bluuebunny/crossref_metadata_2025 huggingface dataset:
THE MAGNETRON GAUGE: A COLD-CATHODE VACUUM GAUGE
Authors: Redhead P. A.
Published: April 2011

A cold-cathode ionization gauge with axial magnetic field is described which is capable of measuring pressure in the range 10−3to 10−12 mm Hg and is primarily useful in the range above 5 × 10−10 mm Hg. The gauge is operated with an anode voltage of 6 kilovolts and a magnetic field of 1000 gauss. The relationship between ion current and pressure is linear in the pressure range 10−4 to 5 × 10−10 mm Hg; at lower pressures the relationship i+ = cP1.7 obtains. In the linear region the ion current per unit pressure is given by i+ (amperes) [Formula: see text](mm Hg) for nitrogen (i.e., a sensitivity about 45 times greater than obtainable with a thermionic triode gauge).
THE SPECTRUM OF Li+:
Authors: Herzberg G. , Moore H. R.
Published: April 2011

The spectrum of the Li+ ion has been reinvestigated under high resolution in the region 10,000 to 1000 Å with a view to determining the Lamb shifts in the ground state and first-excited state. The hyperfine structure of the line 5485 Å has been studied under improved resolution both with the natural isotopic mixture and with a 96% Li6 sample. For many of the higher levels the hyperfine structure is larger than the fine structure and for large n and l it is even larger than the singlet–triplet separation. The coupling conditions in these cases are discussed in some detail and theoretical intensity distributions in the combined line structure and hyperfine structure are presented for comparison with the partially resolved observed structures. The selection rule ΔG = 0 for the quantum number of the total spin G = I+S is found to be obeyed.On the basis of this detailed analysis a table of energy levels of Li+ is presented including, where possible, the hyperfine splittings. The absolute accuracy of the energy values is only ±3 cm−1 because of the error introduced by the resonance lines at 1 1S–n1P below 200 Å not remeasured in the present work. However, the relative accuracy of the levels with reference to the 2 3S level is considered to be within ±0.05 cm−1 in most cases.The limits of the observed series have been determined with an accuracy of ±0.10 cm−1 and lead to an ionization potential of[Formula: see text]with an error (±3 cm−1) caused entirely by the error in the resonance lines. The term values (ionization potentials) of the 2 3S and 2 1S states[Formula: see text]are much more accurate. The difference of the observed ionization potential of Li+ and that calculated from relativistic quantum mechanics is −8.0±3 cm−1, which agrees within the rather large limit of error with the predicted Lamb shift (−7.8 cm−1).
PRINCIPE D'UNE ANALYSE DES COURBES EXPÉRIMENTALES COMPOSÉES : APPLICATION À LA MESURE DE LA DENSITÉ DES GRAINS DANS LES TRACES FORTEMENT IONISÉES DANS LES ÉMULSIONS NUCLÉAIRES
Authors: Paskievici W.
Published: April 2011

not available
A THERMISTOR HYPSOMETER
Authors: Blackmore W. R.
Published: April 2011

A thermistor hypsometer used as a sensitive, recording, gas-pressure measuring device is described. It is shown that the limitation on this device is the noise introduced by the pressure fluctuations over the surface of the boiling liquid. These fluctuations are about ±(5–10) μ(microns) Hg peak-to-peak. When a pressure measurement is averaged over a moderately short period of time it may be estimated to ± 1 μHg.
FINE STRUCTURE IN THE O16(γ, n)O15 YIELD CURVE
Authors: King H. , Katz L.
Published: April 2011

Fine structure in the OI6(γ, n)O15 yield curve near threshold was examined using improved experimental techniques. Breaks were observed at threshold, 15.85, 16.14, 16.45, 16.74, 16.88, 17.05, 17.15, and 17.21 Mev. These energies are established to within ± 0.04 Mev. The integrated photon absorption cross section in these breaks resulting in (γ, n) reactions was found to be 0.47 ± 0.11 Mev-mb. Our results are in good agreement with the measurements of other workers.
MULTILAYER PROBLEMS IN THE MULTIGROUP SPHERICAL HARMONICS METHOD
Authors: Davison B.
Published: April 2011

In applying the spherical harmonics method to multilayer neutron transport problems it is necessary to invert certain matrices. It is already known that in the case of one-group theory for the problems with plane, spherical, or cylindrical symmetry, these inverse matrices can easily be written down explicitly, so that there is no need for numerical matrix inversion. In the present paper this result is extended to the case of multigroup theory.
ON THE THEORY OF THE SPECTROPHONE
Authors: Kaiser R.
Published: April 2011

The spectrophone consists essentially of a constant gas volume that is exposed to intensity-modulated infrared radiation of a spectral range corresponding to one of the vibration–rotation bands of the gas.After a brief review of the history of the instrument a theoretical analysis of the processes in the spectrophone cell is presented on the basis of a two-state gas model. Expressions are derived for the time dependence of the upper-state population, of the gas pressure, and of the infrared absorption, emphasizing the effects due to a finite rate of exchange between vibrational and translational energy of the gas molecules. Numerical values are calculated for the 15-μ CO2 band and it is suggested that information on the mechanism of vibrational relaxation in polyatomic gases and gas mixtures can be obtained from experimental studies of the gas pressure in the spectrophone cell.
THE SPECIFIC HEAT OF A LITHIUM–MAGNESIUM ALLOY. THE MARTENSITIC TRANSFORMATION
Authors: Martin Douglas L.
Published: April 2011

The specific heat of an alloy of lithium with 0.95 at.% magnesium has been measured from 20° to 300 deg;K. The specific heat of the body-centered cubic phase is less than that calculated from the Kopp–Neumarin rule. A specilic heat anomaly, due to the martensitic transformation, is observed and has almost the same heat content as the corresponding anomaly for pure lithium but the high-temperature end is of signilicantly different shape.
THE FREEZING POINTS OF HIGH PURITY METALS AS PRECISION TEMPERATURE STANDARDS:V. THERMAL ANALYSES ON 10 SAMPLES OF TIN WITH PURITIES GREATER THAN 99.99+%
Authors: McLaren E. H. , Murdock E. G.
Published: April 2011

Extensive thermal analyses have been made on 10 samples (suppliers' analyzed impurity contents <0.2 to <100 p.p.m.) of high purity tin, including zone-refined metal; liquidus points have been intercompared with a precision of about 0.0002 °C and alloy melting ranges have been examined following different types of freezing with and without overnight anneals near the solidus temperature. Samples of nominal 99.9999% purity tin were found to have such narrow alloy melting ranges that any ambiguity, arising from unknown impurity concentrations, in specifying the liquidus point of pure tin is well inside 0.001 °C; a value of 231.913 °C (Int. 1948) was found for the standard liquidus point of pure tin. An account is given of the supercooling that was observed on the bulk samples and of anomalous structures that were found on melting curves. An appendix gives the results of long-term intercomparisons of the temperatures realized in four water triple point cells.
A STUDY OF METHODS FOR OBTAINING HIGH RESOLUTION WITH A PAIR SPECTROMETER
Authors: Bartholomew G. A. , Campion P. J. , Robinson K.
Published: April 2011

Methods of improving the resolution and line shape of a flat magnetic field pair spectrometer with the aid of specially designed detector apertures are described. The performance of two such apertures is described in detail. The theoretical line shape and resolution for one type of aperture are calculated and compared with experiment.
NEGATIVE RESISTANCE IN SEMICONDUCTOR DEVICES
Authors: Burgess Ronald E.
Published: April 2011

Negative resistance can appear in the static and high-frequency characteristics of devices in which the current is determined by both voltage and temperature. The properties of the a-c. impedance arising from the interaction of thermal and non-thermal effects are discussed and criteria for the appearance of negative resistance over certain ranges of frequency are derived. The application of this analysis to devices which do and which do not exhibit isothermal negative resistance is considered. In an Appendix, a current-temperature relation depending on two activation energies is shown to provide a quantitative model for interpreting the observed turnover behavior of germanium diodes.
LIQUID–SOLID INTERFACE SHAPE OBSERVED IN SILICON CRYSTALS GROWN BY THE CZOCHRALSKI METHOD
Authors: Edwards W. D.
Published: April 2011

A study has been made of the macroscopic structure of the liquid–solid interface which exists during growth of silicon crystals by the Czochralski method. In two crystals the interface was seen to contain a (111) facet. The development of such facets is discussed with reference to current crystal growth theories.
AN ANALYSIS OF A SPECTROGRAM OF THE RED AURORA OF FEBRUARY 10/11, 1958, IN THE WAVELENGTH RANGE 7300–8700 Å
Authors: Jones A. Vallance
Published: April 2011

A high-dispersion photographic infrared spectrum covering the 7300–8700 Å region was obtained from the great red aurora of February 10/11, 1958. This spectrum shows the λλ7774 and 8446 OI lines to have been enhanced at least five times relative to normal aurora. The most striking feature of the spectrum was the appearance with high intensity of the forbidden 2D–2P multiplet of OII. The measured wavelengths and relative intensities of the features of the spectrum are listed.
ROTATIONAL AND VIBRATIONAL INTENSITY DISTRIBUTION OF THE FIRST NEGATIVE BANDS IN SUNLIT AURORAL RAYS
Authors: Jones A. Vallance , Hunten D. M.
Published: April 2011

Spectra of sunlit auroral rays were obtained from Saskatoon during the auroras of September 3/4 and 4/5, 1958. The resolution of these spectra was sufficiently high to enable measurements to be made of the relative intensities of the lines of the 0–0 first negative [Formula: see text] band as well as the relative intensities of bands of the Δυ = −1 sequence of this system. An analysis of the rotational line intensities shows they are consistent with an excitation process in which [Formula: see text] ions in thermal equilibrium with the atmosphere at 2200 °K fluoresce under the influence of solar radiation. The vibrational intensity distribution also is consistent with a fluorescent excitation from a state of thermal equilibrium at about 2050 °K. It is shown that the results are not consistent with a fluorescent excitation process in which the rotational and vibrational degrees of freedom of the [Formula: see text] ions come into radiative equilibrium with the solar radiation. Earlier conclusions that radiative equilibrium did hold for vibration are shown to be in error as a result of the high rotational temperature and the low dispersion used. It is concluded that the destruction of [Formula: see text] ions as a result of dissociative recombination proceeds sufficiently fast to prevent any significant approach to radiative equilibrium. This investigation provides a strong indication that the kinetic temperature of a sunlit auroral ray (perhaps in the 400–500 km region) is in the neighborhood of 2000 °K. This may be somewhat higher than the temperature of the normal atmosphere at this height.
ON THE GEOMETRY OF RADIO REFLECTIONS FROM AURORA
Authors: Forsyth P. A.
Published: April 2011

By assuming that auroral radio reflections are produced by volume scattering in clouds of ionization having the same spatial configuration as the visible auroral structures, and by taking into account the radar pulse duration and antenna beam width, it is possible to predict the probability of echo occurrence as a function of range and azimuth. This echo distribution is quite similar to that observed experimentally even when "aspect sensitivity" of the individual scatterer is neglected. Unfortunately, the optical evidence is not sufficiently extensive to permit precise calculations to be made, nor the radio evidence to permit detailed comparisons, but previous estimates of the shape of the scattering structures that have been based on the azimuthal echo distribution without regard to the factors discussed here are likely to be seriously in error.
THE THIRD SPECTRUM OF COBALT (Co III)
Authors: Shenstone A. G.
Published: April 2011

A nearly complete analysis of the third spectrum of Co (Co III) is given, based chiefly on observations in the vacuum ultraviolet region. The chief structures found are 3d7, 3d6 4s, 3d6 4p, and 3d6 4d. The last of these is not commonly found in third spectra and it is here very incomplete. Some cases of unusual intensities in intersystem combinations are pointed out, especially ones in which the intensity in the combinations with the central of three J values is zero or very small. The complete line list is given.
AN IMPROVED ELECTROSTATIC ELECTRON SELECTOR
Authors: Marmet Paul , Kerwin Larkin
Published: April 2011

A cylindrical electrostatic electron selector is described which provides a 10−7 ampere beam of electrons whose energy may be varied from 0 to 50 ev and whose energy spread is less than 100 mv. Space-charge problems involved in the construction of the device were overcome by the use of grids for focusing electrodes with exterior electron traps, and a non-reflecting surface for electrons made from a network of tiny tubes. The selector is provided with an energy analyzer. When used to determine the appearance potential curve of argon, the selector resolved the 2P3/2 and 2P1/2 states separated by 0.18 ev, and indicated the formation of [Formula: see text] at an energy of 0.8 ev below the threshold for A+.
SOME RECENT DETERMINATIONS OF ATOMIC MASSES IN THE STRONTIUM–ZIRCONIUM REGION
Authors: Isenor N. R. , Barber R. C. , Duckworth H. E.
Published: April 2011

A large double-focusing mass spectrometer has been used to obtain new values for the masses of Sr86, Sr88, and Zr90. Mass differences calculated from these values are found to be in better agreement with nuclear transmutation information than were previous mass spectroscopically derived values.
THE WAVELENGTH DISPLACEMENTS OF SOME INFRARED LINES BETWEEN LIMB AND CENTER OF THE SUN. II
Authors: Herzberg Luise
Published: April 2011

The differences between the wavelengths at the solar limb and at the center of the disk have been measured for lines of Fe I, Si I, and Ca II in the λ8500 Å and λ8900 Å regions of the spectrum. The values of the limb–center displacements (in km/sec) of the Fe I lines in the two wavelength regions studied are found to be the same as those obtained by M. G. Adam for neutral metal lines at λ6100 Å. The limb–center displacements of the Si I lines are similar in magnitude and in the same direction as those of Fe I. Although the data are insufficient to decide the question as to term dependence of the solar wavelength shifts of Si I, any relation to the shifts observed in a laboratory light source can be excluded. For the Ca II lines at λ8500 Å and λ8900 Å, corresponding to two different transitions, the limb–center displacements differ from each other both in magnitude and in direction. The limb–center displacements of the λ8900 Å Ca II lines are smaller than those of the Fe I lines, while those of the λ8500 Å Ca II lines are significantly larger and in direction opposite to those observed for lines of Fe I.Where possible, comparison has been made between the wavelengths observed at limb and center of the disk and the solar wavelengths predicted by General Relativity Theory. In all cases the wavelengths at the limb were found to be closer to the predicted values than the wavelengths measured at the center of the disk. While for the lines of Fe I the predicted solar wavelengths and those observed near the limb (r/R = 0.982) are in good agreement, the wavelengths close to the solar limb of the λ8500 Å Ca II lines are found to be significantly larger than those predicted by relativity theory.
THE REPRODUCIBILITY OF THE SULPHUR POINT
Authors: Berry R. J.
Published: April 2011

The reproducibility of the normal boiling point of sulphur, a fixed calibration point on the International Temperature Scale, has been investigated using a closed manometer-boiler system. Measurements embracing several sources of sulphur and a number of changes in the operating conditions have shown that the sulphur point can be reproduced with a standard deviation of about 0.001 °C with our apparatus.Tests were made on eight samples of sulphur from three different sources in an attempt to resolve the uncertainty in the time the sulphur takes to reach temperature equilibrium after it has been brought to the boiling point. The results indicate that pure sulphur will reach equilibrium almost immediately but that an impurity content of as little as 0.01% can delay equilibrium up to 10 days. The temperature–time dependence can be ascribed to the effect of impurities on the time required for allotropic equilibrium to be attained. This hypothesis is discussed in detail and it is shown that it gives a consistent interpretation of the results presented here and those of previous investigations. The merits of replacing the sulphur point with the freezing point of zinc on the International Temperature Scale are also examined.The long-term stability of the coefficients of a Meyers platinum resistance thermometer is determined and a method of improving this stability for prolonged use at high temperatures is outlined.
THE GAMMA-NEUTRON CROSS SECTION FOR F19
Authors: King J. D. , Haslam R. N. H. , McDonald W. J.
Published: April 2011

The F19(γ,n)F18 reaction has been studied by irradiating teflon samples in the X-ray beam of a 25-Mev betatron and detecting the annihilation radiation emitted during the decay of the residual nuclei. The cross section shows maxima at 10.6 (very small), 12.4, 14.0, 16.1, 17.2, and 19.3 Mev. The peak at 12.4 Mev is possibly due to excitation of the last neutron in F19 with only a small disturbance of the core nucleons. The peaks at 14.0 and 19.1 Mev are interpreted as the components of a split giant resonance, indicating an intrinsic quadrupole moment, Q0, of approximately 0.30 × 10−21 cm2 for F19.
AN ELECTROMAGNETIC DIFFRACTION PROBLEM INVOLVING UNIDIRECTIONALLY CONDUCTING SURFACES
Authors: Hurd R. A.
Published: April 2011

The exact value of the electromagnetic field scattered by a unidirectionally conducting surface under plane wave excitation is obtained. The surface, which is an entire plane, is the junction of two unidirectionally conducting half-planes whose conductivity directions are inclined at an arbitrary angle to each other, and to the boundary line.
TIME DELAY AND FREQUENCY RESPONSE OF RESONANT CAVITIES
Authors: Mungall A. G. , Morris D.
Published: April 2011

The frequency response and time delay characteristics of resonant cavities are discussed. It is found that a signal travelling through a resonant cavity undergoes a time delay dependent on both the cavity Q and also the difference between the signal and resonant frequencies. The time delay for a frequency-modulated wave is calculated and checked experimentally.
HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: XIII. ROTATIONAL SPECTRA AND STRUCTURES OF THE ZINC-, CADMIUM-, AND MERCURY-DIMETHYL MOLECULES
Authors: Rao K. Suryanarayana , Stoicheff B. P. , Turner R.
Published: April 2011

The pure rotational spectra of gaseous Zn(CH3)2, Cd(CH3)2, Hg(CH3)2, and of the fully deuterated molecules have been photographed with a 21-ft grating. The spectra are typical of symmetric top molecules and consist of many evenly spaced rotational lines having a separation of about 0.45 cm−1. An analysis of the spectra yielded the rotational constants (in cm−1)[Formula: see text]From these constants the following metal—carbon bond lengths were determined: Zn—C = 1.929 Å, Cd—C = 2.112 Å, and Hg—C = 2.094 Å. Relations for the C—H bond lengths and HCH angles were also obtained.
REPRESENTATION OF SPACE INVERSION, TIME REVERSAL, AND PARTICLE CONJUGATION IN QUANTUM FIELD THEORY
Authors: Kaempffer F. A.
Published: April 2011

The unitary operators of space inversion and particle conjugation and the unitary factor of the antiunitary operator of time reversal can each be written in the form eiΩ, where Ω is the direct sum of two terms, Q = Ω1θ1 + Ω2θ2, with Ω1, Ω2 Hermitean bilinear forms in the creation and annihilation operators of the boson or fermion field under consideration, and θ1 θ2 singular operators which separate the appropriate half spaces needed for the formulation of the symmetry operations. Explicit expressions are given for the generators Ω in case of a non-Hermitean boson field of spin 0, and in case of a four-component fermion field of spin [Formula: see text].
HIGH-FREQUENCY RADIO-WAVE BLACK-OUTS AT MEDIUM AND HIGH LATITUDES DURING A SOLAR CYCLE
Authors: Collins C. , Jelly D. H. , Matthews A. G.
Published: April 2011

Recent studies at the Defence Research Telecommunications Establishment, Ottawa, comparing v.h.f. riometer and h.f. ionosonde data for the International Geophysical Year, have shown that the two types of absorption events, 'polar cap' and 'auroral', can be identified in the occurrence patterns of ionosonde black-outs. A study based on this comparison has been made of all black-outs observed at a number of medium- and high-latitude ionosonde stations during the period 1949 to 1959. It has been found that the two kinds of absorption events show markedly different variations during the 11 years. Several other temporal and spatial features of the phenomena are also discussed.
MAXIMUM OF THE FACTOR OF ENCIRCLED ENERGY
Authors: Lansraux Guy , Boivin Germain
Published: April 2011

It is recognized that the most favorable distribution of radiant energy in a diffraction pattern is that which corresponds to the best concentration around the center O. This hypothesis is expressed by an extremal condition on the factor of encircled energy E(W), that is, the ratio of the energy inside a circle of radius W and centered on the diffraction pattern, to the total energy in the same.A study of the effects of spherical aberration on this factor of encircled energy has shown that aberration always tends to decrease the factor from the value obtained with an Airy pattern. However, this factor may be increased by the use of an amplitude filter at the pupil of the optical system.In treating the case of amplitude filters one may use a rigorous analysis in terms of Taylor's series in (1−x2)p−1 or a polynomial Tn(x) of degree n−1 in terms of (1−x2).The corresponding amplitudes in the diffraction pattern are Г(W) and Гn(W); the maximum factor of encircled energy E(Wm) and En(Wm). The following convergences are established: En(Wm) → E(Wm), Tn(x) → T(x), and Гn(W) → Г(W) as n → ∞.When the interval (0, Wm) of the diffraction pattern is made to correspond to the interval (0, 1) of the pupil by means of a suitable normalization the amplitude distributions T(x) and Г(W)—with W = Wmx—are identical. Some properties are deduced from this relation; for example, the Airy pattern is the limit of Г(W) when Wm → 0; on the other hand, the Gauss function [Formula: see text] is an asymptotic expression of T(x) when Wm → ∞. In any case, the factor of encircled energy is connected to the marginal amplitude in the pupil by the relation E(Wm) = 1−T2(1).The numerical determination of E(W) given up to W = 10 and Wm = 2, 3, 4, and 5 can be extended by use of an asymptotic expression of the factor of encircled energy.Finally, a curve M(W) has been obtained, which is an envelope of the curves E(W) corresponding to various values of Wm. This gives the locus of the maximum factor of encircled energy and represents the limiting performance of optical systems.
THE EMISSION SPECTRUM OF THE CCI RADICAL
Authors: Gordon R. D. , King G. W.
Published: April 2011

A rotational analysis of the 2780 Å emission band obtained in a microwave discharge through CCl4 vapor and photographed on a 20-ft grating spectrograph shows that a 2Δi(b) → 2Πr(a) transition of the CCl radical is responsible, not 2Σ → 2Π(a) as reported by previous workers. Molecular constants are given for the combining states, as well as a vibrational analysis that identifies the 2780 Å band as the (0–0) band.
ON THE THERMAL EXPANSION OF METALS AT LOW TEMPERATURES
Authors: Horton G. K.
Published: April 2011

A theory is developed which correlates the thermal expansion of crystals to the anharmonicity introduced into Born's lattice dynamics by allowing the force constants of the crystal to vary with volume. This is achieved by identifying the force constants with the elastic constants of the crystal by the method of long waves. It is then assumed that it is primarily the volume dependence of the elastic constants that give rise to their temperature variation. A central force nearest and next-nearest neighbor force model analogous to Leighton's is applied to copper. The values of the lattice thermal expansion coefficient and of Grüneisen's parameter are given as a function of the temperature and found to agree quite well with the latest experimental results. It is pointed out that the description of the interionic potential in metals by a two-body central force is certainly a serious oversimplification and that the theory is likely to be more realistic for, say, the ideal inert solid gases, as soon as the experimental data becomes available.
EXCITED STATES OF O18 STUDIED BY THE REACTION
Authors: Litherland A. E. , Batchelor R. , Ferguson A. J. , Gove H. E.
Published: April 2011

Gamma rays from the excited states of O18 at 3.63 and 3.92 Mev have been observed using the reaction [Formula: see text] at an incident O16 energy of 14 Mev. Both states were observed to emit gamma rays to the 1.98-Mev 2+ first excited state of O18. No evidence for crossover transitions was found and in each case the crossover transition was estimated to be [Formula: see text] of the cascade transition. Angular correlations of the gamma rays were obtained and these strongly support an assignment of spin 0 to the 3.63-Mev state and a spin of 2 for the 3.92-Mev state. These assignments have been confirmed by a recent experiment on the O16(H3, p)O18 reaction which gives the assignments 0+ and 2+ for these two states. Thus the states at 3.55, 3.63, and 3.92 Mev form a triplet with assignments 4+, 0+, and 2+ which strongly resembles the vibrational spectra found in heavier nuclei. However, the measured angular correlations of the gamma rays from the 3.92-Mev state show only a small admixture of electric quadrupole in the 1.94-Mev gamma ray with relative amplitude +0.1 ±.1. A lower limit of ~10−12 seconds on the lifetime of the 3.63-Mev state was obtained from the absence of a doppler shift of the 1.65-Mev cascade gamma ray.
EFFECTS OF EQUATORIAL SPREAD-F IRREGULARITIES ON C. W. TRANSMISSIONS
Authors: Rao M. S. V. Gopal , Rao B. Ramachandra
Published: April 2011

A study is made into the effects of spread-F conditions on continuous wave (c. w.) transmissions between Colombo and Waltair over a distance of about 1300 kilometers. It is shown that under suitable conditions increased fading rate of the received c. w. signals is a sufficient indication of spread F and gives a genuine index of its intensity. Pulse and c. w. methods are used simultaneously to study the time variations of spread-F intensity at separated points. The results indicate that the horizontal extent of spread-F occurrence in the N.–S. direction is greater than 650 km.The probability distributions of signal amplitudes in the c. w. fading records were closer to Rayleigh type under normal conditions than during spread-F conditions. It is suggested that the c. w. flutter fading is caused by the presence of spread-F irregularities in the appropriate zone of reflection in the F-region of the ionosphere.
PHOTONEUTRON REACTIONS IN G12 AND O16
Authors: Roalsvig J. P. , Gupta Ishwar C. , Haslam R. N. H.
Published: April 2011

Absolute yields of the reactions C12(γ,n)C11 and O16(γ,n)O15 have been determined at 22-Mev maximum bremsstrahlung energy using the University of Saskatchewan 24-Mev betatron. For the reaction C12(γ,n)C11 a yield curve from threshold to 24 Mev has been obtained and the cross-section curve for the reaction computed. A thorough comparison with other results has been made.
ON THE NUCLEAR SPIN RELAXATION IN HYDROGEN GAS
Authors: Needler G. T. , Opechowski W.
Published: April 2011

The Schwinger formula for the relaxation time T1 of nuclear spins in hydrogen gas is valid only for sufficiently low temperatures. In this paper an approximate theory of T1 is developed valid for any temperature. An explicit expression is given for T1 valid for temperatures up to room temperature; this expression reduces to the Schwinger formula for sufficiently low temperatures.
VARIATIONS IN SOLAR TIME OF EXTENSIVE AIR SHOWERS
Authors: Wilson B. G. , Dionne J. G. G. , Terentiuk F.
Published: April 2011

150,000 extensive air showers of high electron density have been recorded at an altitude of 2283 meters. Analysis of the data in solar time for a wide range of densities shows no evidence for the large semidiurnal variations previously reported by other groups. A possible explanation of this difference may lie in the different methods of selecting the showers.
OBSERVATION OF THE TRANSITION IN O2
Authors: Noxon J. F.
Published: April 2011

The Q branch of the (0,0) band of the electric quadrupole [Formula: see text] transition in O2 has been observed at 1.908 μ in the emission spectrum of a discharge through O2 and He. By a comparison with the (0,0) atmospheric O2 band [Formula: see text], the absolute transition probability for the (b–a) system has been found to be 2.5 × 10−3 sec−1, with an uncertainty of a factor of 2. The (0,0) band of the infrared atmospheric [Formula: see text] system of O2 has also been observed in emission. Using the observed intensity of the (0,1) atmospheric O2 band in the aurora and airglow one may predict that the (0,0) (b–a) band should be detectable in a strong aurora if observations are made from high altitude.
STUDY OF THE EFFECT OF GAMMA RADIATION ON THE MOLECULE OF PENTOBARBITAL
Authors: Cloutier J. A. R. , Flann Bruce C. , Manson Jane M.
Published: April 2011

Modern instrumental techniques were used to investigate the effect of gamma radiation on the molecule of pentobarbital. The results were correlated with each other and with those from a biological test. The main effect of radiation appeared to be centered about the two substituents of the molecule at the number 5 position.
HIGH-FREQUENCY DIFFRACTION BY A SPHERE
Authors: Tang C. L.
Published: April 2011

A systematic procedure is given for the determination of the asymptotic series directly from the Helmholtz equation and the boundary conditions for the field in the shadow region of a sphere illuminated by a plane wave at high frequencies. The first two terms in the series for the shadow region, including the regions near the axial caustic and the boundary layer near the surface of the sphere, are explicitly evaluated. The present procedure can be generalized to any smooth convex three-dimensional object with a rotational symmetry, illuminated by a plane wave in the direction of the axis of rotational symmetry.
THE LIFETIMES OF POSITRONS IN METALS
Authors: Jones G. , Warren J. B.
Published: April 2011

The lifetimes of positrons annihilating in some 21 metals have been measured comparatively with the lifetime in aluminum. Significant variations have been found, as large as 30% of the absolute lifetime in aluminum, and the lifetime shows a more marked dependence on the atomic density than on the valence electron density of the metal. By comparison of lifetime and angular distribution data a mechanism of the annihilation process is proposed. In metals with large lattice spacings the annihilation is primarily with valence electrons, but slightly enhanced by pick-off annihilations with outer electrons of the ions; as the spacing decreases the pick-off probability increases, resulting in larger high momentum tails to the parabolic angular distributions and shorter lifetimes. The annihilation rate increases with valence electron density but levels off at higher densities at a rate similar to the theoretical value for positronium ions. With very reduced lattice spacing the annihilation with ionic electrons becomes comparable with that with valence electrons, so that bell-shaped angular distributions and shorter lifetimes result.
TRANSMISSION AND REFLECTION OF ELECTROMAGNETIC WAVES AT A PLASMA BOUNDARY FOR ARBITRARY ANGLES OF INCIDENCE
Authors: Graf K. A. , Bachynski M. P.
Published: April 2011

The interaction of a plane electromagnetic wave with a flat free-space – plasma interface has been considered for arbitrary angles of incidence. It is shown that the plasma can support independent horizontally and vertically polarized waves. Expressions and graphical representations are given showing the amount of energy entering the plasma as a function of angle of incidence and plasma parameters. The vertically polarized case shows a maximum in the energy entering the plasma at the "Brewster angle". For a lossy plasma, at this maximum, there will be reflection. Loci of constant Brewster angle appear as concentric curves centered on the origin of the complex dielectric coefficient plane.The elliptical polarization of a plane wave reflected from the interface, when a wave with equal horizontally and vertically polarized components is incident on the interface, suggests the similarity of lossless plasmas to ordinary dielectrics and of lossy plasmas to metals.
THE ABSORPTION SPECTRUM OF BO2
Authors: Johns J. W. C.
Published: April 2011

The boron flame bands have been observed in absorption during the flash photolysis of mixtures of boron trichloride and oxygen. Detailed analysis of the spectrum has shown that the bands arise from two electronic transitions in the linear symmetric molecule BO2, [Formula: see text] and A2Πu−X2Πg. The main molecular constants, in cm−1 except for r0, are summarized below:[Formula: see text]Both 2Π states show the Renner effect. In the ground state the Renner parameter, εω2, was found to be −92.2, whereas in the first excited state it is much smaller, −13.1 cm−1.
THERMAL NEUTRON CROSS SECTIONS AND RESONANCE INTEGRALS OF THE REACTIONS O17(n,α)C14, Ar36(n,α)S33, AND N14(n,p)C14
Authors: Hanna G. C. , Primeau D. B. , Tunnicliffe P. R.
Published: April 2011

The thermal neutron cross sections of the exothermic reactions O17(n,α)C14, Ar36(n,α)S33, and N14(n,p)C14 have been measured, relative to the activation cross section of gold, by using a pulse ionization chamber technique. The results obtained are 0.235 ± 0.005 barn, 5.52 ± 0.11 millibarns, and 1.83 ± 0.03 barns respectively. All the reactions were shown to have the same cadmium ratio as the B10(n,α)Li7 reaction with accuracies of ±10%, ±40%, and ±3% respectively. The O17 result shows that capture in this nuclide contributes significantly to neutron absorption in heavy water.
THE DECAY OF Er171
Authors: Artna A. , Johns M. W.
Published: April 2011

The decay of Er171 has been studied with a magnetic beta-ray spectrometer at a resolution of 0.5%. The energies and intensities of 30 transitions in Tin171 have been established. The energies (Mev) and intensities (%) are as follows: 0.086 (~0.1), 0.1117 (68.8), 0.1166 (6.05), 0.1240 (20.5), 0.1664 (0.65), 0.2104 (0.67), 0.2364 (0.57), 0.2770 (0.74), 0.2956 (28.7), 0.3082 (64.4), 0.3712 (~0.4), 0.4040 (0.03), 0.4189 (0.09), 0.5437 (0.04), 0.5571 (0.08), 0.5727 (0.07), 0.6061 (0.10), 0.6187 (0.13), 0.6703 (0.30), 0.6753 (0.39), 0.7321 (0.18), 0.738 (0.06), 0.7835 (0.31), 0.7962 (0.80), 0.842 (0.04), 0.869 (0.06), 0.882 (0.07), 0.906 (0.88), 0.9105 (0.25), 0.962 (0.11). These transitions are interpreted in terms of 12 levels whose energies and spins are: 0 (1/2+), 0.0051 (3/2+), 0.1167 (5/2+), 0.1291 (7/2+), 0.4251 (7/2−), 0.5915 (9/2−), 0.6355 (7/2+), 0.675(3/2+), 0.737 (5/2+), 0.912 (5/2+), 0.963 (5/2+), 0.997 (7/2+). The decay energy of Er171 is 1.490±0.002 Mev.
NEUTRONS AND GAMMA RAYS FROM Po210–B10(α,n) AND Po210–B11(α,n) SOURCES
Authors: Geiger K. W. , Jarvis C. J. D.
Published: April 2011

The neutron energy spectra from Po–B10(α,n) and Po–B11(α,n) sources have been determined by the nuclear emulsion method and with a proton recoil spectrometer. Gamma spectra have also been measured. The Po–B10 neutron spectrum extends to an energy of 6.0 Mev and shows two peaks, at 1.0 and 3.0 Mev. The lines in the gamma spectrum are not in coincidence with neutrons but are caused by competing reactions. The Po–B11 neutron spectrum shows one peak at 2.7 Mev; the maximum energy observed is 5.0 Mev. One γ-ray line at 2.32 Mev with an intensity of 5% of the neutron emission rate is detected in the gamma–neutron coincidence measurements. The experimental neutron energy spectra have been compared with calculated spectra and are compatible with the gamma measurements, as well as with published level schemes for the residual N13 and N14 nuclei. In the case of the Po–B10 source only one-third of the neutrons are produced by the B10(α,n)N13 reaction and the remainder has to be accounted for by the B10(α,np)C12 reaction.
COMPOUND NUCLEUS FORMATION IN NITROGEN–OXYGEN AND OXYGEN–OXYGEN REACTIONS
Authors: Cartledge W. A.
Published: April 2011

The experimental cross section for the reaction O16(N14,2p)Al28 is compared with the predictions of the square-well model of compound nucleus formation over the range 6.3 to 12 Mev (center of mass energy). The branching ratio is estimated from the experimental cross section for the comparison reaction Si29(p,2p)Al28 over the same range of excitation in the compound nucleus P30*. It is found that the branching ratio probably increases from about 10% to 20%, which requires the nuclear interaction radius for N14 + O16 to decrease from about 8.5 to 7.5 fermis as the energy is increased over this range.Because of the similarity in mass and observed charge distributions in N14 and O16, the interaction radius for compound nucleus formation in a collision between two oxygen nuclei is probably also similar and in the range 8.0 to 9.1 fermis at energies far below the Coulomb barrier. A consequence of this result is that oxygen ions, which may be present in the cores of sufficiently developed red giant stars, will be destroyed by O16 + O16 collisions in about 105 years and 1 year respectively, at temperatures in the vicinity of 13.0 and 18.5 × 108 °K.
TEMPERATURE OF A SHIELDED SURFACE
Authors: Stephas Paul
Published: April 2011

Expressions have been derived for the correction of the brightness temperature of a body which is surrounded by radiation shields. Calculations have been made for plane parallel, coaxial cylindrical, and concentric spherical surfaces. Both diffusely and specularly reflecting surfaces have been considered. The error involved in ignoring this correction for tantalum or tungsten may be several hundred degrees, according to the geometry, at 3000° K.
THEORY OF THE PHONON BRANCHES IN THE INFRARED SPECTRUM OF SOLID HYDROGEN
Authors: Poll J. D. , Kranendonk J. Van
Published: April 2011

The effect of the lattice vibrations on the infrared absorption spectrum of solid hydrogen is investigated theoretically. General expressions are derived for the integrated intensities of the phonon branches in the rotational and vibrational spectrum of solid parahydrogen. It is shown that the intensities of the pure rotational and vibrational absorption features are not appreciably affected by the lattice vibrations. A general criterion is derived for the vanishing of the contribution of instantaneous phonon processes to the integrated intensities of the phonon branches. The integrated intensities are expressed in terms of the mean square displacements of the molecules from their equilibrium positions. Explicit calculations are presented, based on the Einstein and Debye models for the lattice vibrations, and the results are compared with the available experimental data.
SHORT-RANGE SPATIAL COHERENCE OF GEOMAGNETIC MICROPULSATIONS
Authors: Duffus H. J. , Shand J. A. , Wright C. S.
Published: April 2011

An experiment designed to measure the coherence of natural geomagnetic signals at two stations 10 kilometers apart is described. A qualitative measurement was performed on a section of 1 c.p.s. signal (of unusual occurrence) and a quantitative measurement on a section of normal daytime record. The coherence tends to be high for moderate signal levels.
DIFFRACTION ANGLE MEASUREMENTS BEARING ON THE DEUTERIUM BINDING ENERGY AND ON THE X-UNIT-TO-MILLIANGSTROM CONVERSION CONSTANT
Authors: Knowles J. W.
Published: April 2011

Precise angle measurements of the deuterium de-excitation and annihilation radiations have been made with a double flat crystal diffraction spectrometer. The deuterium γ-ray was diffracted from the (211), (211); (211), (633); (211), (844); and (844), (844) planes of two calcite crystals. The energy comparison, based on angle measurements of the deuterium γ-ray diffracted from the (844), (844) and the annihilation γ-ray from the (211), (211) planes of the two crystals, is particularly insensitive to systematic geometric error. If the energy and standard error of the annihilation radiation is taken to be 510.978 ± 0.007 kev, the deuterium binding energy is 2224.52 ± 0.20 kev. Absolute angles were measured for both diffracted γ-rays. A knowledge of the absolute diffraction angle and the absolute wavelength of the annihilation γ-ray determines the absolute spacing of the diffraction plane of calcite, d211 = 3035.70 ± 0.15 mÅ at 18 °C. With reference to the standard d211 spacing of calcite, 3029.494 X-units, the conversion constant from X-unit to mÅ is 1.002049 ± 0.000057. The presently accepted value for the absolute wavelength of the annihilation radiation and the precise meaning of the term X-unit is more completely specified in the text.
KINETIC EQUATION DESCRIBING IRREVERSIBLE PROCESSES IN IONIZED GASES
Authors: Wu Ta-You , Rosenberg R. L.
Published: April 2011

The present work deals with the formulation of the theory of irreversible processes in ionized gases on the basis of the theory of Bogoliubov for neutral gases. In an extension of the work of Guernsey and Uhlenbeck, the kinetic equation is obtained for a spatially inhomogeneous system in an approximation to the "first order" in the interaction strength (e2) and to all orders in the correlation effect (e2/v, v being the specific volume). The equation, unlike the usual Vlasov equation, is not invariant with respect to time-reversal and shows a genuine "damping" in the sense of an irreversible approach to equilibrium.In the present paper, brief discussions have also been given of the nature of a theory of irreversible processes, the so-called "divergence difficulty", due to the long-range Coulomb forces, the Landau damping, the recent general theory of irreversible processes of Prigogine and Balescu, and the theory of ionized gases of Balescu.
THE EFFECT OF WINDS ON THE GRAVITY WAVE
Authors: Weston V. H. , VanHulsteyn D. B.
Published: April 2011

The effect of wind upon the gravity waves produced by a large explosion is considered. The uniform horizontal wind is applied to the hydrodynamic equations; application of perturbation techniques results in an equation for excess pressure which involves the wind velocity. In the limiting case, as this velocity approaches zero, this equation becomes identical with the non-wind case. This equation is solved by numerical methods with appropriate boundary conditions for the particular model of the atmosphere considered. For a pulse traveling down wind, the effect is to increase the dispersion and the phase velocity in the gravity wave mode.
ISOMERIC STATES OF Ag103, In116, AND Sb118
Authors: White W. , Martin W. M.
Published: April 2011

The internal beam of a 100-Mev proton synchrocyclotron has been used in conjunction with a rapid target extraction unit to study isomers of a few seconds' half-life. The results are tabulated below.[Formula: see text]
ELECTROMAGNETIC WAVES IN A BOUNDED, ANISOTROPIC PLASMA
Authors: Graf K. A. , Bachynski M. P.
Published: April 2011

The interaction of a plane, electromagnetic wave with a flat, uniform free-space – plasma interface in a static magnetic field has been considered for arbitrary angles of incidence. The dispersion relation for the plasma is a complex quartic equation which reduces to a quadratic if the static magnetic field and plasma boundary are oriented along any one of the rectangular co-ordinate axes. (These axes need not simultaneously be the same for the plasma and the magnetic field.)Numerical results are presented for the attenuation and phase constants for each of the two possible waves in the plasma, for each orientation of the static magnetic field. Data are given for various angles of incidence, plasma properties, and orientations of the static magnetic field relative to the plasma boundary.Inspection of the fields in the plasma reveals some interesting aspects. In certain cases, waves which appear to move upward towards the plasma interface exist. Since these waves may carry energy into the plasma, they have been referred to as "backward" waves. Totally reflected waves which have both finite attenuation and finite phase coefficients can also exist in the plasma. These have been termed "modified Sommerfeld" waves.
ATOMIC CHARGE STATES IN CARBON OF 10- TO 40-MEV IONS; APPLICATION TO TANDEM ACCELERATORS
Authors: Almqvist E. , Broude C. , Clark M. A. , Kuehner J. A. , Litherland A. E.
Published: April 2011

The distribution of charge states of ions of F19, Cl35, and Br79 emerging from thin carbon foils at energies of 10 to 40 Mev have been measured. Atomic charges of 7, 9, and 11 electron units for the three elements respectively are produced at 10 Mev with an intensity of greater than 15% of the incident beam. These results show that a tandem accelerator with 10 Mv on the terminal can deliver good ion beams at the following energies (the values in parentheses require two-stage stripping resulting in a further reduction in beam intensity by a factor of 5 to 10): 80 Mev (95 Mev) F19 ions, 100 Mev (125 Mev) Cl35 ions, and 120 Mev (160 Mev) Br79 ions. The measurements show that heavy ions from a tandem accelerator can be injected into a cyclotron and stripped to give appropriate magnetic rigidity for acceleration to very high energies; for example, a 90-in. diameter magnet with a field of 14 kilogauss will yield [Formula: see text] Cl or Br ions.
NUCLEAR MAGNETIC RELAXATION IN GAS MIXTURES
Authors: Williams D. Llewelyn
Published: April 2011

Measurements of the proton spin–lattice relaxation time using pulse techniques have been made on the hydrogen–nitrogen, hydrogen–neon, and hydrogen–helium systems from room temperature to 60° K. The results are in good agreement with the Oppenheim–Bloom theory and illustrate the importance of the radial distribution of the gas molecules and of diffraction effects associated with the de Broglie wavelength.
ELECTRODELESS TECHNIQUES FOR SEMICONDUCTOR MEASUREMENTS
Authors: Nyberg D. W. , Burgess R. E.
Published: April 2011

Electrodeless methods, based on the inductive coupling of samples to coils, for determining the electrical conductivity, the Hall mobility, and the magneto-resistance of a semiconductor are described. The theory is developed for cylindrical and spherical geometry samples and design considerations and experimental techniques are discussed. These methods eliminate problems encountered with standard four-probe methods, such as obtaining non-rectifying and non-injecting contacts, and applying electrodes to liquid or chemically active samples.