bluuebunny/crossref_metadata_2025 huggingface dataset:
DIELECTRIC RELAXATION OF SOME NEARLY SPHERICAL MOLECULES IN THE LIQUID AND SOLID PHASES
Authors: Mansingh Abhai , McLay David B.
Published: April 2011

The dielectric constant and loss at a microwave frequency of 9 GHz and also the static dielectric constant at either 10 kHz or 200 kHz have been measured for the nearly spherical molecules Br3CNO2, Cl3CNO2, BrC(CH3)3, ClC(CH3)3, and ClSi(CH3)3 over a range of temperature from below the respective melting point to above this melting point. The measurements combined with the tabulated values for the optical index of refraction allow a determination of the dielectric relaxation times at each temperature if it is assumed that either the Debye theory or the modification of this theory by Cole and Cole is valid. In the cases of the five liquids, the data are consistent with the Debye model. In the solid phase, however, only Cl3CNO2 and ClSi(CH3)3 do not exhibit solid rotator phases, while each of the other three molecules exhibits at least one solid rotator phase. The results are consistent with the interpretation that each liquid has a single dielectric relaxation time but that the transition to a solid rotator phase involves a distribution of relaxation times which are only slightly different in value from the appropriate single value in the liquid phase.
THE RAMAN SPECTRUM OF ETHANE-1,1,1-d3
Authors: Shaw D. E. , Welsh H. L.
Published: April 2011

The Raman spectrum of CH3–CD3 at 1 atm pressure was photographed with a spectral resolution of ~0.3 cm−1. The nondegenerate ν1 and ν3 and the doubly degenerate ν7 and ν11 fundamentals were observed. Analyses of the rotational structure of the ν3 and ν7 bands gave the rotational constants, B0 = 0.549 1 ± 0.000 3 cm−1 and A0 = 1.7809 ± 0.0016 cm−1, respectively. These are consistent with rotational constants previously obtained for C2H6 and C2D6.
WEAK GAMMA-RAY TRANSITIONS IN 20Ne
Authors: Broude C. , Litherland A. E. , Ollerhead R. W. , Alexander T. K.
Published: April 2011

Various techniques have been applied to the measurement of weak gamma-ray decay modes of the 4.97-MeV 2− and 7.02-MeV 4− states in 20Ne excited by the reaction 12C(12C, αγ)20Ne. The M2 decay of the 4.97-MeV state to the ground state is 0.6 ± 0.2% of the total level width, corresponding to an M2 width of 2 × 10−3 Weisskopf units. The M2–E3 transition from the 7.02-MeV state to the 1.63-MeV 2+ state is 0.5% ± 0.2% of the level width; if all M2, this would correspond to an inhibition of 1.4 × 10−2 Weisskopf units, if all E3, to an enhancement of 6 Weisskopf units. The reliability of the measurements has been checked by angular correlation measurements of the weak transitions.
MOMENTUM DISTRIBUTIONS OF TWO PHOTON ANNIHILATING POSITRON–ELECTRON PAIRS IN HEXANE AND DECANE
Authors: Chuang S. Y. , Hogg B. G.
Published: April 2011

Momentum distributions are calculated for electrons in the C–C and C–H bonds in hydrocarbons, using analytic SCF functions for atomic carbon orbitals and Heitler–London-type functions for the two paired electrons in the C–C and C–H bonds. The positron wave function is assumed to be a constant. The computed momentum distributions are then compared with high-precision experimental distributions obtained from positron-annihilation angular correlation experiments.
SPECTRAL FUNCTION SUM RULES IN SU(3) × SU(3)
Authors: Moffat J. W. , O'Donnell P. J.
Published: April 2011

Recently derived spectral function sum rules have been used to obtain mass ratios, assuming that the spectral functions are dominated by certain low-lying states. The strangeness-carrying resonance mass ratio is investigated and the predicted value is found to depend critically upon the ratio FK/Fπ. Using the experimental value FK/Fπ = 1.28 ± 0.02, it is found that [Formula: see text]. On the other hand, from the input value [Formula: see text] we get [Formula: see text].
THE MEASUREMENT OF THE TEMPERATURE DEPENDENCE OF ATOMIC AND MOLECULAR ION MOBILITIES IN HELIUM
Authors: Orient O. J.
Published: April 2011

The mobilities of atomic and molecular helium ions were measured with an apparatus similar to that described by Biondi and Chanin, but with some modifications. Three species of ions were found. For the mobility of atomic ions a value of μ0(He+) = 10.6 ± 0.15 cm2/V s, for that of the two species of molecular ions μ0(He2+) = 16.0 ± 0.28 cm2/V s, and μ0(He2+) = 20.4 ± 0.26 cm2/V s have been obtained at 296 °K. The three kinds of mobilities have been measured in the temperature range from 195 to 665 °K. The mobility of the atomic ions decreased with the rise of temperature, while the mobilities of both molecular ions increased. The measurement results have been compared with those of theoretical calculations found in the literature.
A THEORY OF VOLUME VISCOSITY
Authors: Narasimham A. V.
Published: April 2011

A simple theory has been worked out for the complex and frequency-dependent nature of the volume viscosity of a liquid. This is related to the absorption and dispersion (variation of velocity with frequency) of compressional waves in the liquid. It is found that the particles that execute simple harmonic motion, on the application of an ultrasonic wave to the medium, are not single molecules but groups of molecules known as cells. Calculated values of the ultrasonic absorption and velocity, made on the basis of the present theory, are found to agree reasonably well with the existing ultrasonic data pertaining to nonassociated liquids.
ISOTOPE SHIFT IN THE SECOND SPECTRUM OF BARIUM
Authors: Kelly F. M. , Tomchuk E.
Published: April 2011

Measurements of isotope shifts and magnetic hyperfine structures have been made in λ 4 934 Å in the second spectrum of barium. The measurements are compared with those of other authors.
MEDIUM FREQUENCY CONJUGATE ECHOES OBSERVED ON TOPSIDE-SOUNDER DATA
Authors: Muldrew D. B.
Published: April 2011

The results of a statistical study of conjugate echoes observed on Alouette II topside-sounder data are presented and compared, where possible, with Alouette I and Explorer XX results. The percentage occurrence of conjugate echoes is either independent of Kp or decreases slightly as Kp increases from 0 to 6. Most of the data show a nighttime maximum in the occurrence of conjugate echoes; however, the occurrence of higher-frequency echoes tends to peak near 07 hours local time, which agrees with the Explorer XX results. The occurrence of conjugate echoes increases as the L value decreases from 4 to about 1.35. There is an oscillation in the occurrence of conjugate echoes with either local time or calendar date (day of the year); because of the characteristics of the satellite orbit, it is difficult to distinguish between these two possibilities at the present time.
CHARACTERISTICS OF A TOROIDAL RESONATOR FOR PLASMA DIAGNOSTICS
Authors: Šícha M. , Cloutier G. G. , Bolton R.
Published: April 2011

In this paper an experimental investigation of the electric-field configuration in a toroidal resonator has been carried out by measuring the shift of the resonant frequency when a small dielectric sphere is introduced in the resonator. The good agreement between the experimental and the theoretical results shows that the assumptions concerning the electromagnetic-field configuration are correct and the method can be used in measuring the electrical conductivity of a plasma.
NONLINEAR DEMODULATION OF AN AMPLITUDE-MODULATED ELECTROMAGNETIC WAVE PROPAGATING IN A MAGNETOPLASMA
Authors: Ram Sant , Kaw P. K.
Published: April 2011

Explicit expressions for the electric vector of an amplitude-modulated electromagnetic wave propagating along the direction of an applied magnetic field in a nonlinear ionized medium have been obtained, when the wave frequency is equal to the gyrofrequency of the electrons. It is seen that the wave gets strongly demodulated after propagation through the magnetoplasma as well as after reflection from a magnetoplasma-free space interface. Some numerical results, illustrating the variation of the demodulation with various plasma parameters have been presented in the discussion.
ON THE SPECTRUM OF OCS IN THE VACUUM ULTRAVIOLET
Authors: Kopp I.
Published: April 2011

The absorption spectrum of OCS in the region 1 350–1 420 Å has been investigated under high resolution. A vibrational analysis including most of the bands has been carried out. The bands in this region show no rotational fine structure. For double-headed bands, approximate B values of the upper states have been obtained from the separation of the heads. The following constants were determined (cm−1):[Formula: see text]
ION IMPLANTATION OF SILICON: I. ATOM LOCATION AND LATTICE DISORDER BY MEANS OF 1.0-MeV HELIUM ION SCATTERING
Authors: Davies J. A. , Denhartog J. , Eriksson L. , Mayer J. W.
Published: April 2011

The implantation behavior of Sb in silicon has been investigated by studying the orientation dependence of the backscattering yield of a 1.0-MeV helium beam. This orientation dependence ("channeling") provides quantitative information on the location of implanted atoms in the lattice and also on the amount of lattice disorder accompanying the implantation. The general principles of the channeling technique and the advantages of using a beam of He+ rather than H+ are discussed. Results for 25 °C and 450 °C implantations are presented and compared. The hot implant introduces very little lattice disorder, and a large fraction (up to 95%) of the Sb atoms is found on substitutional sites. In the 25 °C implants, however, a heavily damaged region is formed around the track of each implanted Sb. At doses greater than ~1014 ions/cm2, these damaged regions overlap to produce an essentially amorphous layer, which then requires an annealing temperature of ~650 °C to reorder the lattice and to achieve a high level of substitutional Sb. "Hot implant" studies have also been made for several other dopants—Ga, As, In, and Xe; however, unlike Sb, the substitutional level in all these cases never exceeded 60%. This unique behavior of Sb implants in silicon has also been found in a corresponding study of the electrical characteristics (Paper II). A preliminary investigation of boron-doped silicon, using the orientation dependence of 670-keV protons, indicates that substitutional boron atoms are removed from lattice sites by relatively small doses of energetic protons. This enhanced sensitivity to radiation does not occur for the Sb-doped samples.
ION IMPLANTATION OF SILICON: II. ELECTRICAL EVALUATION USING HALL-EFFECT MEASUREMENTS
Authors: Mayer J. W. , Marsh O. J. , Shifrin G. A. , Baron R.
Published: April 2011

Hall-effect and sheet-resistivity measurements have been made on silicon samples implanted with Sb, Ga, and As ions at energies between 20 and 75 keV. These measurements determine the weighted average of the number Ns of carriers/cm2 and the carrier mobility in the implanted layer. A combination of Hall measurements and layer-removal techniques was used in some cases to obtain a more accurate value of the number of carriers/cm2 and the depth dependence of the carrier concentration and mobility.For Sb implantations both temperature and dose affect the anneal characteristics. Silicon samples implanted with Sb at room temperature exhibited n-type behavior following anneal at 300 °C, with little increase in Ns up to about 550 °C anneal temperatures. A 600 °C 10-minute anneal produced an order-of-magnitude increase in Ns. This change is associated with reordering of the amorphous layer created during room-temperature implantations. This amorphous layer is not produced in implantations made at temperatures above 450 °C. In low-dose (<1014/cm2) Sb implantations at 500 °C, Ns increased by a factor of 2 to 3 during anneal to 800 °C. In high-dose (>5 × 1014/cm2) Sb implantations, the carrier concentration exceeded the limit set by thermal equilibrium solubility of Sb in silicon. Under these conditions, annealing caused a decrease in Ns toward the value associated with the solubility.Such supersaturation effects were not observed in Ga and As implantations at 500 °C. Annealing to temperatures of 800–900 °C produced a one-to-two order-of-magnitude increase in the number of carriers/cm2. In Ga implantations annealed to 800–900 °C, the number of carriers/cm2 increased approximately linearly with increasing dose and then leveled off at a value near that expected from thermal solubility.The Rutherford-scattering data in the preceding paper indicates that the difference in implantation behavior between various ion species is due to differences in the relative number of ions on substitutional sites.
Ranges of projectiles in amorphous materials
Authors: Sanders J. B.
Published: April 2011

By using an inverse power-law approximation for the interaction potential between a fast-moving projectile and the atoms of an amorphous target into which it penetrates, it is possible to calculate moments of any order of different combinations of range quantities as functions of the initial kinetic energy of the projectile. By the moment of order n of a statistically distributed quantity X we mean the average value of Xn. The quantities concerned are the projection of the total distance from its point of entrance, reached by the projectile on its initial direction of motion, and the projection on the plane, perpendicular to this direction. From these moments, a distribution function of the penetration depth can be constructed. This calculation has been performed for 85Kr ions entering amorphous Al2O3 with different energies. The result is compared with measurements made by Domeij et al.
Sputtering and depth-distribution phenomena in KCl, Al2O3, and TiO2
Authors: Kelly Roger
Published: April 2011

If a solid is bombarded with an inert gas, the thickness removed by sputtering is proportional to (S) (μA min/cm2), where S is the sputtering coefficient. We have used this effect first to evaluate S for Kr–Al2O3, O2–Al2O3, Kr–TiO2, and O2–TiO2 in the region 2–10 keV. With Al2O3, pieces of free anodic oxide were bombarded until perforated, while with TiO2 the changes in the interference colors of anodized Ti were noted. Knowing the values of S, we have then obtained depth distributions for 10-keV Kr in KCl, Al2O3, and TiO2 at doses of 1–50 μA min/cm2, the amount of Kr remaining in the targets being determined by radioactivity measurements. Rm, the median range, was 105 Å with KCl, and thus within a factor-of-2 agreement of other range data for crystalline materials; with Al2O3 and TiO2, however, Rm was only 11–18 Å, and thus a factor of 4–6 lower than expected on the basis of low-dose data for anodic oxides. In the case of Al2O3, the low values of Rm were explicitly shown to be due in part to a dose effect, such that Rm is at least a factor of 2.3 lower for doses over 1 μA min/cm2, and similar behavior can probably be assumed also for TiO2. In addition, however, gas sputtering or surface roughening may possibly play a role with Al2O3 and TiO2.
Range studies using a new chemical film technique
Authors: Andersen T. , Sørensen G.
Published: April 2011

The formation and stripping of corrosion films produced by immersion of metal foils of Cu, Ag, Au, Sn, or Pb in organic solvents containing corrosive agents such as iodine or bromine have been studied using a radioactive tracer technique. The data show that the formation and stripping of metal–halogen films may be a suitable method for the peeling of layers from 0.5–30 μg/cm2 metal.The film technique has been applied for Cu and Au, using iodine in chloroform as the corrosive agent and potassium iodide as the stripping solution for Cu, whereas bromine in carbon tetrachloride or bromine vapor was used as the corrosive agent for Au, with chloroform as the stripping agent. Experimental range data of 24Na, 32P, and 42K in gold at energies higher than 100 keV are reported and compared with theory.
Stopping cross section in atmospheric air of 0.2–0.5 MeV atoms with
Authors: Fastrup B. , Borup A. , Hvelplund P.
Published: April 2011

The stopping cross section S = dE/NdR in atmospheric air has been measured for ions with [Formula: see text] and the energy ranging from 0.2 to 0.5 MeV. The experimental data have been corrected numerically for nuclear stopping, and the electronic stopping cross sections Se obtained are compared with theory. The previously reported periodic dependence of Se in solids on the atomic number Z1 of the incoming ion for constant velocity is also seen in the present data for a gas target. The structure of the oscillations is found to be insensitive to whether the target is a solid or a gas. In the last part of the paper, some preliminary measurements of the charge-state distributions of the ions emerging from the gas target for various Z1 values are discussed.
Low-energy electronic stopping cross sections in nitrogen and argon
Authors: Ormrod J. H.
Published: April 2011

The rate of energy loss in nitrogen and argon targets for ions with [Formula: see text] and E < 200 keV has been measured. The contribution to the energy loss from nuclear stopping was calculated using Fastrup's method, and was subtracted from the observed stopping cross section to give the electronic stopping cross section. Over the energy interval studied, the electronic stopping cross sections obtained are below the theoretical values and the energy dependence in argon is much greater than [Formula: see text].A target gas pressure of ~10 μ was used. This reduces the collision frequency eight orders of magnitude below that in a solid. The periodic dependence of the electronic stopping cross section on the atomic number of the incident projectile, previously observed in solid targets, occurs also for such low-pressure gas targets; it is concluded that this dependence is not affected by the collision frequency.
Computer studies of fast ion trajectories in crystals
Authors: Morgan D. V. , Vliet D. van
Published: April 2011

A computer program has been developed which follows the trajectories of fast ions in crystals, based on the assumption of classical dynamics and binary collisions. Initial work has been directed at various aspects of proton channeling in copper in the energy range 5–500 keV. The critical angle and distance of closest approach in a perfect lattice have been evaluated for both rows and planes and compare well with the predictions of the continuum model as developed by Lindhard (1965). We also discuss the overlap of close-packed rows and planes, and the modifications necessary to the basic theory when thermal vibrations are introduced. Experiments have been simulated directly by obtaining a statistical analysis of the velocity distribution of protons reflected from a (100) face of copper and transmitted through a thin (~1800 Â) crystal. In reflection, distinct minima were obtained along directions corresponding to close-packed rows and planes, in good agreement with experimental "blocking patterns" (Nelson 1967a). Transmission patterns also revealed a lack of large-angle scattering parallel to close-packed planes, analogous to the white arms observed experimentally with thinner crystals.
Channeling studies through characteristic radiations
Authors: Brandt W. , Dobrin R. , Jack Jr. H. , Laubert R. , Roth S.
Published: April 2011

The yield of K-shell fluorescence radiation emitted from aluminium crystals is measured during bombardment with 1H+, 3He+, 4He+, and 20Ne+ ions in the energy range 100–200 keV under channeling conditions. The yield as a function of the angle between the beam and a crystallographic direction shows a minimum; the half-width is independent of the ion mass and varies as the square root of the incident charge. Under proton bombardment the yield curve for copper K-shell excitation is somewhat wider than for L-shell excitation. The difference diminishes with increasing energy and vanishes near the upper end of our energy range. Channeling in organic crystals is demonstrated along the c direction of thin anthracene crystals in penetration experiments with 5.48-MeV alphas. The yield of optical fluorescence radiation emitted from the anthracene target during alpha bombardment shows a minimum when particles are incident along this channeling direction.
Charged-particle energy loss in thin gold crystals
Authors: Gibson W. M. , Rasmussen J. B. , Ambrosius-Olesen P. , Andreen C. J.
Published: April 2011

The energy loss of 400-keV protons and 800-keV helium ions transmitted through thin gold crystals has been studied. The effects of mosaic spread in gold crystals grown on sodium chloride substrates and the effects of twinning in crystals grown on mica substrates are examined in detail. Conditions and measurements necessary to minimize such crystal effects are described. The directional dependence of the relative intensities of resolved components in the energy-loss spectra has been measured. The results are used to evaluate suggestions of the origin of structure in the energy loss of transmitted particles.
Impurity distribution profiles in ion-implanted silicon
Authors: Kleinfelder W. J. , Johnson W. S. , Gibbons J. F.
Published: April 2011

A p–n junction location technique for determining ion-implanted profiles of dopant ions in semiconducting substrates is described. This method allows detection of the implanted concentration up to eight orders of magnitude below the peak. Distributions of boron, nitrogen, phosphorus, and arsenic ions implanted in [Formula: see text] oriented silicon crystals as well as boron in [Formula: see text] silicon crystals are given. The samples were implanted at energies from 10 to 70 keV and were annealed during implant at 625 °C. The results are compared to theoretical estimates. In the cases of boron and arsenic in [Formula: see text] silicon, and boron in [Formula: see text] silicon, a definite maximum range Rmax is apparent. In these cases Rmax increases as the square root of the incident energy, indicating a channeling phenomenon. The phosphorus profiles do not show a maximum range, but rather decrease exponentially with depth for five orders of magnitude in concentration.
Theory of charged particles in semiconductors
Authors: Brandt Werner , Reinheimer Julian
Published: April 2011

The dielectric response function of semiconductors is derived for an isotropic model characterized by an effective Fermi energy, EF, corresponding to a mean valence electron density, and an energy gap of width Eg. The response to the fields set up by impurity atoms and by moving charged particles is investigated. The screening of impurities changes with the energy gap: as Eg increases from zero, the potential expands in range and approaches the bare Coulomb potential, while the Friedel oscillations in the induced electron density about the impurity are suppressed. The contribution of electronic excitations from the valence band of semiconductors to their stopping power for swift heavy particles is calculated.
Defect studies in crystals by means of channeling
Authors: Bøgh E.
Published: April 2011

Channeling of fast, light ions (e.g. protons and α particles) in crystals containing displaced atoms is discussed on the basis of Lindhard's theory, with the particular purpose of applying channeling as a tool for studying crystal defects. Measurements of the orientation dependence of the yield of close-encounter processes, such as nuclear reactions and wide-angle elastic scattering, can provide information about the depth distribution of structural defects in the first few microns beneath the surface of a single crystal. The relation between the yield and defect concentration is derived. This relation has led to a new double-alignment technique that combines channeling and blocking, and increases considerably the sensitivity for detecting structural defects.Scattering yield measurements in tungsten and silicon crystals covered with amorphous oxide layers of accurately known thickness are used to verify the results of the theoretical discussion. Double alignment is demonstrated. Criteria for selecting the optimal experimental conditions are set up. The sensitivity of the method for detecting lattice disorder corresponds to the displacement of ~1014–1015 atoms per cm2 (i.e. less than one atomic layer); the depth resolution with which, for example, radiation damage may be determined is ~50 Å.
Ion implantation of silicon and germanium at room temperature. Analysis by means of 1.0-MeV helium ion scattering
Authors: Mayer J. W. , Eriksson L. , Picraux S. T. , Davies J. A.
Published: April 2011

The orientation dependence of the backscattered yield of 1.0-MeV helium ions has been used to investigate the lattice characteristics of silicon and germanium implanted at room temperature with 40-keV heavy ions (Ga, As, Sb, In, P). The method gives directly the number of substrate atoms displaced from their lattice sites by more than the Thomas–Fermi screening distance (≈ 0.2 Å) and also the location of the implanted atoms.Each heavy ion is found to displace several thousand lattice atoms in a localized region around its track. At doses where the individual disordered regions do not overlap (~1013 ions/cm2, or less), the silicon lattice reorders at 260 °C and the germanium lattice at 180 °C. At doses greater than ~1014 ions/cm2, a completely amorphous layer is formed in both silicon and germanium. During annealing, the reordering of the lattice is initiated at the interface between the amorphous region and the underlying crystal. The reordering of this amorphous layer occurs at significantly higher temperatures (570 °C in Si and 380 °C in germanium) than those required for the isolated disordered regions. At doses much greater than 1015/cm2, even higher anneal temperatures are required.Following a room-temperature implantation, each implanted atom is embedded in a highly disordered region (at least, for doses > 1014/cm2) and consequently the backscattered spectra from these atoms do not show orientation effects. As the lattice reorders during annealing, the number of implanted atoms lying along the [Formula: see text] lattice row increases. Following anneal, ~75% of the As atoms and ~90% of the Sb atoms are found on substitutional sites in silicon, while in germanium, ~80% of the In atoms are found on substitutional sites. Annealing to higher temperatures (700–900 °C in the case of silicon) often causes the number of substitutional atoms to decrease again, owing to the effect of internal precipitation or diffusion to the surface.
Electrical and physical measurements on silicon implanted with channelled and nonchanneled dopant ions
Authors: Gibson W. M. , Martin F. W. , Stensgaard R. , Jensen F. Palmgren , Meyer N. I. , Galster G. , Johansen A. , Olsen J. S.
Published: April 2011

Hall effect and resistivity measurements from room temperature to 4.2 °K have been carried out on silicon samples implanted with 400-keV phosphorus, lithium, and boron ions. Implantations were carried out at 25 °C in random as well as precisely controlled channeling directions, and the electrical measurements were made after successive annealing treatments. These measurements are interpreted in terms of the final lattice position of the injected impurity ions and the amount and type of crystal defects produced during the implantation and are correlated with physical measurements of lattice position and radiation damage studied by using nuclear-reaction, beta-particle emission, and Rutherford-scattering techniques.
The influence of temperature and channeling on ion-bombardment damage in Si
Authors: Nelson R. S. , Mazey D. J.
Published: April 2011

The ion bombardment of silicon results in the formation of an amorphous phase in the vicinity of the bombarded regions. This gives rise to a milky appearance which is easily distinguishable from an adjacent unbombarded region. Experiments are described which were designed specifically to study the influence of bombardment temperature and channeling on the formation of this phase.
Radiation damage and substitutional chemical impurity effects in single-crystal germanium bombarded with 40-keV B+, Al+, Ga+, Ge+, P+, As+, and Sb+ ions
Authors: Alton G. D. , Love L. O.
Published: April 2011

Isochronal anneal studies have been made on n- and p-type germanium bombarded with germanium and several substitutional impurities, using the four-point and thermoelectric probes as means of indicating changes in sheet resistivity and majority carrier type. Electrical properties of diodes made from type converted samples were also determined. All bombardments were performed at 40 keV in a 24-in.-radius electromagnetic isotope separator at room temperature. These studies revealed the following. (1) Heavy-particle bombardment of germanium introduces acceptor states regardless of the identity of the bombarding species. (2) Annealing curves for n-type germanium indicate a two-stage process; details of the annealing process are dependent on the ion species used and the crystal orientation bombarded. (3) There is a crystallographic and mass dependence on the amount of change in sheet resistivity produced in n-type germanium. (4) Type conversion temperatures in p-type germanium were observed to occur at 450–475 °C for phosphorus, ~500 °C for arsenic, and slightly greater than 500 °C for antimony, suggesting that the ease of moving a particular species into an active lattice position is related to its atomic size. (5) Voltage–current and capacitance measurements indicate that large-area diodes of relatively good properties and reproducibility can be made by ion implantation in germanium.
Ion-bombardment-induced resistivity changes in thin films of silver, gold, titanium, and tungsten
Authors: Navinsek B. , Carter G.
Published: April 2011

Energetic argon ions were injected into thin films (100–500 Å) of Ag, Au, Ti, and W, and changes in the electrical resistance of the films were observed. Three stages in the resistance change/ion dose relation were observed. The first at low ion doses, where the resistance falls, is believed to be a result of removal of contaminant gas from the surface. The next stage at higher ion doses, where the resistance increases to a quasi-constant value, is believed to be associated with damage production at and near the film surface. At still higher ion doses, the resistance increases to infinity as a result of sputtering of the film.
Thermal release of rare gases implanted in metal targets by high-energy ion bombardment
Authors: Rickers G. , Sørensen G.
Published: April 2011

Results of thermal gas release from copper, silver, and gold targets bombarded with krypton and xenon ions of energies between 20 and 450 keV will be presented. The influence of bombardment doses is shown. The desorption carried out under high-vacuum conditions was examined with the tracer technique, and the fractional release was determined as a function of temperature, energy, and dose. Depth distributions were studied using a corrosion film technique, and the correlation between such distributions and the gas release was investigated. The results are compared with earlier work, and an attempt to elucidate inert-gas diffusion in copper is described.
Single-crystal sputtering including the channeling phenomenon
Authors: Onderdelinden D.
Published: April 2011

Measurements of the angular behavior of the sputtering ratio for Ar+ on (100) Cu turned around a [011] axis are presented for Ar+ energies of 5, 10, 15, 20, and 35 keV. It is shown that the widths of the [100] minima can be related to the acceptance angle for channeling, as described by the theory of Lindhard. This is taken as evidence for the assumption that a channeled particle does not contribute to sputtering. On the basis of the assumption that the sputtering ratio is proportional to the energy dissipation of the nonchanneled part of the beam within a layer x0, a two-parameter expression for the sputtering ratio has been obtained.Calculations have been performed for normally incident Ar+, Kr+, and Cu+ ions on (111), (110), and (100) Cu crystals in the energy range 2–40 keV. The best fit has been obtained for x0 values of the order of 80 Å. From the description of Ar+ on (100) Au, x0 is about 135 Å. This is thought to be due to the influence of the focusing collision chain length on the thickness of the layer important for sputtering. Furthermore, it is shown that a satisfactory description of the angular behavior of the sputtering ratio can be obtained with the proposed model.
The role of focusing collisions in sputtering
Authors: Nelson R. S. , Jan R. von
Published: April 2011

A theoretical model provides a better understanding of the mechanism of sputtering from close-packed crystal directions, for high-energy sputtering in particular. The results show that focusing collisions must play a major part in producing the observed preferential ejection and that the contribution of long-range sequences is important for materials with high focusing energies. The model also provides information on the influence of thermal vibrations.
The angular distribution of scattered and sputtered 40-keV particles on polycrystalline targets
Authors: Formann E. , Viehböck F. P. , Wotke H.
Published: April 2011

Based on the hard-sphere potential approximation, angular distributions of scattered particles at different mass ratios M1:M2 were calculated. The results were compared with experiments carried out with the following atoms:[Formula: see text]The sputtered particles from the target as well as from the incident-ion beam were collected on graphite rods and measured by either activation analysis or a radioactive tracer technique.
Ion reflection from a single crystal
Authors: Yurasova V. E. , Shulga V. I. , Karpuzov D. S.
Published: April 2011

The scattering of Ar, Ne, and He ions from the Cu {100} face has been investigated by a digital computer technique; only binary elastic collisions of ions with the lattice atoms have been considered; the angular and energy distribution at various directions of incidence are discussed. The scattering by surface atomic chains and its contribution to the general picture of ion reflection were also studied.
The elastic scattering of 60Co gamma rays from lead
Authors: Dixon W. R. , Storey R. S.
Published: April 2011

The elastic scattering of 60Co gamma rays from lead has been remeasured using a lithium-drifted germanium detector. For angles less than 90°, there is satisfactory agreement between the measured and calculated values. For angles greater than 90°, the measured values are significantly smaller. The discrepancy is too large to be attributed to destructive interference from Delbrück scattering. An explanation can be found in the possibility that there are phase shifts between the Rayleigh and nuclear Thomson components.
Electron scattering in InAsxSb1−x alloys
Authors: Aubin Marcel J. , Woolley John C.
Published: April 2011

Room-temperature measurements of the thermoelectric power α and Hall coefficient R have been made as a function of the magnetic field B on polycrystalline n-type samples of InAsxSb1−x, alloys of carrier concentration ~1017/cm3. Hence saturation values α∞ and R∞ and zero-field values α∞ and R∞ have been determined. Using these values of α∞ and α∞ and assuming a Kane model for the conduction band, values have been determined for the Fermi energy EF and the scattering parameter s over the whole alloy range. In all cases, the value of s is close to 0.5, indicating that the dominant scattering mechanism in the alloys is piezoelectric scattering. From the EF and R∞ data, values of the bottom of the band effective mass have been calculated and these are compared with similar values obtained from Faraday rotation results.
Energies and quantities of ions in laser-produced metal plasmas
Authors: Paton B. E. , Isenor N. R.
Published: April 2011

Mean kinetic energies and abundances of ionic species from plasmas of Al, Cu, and Au produced by focused Q-switched ruby laser light have been measured. Electrostatic and time-of-flight methods are used. General agreement is found with existing theory regarding the mean energies of the different ionic species, but the relative abundances display anomalies.
Extensions to the spark spectra of zinc. I. Zinc II and zinc IV
Authors: Crooker A. M. , Dick K. A.
Published: April 2011

The spectrum of Zn II has been extended to complete the configuration 3d94s(3D)4p′ and 3d94s(1D)4p″. The configurations 3d109f, 3d1010f, and 3d94s(3D)5s′ have been added and a number of levels of the configurations 3d94s(3D)4d′, 3d94s(1D)4d″, and 3d94s(3D)6s′ have been tentatively established. Our list of Zn II lines contains 363 classified lines.Improved wavelength measurements have necessitated a revision of our earlier report on the spectrum of Zn IV. All the energy levels have been shifted slightly with respect to the ground state doublet 3d92D. In addition, 3 of 17 even levels and 10 of 43 odd levels have been changed. The new energy-level scheme results in the classification of 329 spectral lines as compared with 200 lines in the previous report.
Experimental facilities at the Haverah Park 500-m EAS array
Authors: Tennent R. M.
Published: April 2011

The Haverah Park 500-m EAS array is described with special reference to the accuracy of the estimation of shower parameters. The shower core location is found to within 10 m for near-vertical showers, but estimates are less accurate for inclined showers. The direction of the shower axis is found by measuring the time of arrival of particles at the different detectors, and the direction can be placed within a cone of semiangle 4° for a wide range of zenith angle. Estimates of the curvature of the shower front have a standard deviation of 0.08 km−1.
The structure of the shower front of large extensive air showers
Authors: Baxter A. J. , Watson A. A. , Wilson J. G.
Published: April 2011

Using a method described previously (Baxter et al. 1966), an experimental study has been made of the time distribution of energy from the shower front of large extensive air showers detected by the Haverah Park 500-m array. Data are given on the mean time of arrival of energy in showers at axial distances over the range 250–950 m for all zenith angles, while average time distributions of the energy in the shower front are presented for some typical distance and zenith angle intervals. Experimental observations are compared with a theoretical prediction; a real discrepancy appears to exist between theory and experiment since about 25% more energy is observed in the 25 ns after the first detectable signal than is predicted. The result suggests a higher or more concentrated origin for muons than normally assumed.Assessment of measurement errors, particularly those arising from the sampling of a diffuse shower front by detectors of finite size, suggests that no intrinsic differences in the properties of the majority of air showers have yet been detected by this method.
Study of extensive air showers at Mount Norikura. II. Direct measurement of attenuation length
Authors: Miyake S. , Hinotani K. , Ito N. , Kino S. , Sasaki H. , Yoshii H. , Sakuyama H. , Kato E.
Published: April 2011

Attenuation lengths for individual EAS passing through a 2 m layer of water have been measured by means of two layers of plastic scintillators. The attenuation lengths obtained vary over a wide range from about 70 g/cm2 to several hundreds of g/cm2 and, very rarely, the negative attenuation length of the growing stage has been obtained. The attenuation lengths observed are not sensitive to core structure (single or multiple core), but are sensitive to the age parameter of EAS determined from the lateral structure function. However, there are some discrepancies between age parameters estimated from longitudinal development and from lateral structure, the former yielding greater ages than the latter.The average value of attenuation length observed is significantly short compared with those for other methods so far used in a statistical way, especially for larger-sized EAS. Considering the calculated transition curve for EAS, and fluctuation in the level of the first interaction, the distribution of the attenuation length obtained is consistent with a model of EAS whose primary energy is 106 GeV, interaction mean free path 90 g/cm2, and inelasticity 0.7. A model of multiple production of baryons at an early stage of EAS is discussed.
Simultaneous observation of air shower cores at sea level and under 800 g/cm2 of shielding
Authors: Böhm E. , Fritze R. , Kassner F. , Mie F. , Roose U. J. , Samorski M. , Staubert R. , Trümper J.
Published: April 2011

Using a 14-m2 neon hodoscope installed under 800 g/cm2 of concrete and vertically below the 32-m2 neon hodoscope, observations have been made on the strongly interacting and the muon component in air shower cores. A preliminary analysis has yielded the following results: (a) The energy spectrum of strongly interacting particles in air shower cores has been obtained in the energy range from 1 to 10 TeV, yielding an exponent of ~ −1.2 for the integral spectrum. (b) The lateral distribution of muons exhibits a distribution as steep as r−0.9 ± 0.1 down to distances of the order of 1 m from the air shower axis. However, at the present state of evaluation contamination of muon data, due to unrecognized cascades, cannot be ruled out completely.
Fine structure of air shower cores
Authors: Matano T. , Nagano M. , Shibata S. , Suga K. , Tanahashi G. , Hasegawa H.
Published: April 2011

The fine structure of air shower cores has been studied by the INS 20-m2 spark-chamber array. Fifteen multicore events were found, one of which is a triple-core event. The frequency of occurrence of multicore events is 3% of all showers of size larger than 105. The production height and energy of each subcore were estimated using the calculation of Nishimura and Kidd. The energies of the subcores are found to be above 1013 eV. From the production height and the energy of each subcore, the transverse momentum of the interaction Pt which produced the subcore was estimated. The maximum transverse momentum is about 50 GeV/c. From the 16 transverse momenta, we obtained the spectrum of the transverse momentum above 5 GeV/c. The spectrum is represented by a power law Pt−1.7 ± 0.2, which is quite different from the conventional exponential law.
High-energy nuclear interactions of cosmic rays (> 1012 eV) observed at 5 200 m above sea level
Authors: Kamata K. , LaPointe M. , Gaebler J. , Escobar I. , Shibata S. , Saavedra O. , Alarcon A. , Suga K. , Murakami K. , Toyoda Y.
Published: April 2011

The shielded 60-m2 scintillation detector in the center of the Chacaltaya air shower array was used to observe large bursts of size greater than 3 000 particles. These bursts are produced mainly by nuclear interactions in the absorber above the scintillator of nuclear-active particles with energy greater than 3 × 1012 eV. The majority of these bursts are accompanied by extensive air showers, which were detected by the BASJE array. However, there are some events which are not accompanied by air showers and are considered to be due to residual primary nucleons. Some features of the data and results of preliminary analysis of these events will be presented.
Remarks on mu-poor EAS
Authors: Gawin J. , Maze R. , Wdowczyk J. , Zawadzki A.
Published: April 2011

The possibility of interpreting mu-poor EAS as the result of fluctuations in the amount of energy transferred to the electromagnetic component is discussed. It is concluded that this interpretation is not very likely since an assumption of a special discontinuous mechanism of energy transfer in elementary interaction is necessary. Supposing that the mu-poor EAS are initiated by primary photons, the flux of the latter has been found to be [Formula: see text] × 10−9 m−2 s−1 sr−1 at energies above 8 × 1014 eV. The possibility of the existence of such energetic primary photons in space is discussed.
Arrival directions of extensive air showers of primary energy ~1017 eV
Authors: Blake P. R. , Hollows J. D. , Hunter H. W. , Reid R. J. O. , Tennent R. M. , Watson A. A. , Wilson J. G.
Published: April 2011

A detailed study of the arrival directions of primary particles of mean energy 2 × 1017 eV recorded by the Haverah Park Stage 1 (500-m) EAS array is reported. After rejecting time intervals randomly to equalize the sidereal running time of the array, upwards of 30 000 showers were available for analysis. In two energy intervals with mean energies about 1017 eV and 5 × 1017 eV significantly lower upper limits have been set on primary particle anistropy, and for all showers the amplitude of the first harmonic in right ascension is 0.6 ± 1.1% with a maximum at about 210°.An azimuthal asymmetry in detected showers (mainly arising from a 2° tilt of the array plane) limits the precision with which variations in declinations could be detected, and no analysis in galactic coordinates has been attempted. However, a plot in squares 10° RA by 10° declination reveals no deviations from isotropy within declination bands, and the overall distribution of intensity fluctuations is consistent with statistical expectation.Some general remarks are made on isotropy measurements.
Search for point sources of neutral cosmic rays above 1012 eV
Authors: Tornabene Hugh S. , Cusimano Frank J.
Published: April 2011

A new installation for the detection of Cerenkov light from extensive air showers is being used to search for point sources of high-energy neutral cosmic rays. By measuring the relative arrival times of the Cerenkov light front at four well-spaced independent light detectors, an area of sky is examined simultaneously, with angular resolution near 1.5° half-width at half-maximum and energy threshold to gamma rays near 2 × 1012 eV. Results from preliminary scans of 3C144, 3C157, 3C219, 3C274, 3C295, and the constellation of Leo near declination 20° and right ascension 1100 h are given.
The distribution in arrival times of muons in EAS
Authors: Blake P. R. , Allan H. R. , Neat K. P.
Published: April 2011

An appreciable fraction of the muons in large air showers (N > 107 particles), observed at distances of 200–500 m from the shower axis, are found to arrive more than 100 ns later than the shower front. The distribution of arrival times has been studied, and related to shower structure.
Lateral distribution of the muon component in the central part of EAS
Authors: Bonczak B. , Firkowski R. , Gawin J. , Hibner J. , Maze R. , Wdowczyk J. , Zawadzki A.
Published: April 2011

Using 50 000 recordings of muon densities at distances from the axis established with very high accuracy, the lateral distribution of muons from 2 to 30 m has been obtained. The interpretation of the shape of this distribution is discussed and compared with theoretical calculations. The experimental distribution is flatter than the theoretical one at small distances from the axis. This may be explained by the relative deficiency of small transverse momentum transfer in nucleon – air nucleus collisions.
The distribution of the transverse momentum among the secondaries of ultra-high-energy interactions
Authors: Earnshaw J. C. , Maslin G. C. , Turver K. E.
Published: April 2011

A possible distribution of transverse momentum among the secondaries of ultra-high-energy interactions is deduced from the lateral distributions of muons in the momentum range 1–100 GeV/c, the directions of muons of various momenta in EAS, and the occurrence of high-energy nuclear interacting particles far from the shower cores. The distribution can be represented by an expression of the form given by Cocconi et al. (1961) for the secondaries of low-energy interactions, together with a tail of median momentum of about 4 GeV/c containing ~6% of the particles.