bluuebunny/crossref_metadata_2025 huggingface dataset:
SUPERLATTICE STUDIES IN THE SYSTEMS SILVER–MAGNESIUM–TIN AND SILVER–MAGNESIUM–ZINC
Authors: Henry W. G. , Raynor G. V.
Published: April 2011

The 3/2 electron compound in the system silver–magnesium, in which tin and zinc are soluble, has an ordered structure of the cesium chloride type (second zone superlattice). The first additions of tin to this phase do not affect the ordered structure. Above a certain limit, a third zone superlattice is formed, and the tin atoms themselves occupy ordered positions. X-ray examination at high temperatures shows that the third zone superlattice disorders independently of the main, second zone superlattice. The transformation temperature increases with increasing tin content; that of the cesium chloride superlattice, however, decreases with increasing tin content. In the silver–magnesium–zinc system, the introduction of zinc into the binary silver–magnesium 3/2 electron compound causes no development of a third zone superlattice. The temperature at which the second zone superlattice disorders decreases with increasing zinc content.It is suggested that the reason for the existence of the second superlattice depends upon a combination of the following factors:(i) The lattice distortion due to the high valency of tin creates a long-range distortion which is more easily distributed, leading to a minimum interaction strain energy, by the formation of a doubly ordered structure.(ii) The electrochemical effect between magnesium and tin atoms at a distance "a" apart (where "a" is the lattice spacing of the body-centered cubic cell) contributes to the lowered free energy of a doubly ordered structure.
SELF-DIFFUSION AT SILVER SURFACES
Authors: Winegard W. C. , Chalmers B.
Published: April 2011

The surface self-diffusion of silver on specific crystallographic surfaces of silver single crystals and on polycrystalline specimens was investigated. Various methods of surface preparation were used and the general conclusion was reached that surface diffusion is accelerated during changes of surface shape. The theory is advanced that "surface" diffusion takes place by a lattice vacancy mechanism; an abnormally high concentration of lattice vacancies is believed to be necessary for changes of surface shape to occur. This accounts for the accelerated surface diffusion observed under these conditions.
SLOW π-MESONS IN COSMIC-RAY STARS AND THE NEGATIVE–POSITIVE π-MESON RATIO
Authors: Mei J. Y. , Pickup E.
Published: April 2011

In a survey of mesons ending in the emulsion no τ- or κ-mesons have been observed so far. The variation of the negative–positive π-meson ratio with energy shows up the effect of the Coulomb barrier on π-meson production at very low energies. The variations of this ratio at mountain and balloon altitudes are discussed. Examples have been obtained of the emission of slow π-mesons in hydrogen collisions in the emulsion, and also in energetic stars with several shower particles and few evaporation particles.
THE PHOTONEUTRON CROSS SECTIONS FOR THE REACTIONS Br81 (γ,n) Br80 AND Br81 (γ,n) Br80* AND AN ANALYSIS OF THE RATIO BETWEEN THESE CROSS SECTIONS
Authors: Katz L. , Pease L. , Moody H.
Published: April 2011

Cross-section curves have been measured as a function of energy for the reactions Br81(γ,n)Br80 and Br81(γ,n)Br80* and the ratio between these cross sections has been examined critically. The curves exhibit the peaked shape characteristic of photonuclear reactions with maximum cross sections of 88 and 42 millibarns respectively. It is shown that the ratio of the cross sections depends on the spins of the excited levels in which the Br80 nucleus is left prior to γ cascading and thus on the reaction leading to it. An elementary analysis based on this point of view gives results consistent with the ratio measured for six different types of reactions.
FURTHER OBSERVATIONS ON DENDRITIC GROWTH IN METALS
Authors: Weinberg F. , Chalmers Bruce
Published: April 2011

The direction of dendrite growth has been determined as a function of crystallographic orientation for high purity tin and zinc, using a single crystal decanting technique. Measurements are reported on the rate of dendrite growth in lead, and the spacing between dendrite rows of a lead crystal for varying amounts of supercooling. The initial formation of dendrite stalks appears related to a cell structure observed on the exposed solid liquid interface.A mechanism of dendrite growth is advanced and compared with the experimental observations. It is shown that dendritic growth occurs only during the initial part of solidification. The remainder is a result of the nondendritic advance of a solid liquid interface with some thickening of the existing branches.
NOTE ON THE RESOLVING POWER OF MASS SPECTROMETERS
Authors: Kerwin Larkin
Published: April 2011

In calculating the resolving power of a homogeneous field mass spectrometer, one must consider the dispersion and the beam width of the instrument. The latter is the sum of at least 10 components, which are discussed. Formulae giving the resolving power of three types of spectrometer of current interest are developed, as well as formulae for positioning the exit slits.
DESIGN AND PERFORMANCE OF A FUSED SILICA MICROBALANCE
Authors: Carmichael Hugh
Published: April 2011

The construction and the use of a robust microbalance with a fused silica beam are described. The design is such that the microbalance is undisturbed by convection even in surroundings where it would be impossible to use an ordinary microbalance; nevertheless the instrument is very convenient to operate. A comprehensive theoretical treatment of the silica torsion balance and of the effects of constructional imperfections is given and shown to be in good agreement with experiment. The performance of the microbalance is illustrated by means of an example from the microchemical work of B. G. Harvey, where four samples of americium oxide, of masses between two and six micrograms, were weighed on 100 mgm. scale pans, with a proven accuracy better than 0.3%. The precautions that were taken to minimize the harmful effects of adsorption and dust are described. A commercial version of this microbalance is now available.
HIGH FREQUENCY GAS DISCHARGE BREAKDOWN IN NEON
Authors: MacDonald A. D. , Betts D. D.
Published: April 2011

Electrical breakdown of neon at high frequencies has been treated theoretically on the basis of the Boltzmann transport equation. Exciting and ionizing collisions are accounted for as energy loss terms in the Boltzmann equation and measured values of the ionization efficiency are used in the integral determining the ionization rate. Electrons are lost to the discharge by diffusion. The equations are treated separately for the cases in which the collision frequency is much less than or much greater than the radian frequency of the applied field. The electron energy distribution functions are expressed in terms of Bessel functions, confluent hypergeometric functions, and simple exponentials. The ionization rate and the diffusion coefficient are calculated using these distribution functions in kinetic theory formulas, and combined with the diffusion equation to predict breakdown fields. The theoretically predicted fields are compared with experiment at 3000 Mc. per sec. The breakdown equations, calculated from kinetic theory and using no gas discharge data other than collision cross sections, predict breakdown electric fields within the limits of accuracy determined by these cross sections over a large range of experimental variables.
RAMAN SPECTROSCOPY OF LOW PRESSURE GASES AND VAPORS
Authors: Welsh H. L. , Crawford M. F. , Thomas T. R. , Love G. R.
Published: April 2011

Raman spectra of gases and vapors at pressures of a few atmospheres were obtained with a carefully diaphragmed Raman tube of large volume, irradiated by five high intensity mercury lamps with water-cooled electrodes. Frequencies and intensity contours of 32 of the 35 fundamental bands of CH4, CH3Cl, CH2Cl2, CHCl3, CCl4, and CH3Br were measured. Vibrational assignments, based on the intensity contours of the bands, showed no discrepancies in previous assignments. The integrated intensities of the bands, determined on the same intensity scale for all compounds of the series, show the inadequacy of the bond polarizability theory of Raman intensities. Depolarization factors, calculated from the intensity distribution in totally symmetric bands, are somewhat greater than those measured for the liquid. Asymmetries in the Q branches of some totally symmetric bands are explained quantitatively in terms of anharmonicity and isotope effect.
A SIMPLIFIED IONIZATION GAUGE CIRCUIT
Authors: Osborne F. J. Fitz
Published: April 2011

By measuring the ratio of ion current to electron current present in the usual ionization gauge, an extremely stable circuit has been developed, comparing favorably with standard circuits. A simple calibration made during construction makes this gauge direct reading. The circuit may be used for outgassing the gauge, and for leak hunting, being very sensitive in this respect. It incorporates a safety cutoff. It has relatively few controls, and is extremely cheap. For several months we have operated gauges in this laboratory with several types of circuit, and find that the one described in this paper is simpler and more rugged although just as useful and versatile as our modified Rainwater instrument.
A PRISMATIC SUBSTRUCTURE FORMED DURING SOLIDIFICATION OF METALS
Authors: Rutter J. W. , Chalmers B.
Published: April 2011

Single crystals of tin grown from the melt under a wide range of conditions are shown to exhibit a fibrous structure which manifests itself as parallel ridges ("corrugations") on the free surface of the specimen and as a hexagonal network ("hexagonal cells") on the growing solid–liquid interface. The center of each cell projects into the liquid. Segregation of impurities is shown to occur during solidification in a manner intimately related to the structure. The structure is suppressed by growth at low speeds or under a steep temperature gradient. The size and regularity of the elements of the structure depend upon speed of growth, temperature gradient, and impurity content. A theory is advanced which accounts for the origin and observed properties of the structure. This theory shows that the structure consists essentially of a particular distribution of impurities resulting from nonequilibrium solidification.
ENERGY LOSS OF HIGHLY CHARGED PARTICLES PRODUCED BY FISSION AND BY COSMIC RAYS: SECTION I. OBSERVATIONS OF FISSION FRAGMENTS
Authors: Demers Pierre
Published: April 2011

Measurements on the range of the tracks of fission fragments recorded in special laboratory-made emulsions are reported. The origin was marked so that observations on length not possible otherwise were made. Stopping power and straggling for such tracks in different media are discussed. It is shown, that the range of one fragment is little dependent on the range of the other paired fragment. The blackening of the two tracks near the origin is on the average unequal, that of the light fragment L being darker. It is inferred that ionization is greater near the origin for the L fragment. Knock-on protons allow a range velocity curve to be drawn, and evidence is advanced to prove that the light associated particles are indeed knock-on protons.
ON THE CHARACTERISTIC TEMPERATURES OF SINGLE CRYSTALS AND THE DISPERSION OF THE "DEBYE HEAT WAVES”
Authors: Post E. J.
Published: April 2011

A procedure for the calculation of the number of normal modes of a single crystal is proposed which takes an intermediate position between the methods of Debye and Born–von Karman. The method of Debye is extended to an anisotropic continuum, where the cutoff and dispersion phenomena, which are due to the lattice structure, are accounted for in a semiempirical way. It appears possible to define a finite number of characteristic temperatures (one for cubic crystals and at most three for crystals of low symmetry) independent of direction. This ensures a comparatively simple calculation from the phenomenological elastic constants of the crystal, as such retaining one of the pleasing features of Debye's theory, i.e., a straightforward correlation between thermal and elastic data.The method is applied to eight cubic monatomic crystals for which elastic data are available. The results provide some additional evidence to emphasize the significance of the dispersion of the Debye heat waves.An application to the hexagonal crystals of cadmium and zinc leads to results similar to those obtained by Grüneisen and Goens who produced with these crystals the first experimental evidence of the dispersion phenomenon using the concept of a characteristic temperature dependent on direction.In the last section the correlation between the elastic constants of single crystals and the corresponding quasi-isotropic materials is discussed and illustrated with data found in the literature. It is shown that the polycrystalline state is more "elastic" (sometimes very considerably) than the single crystal state. The consequences of this "boundary layer elasticity" for the calculation of θ values are discussed.
THE INITIAL MAGNETIZATION OF NICKEL UNDER TENSION
Authors: Brockhouse B. N.
Published: April 2011

In an attempt to resolve apparent discrepancies in the literature the initial susceptibility (χ) and Rayleigh constant (a) of pure nickel wire were measured between room temperature and the Curie point under various tensions (Z). For annealed nickel the quantity χZ is independent of Z, as required by Becker's theory, if the stresses are applied in order of increasing magnitude and if no plastic deformation occurs. χ and a are found to be connected by Néel's relation a = c χ2J0/Js. The same temperature dependence is shown by χZ as by the initial susceptibility of unstressed nickel given in the literature. At temperatures below 150 °C. the temperature dependence of χZ is consistent with the recent theory of Döring. At higher temperatures χZ increases monotonically to the Curie point but at a smaller rate than Döring's low temperature theory predicts. This temperature dependence is in apparent conflict with Becker's theory and magnetostriction measurements of Döring and Kirkham. It is possible, but unlikely, that the conftict arises from the presence of textures in the various specimens. An appendix gives the textures of the wire specimens as found by neutron diffraction.
COUNTING RATE MEASUREMENT BY INTERVAL SAMPLING
Authors: Crouch M. F. , Haynam G. E.
Published: April 2011

Two methods are described for measuring high counting rates with a counting device having a long resolving time. Both methods are based on the deliberate introduction of a large but calculable counting loss to transform a high counting rate to a lower rate. Formulas giving the counting rate in terms of the reduced rate are presented, together with formulas for the standard deviation of the counting rate. The performance of circuits used to study one of the methods is described, and a comparison is made with conventional rate measurement methods. It is found that, while the relative simplicity of equipment is gained at the expense of speed of measurement, the latter sacrifice is not as severe as might be expected.
PLAFONNEMENT DES AEROSTATS A GRANDE ALTITUDE
Authors: Demers Par Pierre
Published: April 2011

A sinlple procedure is described, combining the use of closed rubber balloons with that of an open Polythene balloon of medium size, which has allowed us to keep cosmic ray sensitive emulsions for 9 to 10 hr. at a ceiling of 24 to 32 km.
THE SOUND FIELD OF A PISTON SOURCE
Authors: Guptill Ernest W.
Published: April 2011

An exact solution is presented for the sound field between two infinite walls when the source is a piston in one of the walls. A method is also outlined for the case of a source having any amplitude distribution which is a function only of radial distance from the center of the source. Several graphs are shown and they are intended to illustrate how the pressure on a receiving crystal would vary when the wall separation is changed.
FISSION YIELDS OF THE STABLE AND LONG-LIVED ISOTOPES OF CESIUM, RUBIDIUM, AND STRONTIUM AND NUCLEAR SHELL STRUCTURE
Authors: Wiles D. R. , Smith B. W. , Horsley R. , Thode H. G.
Published: April 2011

The relative yields of the isotopes of cesium, rubidium, and strontium from thermal neutron fission of U235 have been determined mass spectrometrically. The cesium isotope yields are combined with those obtained previously for the xenon isotopes to give high precision yields for mass chains from 131 to 137. In this work neutron capture reactions have been considered and corrections made where these take place to an appreciable extent. The results give further evidence of abnormal yields in the 82 neutron shell region. The half-life of Cs137 was determined and found to be 33 ± 2 years.
AUGER TRANSITIONS IN SILVER
Authors: Johnson F. A. , Foster J. S.
Published: April 2011

Twenty of the K Auger lines of silver have been resolved and estimates of their relative intensities obtained. Comparison with the theoretical intensities calculated by Burhop indicates that the existing theory is not quantitatively correct and that relativistic modifications offer little hope of improvement. Special attention is directed to the K → LL lines where disagreement with theory is most marked. Comparison with similar observations previously reported for gold and bismuth shows an interesting agreement in the observed ratio of the intensity of the K → LIILIII line to that of the K → LIIILIII line, and in the ratio of the intensity of the K → LILIII line to that of the K → LILI line.
ENERGY LOSS OF HIGHLY CHARGED PARTICLES PRODUCED BY FISSION AND BY COSMIC RAYS: III. THE LINEAR DENSITY OF DELTA RAYS. EXPERIMENTS
Authors: Demers Pierre , Lechno-Wasiutynska Zofia
Published: April 2011

Delta rays having an energy as low as 2–5 kev. have been counted along the tracks of mesons, protons, and α rays of low velocity, allowing the identification of each. Three methods are presented and applied to determine the efficiency ƒ of counting delta rays of various energies; measured values of ƒ vary between 0.05% at 2 kev. and 100–180% near 50 kev. The number of grains, and the energy distribution among visible delta rays, are analyzed. A new method of determining velocity, based on the analysis of the number of grains in the delta rays, is presented. In the Appendix, the effect of relativistic corrections is computed and discussed. It is small except at large velocities where comparison with experiment is difficult.
FERROMAGNETISM AND ORDER IN NICKEL MANGANESE ALLOYS
Authors: Piercy G. R. , Morgan E. R.
Published: April 2011

An investigation of ferromagnetism in nickel manganese alloys containing up to 40 atomic per cent manganese has been carried out. Twenty alloys within this composition range were subjected to heat treatments such that the atomic arrangement within the alloys varied from disorder to a high degree of long range order.The degree of order of Ni3Mn calculated from measured saturation magnetization using the atomic model of ferromagnetism was consistent with the value calculated from the ratio of measured integrated intensity of the (110) X-ray diffraction superlattice line to that of line (111).The relationship between saturation magnetization and concentration for the disordered alloys can be explained adequately by the existence of short range order. A value of 3.4 Bohr magnetons for the effective magnetic moment of manganese atoms in a nickel lattice was deduced.
FORBIDDEN TRANSITIONS IN DIATOMIC MOLECULES: III. NEW AND ABSORPTION BANDS OF THE OXYGEN MOLECULE
Authors: Herzberg G.
Published: April 2011

Two new forbidden transitions of the O2 molecule have been found. They give rise to very faint absorption bands overlapping the much stronger forbidden [Formula: see text] bands previously described. The upper states are identified as [Formula: see text] and 3Δu respectively, both of which arise from the same electron configuration as the known states [Formula: see text] and [Formula: see text]. For the [Formula: see text] state the following vibrational and rotational constants have been determined: Te = 36678.91, ωe = 650.49, ωexe = 17.036, ωeye = −0.1056, ωeze = −0.00744, Be = 0.8261, αe = 0.0205, γe = −0.000830 cm.−1, γe = 1.597 × 10−5 cm. The constants are based on the assumption of a certain vibrational numbering which may have to be revised (increased). For the 3Δu state the data are quite fragmentary and only two rotational constants, B5 = 0.8177, B6 = 0.7915, and one vibrational quantum, [Formula: see text], have been determined. The bands of the [Formula: see text] system are very close to those of the [Formula: see text] system and represent in all probability the analogue in free O2 of the diffuse triplet bands of Wulf, Finkelnburg, and Steiner ascribed to O4. The positions of the new [Formula: see text] and 3Δu states agree closely with those predicted by Moffitt. Almost half of the unidentified features of the spectrum of the nightglow agree within 5 Å with the predicted positions of emission bands of the [Formula: see text] system.
A CONDUCTING PERMEABLE SPHERE IN THE PRESENCE OF A COIL CARRYING AN OSCILLATING CURRENT
Authors: Wait James R.
Published: April 2011

The analysis is carried out for the problem of a current-carrying coil in the neighborhood of a spherical body whose conductivity and magnetic permeability differ from the surroundings. The case is considered in detail where the frequency is low enough so that the primary field of the coil can be derived from a magnetic scalar potential. The secondary magnetic fields due to the sphere are then derived. The "in-phase" and "quadrature" components of the secondary field are discussed numerically and illustrated by graphs. The results have application to electrical prospecting.
GRID IONIZATION CHAMBER MEASUREMENTS OF ELECTRON DRIFT VELOCITIES IN GAS MIXTURES
Authors: English W. N. , Hanna G. C.
Published: April 2011

Electron drift velocities have been measured in the low X/p region from 0.05 to 0.5 volts per cm. per mm. mercury which is an important one for the calculation of collection times in electron pulse chambers. The grid ionization chamber method is rapid and convenient and gives an accuracy of about 10%. Mixtures of the noble gases neon, argon, krypton, and xenon with carbon dioxide and/or methane have been studied, as well as a number of unpurified "tank" gases. In the mixtures used there are anomalies, or humps, in the drift velocity curves which seem to be correlated with the "Ramsauer" electron free paths in the four noble gases. There is a striking difference in the effect of carbon dioxide and of methane when added in small amounts to the noble gases, which is attributed mainly to the difference in electron mean free path in these two gases, but may also be an indication of a difference in electron energy distributions.
THE O16(γ, n)O15 and O18(γ, p)N17 REACTIONS
Authors: Montalbetti R. , Katz L.
Published: April 2011

The cross section for the O16(γ, n)O15 reaction has been determined by detecting the emitted neutrons, and the cross section for the O18(γ, p)N17 reaction has been determined by detecting the delayed neutrons following the decay of the N17 nucleus. Both cross sections exhibit a slowly rising portion for some 3 Mev. above threshold, followed by the usual large resonance shaped curve. This anomalous behavior is discussed in the light of present photonuclear theories.
SECOND ORDER NUCLEAR QUADRUPOLE EFFECTS IN SINGLE CRYSTALS: PART I. THEORETICAL
Authors: Volkoff G. M.
Published: April 2011

The dependence of electric quadrupole splitting of nuclear magnetic resonance absorption lines in single crystals on crystal orientation in an external magnetic field is investigated theoretically following earlier work of Pound, of Volkoff, Petch, and Smellie, and of Bersohn. Explicit formulae are given, applicable to non axially symmetric crystalline electric field gradients (η ≠ 0), and valid up to terms of the second order in the quadrupole coupling constant [Formula: see text], for the dependence of the absorption frequencies on the angle of rotation of the crystal about any arbitrary axis perpendicular to the magnetic field. Some formulae including third order effects in Cz are also given. It is shown that an experimental study of the dependence of this splitting on the angles of rotation about any two arbitrary mutually perpendicular axes is sufficient, when second order effects are measurable, to yield the values of | Cz |, η, and the orientation of the principal axes of the electric field gradient tensor at the nuclear sites. In the case that the direction of one of the principal axes is known from crystal symmetry, a single rotation about this axis gives the complete information.A new method of determining nuclear spin I is proposed which depends on comparing first and second order shifts of the resonance frequencies of the strong inner line components. The method will be of interest in those cases where the total number 2I of line components can not be unambiguously ascertained owing to the outer line components being excessively broadened and weakened by crystal imperfections.
SECOND ORDER NUCLEAR QUADRUPOLE EFFECTS IN SINGLE CRYSTALS: PART II. EXPERIMENTAL RESULTS FOR SPODUMENE
Authors: Petch H. E. , Cranna N. G. , Volkoff G. M.
Published: April 2011

Experiments on the splitting of the Al27 resonance absorption line in a single crystal of LiAl(SiO3)2 (spodumene) are described, and are used to illustrate the second order theory of Part I. [Formula: see text] for Al27 nuclei in spodumene is found to be 2950 ± 20 kc./sec. [Formula: see text] at Al sites is found to be 0.94 ± 0.01. The x principal axis (corresponding to the smallest eigenvalue [Formula: see text]) of [Formula: see text] at the Al sites is found to coincide with the b axis of the monoclinic spodumene crystal. The other two principal axes lie in the ac plane with the y axis (corresponding to the intermediate eigenvalue [Formula: see text]) making an angle of [Formula: see text] with the crystal c axis towards the a axis. The y principal axis at the Al sites and the z principal axis at the Li sites appear to point at the projection of the nearest oxygen ion in each case. The new method of spin determination proposed in Part I is checked by confirming the known value I = 5/2 for Al27.
THE INTENSITIES OF ATOMIC AND MOLECULAR FEATURES IN THE AURORAL SPECTRUM
Authors: Petrie W. , Small R.
Published: April 2011

A considerable number of auroral spectrograms (dispersion 85–28 Å/mm.) have been analyzed with a recording microphotometer, and integrated intensities obtained for the main features. Relative population rates of the relevant levels are determined from the measured intensities. Excitation mechanisms are discussed and the absence from the spectra of certain low level atomic lines does not appear to be anomalous. It seems that atomic lines are emitted as the results of several processes, while the ionic lines are produced during simultaneous ionization and excitation through electron exchange. Vibrational temperatures of First Negative, First Positive, and Second Positive nitrogen bands are comouted.
THE NEUTRON CAPTURE 7-RAYS FROM POTASSIUM
Authors: Bartholomew G. A. , Kinsey B. B.
Published: April 2011

The capture γ-rays from potassium have been re-examined with greater resolution than was used in previous experiments. The upper end of the spectrum has been carefully studied both with a sample of natural potassium carbonate and with another in which the potassium was enriched in K40. From a comparison of the spectra two γ-rays with energies of 9.39 ± 0.06 and 8.45 ± 0.02 Mev. are assigned to capture by that isotope. The strong γ-ray at 7.757 ± 0.008 Mev. previously ascribed to the ground state transition in K40 is now found to represent a transition to a low-lying excited state in that nucleus.
DETERMINATION OF RATES OF CHANGE OF POLARIZABILITY FROM RAMAN AND RAYLEIGH INTENSITIES
Authors: Stansbury E. J. , Crawford M. F. , Welsh H. L.
Published: April 2011

Mean values of the rate of change of polarizability with respect to internuclear distance were determined for several molecules from the ratio of Raman and Ray-leigh intensities in the gas. The values obtained are: hydrogen, 1.2 × 10−16 cm.2; deuterium, 1.1; hydrogen chloride, 1.0; hydrogen bromide, 1.2; nitrogen, 1.6; oxygen, 1.4; carbon dioxide (ν1 vibration), 4.2; methane (ν1 vibration), 4.1. It is noteworthy that the values for the partially ionic molecules, hydrogen chloride and hydrogen bromide, are nearly the same as for hydrogen and deuterium.
INTERPRETATION OF THE FLUCTUATING ECHO FROM RANDOMLY DISTRIBUTED SCATTERERS. PART I
Authors: Marshall J. S. , Hitschfeld Walter
Published: April 2011

The radar echo from randomly distributed scatterers fluctuates in intensity about a mean equal to the sum of the intensities contributed by each particle. If k independent intensity values are averaged, the r.m.s. deviation of the fluctuation is reduced by a factor √k. Counting the fraction of signals falling above one or more thresholds is a practically simpler, though somewhat less rapid, alternative to averaging. As a further alternative, one can superimpose many independent sweeps of amplitude or signal level on an A-scope, and so observe the most probable value.In range interval l, a single sweep contains 2l/h independent data, where h is the pulse length. The intensity averaged under the continuous trace is slightly more accurate than the average of the independent data.Pulses sent through the same scatterers yield identical returns until the scatterers have had time to reshuffle themselves. Successive pulses give independent echoes, however, if their frequencies differ by about 1/τ, τ being the pulse duration. Echoes from the same pulse received at separate antennas are similarly independent.Several (k) independent echo values are helpful in measuring steady echoes against a noise background. For fluctuating echoes, k must be large, regardless of the relative strengths of echo and background. Large values of k in addition materially enhance the detectability of fluctuating echoes weak compared to the noise.
A THEORETICAL INVESTIGATION OF THE NUCLEAR RESONANCE ABSORPTION SPECTRUM OF Al27 IN SPODUMENE
Authors: Lamarche G. , Volkoff G. M.
Published: April 2011

A theoretical investigation is presented of the energy levels of a nucleus of spin I = 5/2, a given magnetic moment μ, and electric quadruple moment eQ, placed in a uniform magnetic field H0, and a crystalline electrostatic potential [Formula: see text] without axial symmetry. The dependence of the energy levels, line frequencies, and transition matrix elements on the dimensionless parameter [Formula: see text] is calculated for Al27 for one orientation of a spodumene crystal in the magnetic field H0 over the interesting range of the parameter R linking up the pure quadrupole with the Zeeman spectrum. Other orientations of the crystal are discussed briefly.
A METHOD FOR THE EVALUATION OF SOME LATTICE SUMS OCCURRING IN CALCULATIONS OF PHYSICAL PROPERTIES OF CRYSTALS
Authors: van der Hoff B. M. E. , Benson G. C.
Published: April 2011

A method is described for the evaluation of sums of the inverse nth power of the distances from a point P to all points of a lattice. The sums are expressed in sums of Bessel functions or e-powers that converge rather rapidly and Riemann ζ functions. The procedure can be used for any position of P with respect to the lattice.
THE EFFECT OF THERMAL RADIATION ON THE ELECTRICAL RESISTANCE OF HYDROPHILIC ORGANIC FILMS
Authors: Niven C. D.
Published: April 2011

When thermal radiation falls on certain organic films it increases their electrical conductivity markedly; these films are all hydrophilic. Gelatin showed this effect in the most satisfactory manner but the noise in the film was quite large. In some cases the relative humidity of the air surrounding the film had a definite influence on the noise but there was apparently some other and more important factor involved which it has not been possible so far to identify and eliminate; consequently the hydrophilic film cannot compete with the inorganic detectors. The films were also found to be electrically sensitive to minute atmospheric pressure changes.
ON THE SHRINKAGE FACTOR OF NUCLEAR EMULSIONS
Authors: Greenberg L. H. , Haslam R. N. H.
Published: April 2011

A simple and accurate method to determine the shrinkage factor of nuclear emulsions is presented. Its use shows that the shrinkage factor is not a function of the angle of inclination of the alpha particle tracks in the emulsion.
ON SOME PHYSICAL ASPECTS OF THE THEORY OF THE ORIGIN OF MOUNTAIN BELTS AND ISLAND ARCS
Authors: Scheidegger Adrian E.
Published: April 2011

It is shown that a physical explanation can be given within the framework of the contraction hypothesis of orogenesis for the four types of junctions of island arcs and mountain belts observed by geologists.
FIRST SOUND IN LIQUID HELIUM AT HIGH PRESSURES
Authors: Atkins K. R. , Stasior R. A.
Published: April 2011

The velocity of ordinary sound in liquid helium has been measured in the temperature range from 1.2 °K. to 4.2 °K. at pressures up to 69 atm. A pulse technique was used with a carrier frequency of 12 Mc.p.s. Curves are given for the variation of velocity with temperature at constant pressure and also at constant density. There is no detectable discontinuity along the λ-curve. The results are used to discuss the ratio of the specific heats, the coefficient of expansion below 0.6 °K., and the specific heat above 3 °K.
RAYLEIGH SCATTERING OF CONDENSED MATTER
Authors: Theimer O. , Lell E.
Published: April 2011

The scattering power S(λ) = Is/Id (Is, Id are the intensities of the scattered and the incident light) for visible light is investigated experimentally for ordinary glass, optical glass, water, and air. It is found that S(λ) for glass shows pronounced deviations from Rayleigh's 1/λ4 law, e.g., a relative maximum of S(λ) for λ = 5200 Å in the case of ordinary glass. A theory for the Rayleigh scattering of condensed matter is developed and compared with the ideas brought forward by Fürth and Humphreys-Owen in 1951. It is shown that the maxima of S(λ) observed by these authors and in the present work can be equally well derived from localized lattice imperfections or from the mosaic blocks considered by Fürth.
THE POTASSIUM–ARGON METHOD OF GEOLOGICAL AGE DETERMINATION
Authors: Shillibeer H. A. , Russell R. D.
Published: April 2011

The development of the potassium–argon method for dating minerals is discussed. The decay scheme for radioactive potassium-40 is examined. The results of 11 recent counting experiments have been averaged and give a mean value of 29.4 ± 2.7 beta emissions per second per gram of potassium. Averaging the 15 previous determinations of the rate of gamma decay gives a branching ratio of 0.090 ± 0.038 with the above beta decay rate. This is in close agreement with a branching ratio of 0.089 suggested by us in a previous paper on the basis of two potassium–argon determinations.Methods of measuring the radiogenic argon content of potassium minerals are discussed and the method in use at this laboratory is described in detail. Yield runs and grain size experiments have been carried out and are reported. Potassium–argon ages have been calculated for four perthites and two lepidolites. These ages are in excellent agreement with the best available ages obtained by other methods.
H-PLANE BIFURCATION OF RECTANGULAR WAVEGUIDES
Authors: Hurd R. A. , Gruenberg H.
Published: April 2011

Using a method based on the calculus of residues, a rigorous solution has been obtained for the problem of the bifurcation of a rectangular waveguide. Expressions are given for the amplitudes of all the reflected and transmitted modes in the guide. A comparison is made with results obtained by the transform method of Wiener and Hopf.
A METHOD OF CONCENTRATING He3–He4 MIXTURES
Authors: Atkins K. R. , Lovejoy D. R.
Published: April 2011

We have developed a method of increasing the concentration of He3 in He3–He4 mixtures by "superfluid filtration", relying upon the fact that liquid He4 flows rapidly through a small leak while the He3 in solution remains behind. In this way an increase in concentration from 2% to 95% can be achieved in a single operation. The rate of processing is about 200 standard cc. of the initial gaseous mixture per hour.
THERMAL EXPANSION OF LITHIUM, 77° TO 300° K.
Authors: Pearson W. B.
Published: April 2011

Measurements of the lattice parameters of lithium at temperatures below 300° K. have been made and the results are compared with previous work and considered in terms of the Grüneisen relationship. Methods of low temperature X-ray photography are also discussed.
RADIATION FROM A SLOT ON A CYLINDRICALLY TIPPED WEDGE
Authors: Wait James R. , Kahana Sidney
Published: April 2011

A solution is outlined for the electromagnetic field of a distribution of magnetic current and charge in a volume bounded by an infinite wedge with a cylindrical tip both of infinite conductivity. The result is applied to calculate the fields of a thin half-wave transverse slot on the cylindrical surface. Radiation patterns in the equatorial plane are calculated for wedge angles of 90°, 180°, and 270° for various radii of the cylindrical surface. The results have application to the design of slotted cylinder antennas for directional coverage.
NUCLEAR MAGNETIC RESONANCE SPECTRUM OF B11 IN KERNITE
Authors: Waterman H. H. , Volkoff G. M.
Published: April 2011

The radio-frequency spectrum of B11 in a single crystal of Na2B4O7∙4H2O (kernite) is examined experimentally as the monoclinic crystal is rotated in an external magnetic field of 7060 gauss in turn about each of three axes (b, c crystallographic axes, and a third perpendicular direction) held normal to the magnetic field. A maximum of 21 lines (some of which show small additional splitting) is observed, which reduces to 11 when the b symmetry axis is perpendicular or parallel to the magnetic field. The results are interpreted in terms of four essentially non-equivalent B11 sites in kernite characterized respectively by quadrupole coupling constants [Formula: see text], 0.588 ± 0.003, 2.563 ± 0.007, 2.567 ± 0.010 Mc./sec, and asymmetry parameters 77 [Formula: see text], 0.60 ± 0.02, 0.163 ± 0.010, 0.116 ± 0.010. The orientations of the principal axes of the four [Formula: see text] tensors are also determined. These observations on boron are consistent with previous X-ray results, but preliminary observations on Na23 in kernite contradict previous X-ray position assignments.
FORWARD-SCATTERING OF RADIO WAVES BY METEOR TRAILS
Authors: Forsyth P. A. , Vogan E. L.
Published: April 2011

Radio waves which are too high in frequency to be reflected by the ionospheric layers are often reflected back to the earth's surface by the ionization in meteor trails, and may be detected at distances of the order of 1000 kilometers from the transmitting station. These forward-scattered signals have been studied by the use of several transmission paths in Canada. The paper summarizes the characteristics of the individual signals and presents some preliminary results of the investigation. It seems likely that the technique will prove to be useful in meteoric studies.
THE PULSE HEIGHT DISTRIBUTION FROM A SODIUM IODIDE SINGLE CRYSTAL SCINTILLATION COUNTER AND THE MEASUREMENT OF GAMMA RAY FLUXES
Authors: Griffiths G. M.
Published: April 2011

The theory of the interaction of gamma rays with a single crystal of sodium iodide is described and a comparison made between the pulse height distributions, calculated on the basis of primary interactions only, together with the broadening due to the statistics of light production and electron multiplication, and the experimentally measured distributions. The differences are qualitatively accounted for on the basis of secondary interactions, bremsstrahlung, and wall effects. The absolute efficiency of a scintillation counter, calculated from the size and volume and energy corresponding to the bias level of the counting system, has been used to compute the intensity of gamma radiation from a standardized source of Co60 and from the reaction Li7(p, γ)Be8, the yield of which was known from previous work. Good agreement was obtained after allowance was made, experimentally, for the secondary interactions.
FERROMAGNETIC DOMAIN PATTERNS ON SINGLE CRYSTALS AND BICRYSTALS OF NICKEL
Authors: Martius Ursula M. , Gow K. V.
Published: April 2011

Ferromagnetic domain patterns were studied on the (110), (112), and (001) planes of single crystals of nickel. The crystals were grown from seeds of predetermined orientation and no mechanical cutting was required prior to the observation of the domain patterns. The results are compared with data in the literature, existing discrepancies are pointed out and interpreted. The influence of grain boundaries on the domain patterns is shown in experiments with bicrystals.
THE RESOLUTION OF FOUR-DIMENSIONAL VECTOR FIELD AND TENSOR FIELDS, AND ITS APPLICATION TO ELECTRODYNAMICS
Authors: Balazs N. L.
Published: April 2011

We generalize Helmholtz's theorem and apply it to four-dimensional vector fields and tensor fields. For vector fields the generalization is straightforward. Antisymmetric tensor fields of rank two exhibit a beautiful symmetry between the irrotational part of the tensor and the dual of the solenoidal component. The physical applications show that in Maxwell's theory the irrotational part of the four-potential field has no physical meaning and the Lorentz condition makes it identically zero. In Dirac's new electrodynamics an algebraic condition is imposed on the four-potential. Hence in this theory the irrotational part is not zero, and the algebraic condition establishes a relation between the sources and vortices of the four-potential field. If we apply the resolution to the electromagnetic field tensor we can see that the free charges are responsible for the sources, and the magnetic poles, if they exist, for the vortices, provided we use the customary association between the components of the electromagnetic field tensor and the components of the electric and magnetic fields.
LONG DISTANCE V.H.F. FIELDS: I. PARTIAL REFLECTION FROM A STANDARD ATMOSPHERE
Authors: Northover F. H.
Published: April 2011

Reliable propagation of V.H.F. waves and microwaves from high power transmitters to distances of several hundred miles beyond optical range has been demonstrated by an ever increasing number of experiments during the last ten years. The fields which have been observed have consistently been many times greater than the field strengths predicted by the "effective radius" theory. The present paper will be published in two parts. In Part I the theory that the phenomenon can be explained solely in terms of "partial internal reflection" from elementary layers of a dielectric distribution where the rate of decrease of (μ – 1) with height is everywhere continuous and of the same order of magnitude as in a "standard" atmosphere is carefully examined and found to be untenable. In Part II, the case where the distribution contains "sharp layers" (i.e., local regions where (μ – 1) changes relatively rapidly with height) is examined and it is found that these could cause the phenomenon. However, in view of the other characteristics of the observed field, it is concluded that the effect in question is probably more usually due to scattering of the electromagnetic waves from atmospheric turbulence.
ON THE EFFICIENCY OF AN ACOUSTIC LINE SOURCE WITH PROGRESSIVE PHASE SHIFT
Authors: Thiessen G. J.
Published: April 2011

The introduction of a small continuous phase shift along the length of a finite line source does not result in a decrease of energy radiated but simply causes the directionality pattern to change. When the phase shift is such that it corresponds to the phase shift with distance in a sound wave, then the directionality pattern has changed through 90° and the energy radiated begins to drop rapidly. At this point the slope of the energy vs. phase shift parameter curve increases with increasing frequency.
THE FLUCTUATING FIELD MODEL OF FERROMAGNETISM WITH PARTICULAR REFERENCE TO NICKEL
Authors: Stacey F. D.
Published: April 2011

Following Néel's calculations of fluctuations in intermolecular field, a model is suggested in which there is a mutual repulsion of elementary magnets, so that spontaneous magnetization is affected by a process of ordering of the magnets on the lattice sites as well as the ordering in orientation. Specific heat considerations indicate that, if it occurs, the second disordering process is also complete at the Curie point. To explain the observed spontaneous magnetization of nickel it is necessary to assume coupled electron spins and appreciable next-nearest neighbor exchange interactions.
LONG RANGE FORCES BETWEEN HYDROGEN MOLECULES
Authors: Britton F. R. , Bean D. T. W.
Published: April 2011

Long range forces between two hydrogen molecules are calculated by using methods developed by Massey and Buckingham. Several terms omitted by them and a corrected numerical factor greatly change results for the van der Waals energy but do not affect their results for the static quadrupole–quadrupole energy. By using seven approximate ground state H2 wave functions information is obtained regarding the dependence of the van der Waals energy on the choice of wave function. The value of this energy averaged over all orientations of the molecular axes is found to be approximately −11.0 R−6 atomic units, a result in close agreement with semiempirical values.
FIELD THEORETICAL DESCRIPTION OF THE SUPERCONDUCTING STATE
Authors: Pugh Robert E.
Published: April 2011

The superconducting state is described in terms of the electronic plasma in interaction with the electromagnetic potentials. The interaction of the plasma with itself and with the lattice is represented by a potential energy determined such that the equations of motion are self-consistent. The resulting non-linear field equations are solved in the linear approximation. There exist four independent modes of vibration of the field variables corresponding to the plasma oscillations, and one longitudinal and two transverse oscillations of the electromagnetic potentials. The contribution of these modes to the specific heat is discussed.
THE ABSOLUTE FISSION YIELDS OF TWENTY-EIGHT MASS CHAINS IN THE THERMAL NEUTRON FISSION OF U235
Authors: Petruska J. A. , Thode H. G. , Tomlinson R. H.
Published: April 2011

Twenty-eight absolute fission yields totalling 78% of the heavy and 16% of the light fragments have been determined using the mass spectrometer and isotope dilution techniques. The precision of the values obtained is in most cases better than 2% and the absolute accuracy is estimated to be about 3%. Fine structure in the mass–yield curve is discussed in terms of structural preference and various chain branching mechanisms.
A MATHEMATICAL ANALYSIS OF SOLUTE REDISTRIBUTION DURING SOLIDIFICATION
Authors: Smith V. G. , Tiller W. A. , Rutter J. W.
Published: April 2011

A mathematical analysis is made of the redistribution of solute which occurs during the solidification, without convection, of a single-phase alloy. Calculations of solute distributions are carried out for steady state conditions, and for the transient changes in solute concentration, both in the solid and in the liquid, which occur at the beginning and end of solidification and as a result of a change in the speed of solidification. The solute distributions in the transient regions are considered for the case of two solutes present in the melt. It is shown that, under certain conditions, p–n junctions may be produced in the transient regions of solidification in germanium or silicon melts containing two suitable solutes.
COSMIC-RAY EXPERIMENTS WITH A PROTON VELOCITY SELECTOR
Authors: Ogilvie K. W.
Published: April 2011

Experiments with a selector of slow heavy cosmic-ray particles are described. The pressure coefficient of protons at sea level in the momentum region 700 to 1100 Mev./c is found to be 0.64 ± 0.08% per mb. Points are obtained on the differential momentum spectrum of protons at sea level between 650 and 1250 Mev./c, in agreement with the results of Mylroi and Wilson. This spectrum is discussed in connection with the experiments of Filthüth between 200 and 900 Mev./c.