bluuebunny/crossref_metadata_2025 huggingface dataset:
THE RESONANT FREQUENCIES OF CAVITIES IN A MAGNETOIONIC MEDIUM
Authors: Budden K. G.
Published: April 2011

The resonant frequencies for a hollow cylindrical or spherical cavity in a magnetoionic medium are derived using a simple model in which the boundary of the cavity is sharp and the medium outside it is homogeneous and loss free, but anisotropic. The effects of electron temperature and of nonlinearity are ignored. The problem is complementary to a similar problem treated by Herlofsen (1951), who discussed the resonant frequencies of a uniform cylindrical or spherical mass of isotropic plasma surrounded by a vacuum. It is found that the resonant frequencies are not equal to the characteristic frequencies of the plasma as usually described by the formulae X = 1, X = 1 ± Y, but are more complicated functions of the plasma frequency and the electron gyrofrequency. It is concluded that, for a plasma sheath or cavity of any structure, with a sharp or gradual boundary region, the resonant frequencies will in general differ from the characteristic frequencies of the undisturbed plasma. For a cylindrical cavity the resonant frequencies depend upon the angle between the axis of the cavity and the constant magnetic field. The results may have applications to the interpretation of plasma "spikes" observed with space vehicles, and to the theory of the radar cross section of a space vehicle within the ionosphere.
RECIPROCITY AND NONRECIPROCITY WITH MAGNETOIONIC RAYS
Authors: Budden K. G. , Jull G. W.
Published: April 2011

Although the reciprocity theorem of electromagnetism is not generally true when magnetoionic media are present, there can be reciprocity in certain special cases for a radio-communication link. Here the problem is investigated when the approximations of ray theory are valid, where the term "ray theory" is used in a very general sense. For a solution of the electromagnetic equations consisting of rays with a single magnetoionic component, there is a vector W which has zero divergence and is in the same direction as the ray. It can be used to get expressions for the received signals at two stations for transmission in either direction, and these apply for signals consisting of any number of rays. From them it is possible to show when there is reciprocity, and when there is antireciprocity, which means signals of equal amplitudes but with the phase shifts differing by 180° for transmission in the two directions.A known reciprocity theorem for stations in the magnetic meridian plane is extended and shown to apply in a modified form for any azimuth of propagation, but the extension is valid only under the approximations of ray theory.The results are applied to the theory of polarization fading and it is shown that there can be a time displacement of the fading cycles at the two ends of the ray path.
THERMAL AND ELECTRICAL PROPERTIES OF INCONEL 702 AT HIGH TEMPERATURES
Authors: Laubitz M. J. , Cotnam K. D.
Published: April 2011

The thermal conductivity, the electrical resistivity, and the thermoelectric power of Inconel 702, a material recently proposed as a thermal conductivity standard, have been measured in the temperature range of 0° to 1100 °C. It was found that these properties are complex functions of both the temperature and the heat treatment of the alloy; some of the observed variations can be correlated qualitatively with the interactions of the known phase-structures in Inconel 702, and with the formation of the "K state". It is the opinion of the authors that the observed dependence of the properties on the thermal history of the specimen renders Inconel 702 unsuitable as a thermal conductivity standard.
A QUANTITATIVE STUDY OF SCATTERING PHENOMENA IN AN ELECTROMAGNETIC SEPARATOR
Authors: Menat M.
Published: April 2011

A series of recent experiments has shown that the elastic scattering of a directed ion beam by residual gas is one of the dominant factors causing contamination in an electromagnetic mass separator. This phenomenon is treated numerically, based on geometrical considerations and on an appropriate and reliable interaction potential between the ions and the residual gas molecules. The result is a relation[Formula: see text]expressing the fractional contamination as a function of: the residual gas molecule concentration nr, the fractional mass difference ΔM/M, the collector slit width Δx, the configuration factor [Formula: see text] and constants (σ0 and n) which appear in the expression for the differential cross section. The reciprocal value [Formula: see text] imposes an upper limit to the enhancement factor. By performing the various integrations in a different sequence, a general expression for the transmission from source to collector is obtained. The influence of losses caused by inelastic scattering can be easily incorporated. For elements with a mass number of about 200, scattered by air and for an accelerating voltage of about 30 kv, this expression takes the form:[Formula: see text]where L is the total ion path length in the separator.
EFFECTS OF COULOMB COLLISIONS ON LONGITUDINAL PLASMA OSCILLATIONS
Authors: Johnston T. W. , Shkarofsky I. P.
Published: April 2011

This theoretical analysis shows that the Fokker–Planck equation can be applied to obtain identical wavelength-dependent (k2) damping as previously derived from the much more complicated Liouville equation approach. It is also noted that electron (ω ~ ωp) and ion (ω ~ Ωp) oscillations are only slightly damped by Coulomb collisions. The k2 dependent damping is difficult to observe for electron oscillations but perhaps not for ion oscillations (where it is the only Coulomb damping) if Landau damping effects do not obscure the observation and if the electron temperature is not too high compared with the ion temperature. The electron and ion oscillations are effectively free (the ratio of specific heats γ multiplying the temperature is effectively 3). The low-frequency sound oscillations [Formula: see text] are isothermal for electrons (γ = 1) and can be adiabatic (γ = 5/3) or free (γ = 3) for ions as the ion–ion collision frequency is much more or less than ω.
THE STRUCTURE OF AGGREGATES AND THE MOLECULAR KINEMATICS OF THE VISCOSITY OF A BERNAL LIQUID
Authors: Smith F. W.
Published: April 2011

The structure of 3-dimensional aggregates is discussed as a set of points on which graphs are constructed. By constructing the Voronoi honeycomb (Dirichlet regions) for the points and applying a small "irregularizing transformation", a "simplicial graph" and a "primitive coordination number" (whose value is close to 14 for all aggregates) can be defined universally for both regular and irregular aggregates. Recent studies of the geometry of irregular aggregates (of steel balls, crystal grains, etc.) are reviewed. The theory of liquids of J. D. Bernal is discussed and the simplicial graph is used to show that the "activation volume" of a Bernal liquid is about one-tenth of the molecular volume. The kinematics of flow of aggregates is discussed in terms of their graphs and in terms of a process of "volume exchange"—the production and destruction of free volume. Using these concepts, an equation is derived for the viscosity of a Bernal liquid as a product of five terms expressing respectively the kinematic, stoichiometric, kinetic, pressure-dependent, and shear-dependent factors.
NONLINEAR PROPAGATION OF ELECTROMAGNETIC WAVES IN MAGNETOPLASMAS. II
Authors: Sodha Mahendra S. , Palumbo Carl J.
Published: April 2011

In this communication the authors have investigated the nonlinear propagation of an electromagnetic wave at an arbitrary angle to the direction of the magnetic field in a plasma. The authors have derived an expression for the complex conductivity tensor of a Lorentzian magnetoplasma, which is correct to terms involving the square of the amplitude of the electric vector. This expression, along with the wave equation, has been used to analyze two specific problems, viz. the propagation of an electromagnetic wave in an infinite magnetoplasma and reflection and refraction at the interface of a nonlinear magnetoplasma and a linear isotropic medium.
THE IONIC ENTRAPMENT AND THERMAL DESORPTION OF INERT GASES IN TUNGSTEN FOR KINETIC ENERGIES OF 40 EV TO 5 KEV
Authors: Kornelsen E. V.
Published: April 2011

A clean polycrystalline tungsten wire was bombarded with monoenergetic ions of neon, argon, krypton, and xenon in the energy range 40 ev to 5 kev. The gas trapped in the tungsten was desorbed by then heating the wire to 2400 °K at 66 °K/second. Ion sticking probabilities determined from the quantities of gas desorbed ranged from ~0.6 for all gases at 3 kev to <10−5 at ion energies (ev) ~4 times the ion atomic number. From the variation of the desorption rates with temperature, six activation energies of thermal desorption were found which were not dependent on the ion or its incident energy. The lowest four (33 to 63 kcal/mole) are believed to be associated with gas trapped within a few atom layers of the metal surface, and the highest (102 kcal/mole) with normal impurity diffusion in the bulk tungsten.
POTENTIAL ENERGY CURVES AND DISSOCIATION PRODUCTS OF THE K2 MOLECULE
Authors: Rai D. K. , Tripathi A. N.
Published: April 2011

A R.K.R.V. calculation has been performed for the [Formula: see text] and B1Πu state of the K2 molecule. By fitting an empirical potential curve to the known true potential curve (the one obtained by the R.K.R.V. method) the dissociation energies of the corresponding states can be estimated. These estimated values allow the states of the dissociated atom to be determined. We have used the four-parameter Lippincott and the five-parameter Hulburt–Hirschfelder functions to approximate the R.K.R.V. curves of the two states. The agreement between the curves is of the same type as already found in previous cases.
RADIO STAR SCINTILLATION NEAR THE AURORAL ZONE
Authors: Ryan W. D.
Published: April 2011

The Queen's University Radio Observatory at Kingston, Ontario, geomagnetic latitude 55° 33′ N, is particularly well situated for radio star scintillation observations looking both north into the auroral zone and south away from the auroral zone. An analysis of the scintillation data has indicated that radio sources observed to the south of the zenith have scintillation characteristics which are typical of observations made at lower geomagnetic latitudes, while sources observed near and to the north of the zenith exhibit the highly disturbed "auroral zone" characteristics. If the scintillation is assumed to be imposed on the incident radiation at a height of 350 kilometers, the transition described above occurs in a north–south distance of about 240 kilometers.
DIPOLAR INTERACTION IN SELECTED PARAMAGNETIC CRYSTALS
Authors: Vanier Jacques
Published: April 2011

Broadening of the paramagnetic resonance lines of Cr3+ in each of two salts, rubidium alum and potassium cobalticyanide, has been measured as a function of concentration. In rubidium alum the width between the peaks of the derivative was 6.3 oersteds up to 0.5% and increased with concentration above this value. In K3Co(CN)6 the width increased with increasing concentration from 2.4 oersteds at the lowest concentration of 0.01%. Calculations indicate that a major portion of the observed widths is due to dipolar interactions of the Cr3+ with neighboring nuclei and other Cr3+ ions. The greater width observed for the nominal (1/2 ± 3/2) lines over the (1/2–1/2) line in every sample at every orientation may be associated with concentration-dependent crystalline imperfections.
THE ATTENUATION OF HIGH-AMPLITUDE WAVES IN ROCKS
Authors: Mereu R. F.
Published: April 2011

The pin-contactor method was modified so that it could be used to measure coefficients of absorption of high-amplitude waves in cylinders of rocks and metals. Experiments performed with granite, marble, and aluminum showed that the coefficients of absorption for marble and aluminum for pressures below 100 kb are more than three times that for granite. Also, for pressures greater than 22 kb the absorption coefficient for marble is more than twice that for pressures below this level. It should be emphasized that the absolute values of the absorption coefficients found in these experiments depend on the geometry; however, the relative values indicate the extent of the differences in the properties of the rocks. The compressibilities of both marble and granite were found to be constant for pressures in the 2 to 100 kb range. The results of these experiments and similar ones could lead to a better understanding of how the energy of explosions can be coupled into seismic energy more efficiently.
SENSITIZED FLUORESCENCE IN VAPORS OF ALKALI METALS: I. ENERGY TRANSFER IN POTASSIUM–POTASSIUM COLLISIONS
Authors: Chapman G. D. , Krause L. , Brockman I. H.
Published: April 2011

Sensitized fluorescence in potassium vapor at pressures between 10−5 mm Hg and 10−1 mm Hg was investigated to determine the cross sections for collisions of the second kind between unexcited and excited potassium atoms. An idealized fluorescence tube was used in the experiment and the fluorescent light was analyzed with a photoelectric recording spectrometer. The collision cross sections at low vapor pressures, where imprisonment of radiation is absent, are identical for both the 42P1/2 → 42P3/2 and 42P1/2 ← 42P3/2 transitions and equal 6.6 × 10−12 cm2 at 2 × 10−4 mm Hg. The experimental results are interpreted on the basis of new selection rules for sensitized fluorescence.
AIR-MASS EFFECTS ON TROPOSPHERIC RADIO SCATTER
Authors: Doherty Lorne H.
Published: April 2011

Significant differences in signal level and variability on a 2720-Mc/s 90-mile scatter propagation path are shown to be related to the air mass present over the path. Periods of superrefraction are almost always associated with maritime arctic air. Maritime tropical air results in a very stable relatively high signal level. Continental arctic air on the other hand is associated with low signal levels which exhibit a reversed diurnal variation.
THE 2100 Å BANDS OF CS2
Authors: Douglas A. E. , Zanon I.
Published: April 2011

The CS2 bands which lie near 2100 Å have been photographed in absorption with a high-dispersion spectrograph and a partial analysis has been made of the band system. Though a number of features remain unexplained, strong evidence has been obtained that in the upper state (a 1B2 state) the molecule is nonlinear with an S–C–S bond angle of 153° and a C–S bond distance of 1.66 Å.
EXCITATION OF COUPLED ELECTRO–ACOUSTICAL WAVES BY A RING SOURCE IN A COMPRESSIBLE PLASMA CYLINDER
Authors: Samaddar S. N. , Yildiz M.
Published: April 2011

Propagation of coupled electromagnetic and plasma waves (acoustical) excited by a magnetic ring current in an infinitely long compressible plasma cylinder surrounded by vacuum is studied. It is known that in an incompressible plasma a slow surface wave can propagate only when the electron–plasma frequency, ωP, is higher than the frequency, ω, of the source. However, in the present problem it is shown that under suitable conditions slow surface waves can propagate along the interface of the compressible plasma column and vacuum for values in the range either ωP > ω or ωP < ω. The surface waves for which ωp < ω are supposed to be a new phenomenon. Numerical results for these surface waves have been presented. In addition, an expression for a radiated field is obtained by the usual saddle-point method of integration. The possibility of the existence of leaky waves is also discussed for a special case.
THE FORMATION AND STRUCTURE OF VORTEX RINGS
Authors: Magarvey R. H. , MacLatchy C. S.
Published: April 2011

A preliminary examination was made of the formation and structure of the classical vortex ring. It is inferred from the experimental evidence that the configuration is not a true ring, but a layer of disperse fluid rolled about a circular axis. The stability of this pseudo-ring was found to be a result of the stability of its two rolled layers. The evidence suggests that a thin layer of fluid demarcated by two surfaces of discontinuity of opposite vorticity is relatively stable. A qualitative investigation was made of the flow patterns within the structure, but no attempt was made to relate velocities to ring geometry or to the physical characteristics of the ambient fluid.
ROTATIONAL ANALYSIS OF THE VISIBLE EMISSION BANDS OF THE PbF MOLECULE
Authors: Rao K. Madhusudana , Rao P. Tiruvenganna
Published: April 2011

The rotational structure of the (0, 0), (0, 1), (0, 2), and (1, 0) bands of the visible band system (A–X1) of PbF has been examined in the second order of a 21-ft concave grating spectrograph having a dispersion of 1.25 Å/mm. A rotational analysis of the bands has led to a determination of the rotational constants of the upper and lower states. From consideration of electron configurations it is suggested that the system arises from a [Formula: see text] transition which is a case c equivalent of [Formula: see text].
VELOCITY-DEPENDENT NUCLEON–NUCLEON POTENTIALS AND SATURATION IN NUCLEAR MATTER
Authors: Bhaduri R. K. , Preston M. A.
Published: April 2011

Recently, nonsingular velocity-dependent potentials have been constructed which fit the the two-nucleon data, but do not give saturation in nuclear matter at reasonable densities. In this paper, we have asked what features a potential should have in order to give saturation, and we have found that the short-range wave-function distortion (defined in the text) is important. Reasons are given for the failure of the earlier potentials to saturate, and a new velocity-dependent potential is proposed which gives results similar to the standard hard-core potential model. We speculate on the usefulness of such potentials for future calculations of nuclear properties.
GAMMA–ALPHA REACTIONS IN THE LIGHT NUCLEI OF NUCLEAR EMULSIONS
Authors: Greenberg L. H. , Roalsvig J. P. , Haslam R. N. H.
Published: April 2011

Ilford E.1 nuclear emulsions were loaded with various amounts of glycerine to vary the content of carbon and of oxygen, and were then irradiated in the beam of the University of Saskatchewan betatron. The numbers of single alpha-particle tracks and of four-pronged alpha-particle stars were correlated to the oxygen content of the plates and the number of three-pronged stars to the carbon content. The yields for the reactions O16(γ, α)C12, O16(γ, 4α), and C12(γ, 3α) for bremsstrahlung of 24-Mev maximum energy were found without confusion with reactions in other nuclides of the emulsion and without having to rely on momentum balances for identification of the events. It was shown that the method of identification of 016(γ, α)C12 events by the measurement of the track of the C12 was not reliable. The large number of alpha tracks in the energy range 4 to 5 Mev, few of which showed a C12 track, was shown to be due largely to reactions in O16. It was also possible, by irradiating emulsions at 17- and at 24-Mev maximum bremsstrahlung energy, to find the energy levels in O16 and in C12 through which the reactions passed.
THE SPECTRUM OF ZINC IV
Authors: Crooker A. M. , Dick K. A.
Published: April 2011

The basic term structure in the third spark spectrum of zinc, Zn IV, is established herein for the first time. The spectral lines, excited in both sliding-spark and condensed-spark discharges in helium, were divided into their probable excitation classifications according to their behavior in these sources. Some 200 lines are classified as transitions between 17 even levels, arising from the configurations 3d9 and 3d84s, and 43 odd levels, arising from the configuration 3d84p. The analysis is shown to account for the principal Zn IV lines observed by Bloch and Bloch in the region λ < 500 Å, as well as our own data involving these and longer wavelengths. Comparisons made with the isoelectronic sequence Co I, Ni II, Cu III, and Zn IV show satisfactory agreement with anticipated regularities.
THERMAL CONDUCTIVITY OF A FULLY IONIZED GAS
Authors: Sundaresan M. K. , Wu Ta-You
Published: April 2011

The present work deals with the formulation of the theory of the hydro-dynamical stage in the approach of a plasma towards equilibrium, on the basis of the kinetic equation obtained by Guernsey and by Rosenberg and Wu along the line of the Bogoliubov theory for neutral gases. The equations of continuity, momentum transport, and energy transport are given. The solution of the kinetic equation has been obtained in the hydrodynamical stage for a plasma deviating only slightly from equilibrium. This solution has been used to calculate the thermal conductivity of the plasma. The result agrees very well with an earlier calculation of Spitzer and Härm based on the use of a Fokker–Planck kinetic equation with a Debye–Hückel screened potential to avoid the divergence for distant collisions.
RÉSEAU ZONÉ ÉQUIVALENT À UN FILTRE D'AMPLITUDE
Authors: Boivin Germain
Published: April 2011

The diffracted amplitude in a diffraction pattern is evaluated by means of the classical definition of the Riemann integral. This process leads to the substitution of the continuous pupil function T(x) by a step function T′(x) which, physically, corresponds to a zone plate of constant pitch, uniformly illuminated, whose concentric zones have a width proportional to T(x).The method was used to produce a gaussian amplitude distribution in order to provide a maximum concentration of light energy in the focal plane.An experiment comparing the filtered pupil with the unfiltered pupil shows that the former increases the fidelity of contrasts in the images.
ABSORPTION SPECTRUM OF THE NO MOLECULE: IV. THE G2Σ−–X2Π SYSTEM
Authors: Lofthus A. , Miescher E.
Published: April 2011

High-dispersion plates of the NO absorption spectrum have been studied between 1600 and 1390 Å for the three isotopic molecules N14O16, N15O16, and N14O18, and G2Σ−–X2Π bands were sorted out from the many overlapping bands in the spectrum. The well-defined band system satisfies the established isotope relations. In contrast with most of the other known NO band systems G2Σ−–X2Π shows almost no perturbations. Vibrational and rotational analyses gave the following constants for the G2Σ− state of N14O16: Te = 62911.7 cm−1; ωe = 1085.54 cm−1, ωexe = 11.083 cm−1, ωeye = −0.1439 cm−1, Be = 1.2523 cm−1, αe = 0.0204 cm−1, γe = 1.3426 Å. The combination defect observed in the G2Σ−–X2Π bands agrees with the defect found in the A2Σ+–X2Π(γ) bands except in sign, which is opposite. Therefore, the symmetry of the G state is confirmed as 2Σ−. The "pure precession" relation between G2Σ− and X2Π is found to hold for the Λ-type doubling of X2Π. The diffuse structure of the band assigned to ν = 10 indicates that G2Σ− is predissociated by a repulsive 2Σ− state dissociating into 2D(N)+3P(O) atoms at 71660 cm−1. The dissociation energy and electron configuration for G2Σ− are discussed.
SCATTERING BY A PERFECTLY CONDUCTING CYLINDER IN A GYROELECTRIC MEDIUM: NUMERICAL RESULTS
Authors: Seshadri S. R.
Published: April 2011

The numerical results on the various scattering cross sections of a perfectly conducting circular cylinder embedded in a gyrotropic medium are presented for the case in which both the gyrotropic axis and the magnetic vector of the incident plane electromagnetic wave are parallel to the axis of the cylinder.
ANALYSIS OF THE PROFILE OF THE FUNDAMENTAL INFRARED BAND OF HYDROGEN IN PRESSURE-INDUCED ABSORPTION
Authors: Hunt J. L. , Welsh H. L.
Published: April 2011

The pressure-induced fundamental infrared absorption band of hydrogen was measured for a series of pressures in the pure gas and in a H2–He mixture at 300 °K, 195 °K, and 78 °K, and in H2–A and H2–N2 mixtures at 300 °K. The band profiles were separated by a computational procedure into QP and QR (overlap) components and QQ and S(J) (quadrupole) components using a dispersion line shape modified by the Boltzmann law. The dispersion half-width obtained for the overlap components was about twice as great as for the quadrupole components; both half-widths varied as the square root of the temperature. The S(J) lines in pure hydrogen consisted of single and double transitions, the relative intensities of which were in accordance with the assumption of quadrupole interaction. Ortho–para ratios of 3:1 and 1:1 were used in the experiments; the integrated intensities of the band showed very little dependence on the ortho–para ratio, in disagreement with a previously reported result.
INTERACTION OF SLOW ELECTRONS WITH CHEMISORBED OXYGEN
Authors: Redhead P. A.
Published: April 2011

Measurements have been made of the effects of low-energy electron bombardment (0–300 ev) on a chemisorbed layer of oxygen on polycrystalline molybdenum. Oxygen is adsorbed in two states at room temperature with approximate heats of adsorption of 60 and 110 kcal/mole, respectively. O+ ions are released from the weakly bound state with a maximum probability of 10−5 ion/electron at an electron energy of 90 ev. The ion-energy distribution, measured by a retarding-field method, has a maximum at about 6 ev and a half-width of 5 ev. About 50 neutrals are released for every ion. The measured threshold energy, 17.6 ± 0.2 ev, for ion formation is in good agreement with the calculated value. The probability of ion and neutral release from the strongly bonded state is about 2 × 103 times smaller than for the weakly bonded state. A qualitative explanation of the formation of neutrals is proposed in terms of Auger neutralization of the ions near the surface. Reflection of the ion-energy distribution in the calculated curve of the potential energy of the O+ ion yields, after correction for Auger neutralization, the probability density distribution of the adsorbed oxygen atom. The equilibrium spacing of the chemisorbed atom is then estimated to be 1.67 Å.
TRANSVERSE WAVES PROPAGATING ALONG AN APPLIED MAGNETIC FIELD IN A PLASMA
Authors: Burgess R. E. , Cook J. G.
Published: April 2011

Transverse waves propagating along an applied magnetic field are studied, with special attention to the role of the magnetic field in determining the behavior of the wave. No restrictions are placed on the hole (or ion) mass, and the electron and hole densities may differ. The behavior of the magnetic-field-dominated waves is studied, and it is shown that it is profitable to extend the concept of an Alfvén wave to include those waves for which essentially B0 instead of B02 appears in the dispersion equation. Both intrinsic and extrinsic cases are studied.The dispersion equation approach is compared with the equation of motion and Ohm's law approach used by Watanabe for a study of Alfvén waves, and Watanabe's starting equations are generalized to make a study of Alfvén waves in solid-state plasmas with Watanabe's approach possible.
SOME NEW NEUTRON SEPARATION ENERGIES FOR ISOTOPES OF Hg, Tl, Pb, AND Bi
Authors: McLatchie W. , Barber R. C. , Bishop R. L. , Duckworth H. E. , Hogg B. G. , Macdougall J. D. , Rookhuyzen P. Van
Published: April 2011

Values derived from mass spectral doublets are reported for the following mass differences: Hg200−Hg198, Hg201−Hg199, Hg202−Hg200, Hg204−Hg202, Tl205−Tl203, Pb206−Pb204, Pb208−Pb206, Bi209−Pb207, Pb207−Tl205, Pb206−Hg204, and Tl203−Hg201. These mass differences are combined with existing reaction and disintegration data to yield single- and double-neutron separation energies for several of the isotopes of the above elements. The resulting neutron separation energy curves for even N are strikingly similar in shape and all exhibit an abrupt change in slope at N = 124. The curves for odd N do not display the same regularity. Currently accepted values for the total decay energies Tl204–Hg204 and Tl202–Hg202 are probably too large and too small, respectively, but current values for Pb205–Tl205 and Bi208–Pb208 are confirmed.
LITHIUM, SODIUM, AND POTASSIUM IN THE TWILIGHT AIRGLOW
Authors: Sullivan H. M. , Hunten D. M.
Published: April 2011

A birefringent filter photometer has been used to measure the weaker twilight emissions due to free lithium and potassium atoms, the twilight sodium emission having been monitored simultaneously with an interference wedge photometer. Comparisons of the relative abundances Na/Li and Na/K with those found in meteorites and in sea water suggest that the principal sources are meteorites for the lithium, and the sea for the sodium and potassium.A spectacular seasonal variation of the twilight lithium has been found, showing a correlation with the occurrence of the Leonid meteor shower and with two unusual interplanetary dust showers, one during the interval November 15–18, and the other on February 2. Effects of high-altitude thermonuclear explosions are discussed and it is concluded that these can increase the brightness of twilight lithium emission by 1 to 2 powers of 10.The vertical distributions of all three elements have roughly the same shape. However, the maximum concentration of lithium occurs at 80 km, approximately 11 km below the sodium peak, while the maximum concentration of potassium occurs at about the same height as the sodium peak.The chemistry and ionization of alkalis in the upper atmosphere are considered. It is suggested that the degree of ionization is negligible, and a fast recombination process is discussed. A mechanism for vertical transport of sodium from the lower atmosphere is suggested.
THE EFFECT OF VIBRATIONAL EXCITATION OF H2+ ON ITS COLLISION-INDUCED DISSOCIATION
Authors: McGowan J. Wm. , Kerwin Larkin
Published: April 2011

A study is reported of the production of fast protons resulting from the collision-induced dissociation of H2+ in collision with H2. Ion energies between 0.6 and 2 kev are considered. For fixed ion energy, a direct relationship is observed between the relative population of the vibrational levels (a function of the ionizing electron energy) and the cross section. As the electron energy is increased, the relative population of the upper states is increased, which gives rise to a marked increase in total cross section. Several mechanisms of ion collisional dissociation obtain. One involves a vertical Franck–Condon transition between electronic states; the other appears to involve a diagonal transition which may occur when Franck–Condon conditions do not apply.
EXCITATION CURVES FOR THE REACTIONS Fe56(n, p)Mn56 AND Co59(n, α)Mn56
Authors: Santry D. C. , Butler J. P.
Published: April 2011

Excitation curves for the reactions Fe56(n, p)Mn56 and Co59(n, α)Mn56 have been measured by the activation method from near threshold energies to 20.3 Mev. The measurements are relative to the known cross section for the S32(n, p)P32 reaction. Cross sections for both reactions increase smoothly with neutron energy and reach maximum values of 119 ± 4 mb for the Fe56(n, p) reaction at 13.6 Mev and 30.0 ± 0.9 mb for the Co59(n, α) reaction at 14.5 Mev. Above 15 Mev both cross sections decrease with neutron energy. From the excitation curves effective cross-section values for a fission-neutron spectrum have been calculated as 1.04 ± 0.05 mb for the (n, p) reaction and 0.140 ± 0.007 mb for the (n, α) reaction.
VIBRATIONAL FREQUENCY PERTURBATIONS IN THE RAMAN SPECTRUM OF COMPRESSED GASEOUS HYDROGEN
Authors: May A. D. , Varghese G. , Stryland J. C. , Welsh H. L.
Published: April 2011

The frequencies of the Q(J) lines of the fundamental Raman band of compressed hydrogen gas were measured with high spectral resolution for a series of densities from 25 to 400 Amagat units at 300 °K and 85 °K. The frequency shifts are expressed as a power series in the gas density. The linear coefficient at a given temperature has the form aJ = ai + ae(nJ/n), where ai, constant for all the Q lines, can be interpreted in terms of isotropic intermolecular forces, and ae(nJ/n), proportional to the relative population of the initial J level, arises from the inphase coupled oscillation of pairs of molecules. The temperature variation of ai is analyzed on the basis of the Lennard-Jones intermolecular potential and the molecular pair distribution function. The repulsive overlap forces and the attractive dispersion forces give, respectively, positive and negative contributions to ai, which can be characterized by the empirical parameters Krep and Katt. The values of Katt and ae are in good agreement with calculations based on the polarizability model of the dispersion forces. The relation of the results to the Raman frequency shifts in solid hydrogen is discussed.
AN IDENTITY INVOLVING 9-j COEFFICIENTS
Authors: Talman James D. , True William W.
Published: April 2011

An identity involving 9-j coefficients which may be of some value in spectroscopic calculations is obtained. Two proofs of the identity are described. In one proof the recoupling of matrix elements of tensor operators is considered; in the other the general methods of Yutsis, Levinsonas, and Vanagas are used. Two applications of the identity to nuclear shell-model theory are described.
NEUTRON SPECTRUM OF A Ra–Be(α, n) SOURCE
Authors: Geiger K. W. , Hum R. , Jarvis C. J. D.
Published: April 2011

The neutron energy spectrum of a Ra–Be source has been measured successfully by the nuclear emulsion technique without introducing a significant thickness of lead absorber to reduce the γ-ray background. In comparison with the spectra published by other authors, the part of the spectrum below 4 Mev is found to be somewhat less intense, probably owing to the absence of inelastic scattering in the lead. No observations could be made below 0.75 Mev; however, by comparison with the source emission rate, it was estimated that this fraction of the spectrum contributes (37 ± 15)% of the total neutron emission.
DIURNAL INTENSITY VARIATIONS IN THE OUTER RADIATION ZONE AT 1000 KM
Authors: McDiarmid I. B. , Burrows J. R.
Published: April 2011

A diurnal variation has been observed at 1000 km in the outer radiation zone in the average intensity of trapped electrons with energies greater than 40 kev and in the average intensity and frequency of occurrence of precipitated electrons of the same energy. The amplitude of the variation is greatest near the high-latitude boundary of the outer zone, but extends down to invariant latitudes of λ = 60° (L ~ 4.5). In the latitude range λ = 60° to 68° the shape of the distributions of average intensity against local time is very similar for both the trapped and precipitated electrons with the daily maximum occurring around 0800 hours local time. Good statistical agreement is obtained between the frequency of occurrence of precipitation and auroral absorption at two different local times.
PLANE WAVE SPECTRA IN GRATING THEORYL III. SCATTERING BY A SEMIINFINITE GRATING OF IDENTICAL CYLINDERS
Authors: Millar R. F.
Published: April 2011

A time-harmonic, plane wave is incident on a semiinfinite grating of identical, but otherwise arbitrary, cylinders. The scattered field is expressed as an angular spectrum of plane waves with an unknown scattering amplitude function. By decomposing the grating into two "bodies" (namely the first N elements and the remaining infinity of elements), integral equations are derived for the unknown. The case N = 1 leads to two integral equations which relate the scattering functions of the grating and its end element to the scattering function of the end element in isolation. The case N → ∞ provides an equation relating the scattering function of the grating to that of an element in an infinite grating. The scattering function of the grating is shown to possess branch points in the complex planes of the angles of incidence (α) and observation (θ), and poles whose positions depend on both. The scattering function is examined in the neighborhood of the branch points. For all relative configurations of poles, θ, and branch points, the field far from the end element is calculated by asymptotic methods. Contributions arise from poles, branch-cut integrals, and a steepest-descent integral. Poles give rise to plane waves existing in wedge-shaped regions bounded on one side by the grating. Branch-cut integrals also yield waves in wedge-shaped regions; their contribution is usually negligible in comparison with that of the steepest-descent integral.
DISTRIBUTION OF CHARGED PARTICLES TRAPPED IN A VARYING STRONG MAGNETIC FIELD (ONE-DIMENSIONAL CASE) WITH APPLICATIONS TO TRAPPED RADIATION
Authors: Watanabe Tomiya
Published: April 2011

The differential equation for the distribution function of charged particles trapped in a strong magnetic field is discussed for the case when the charged particles are constrained in a tube of magnetic lines of force with a small normal cross section (the one-dimensional case). The distribution function is not defined by the six canonical variables, the variables in geometrical space and velocity space, as is done usually when referring to the Boltzmann equation. Instead, it is defined by the space coordinates of the guiding center of a representative particle together with its speed and pitch angle (i.e. five variables, in the three-dimensional case). In some problems, this type of description makes the correspondence between the physical picture and its mathematical description much easier. Several problems relating to trapped radiation are discussed using the differential equation.
RESONANCES IN THE SMITH–PURCELL EFFECT
Authors: Hessel A.
Published: April 2011

A rigorous solution is derived for the problem of radiation of the Smith–Purcell type (Smith and Purcell 1953) extracted from a radio-frequency bunched electric-current sheath, above a plane exhibiting a periodically varying surface reactance. The plane is regarded as a model of an optical reflection grating. The solution indicates that the presence of the grating will give rise to electromagnetic resonance effects which are closely related to the so-called Wood anomalies (Wood 1935; Twersky 1956; Hessel 1960; Hessel and Oliner 1962; Stewart and Gallaway 1962), encountered in optical-grating spectroscopy. Utilization of these resonances may be advantageous in the generation of millimeter waves.
EXCITATION OF N2 BAND SYSTEMS IN AURORA
Authors: Broadfoot A. L. , Hunten D. M.
Published: April 2011

The near-ultraviolet region of the auroral spectrum has been observed by a photoelectric spectrometer for the purpose of deriving accurate relative intensities of the N2 band systems. To increase the signal-to-noise ratio with the faint auroras measured, long "exposures" were accumulated in a memory unit. From the band intensities in the Vegard–Kaplan system, the relative populations of the first three vibrational levels of the metastable [Formula: see text] state could be found; the ratios appear to vary significantly. These bands give a rotational temperature of 800 ± 200 °K; they must therefore be emitted from a height of about 220 km. The vibrational populations are most reasonably explained if nearly all the excitation of the A state is by cascading from higher levels. A detailed discussion is given of these processes, supplemented by measurements of the second positive bands. Cascading is found to supply an appreciable fraction of the excitation of the B3Πg state; the C3Πu state seems to be excited purely by electron impact. Previous evidence that the latter is not always true is examined and rejected.
PULSE INDUCED SUPERCONDUCTING TO NORMAL TRANSITIONS IN THIN FILMS
Authors: Hartlin E. M. , Wertheimer R. M. , Graham G. M.
Published: April 2011

The superconducting to normal transition in thin films of Al, Sn, In, and Pb has been studied by applying square voltage pulses to a coaxial line terminated by the film and observing the reflected pulse shape. Interest has centered on the nearly isothermal transitions which could be induced below the lambda temperature of liquid helium. The results have been analyzed in terms of the nucleation and growth of normal domains. The use of very rapidly rising pulses has allowed an estimation of the nucleation time of a normal domain as not more than 3 × 10−10 second. The number of nucleation sites was a sensitive function of the current density in the film. The subsequent growth of normal domains proceeded with a velocity characteristic of the material, of the order of the velocity of transverse sound waves in the bulk metal. Roughly the same velocity was deduced for normal domain growth both parallel and perpendicular to the direction of the current in the film. Growth velocities smaller than these have not been observed, but the "pinning" of domain boundaries by defects in the film has been encountered.
GAMMA-RAY ANGULAR CORRELATION MEASUREMENTS IN Ne22
Authors: Broude C. , Eswaran M. A.
Published: April 2011

Coincidence gamma-ray angular correlations of the cascade decays from the 3.34- and 4.47-Mev states in Ne22 through the first excited state have been measured. The levels were excited by the reaction F19 (α, p)Ne22. The correlations give an unambiguous spin assignment of 4 to the 3.34-Mev state; the analysis of the correlations from the 4.47-Mev state is not unique, allowing spin 2 or 3. The quadrupole-to-dipole amplitude ratio for the primary radiation is −0.11 ± 0.03 or −1.07 ± 0.10, respectively, for the spin-2 and spin-3 assignments.
A PRECISE MEASUREMENT OF THE C11 PRODUCTION CROSS SECTION FOR 98-MeV PROTONS ON CARBON
Authors: Kavanagh T. M. , Lee J. K. P. , Link W. T.
Published: April 2011

A precise measurement of the cross section for the production of C11 positron activity by the proton bombardment of natural carbon is described. Extensive subsidiary experiments were performed to evaluate the errors in the factors entering the measurement. The cross section is (63.3 ± 0.3) × 10−27 cm2 per atom of natural carbon for protons of range 9515 mg/cm2 of aluminum (indicated energy 98.1 MeV).
THE THERMODYNAMIC DESCRIPTION OF HETEROGENEOUS DISSIPATIVE SYSTEMS BY VARIATIONAL METHODS: III. AN APPLICATION OF THE PRINCIPLE OF MINIMUM ENTROPY PRODUCTION TO FLUID DYNAMICS
Authors: Kirkaldy J. S.
Published: April 2011

The stable free-fall flight of a maple seed gives an exceptionally graphic demonstration of the principle of minimum entropy production. Since the rate of entropy production is proportional to the steady-state rate of loss of potential energy, it is visually obvious that the stable rotary configuration represents a minimum of the entropy production rate relative to an unstable steady-state bomblike trajectory. Regarding this phenomenon as the prototype of many practical steady-state fluid-dynamical systems involving rotational modes, we formally demonstrate the possibility of mathematically defining the stable steady-state configuration by means of this variational principle.
THE LOW-TEMPERATURE ORDERED STATE OF CERIUM MAGNESIUM NITRATE AND ITS INFLUENCE ON NUCLEAR ORIENTATION
Authors: Daniels J. M. , Felsteiner J.
Published: April 2011

The method of Luttinger and Tisza for minimizing the dipole–dipole interaction energy is applied to cerium magnesium nitrate, and an antiferromagnetic ordering of the cerium spins at 0 °K is found. Using this configuration, the magnetic field at the divalent ions is calculated. Next, the anisotropy of γ rays from Co60 aligned in this salt is calculated for temperatures below 0.003 °K. Qualitative agreement is found between these calculations and measurements of γ-ray anisotropy reported in the literature.
A REMARK ON THE ISOTOPE SHIFT IN NUCLEAR MAGNETIC SHIELDING
Authors: Saika A. , Narumi H.
Published: April 2011

Isotope shifts in nuclear magnetic shielding have been calculated in the molecular hydrogen system by a semiempirical procedure, which assumes that the high-frequency term varies with internuclear distance R as Rm. It has been found, through a comparison with other investigations, that the choice of m = −1.9 appears to be reasonable. If this choice is taken, then the isotope shift between HD and H2 becomes (0.047 ± 0.02) × 10−6, while the shielding constant for H2 is (26.51 ± 0.3) × 10−6.
THE DIELECTRIC CONSTANTS OF ARGON, CARBON DIOXIDE, NITROGEN, AND OXYGEN DETERMINED AT AN AUDIO FREQUENCY
Authors: Dunn A. F.
Published: April 2011

Values of the relative permittivities, or dielectric constants, of four gases have been measured at an audio frequency of 1592 c.p.s. with an accuracy comparable to that obtained in the microwave or optical regions. The method is based on the characteristics of the computable cross-capacitance configuration which permit the accurate calculation of changes of capacitance due to variation of dimensions with gas pressure, aided by the improved capacitance measurements now available. The results obtained are as follows:[Formula: see text]These results verify the extrapolation of the optical refractivity data to zero frequency for argon, nitrogen, and oxygen in which the atomic polarization constant is zero. On the other hand carbon dioxide, which has a strong infrared vibration–rotation spectrum, may not be extrapolated from optical data, but must be measured at the lower frequencies.The measured values of these reference gases may be used to calibrate other permittivity apparatus and so extend the data on other substances.
A STUDY OF ELECTRONS ARTIFICIALLY INJECTED INTO THE GEOMAGNETIC FIELD IN OCTOBER, 1962
Authors: Burrows J. R. , McDiarmid I. B.
Published: April 2011

Particle detectors in the Alouette satellite measured the electrons with energy greater than 3.9 MeV which were trapped in the geomagnetic field as the result of three Russian high-altitude nuclear explosions in October and November, 1962. The early spatial distribution is reported. Temporal variations in the flux have been studied during the following three months. Effects of geomagnetic conditions on the electron precipitation are measured and an estimate is made of the total precipitation at L ~ 2.95.
ELECTRICAL CONDUCTIVITY OF INERT GASES—SEED COMBINATION IN SHOCK TUBES
Authors: Lau J.
Published: April 2011

The effect of seeding shock waves with alkali metal smoke is studied. The pressure, density, temperature ratio, electron density, and conductivity were calculated with a digital computer and tabulated for various combinations of gas and seeding material. A hydrogen-driven shock tube was constructed to measure the properties of the seeded gas behind the shock wave. The conductivity of argon seeded with cesium was measured with a conductivity probe and compared with theoretical calculations.
RADIATION FROM ELEMENTARY FLUID-MECHANICAL SOURCES IN AN UNBOUNDED ELECTRON PLASMA
Authors: Seshadri S. R.
Published: April 2011

The radiation characteristics of a line source of fluid flux and a line source of force, embedded in a homogeneous electron plasma of infinite extent, are investigated for the case in which a uniform magnetic field is impressed externally throughout the medium in the direction of the source. It is found that there are two propagating modes which are strictly coupled longitudinal and transverse waves. However, one of the modes is predominantly transverse in the entire frequency range of propagation and the other is predominantly transverse in the lower, and predominantly longitudinal in the higher ranges of frequency of propagation. It is shown that the elementary fluid-mechanical sources considered in this paper radiate significant amounts of power only in the longitudinal-type waves.
AN AURORAL PHOTOMETER FOR THE I.Q.S.Y.
Authors: Watson M. D.
Published: April 2011

A description is given of a simple auroral photometer which is intended to be used in an extended program of auroral photometry during and after the International Years of the Quiet Sun. Absolute auroral intensities will be measured at four wavelengths and recorded on a logarithmic scale. The instrument incorporates a precision timer and automatic control circuits, and is designed for relatively unattended operation.
MODULATION OF ELECTROMAGNETIC WAVES BY ACOUSTIC WAVES IN A PLASMA
Authors: Sodha Mahendra Singh , Palumbo Carl James
Published: April 2011

This communication presents an analysis of the modulation of an electromagnetic wave, propagating in a plasma, in which an acoustic wave is present. The modulation of the transmitted and reflected waves from a plasma-free space interface has also been analyzed. A discussion of the results obtained has also been given.