bluuebunny/crossref_metadata_2025 huggingface dataset:
NUCLEAR ELECTRIC QUADRUPOLE INTERACTION IN SINGLE CRYSTALS
Authors: Volkoff G. M. , Petch H. E. , Smellie D. W. L.
Published: April 2011

Pound's theory of the dependence of electric quadrupole splitting of nuclear magnetic resonance absorption lines in a single crystal on the orientation of the crystal in an external magnetic field is extended to cover the case of a crystal with nonaxially symmetric electric field gradient at the site of the nuclei being investigated. It is shown that an experimental study of the angular dependence of this splitting for three independent rotations of the crystal about any three mutually perpendicular axes will yield complete information about the orientation of the principal axes and the degree of axial asymmetry of the electric field gradient tensor at the site of the nuclei, and also will give the absolute value of the quadrupole coupling constant for those nuclei.The authors' experiments on the splitting of the Li7 absorption lines in a single crystal of LiAl(SiO3)2 (spodumene) are described and are used to illustrate the theory. The absolute value of the quadrupole coupling constant for the Li7 nuclei in spodumene is found to be [Formula: see text]. per sec. The axial asymmetry parameter of the field gradient tensor at the site of the Li nuclei is found to be η≡(ϕxx−ϕvv)ϕzz=0.79 ± 0.01. One of the principal axes of this tensor (the y axis corresponding to the eigenvalue of intermediate magnitude) is experimentally found to coincide with the b crystallographic axis of monoclinic spodumene as required by the known symmetry of the crystal. The other two principal axes are in the ac plane, the z axis (corresponding to the eigenvalue ϕzz of greatest magnitude) lying between the a and c axes at an angle of 48° ± 2° with the c axis.
THE NEAR ULTRAVIOLET BANDS OF N2+ AND THE DISSOCIATION ENERGIES OF THE N2+ AND N2 MOLECULES
Authors: Douglas A. E.
Published: April 2011

The ultraviolet emission bands of N2+ have been photographed using a six meter grating, and a number of new bands of high vibrational quantum number have been found. It has been possible to show that the [Formula: see text] state dissociates at a limit 70,358 cm.−1 above the ground state. It is shown that these results give strong support to the value 9.75 electron volts for the dissociation energy of nitrogen, but the lower value of 7.37 electron volts cannot be eliminated with certainty. The peculiar manner in which the B2Σ state converges to its dissociation limit is interpreted as being caused by an interaction between the [Formula: see text] and the [Formula: see text] states.
A MASS SPECTROGRAPHIC DETERMINATION OF THE DECAY ENERGIES OF Rh102 AND Rh104
Authors: Hogg Benjamin G. , Duckworth Henry E.
Published: April 2011

Mass spectrographic measurements are reported of the following mass differences:½Pb204–Ru102,½Pb204–Pd102,½Pb206–Rh103,½Pb208–Ru104,and0 ½Pb208–Pd104. These results are combined with existing transmutation data to obtain the energies available for the disintegrations Rh102 → Ru102, Rh102 → Pd102, Rh104 → Pd104, and Rh104 → Ru104. In the first three cases the energy values are in substantial agreement with those found by beta-ray spectroscopy. The final disintegration, namely, Rh104 → Ru104, is found to possess enough energy for appreciable K-capture and a lesser degree of positron activity. These activities have not yet been observed. Atomic masses are given for Ru102, Pd102, Rh103, Ru104, and Pd104.
THE NEW RADIOACTIVE ISOTOPES VANADIUM 46, MANGANESE 50, COBALT 54
Authors: Martin W. M. , Breckon S. W.
Published: April 2011

Three new positron activities assigned to V46 (0.40 sec.; Emax > 6.0 Mev.). Mn50 (0.28 sec.; Emax > 6.3 Mev.), and Co54 (0.18 sec.; Emax > 7.4 Mev.) have been induced by (p,n) reactions which take place in the McGill cyclotron at thresholds less than 12.5 Mev. The assignments are based on the thresholds and on the approximate ft values of the transitions.After a brief period of bombardment, controlled through the oscillator, the targets are shot back by a pneumatic extractor to a position of minimum magnetic field near the cyclotron where a suitably shielded anthracene counter system sends pulses to the main laboratory. Finally, the output of a counting-rate meter is displayed against time on an oscilloscope. This visual display reveals immediately new periods in decays, which are then photographed for later analysis.
NOMOGRAM OF LIFETIME–ENERGY–SPIN FOR GAMMA-RAY TRANSITIONS
Authors: Montalbetti R.
Published: April 2011

A nomogram of the recent Weisskopf formula relating the mean life for gamma-ray transitions to the energy and spin change has been constructed. The nomogram is useful in that it allows rapid computations and shows at a glance the dependence of mean lifetime upon the variables involved.
BIREFRINGENCE IN CRYSTALS AND IN THE IONOSPHERE
Authors: Turner C. H. M.
Published: April 2011

Propagation of plane electromagnetic waves in a homogeneous ionized gas in a uniform magnetic field is compared with the propagation of light in an optically inactive birefringent crystal. It is well known that propagation in a crystal may be described by using a system of real orthogonal axes for which the dielectric constant is given by a diagonal matrix. This paper shows that propagation of plane waves in the ionosphere may be described in a similar manner, the medium having an effective dielectric constant given by a diagonal matrix, provided that a system of "complex" orthogonal axes is used for the description of the components of the field vectors. This set of component axes (which is quite different from and not to be confused with coordinate axes) is equivalent to resolving the field vectors into components parallel to the magnetic field and two contrarotating circular components in a plane perpendicular to the magnetic field. An expression giving the velocity of each of the two modes of propagation in a given direction and expressions for the amplitude of each component of the field vectors are obtained (equations 43 and 44). Provided that one accepts the concept of a complex velocity of propagation, the results hold when electron collisions are included. When electron collisions are neglected, it is possible to form a double-sheeted surface, called the normal velocity surface, which is of some assistance in visualizing the manner in which the velocity of propagation of the plane waves in each mode changes with direction.
PHOTONEUTRON CROSS SECTIONS OF SOME ELEMENTS
Authors: Goldemberg J. , Katz Leon
Published: April 2011

The neutron yield from photo-reactions in nine elements has been measured as a function of the maximum energy of the University of Saskatchewan Betatron. Cross sections are given for each of the reactions as calculated from these data. The integrated cross sections are compared with theoretical sum-rule predictions of Levinger and Bethe and good agreement is obtained with x = ½. The data support the conclusions reached in a preceding paper by Montalbetti, Katz, and Goldemberg. The competition between (γ, n) and (γ, p) reactions in chromium and in nickel is analyzed in the light of these experimental results. Good agreement with statistical theory is obtained in both cases.
FINE STRUCTURE OF THE F19(γ, n)F18 ACTIVATION CURVE
Authors: Taylor J. G. V. , Haslam R. N. H. , Robinson L. B.
Published: April 2011

The activation curve for the reaction F19(γ, n)F18 has been re-examined in great detail up to an energy of 17 Mev. It shows discontinuities which are interpreted as being due to the excitation of discrete nuclear levels. The reaction cross section is discussed on the basis of this curve.
THE EMISSION SPECTRUM OF ALUMINUM MONOFLUORIDE. II
Authors: Naudé S. M. , Hugo T. J.
Published: April 2011

Four new band systems of the emission spectrum of AlF are described, viz. the DlΔ – A1II system in the yellow-green, the F1II – A1II and G1Σ – A1II systems in the blue, and the F1II – B1Σ system in the infrared spectral region. A vibrational as well as a rotational analysis of the D1Δ –A1II system is reported. The rotational analyses of the other systems, each of which consists of a single band, are described.
MAGNETIC DISTURBANCES, SPORADIC E, AND RADIO ECHOES ASSOCIATED WITH THE AURORA
Authors: Meek J. H. , McNamara A. G.
Published: April 2011

A comparison of simultaneous data on the visible aurora, the earth's magnetic field variation, vertical and oblique ionosonde echoes, and very-high-frequency radar echoes has been made. Long-range high-frequency and very-high-frequency radio echoes do not appear to correlate individually. Reflections are observed, however, on both frequency ranges coincident with the appearance of low elevation auroral arcs, which are associated with magnetic bays.
SOME COMMENTS ON HELIUM FILMS
Authors: Atkins K. R.
Published: April 2011

The Polanyi potential theory is applied to the helium film and leads to a qualitative understanding of the high density of the first few layers and the differential entropy. Between 1.75°K. and the λ-point the film may consist of an inner solid portion, an intermediate portion of helium I, and an outer portion of helium II. For thick films the variation of zero-point energy with thickness must be considered. The zero-point energy of the Debye waves is shown to be important at film thicknesses of the order of 4 × 10−6 cm. The effect of heat radiation incident upon the film is considered.
THE ATTENUATION OF SECOND SOUND IN LIQUID HELIUM II ABOVE 1°K.
Authors: Atkins K. R. , Hart K. H.
Published: April 2011

The second sound was in the form of a pulsed continuous wave with a pulse length of 1 to 2 msec, and a carrier frequency of 10 or 20 kc./s. The change in amplitude of the pulse was measured as the distance between the transmitter and the receiver was varied. To avoid boundary effects, no propagation tube was used and allowance had to be made for the spreading of the second sound beam. The attenuation was found to increase with increasing second sound amplitude. The attenuation extrapolated to zero amplitude had a finite value which increased rapidly as the temperature was lowered towards 1°K. Its order of magnitude was too large to be explained by viscosity effects, but was in good agreement with a thermal conductivity effect predicted by Khalatnikov.
FURTHER CALCULATIONS ON THE NUCLEAR RESONANCE SPECTRUM OF Al27 IN SPODUMENE
Authors: Volkoff G. M. , Lamarche G.
Published: April 2011

Calculations of the expected dependence of the relative intensities of nuclear quadrupole resonance lines of Al27 on the orientation of a single crystal of spodumene with respect to a linearly polarized resonant magnetic field H1 show that a suitably oriented single crystal should give rise to lines which are approximately twice as strong as those in a randomly oriented polycrystalline sample. The dependence of the matrix elements, which determine expected nuclear magnetic resonance line intensities, on the strength of a uniform external magnetic field H0 is also given for one particular crystal orientation with respect to both H0 and a linearly polarized field H1.
THE MULTIPLICITY OF NEUTRON PRODUCTION BY SPONTANEOUS FISSION OF URANIUM
Authors: Geiger K. W. , Rose D. C.
Published: April 2011

Metallic uranium was placed in a paraffin pile containing two B10F3 neutron counters. The mean life of thermal neutrons in this pile was measured (140 μsec). Neutron counter pulses occurring within a time interval of this order can be assumed to come from an individual fission event and statistical analysis makes it possible to obtain information concerning the actual number of neutrons released in one fission event. The efficiency of the pile for neutron counting was found to be 2.5% using the known neutron rate from spontaneous fission of uranium. Without further assumption, the method does not give the mean multiplicity directly, but the higher moments of the multiplicity spectrum. A Poisson distribution for the multiplicity spectrum fits our data well and gives an average of 2.3 ± 0.2 neutrons per spontaneous fission. This value is in good agreement with the mean multiplicity from other methods.
REFLECTION FROM A WIRE GRID PARALLEL TO A CONDUCTING PLANE
Authors: Wait James R.
Published: April 2011

A solution is outlined for the problem of a plane wave incident obliquely on a parallel-wire grid which is backed by a plane conducting surface. The electric vector of the incident wave is taken to be parallel to the grid wires. The equivalent transmission line problem is pointed out. It is shown that, in certain cases, a resistive wire grid will absorb all the energy in the incident wave.
HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: IV. ROTATIONAL RAMAN SPECTRUM OF CYANOGEN
Authors: Møller C. K. , Stoicheff B. P.
Published: April 2011

The rotational Raman spectrum of cyanogen gas at [Formula: see text] atm. pressure has been photographed in the second order of a 21 ft. concave grating spectrograph. The simplicity of the spectrum and the observed intensity alternation of the lines show that C2N2 is a linear symmetric molecule. An analysis of the spectrum yields for the rotational constants[Formula: see text]By assuming a value for the C≡N bond length of 1.157 Å, the length of the C—C single bond was calculated to be 1.380 Å.
THE ROTATIONAL RAMAN SPECTRUM OF ETHYLENE
Authors: Romanko J. , Feldman T. , Stansbury E. J. , McKellar A.
Published: April 2011

The rotational Raman spectrum of ethylene excited by Hg4358 was photographed with a reciprocal linear dispersion of 10.5 cm.−1 per mm. In addition to S and R branches which, in the symmetric top approximation, can be used to determine B[o] + C[o], the spectrum shows a series of lines which must be interpreted in terms of the asymmetric top model. This series is shown to be due to the transitions, ΔJ = 2, between the two lowest τ levels of each rotational state, and is used to determine C[o]. The rotational constants obtained from the analysis are A[o] = 4.66 ± 0.20, B[o] = 1.0085 ± 0.006, C[o] = 0.8289 ± 0.003 cm−1.
CALCULATION OF DEPOLARIZATION FACTORS IN THE RAMAN SPECTRA OF POLYATOMIC MOLECULES
Authors: Ferigle Salvador M. , Weber Alfons
Published: April 2011

General expressions for the derived polarizability tensor are deduced for non-cyclic molecules having bonds with cylindrical symmetry by assuming the additivity of bond polarizabilities as suggested by Wolkenstein. Full use is made of the Wilson FG matrix technique. As an example, the expressions for the trace and the anistropy for the CX3Y molecular type are obtained explicitly.
THE EFFECT OF A RANDOM NOISE BACKGROUND UPON THE DETECTION OF A RANDOM SIGNAL
Authors: Heaps H. S.
Published: April 2011

A noise distributed in phase and power according to a Rayleigh law is studied in terms of its effect upon the detectability of a signal of similar phase and amplitude distribution. An expression is derived for the probability distribution of the ratio of the power of the signal plus noise to that of the noise in the absence of the signal. The corresponding result is given for the ratio of the averages over several observations. Also derived is the probability distribution of the fractional change in noise plus signal power due to a given fractional change in signal power.
A MEASUREMENT AT OTTAWA OF THE CHANGE IN HEIGHT WITH LUNAR TIME OF THE E REGION OF THE IONOSPHERE
Authors: Littlewood C. A. , Chapman J. H.
Published: April 2011

The method used by Appleton and Weekes to detect the lunar variation of height of the E region of the ionosphere has been used to determine the amplitude and phase of the lunar height variation at Ottawa. Observations were made from October to December, 1952. A sinusoidal variation of height of 1.5 km. amplitude and 12 hr. period was observed. The maximum height occurred about six hours after lunar transit. This result differs in phase by six hours from that observed in Cambridge in 1938.
THE RUBIDIUM TRANSITION AT ~ 180°K.
Authors: Kelly F. M. , Pearson W. B.
Published: April 2011

Resistivity measurements have shown the presence of a "transition" in rubidium at ~ 180°K. The nature of this transition has been further investigated by dilatometric and X-ray studies of thermal expansion, thermoelectric force measurements, and X-ray examination for the possibility of a change of crystal structure. Evidence for the transition in properties other than resistance measurements is very variable and, although the transition does not appear to involve a change of crystal structure, its characterization as an electronic change remains obscure. Analysis of resistance measurements shows that the resistive behavior of rubidium above 180°K. must be regarded as anomalous.
PREDISSOCIATIONS OF THE C12O AND C13O MOLECULES
Authors: Douglas A. E. , Møller C. K.
Published: April 2011

The Ångström bands of C12O and C13O have been photographed with a high dispersion spectrograph and the predissociations previously reported in these bands have been re-examined. The predissociations provide good evidence that C12O has a dissociation limit 89595 ± 30 cm.−1 above the ν = 0 level of the ground state. The fourth positive (A1Π − X1Σ) bands have been re-examined and it has been shown that, contrary to earlier reports, there is no evidence for predissociation in the A1Π state.
THE ν2 RAMAN BAND OF METHANE
Authors: Feldman T. , Romanko J. , Welsh H. L.
Published: April 2011

The doubly degenerate ν2 Raman band of methane was photographed at a gas pressure of 2 atm. with a reciprocal linear dispersion of 10.5 cm.−1 per mm. An analysis of the O and S branches gave ν0 = 1533.6, B0 = 5.270, and B1 = 5.392 cm.−1. When the Raman data are combined with the infrared data of Burgess, Bell, and Nielsen, the effect of the Coriolis interaction of ν2 with ν4 is seen to be a splitting of the rotational levels of the upper vibrational state of ν2 into two sets, each of which can be represented by an effective value of B1. The Raman O, S and the infrared P (strong), Q, R (weak) transitions terminate in states with B1 = 5.392 cm.−1; the Raman P, Q, R and the infrared P (weak), R (strong) transitions terminate in states with B1 = 5.322 cm.−1.
AN APPARATUS FOR COMPARISON OF THERMOCOUPLES
Authors: Dauphinee T. M.
Published: April 2011

This paper describes a semiautomatic apparatus for routine or precision comparisons of thermocouples of the same type in the temperature range 0–1100 °C. The couples being compared are welded together at the tips and placed in a tube furnace which is heated at rates varying from 10 to 100 °C./min. Measurements of carefully annealed thermocouples show that in the temperature range 300–1100 °C. platinum – platinum 10% rhodium thermocouple comparisons may be made to accuracies of ± 0.3 μv. (± 0.03 °C.) at heating velocities as great as 15 °C./min. while accuracies of ± 1.5 μv. at velocities of 100 °C./min. are feasible. The furnace temperature is varied by means of a motor-driven variac with automatic reversal at peak temperature. In addition to this standard comparison procedure, provision is made for comparing corresponding elements of the couples, for suppression of all or part of the measured e.m.f., and for measuring the whole e.m.f. of all couples when a comparison of different types is desired. The system can be adapted to XY recording with total e.m.f. plotted against e.m.f. differences.
A RECORDING MAGNETIC VARIOMETER
Authors: Meek J. H. , Hector F. S.
Published: April 2011

The circuit and detecting head of an electronic recording magnetic variometer are described. The apparatus will give continuous and immediately observable values of variations of magnetic field as small as 10−5 oersted, if necessary.
AN AUDIO-FREQUENCY CIRCUIT MODEL OF THE ONE-DIMENSIONAL SCHROEDINGER EQUATION AND ITS SOURCES OF ERROR
Authors: Blackwell J. H. , Fewer D. R. , Allen L. J. , Cass R. S.
Published: April 2011

An audio-frequency circuit model of the one-dimensional Schroedinger equation has been constructed, based on original suggestions by G. Kron. The previous theory of such devices has been re-examined thoroughly and errors due to the basic finite-difference approximation separated from those due to electrical causes. It is found that the former type of error is likely to be dominant in practice and that in the past discrepancies due to errors of this kind have actually been ascribed to experimental causes.
ÉTUDE EXPÉRIMENTALE DE LA DIFFRACTION DES MICRO-ONDES PAR DES OUVERTURES A SYMÉTRIE DE RÉVOLUTION
Authors: Boivin Par A. , Koenig H. P. , Dion A.
Published: April 2011

not available
INFELD FACTORIZATION AND ANGULAR MOMENTUM
Authors: Coish H. R.
Published: April 2011

The connection between Infeld factorization operators and angular momentum operators, well known for spherical harmonics, is extended to other factorization problems by explicitly recognizing them as angular momentum problems. These other problems are: the symmetric top, electron-magnetic pole system, Weyl's spherical harmonics with spin, free particle on a hypersphere. The Kepler problem is also included for it may be thrown into the form of a four-dimensional angular momentum problem. The transformation to momentum space for this problem is very much simplified by the connection between Infeld factorization and angular momentum.
HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: VI. ROTATIONAL SPECTRUM OF SYMMETRIC BENZENE-d3
Authors: Langseth A. , Stoicheff B. P.
Published: April 2011

The pure rotational Raman spectrum of C6H3D3 vapor at a pressure of 15 cm. Hg was photographed in the second order of a 21 ft. grating. The value of the rotational constant was found to be B0 = 0.17165 ± 0.0001 cm−1. This result confirms the earlier spectroscopic values of the internuclear distances in the benzene molecule.
AN INVESTIGATION OF THE SODIUM-POTASSIUM EQUILIBRIUM DIAGRAM
Authors: MacDonald D. K. C. , Pearson W. B. , Towle Lois T.
Published: April 2011

The study of fundamental properties such as specific heat and electrical resistivity in pure metals has made it very important to know the influence of small amounts of impurity. This has led us to undertake a detailed investigation of the sodium–potassium equilibrium diagram. Previous work had indicated zero solid solubility at each limit (100% Na; 100% K) but the present investigation shows in particular that solubility extends to a few per cent from either limit.
PRODUCTION OF COSMIC RAY MESONS AT LARGE ZENITH ANGLES
Authors: Jakeman D.
Published: April 2011

Events have been selected by coincidences between separated shielded trays of Geiger counters and it is shown that they arise from three types of phenomena, namely, extensive air showers, casual coincidences, and particles travelling in almost a horizontal direction. Selection of the last type of event has enabled the absolute intensity to be determined at zenith angles between 88° and 90°. Using a π meson production spectrum which gives consistency with the established underground absorption curve the intensity of particles in the horizontal direction has been calculated on the assumption that π–μ decay is the only source of μ mesons. The calculated intensity agrees well with the observations. Alternatively, by comparing the rate in the horizontal direction with the known rate underground, a value of 4.5 ± 1.5 × 10−8 sec. is obtained for the lifetime of the parents of μ mesons which, because of the depth of the atmosphere in the horizontal direction (362 m.w.e.), must have energy exceeding 1011 ev. This suggests that at this energy the parents of μ mesons can be identified with the π meson, and the number of μ mesons arising from the decay of a shorter lived meson (e.g. K meson) must be relatively small.
KINETICS OF SOLIDIFICATION
Authors: Jackson K. A. , Chalmers Bruce
Published: April 2011

The kinetic theory of melting and freezing is developed from consideration of atom movements at an interface between solid and liquid. The equations developed are shown to have the same form as the corresponding thermodynamic equations. The homogeneous nucleation of a solid phase in a liquid is then considered from the point of view of this theory. Agreement with experimental observation is obtained on the following points. (1) The supercooling at which homogeneous nucleation occurs is proportional to the absolute equilibrium temperature. (2) The surface free energy per atom used in the quasi-thermodynamic treatment of nucleation should be equal to one-half the latent heat per atom. (3) The amount of liquid supercooled has a very small effect on the temperature at which homogeneous nucleation occurs.
SCATTERING OF ELECTROMAGNETIC WAVES BY COAXIAL CYLINDERS
Authors: Adey Albert W.
Published: April 2011

A scattering system comprising two coaxial, dielectric cylinders has been studied theoretically and experimentally. Calculations have been made of the forward and back scattered fields for several combinations of inner and outer radii. It has been found that, by covering a metal cylinder with a coaxial dielectric shield, it is possible to eliminate to some extent the deep near-field shadow. Experimental results obtained at a wavelength of 3.275 cm. using a parallel-plate transmission line are in good agreement with calculations.
DIFFRACTION OF 3.2 CM. ELECTROMAGNETIC WAVES BY DIELECTRIC RODS: II. LUCITE IN. DIAMETER CYLINDER AND SEMICYLINDER
Authors: McLay A. B. , Subbarao M. K.
Published: April 2011

Diffraction patterns of a lucite cylinder and a half cylinder in a nearly plane beam of square-wave modulated 3.2 cm. waves, with electric vector parallel to the cylinder axis, have been measured in several planes transverse to the incident beam direction. Patterns of the half cylinder were obtained with the plane face toward and away from the source of radiation. Marked trends in the patterns are related qualitatively to the effects of transmission and surface reflection, both external and internal, expected from geometrical optics considerations.
THE RESOLVER, A CIRCUIT FOR REDUCING THE COUNTING LOSSES OF A SCALER
Authors: Bell R. E.
Published: April 2011

The resolver is a circuit that reduces the counting losses of an ordinary scaler by storing up most of the pulses that otherwise would be lost in dead time, and releasing them uniformly at a safe rate for the scaler. Even for very short input pulses, the circuit contains no active elements that need to be fast enough to follow these pulses, and is thus simpler than an equivalent fast scaler. In a typical case the maximum permissible counting rate of the scaler is raised by a factor of the order of 30. The counting losses of such a circuit are computed. A detailed circuit and the results of tests on it are shown.
LOW FREQUENCY RADIATION FROM A HORIZONTAL ANTENNA OVER A SPHERICAL EARTH
Authors: Wait James R.
Published: April 2011

The problem of the radiation from a horizontal antenna at low radio frequencies over a spherical earth is discussed. The solution is facilitated by considering that the surface of the earth can be characterized by a boundary impedance. It is shown that, in general, both vertically and horizontally polarized waves are radiated along the surface of the earth. At short distances for a homogeneous earth, the expressions are in agreement with Norton's formulas for the radiation field of a horizontal dipole over a flat earth.
THE AGING OF EVAPORATED SILVER FILMS
Authors: Aziz R. A. , Scott G. D.
Published: April 2011

The spontaneous aging of thin films of silver was studied by following electrical resistance variations with time immediately after deposition in vacuo. In one series of experiments films, all deposited in a fixed time of 100 seconds and with initial resistances from 170,000 Ω to 20 Ω, were investigated. The resistance of some films rose rapidly with time; in others it dropped rapidly, and in still others resistance changes were less pronounced. In a second series eight films were formed, all with equal initial resistances (5000 Ω) but deposited in different times. The rate of decrease in resistance was greater as the rate of deposition increased. The limiting value of resistance depended on the time of deposition. A possible qualitative explanation of the results on the basis of distortion decay and film aggregation is proposed.
ON THE SPECIFIC HEAT OF SOLIDS AT LOW TEMPERATURES
Authors: Barron T. H. K. , Morrison J. A.
Published: April 2011

The temperature dependence of the specific heat of solids at very low temperatures is examined, using theoretical models and certain recent experimental results. The temperature region over which the continuum approximation (Cν = aT3) is strictly reliable is shorter than has often been supposed, and the series expansion Cν = aT3 + bT5 + cT7 + … is needed for the analysis of accurate experimental results. For insulators θ0 can best be estimated from measured specific heats by plotting Cν/T3 versus T2; the result is a curve whose intercept at T2 = 0 gives the coefficient of T3 (and hence θ0), and whose slopeand curvature give additional information about the vibrational spectrum at low frequencies. For metals the usual plot of Cν/T versus T2 can be used, but here again neglect of curvature may lead to errors in the estimates of γ and θ0. A brief discussion is given of the low temperature specific heats of a number of solids for which suitable data are available: potassium chloride, lithium fluoride, white tin, tungsten, the noble metals, and elements of diamond structure.
ON THE STRESSES IN TWISTED COMPOSITE SPHERES AND SPHEROIDS
Authors: Das Sisir Chandra
Published: April 2011

Stresses have been calculated in the cases of concentric composite elastic spheres and spheroids when they are twisted by couples. The results have been obtained in closed forms.
SPECTRUM OF L AUGER ELECTRONS FROM 81Tl208 AND 83Bi212
Authors: Geoffrion C. , Nadeau G.
Published: April 2011

The spectrum of L Auger electrons emitted by a source of Th(B + C + C″) has been measured with a 180° beta-ray spectrometer. An empirical formula for the calculation of secondary ionization potentials has been used for a tentative identification of the transitions giving rise to the measured lines.
ON FOCUSING ELECTROMAGNETIC RADIATORS
Authors: Bickmore Robert W.
Published: April 2011

The transmission of electromagnetic energy between two apertures is examined as a function of their sizes, separation, excitation functions, and surface shapes with Fresnel approximations made throughout. Relations are derived which show when it is advantageous to focus the apertures by curving about a spherical surface.
NEUTRON CAPTURE GAMMA RAYS FROM LITHIUM, BORON, AND NITROGEN
Authors: Bartholomew G. A. , Campion P. J.
Published: April 2011

The neutron capture γ-rays from Li7, B11, and N15 have been studied. In Li7 γ-rays are observed at 7.26 ± 0.03 Mev. and 6.78 ± 0.05 Mev. In B11 six γ-rays are detected. The spectrum is consistent with J = 7/2 + for the capturing state. In N15 six previously unreported γ-rays are detected. Estimates of thermal neutron radiative capture cross sections are: Li6, 0.028 ± 0.008 b.; B10, 0.5 ± 0.2 b.; and N14, 0.08 ± 0.02 b.
HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: XII. ROTATIONAL SPECTRA OF C2H4 AND C2D4 AND THE STRUCTURE OF THE ETHYLENE MOLECULE
Authors: Dowling J. M. , Stoicheff B. P.
Published: April 2011

The pure rotational Raman spectra of C2H4 and C2D4 were photographed in the second order of a 21-ft grating. The resolution achieved was such that several lines due to single transitions were observed (and identified) in the spectra of both molecules. An analysis of these lines based on the non-rigid asymmetric top yielded the following rotational constants for the ground states:[Formula: see text]The structural parameters obtained from these constants are r0(C=C) = 1.339 ± 0.002 Å, r0(C—H) = 1.086 ± 0.003 Å, and [Formula: see text]. These values are in agreement with the recent preliminary results of the electron diffraction data. There is also agreement between the above values and those obtained from a recent study of the rotation–vibration spectra of C2H4 and C2D4, although the agreement between the ground state rotational constants is not as satisfactory.
STATISTICAL THEORY OF AVALANCHE BREAKDOWN IN SILICON
Authors: Burgess R. E.
Published: April 2011

The current flowing in silicon junctions under conditions of high electric field sufficient to cause avalanche breakdown consists of a sequence of pulses of constant magnitude and with randomly distributed spacing and duration. A statistical model is presented for this intermittent conduction mechanism in which the transition probabilities between the conducting and non-conducting states are Markoffian and depend on the excess of the applied voltage over the breakdown voltage; power-law and exponential dependences are considered and the precise form is shown not to be critical in deriving from these simple conditions a number of predictions about the macroscopic current–voltage characteristic, all of which have been confirmed by experiment.It is demonstrated generally that a randomly switched discharge of positive resistance has a macroscopic current–voltage characteristic which depends upon the d-c. source resistance and can have a region of negative slope. Only with a negligibly small source resistance is the true characteristic obtained.The observable fluctuations of current and their spectral distribution are derived and indicate the noisiness of silicon junctions under avalanche conditions.The influence of illumination on the breakdown statistics and macroscopic characteristic are briefly discussed.
COMPARISONS BETWEEN FREE ENERGIES OF ACTIVATION FOR GRAIN GROWTH, GRAIN-BOUNDARY SELF-DIFFUSION, AND LIQUID SELF-DIFFUSION
Authors: Holmes E. L. , Winegard W. C.
Published: April 2011

A comparison is made between the free energies of activation for boundary migration during normal grain growth, grain-boundary self-diffusion, and liquid self-diffusion. The equality of these, within the accuracy of experiment and analysis, supports the assumption of identical elementary processes in the three cases. A detailed discussion is given regarding the various constants used in the equations from which the free energies of activation of the above-mentioned processes are derived.
RELATIVE ENERGIES OF TILT-TYPE SUBBOUNDARIES IN ALUMINUM
Authors: Aust K. T.
Published: April 2011

The relative energies of subboundaries were obtained, in terms of a reference large-angle grain boundary, in aluminum bicrystals having two different effective impurity concentrations. The data for subboundary energy versus subgrain orientation difference (θ) showed a cusp at [Formula: see text]. The existence of such a cusp was previously predicted by Martius and Chalmers from considerations of impurity effects at boundaries.
THERMAL AND ELECTRICAL PROPERTIES OF ARMCO IRON AT HIGH TEMPERATURES
Authors: Laubitz M. J.
Published: April 2011

Thermal and electrical conductivity, thermoelectric power vs. platinum, and thermal expansion of Armco iron were determined in the temperature range of 0 °C to 1000 °C. All these properties show a discontinuous change at the α–γ transition of iron, and a change in slope at the Curie point. These measurements were carried out as a contribution to a co-operative determination of thermal conductivity of Armco iron at high temperatures.
THE POLAR RADIO BLACK-OUT OF THE IONOSPHERE OF 7 JULY, 1958
Authors: Chapman John H.
Published: April 2011

Ionospheric sounding station data, particularly f-plots, were used to study the ionospheric storm of 7 July, 1958, which is shown to have consisted clearly of two stages. Polar cap absorption began shortly after an importance 3+ flare was observed at 0039 U.T., and a magnetic storm and auroral absorption event followed at 0749 U.T. on July 8.The polar cap absorption spread towards the geomagnetic equator, but the use of higher than first order magnetic dipole terms was found necessary in order to arrange the data properly in latitude. The absorption began some hours earlier at northern stations than at most southern stations, the main cause of the differences in time of onset being thought to be due to the presence or absence of sunlight.The inference is drawn that ionospheric absorption measured at about 3 Mc/s is caused by ionization at 50- to 80-km heights, in which case the data suggest that electrons first precipitated to the earth above 83° corrected geomagnetic latitude, and then protons and helium ions to lower latitudes. The cutoff latitude was 59°, corresponding to a particle magnetic rigidity of 9.6 × 108 ev/c. This storm was compared with the more severe event of 23 February, 1956, and showed to be of a similar nature.
VELOCITY AUTOCORRELATIONS OF CHARGED PARTICLES IN A MAGNETOIONIC MEDIUM WITH APPLICATIONS TO TURBULENT DIFFUSION
Authors: Bourret R. C.
Published: April 2011

A system of charged particles in a slightly ionized medium is considered subject to (1) collisions with members of the neutral species, (2) a constant external magnetic field, and (3) a fluctuating force field, either external or representing the collision forces. On the assumption that their motions are satisfactorily described by the Langevin equation, the cross-correlation functions in time between velocity components of these charged particles are calculated. These functions may be used, as described elsewhere by the author, to describe the self-diffusion of the charged particles. The cases treated are: purely random external forcing, forcing by exponentially correlated (Markovian) forces, and forcing by a random series of pulses corresponding to collision forces.
THE ABSORPTIVITY SPECTRUM OF A UNIFORM, ANISOTROPIC PLASMA SLAB
Authors: French I. P. , Cloutier G. G. , Bachynski M. P.
Published: April 2011

Using a generalized formulation of Kirchhoff's law it is possible to relate the equilibrium electromagnetic radiation spectrum of a body to its absorptivity spectrum. The microwave absorptivity of a uniform anisotropic plasma slab to a normally incident electromagnetic wave is obtained by matching fields at the boundaries and is solved completely for the model chosen.The absorptivity spectrum of the plasma slab is computed for waves propagating parallel to and normal to an applied static magnetic field for various electron densities, electron collision frequencies, and slab thicknesses. Peaks in the absorptivity spectrum occur around the edges of the "stop-bands". In general, the absorptivity increases with slab thickness and collision frequency. The effect of internal reflections is included and gives rise to undulations in the absorptivity spectrum.
THE SUPERCONDUCTING TRANSITION TEMPERATURE OF LEAD
Authors: Franck J. P. , Martin Douglas L.
Published: April 2011

The temperature of the superconducting transition has been measured for high purity lead samples from three different sources. The transition temperature for all samples agreed to within 0.001° and was determined with a gas thermometer to be 7.193° K ± 0.005°. The transition width for all samples was roughly 0.004°. Some comments on the use of carbon radio resistors as thermometers in the temperature range 3° to 30° K are included.
THE TEMPERATURE DEPENDENCE OF THE SHAPE OF PARAMAGNETIC RESONANCE LINES. PART II
Authors: McMillan Malcolm , Opechowski W.
Published: April 2011

At sufficiently low temperatures the temperature dependence of the shape of paramagnetic resonance lines of crystals is mainly due to the temperature dependence of the occupation numbers of the energy levels of the system of interacting paramagnetic ions. The theory of this effect, recently discussed by the authors, is extended to the case of anisotropic exchange interaction and arbitrary shape of the paramagnetic crystal.
NEW SPECTRUM OF CF+
Authors: Verma R. D.
Published: April 2011

A spectrum (A1Π–X1Σ+) of CF+ has been obtained for the first time in the region 2025–1900 Å. The rotational and the vibrational analyses are given. The principal constants of the two states as evaluated are given below in cm−1, except for re which is given in angstroms.[Formula: see text]A brief discussion of the electron configurations is given.
ENERGY TRANSFER BETWEEN A MOVING BODY AND A MAGNETIC FIELD
Authors: Smy P. R.
Published: April 2011

The inductive transfer of energy between a moving body and a magnetic field is discussed together with its significance in the fields of direct energy conversion and plasma propulsion. The investigation is centered upon the interaction between a moving body and a sinusoidally oscillating magnetic field of idealized distribution. Scaling laws governing the various physical variables of the interaction are derived, and the values of the resultant parameters necessary to obtain maximum energy transfer are calculated. It is found that under these conditions the initial kinetic energy of the body can be increased by ~14× or decreased to ~1/14 during the interaction. The relation between these parameters (and hence the energy transfer) and the all important energy transfer/recirculating energy ratio is obtained and it is shown that, in fact, a working energy factor ~6 (or 1/6) is a more feasible proposition.
CALCULATION OF THE SELF-BROADENING OF RAMAN LINES DUE TO DIPOLAR AND QUADRUPOLAR FORCES
Authors: Kranendonk J. Van
Published: April 2011

The impact theory of Raman line broadening due to anisotropic intermolecular forces, developed previously, is applied to the broadening due to dipolar and quadrupolar forces. The optical cross sections are calculated assuming the isotropic intermolecular potential to be a hard-sphere potential, and neglecting the spread in velocities. Explicit expressions are derived for the phase-shift contribution to the width of the isotropic (j = 0) and anisotropic (j = 2) Raman scattered light as a function of the rotational quantum number J. For j = 2 scattering the phase shifts produced in the radiation do not vanish when the initial and final states of the radiation process are identical, and the phase-shift contribution to the width of the anisotropic components of the Q lines is of the same order of magnitude as for the S lines. In all cases the phase-shift contribution tends to zero when J becomes large compared with j. The contribution to the width of the inelastic collisions also tends to zero for large J, but this is characteristic of the long-range interactions considered here and results from the correspondingly short range of the resonance factors. The theory is compared with the available experimental data on H2 and N2. It is pointed out that quite generally an observation of the broadening of the isotropic and anisotropic Raman lines allows a determination of the lifetimes of the rotational levels and of the phase-shift contributions to the width of the anisotropic lines.
EXPERIMENTS WITH MOVING MAGNETIZED PLASMA
Authors: Smy P. R. , Offenberger A.
Published: April 2011

Results of various experiments with moving magnetized plasma produced in a shock tube are presented. It is found that both incident and reflected shock speeds are independent of the applied field strength up to the maximum field strength of 104 gauss. Measurements of the momentum transfer from the magnetized plasma to an essentially diamagnetic ring surrounding the shock tube were accomplished by mechanical and electrical means; the mechanical measurements show good agreement with theory.
THE ELECTROMAGNETIC FIELD WITHIN A DISCONTINUOUS CONDUCTOR WITH REFERENCE TO GEOMAGNETIC MICROPULSATIONS NEAR A COASTLINE
Authors: Weaver J. T.
Published: April 2011

The two-dimensional problem of a low-frequency, plane-polarized electromagnetic wave incident on a semi-infinite conducting medium with a plane surface is treated for the case when the medium has a discontinuity, the regions on either side of a plane normal to its surface being of different conductivities. Arguments are given to show that it is reasonable to assume, as a low-frequency approximation, that the tangential magnetic field is constant on the surface of the conductor. With the aid of this approximation, solutions are obtained for the two cases when (i) the magnetic vector (H polarization) and (ii) the electric vector (E polarization) is always parallel to the trace of the discontinuity.The model is discussed with reference to the behavior of geomagnetic micropulsations near a coastline, particular attention being paid to the E-polarization solution which contains a magnetic component normal to the surface of the conductor. The amplitude of this component at the surface is shown to increase sharply as the region of the discontinuity is approached, thus providing an explanation of the enhanced Z magnetic component in the micropulsation field observed at coastal stations.
PLANE WAVE SPECTRA IN GRATING THEORY: IV. SCATTERING BY A FINITE GRATING OF IDENTICAL CYLINDERS
Authors: Millar R. F.
Published: April 2011

Scattering of time-harmonic plane waves by a finite grating of identical elements is examined by mathematical decomposition of an infinite grating. An equation is derived which relates the scattering function of the finite grating to that of a single element in the infinite grating. This is manipulated to make possible a series solution involving scattering functions for semi-infinite gratings. The first term is equal to the scattering function obtained by assuming that each cylinder of the finite grating scatters as an element of an infinite grating, plus end-effect corrections which involve scattering functions for semi-infinite gratings. Other terms tend to zero as the width of the grating tends to infinity. These higher-order terms are of most importance when circumstances are favorable for the existence of grating anomalies.The qualitative form of the scattered far field is examined. It is suggested that the "single anomaly", observed experimentally, is actually the superposition of two effects. One is dependent on the angle of incidence (α), the other on the angle of observation (θ). This latter effect, although always present, usually occurs in directions of low field intensity and apparently has not been observed. When α is such that a single anomaly is to be expected, the θ-dependent effect occurs in directions of high intensity. Similarly, it is argued that the double anomaly is a superposition of four effects.
EQUILIBRIUM SHOCK-WAVE CALCULATIONS IN INERT GAS, MULTIPLY IONIZED DEBYE–HUCKEL PLASMAS
Authors: McChesney M.
Published: April 2011

This paper reviews the physical basis of existing equilibrium inert-gas shock-wave calculations and points out their limitations. The various solutions to the problems of terminating the electronic excitation partition function and also the lowering of the ionization potentials by a plasma microfield are discussed and coordinated into a family of cutoff procedures.New equilibrium shock-wave equations are derived which allow for multiple excitation and ionization and the presence of Debye–Huckel effects in the shock-heated plasma. It is demonstrated how the use of such a plasma model logically and simply provides a solution to the problem of energy-level cutoff.
The frequency-dependent initial perpendicular susceptibility of the Ising model
Authors: Allan G. A. T. , Betts D. D.
Published: April 2011

The Kubo linear response theory is applied to the quantum mechanical Ising model to obtain a general expression which is valid for all regular lattices for the perpendicular response function in terms of spin correlations. For the honeycomb and the square lattices, exact expressions are found for the frequency-dependent initial perpendicular susceptibility, [Formula: see text] valid for all temperatures. For the honeycomb lattice, the present result for zero frequency agrees with Fisher's static calculation, whereas there is disagreement in the case of the square lattice. The discrepancy is resolved by using an extended calculation which explicitly illustrates the difference between isothermal and adiabatic susceptibilities.
Interaction between longitudinal and transverse plasma waves
Authors: Krishan Som , Selim A. A.
Published: April 2011

The rate at which energy is fed into the transverse waves due to interaction with longitudinal waves is calculated for the case of an infinite, homogeneous, isotropic, collisionless plasma. The method is based on constructing the Hamiltonian for the system in terms of creation and annihilation operators of second quantization. It turns out from the Hamiltonian that the dominate mechanism is the one in which two longitudinal waves collide to yield one transverse wave. Thus, in general, the energy transfer rate decreases with time. In a special case the results agree with the previous work (Aamodt and Drummond 1964).