) and then constructing (λμν) as their stretched product.
Low lying levels in 81Br
Authors: Salomon M. , Hojvat C.
Published: April 2011

Coulomb excitation of Br targets and the reaction 80Se(p,γ)81Br were used to populate the low lying excited states of 81Br and an energy level scheme is proposed. The reduced transition probability from the ground state to the first excited state of 81Br (276 keV) has been measured to be B(E2) = 410 ± 40 e2 f4.
Some comments on the scattering of charge carriers by optical phonons
Authors: Kužel R.
Published: April 2011

The exponent r in the expression [Formula: see text], for the relaxation time due to optical phonon scattering, has been calculated for some of the transport coefficients. The variation of r with temperature is discussed.
An SU3 study of 18O, 19O, and 20F
Authors: Hodgson R. J. W.
Published: April 2011

A method for performing SU3 calculations is outlined which combines the operator expansion procedure of Banerjee and Levinson together with the determinantal wave functions introduced by Moshinsky. The technique is quite suitable for computer calculations and is applied to 18O, 19O, and 20F, using three different central residual interactions together with a spin–orbit force.
Ranges of shielded nuclides from thermal-neutron fission
Authors: Nakahara H. , Harvey J. W. , Gordon G. E.
Published: April 2011

Average ranges in Al of shielded nuclides 86Rb and 136Cs and several chain-yield species from thermal-neutron fission of 233U and 235U have been measured. The values obtained (in mg/cm2 Al) are, for 233U: 86Rb, 3.88 ± 0.04; 136CS, 2.80 ± 0.01; and for 235U: 86Rb, 3.76 ± 0.03; 136Cs, 2.81 ± 0.01. A range–energy transformation was used to determine average kinetic energies [Formula: see text] of the secondary fragments. In agreement with previous work, the shielded nuclides are found to have smaller [Formula: see text] values than neighboring chain-yield species. The deficits of [Formula: see text] are, for 233U, 4 and 8 MeV, and for 235U, 8 and 10 MeV, respectively, for 86Rb and 136Cs. Most of the range experiments were done with the thick-catcher method followed by conventional radiochemical treatment of the catcher foils. Ranges of 20 products from 233U were determined in preliminary experiments in which gross γ-ray spectra of fission products in the catcher foils were observed with a Ge(Li) detector. The kinetic-energy deficits of the shielded species are interpreted by Monte Carlo calculations of prompt-neutron emission.
CO2 laser-induced thermionic emission from metals. Direct energy conversion
Authors: Duley W. W.
Published: April 2011

Electron emission has been observed when tungsten and molybdenum targets are subjected to focussed CO2 laser radiation. The characteristics of thermionic emission for a variety of excitation conditions are reported. The electron temperature is found to be [Formula: see text] for an incident power of 40 W cw. Direct energy conversion processes are discussed. Short circuit currents of 2–7 μA and open circuit voltages of 0.1–0.4 V have been observed.
Effect of finite Larmor radius on Rayleigh–Taylor instability of a plasma
Authors: Ariel P. D. , Bhatia P. K.
Published: April 2011

The effects of a finite Larmor radius of the ions are investigated on the Rayleigh–Taylor instability of a plasma in which there is a density gradient in a direction perpendicular to that of the magnetic field. It is found that the unstable configuration is completely stabilized by the finite Larmor radius effect.
Some exact results for the anisotropic triangular lattice
Authors: Gibberd R. W.
Published: April 2011

The combinatorial approach to the triangular Ising model is shown to be considerably simplified at a given temperature TD. This enables the partition function and spin-correlation functions to be evaluated without the use of pfaffians, thus providing a simple derivation of a few of the results obtained previously by Stephenson. We confirm the results of Stephenson, that at the temperature TD, the correlation functions have the same structure as the correlations of a one-dimensional Ising lattice. The only new result is a general expression for some of the spin–spin correlation functions when the spins do not lie on the axes of the lattice.
Electron and phonon Green functions in a one-dimensional model
Authors: Dunn Dennis
Published: April 2011

We consider a one-dimensional fermion model which is similar to the Luttinger model and which also includes an electron-phonon interaction. We show that in this model the electron, phonon, and plasmon Green functions can all be determined exactly.We examine the dielectric properties of the system and also the more general response of the system to arbitrary external fields and we show that the response is strictly linear in these fields.
Spin–other–orbit and spin–orbit interactions for some rare earth ions
Authors: Saxena K. M. S. , Malli Gulzari
Published: April 2011

The spin–other–orbit and spin–orbit interactions are evaluated for Pr3+ (4f2), Nd3+(4f3), Er3+(4f11), and Tm3+ (4f12) using the general matrices of these interactions for f2 and f3 electron configurations reported earlier2 by us.