bluuebunny/crossref_metadata_2025 huggingface dataset:
Is there any group additive rules in the calculation of electron correlation energies of long straight chain alkane molecules?
Authors: Zhuo Shuping , Wei Jichong , Si Weijiang , Ju Guanzhi
Published: February 2004

According to the definition in the text, the correlation energy of 1sC2 of carbon atoms, the primary and secondary C–H bonding electron pairs in some CH3, CH2 fragments and CH3(CH2)mCH3 (m=1–5) linear alkane molecules are calculated and analyzed. The transferability of the correlation energies of these electron pairs in the linear alkanes is investigated. The results indicate that the correlation energy of 1sC2 is perfectly transferable in the respective methyl and methylene groups, while the correlation energies of the primary and secondary C–H bonding electron pairs are approximately transferable in methyl and methylene groups. The analysis of the results of group correlation energy shows that both of the correlation energies of methyl and methylene groups are transferable in these linear alkanes. The correlation energies of methylene group in CH3(CH2)mCH3 (m=1–5) molecules are slightly decreasing showing a converging trend to a “standard” methylene group in linear alkanes. The excellent fitting relationship between the total correlation energy and the number of methylene groups of the linear alkanes shows that the total correlation energy is a linear function of the number of methylene groups, which means that the total correlation energies of large linear alkanes can be reproduced and predicted by counting the numbers of methylene groups. In this way, total correlation energy of large linear alkane molecule can be approximately calculated using this simple group additive scheme with substantial saving in computational time.
Inertialess instability of a two-layer liquid film flow
Authors: Jiang W. Y. , Helenbrook B. , Lin S. P.
Published: February 2004

The physical mechanism of instability in a superposed two-layer liquid film flow down an incline plane is analyzed. If the layer adjacent to the wall is sufficiently thin and less viscous in certain two-layer parallel Newtonian liquid flows of the same density with an interface but without a free surface, the flows are stable with respect to long waves. This is the so-called “thin lubrication layer effect.” However, when a free surface exists in the two-layered flow, the flow becomes unstable even when the Reynolds number approaches zero. Thus the thin-layer lubrication effect is lost due to the presence of the free surface, and inertialess instability occurs. The reason for the loss of the lubrication effect and the mechanism of inertialess instability are explained by use of the energy budget in the mechanical energy equation. Contrary to the case of two-layer flows without a free surface, the flow with a free surface is stable if the layer adjacent to the solid wall is more viscous. The stabilization is achieved even without help from surface or interfacial tension. The mechanism of stabilization is also elucidated from an energy consideration. Navier–Stokes simulations are then performed to determine the effect of the layer viscosity ratio when nonlinear effects are included.
Ultrafast conductivity dynamics in pentacene probed using terahertz spectroscopy
Authors: Thorsmølle V. K. , Averitt R. D. , Chi X. , Hilton D. J. , Smith D. L. , Ramirez A. P. , Taylor A. J.
Published: February 2004

We present measurements of the transient photoconductivity in pentacene single crystals using optical-pump terahertz-probe spectroscopy. We have measured the temperature and fluence dependence of the mobility of the photoexcited charge carriers with picosecond resolution. The pentacene crystals were excited at 3.0 eV, which is above the bandgap of ∼2.2 eV, and the induced change in the far-infrared transmission was measured. At 30 K, the carrier mobility is μ≈0.4 cm2/V s and decreases to μ≈0.2 cm2/V s at room temperature. The transient terahertz signal reveals the presence of free carriers that are trapped on the time scale of a few picoseconds or less, possibly through the formation of excitons, small polarons, or trapping by impurities.
Rotating disk flow stability in electrochemical cells: Effect of viscosity stratification
Authors: Pontes J. , Mangiavacchi N. , Conceição A. R. , Barcia O. E. , Mattos O. R. , Tribollet B.
Published: February 2004

This work is about the effect of viscosity stratification on the hydrodynamic instability of rotating disk flow, and whether or not it can take into account experimental observations of the lowering of critical Reynolds numbers in electrochemical systems, where a viscosity stratification is assumed to result from the gradients of chemical species existing in the convective boundary layer near the disk electrode. The analysis is for temporal stability of a class of von Kármán solutions: fully three-dimensional modes are considered and the neutral curves are therefore functions of not only the Reynolds number but also the wave frequency and the two wave numbers. Global minimization over wave numbers and also over the frequency gives the critical Reynolds number. The neutral curves exhibit a two-mode structure and the dependence of both modes on parameters is studied. It is shown that viscosity stratification leads to an increase in the range of parameters where perturbations are amplified and to a reduction of the critical Reynolds number, in a wide range of perturbation frequencies. The results support the hypothesis that the current oscillations may originate from a hydrodynamic instability.
Lagrangian statistics in turbulent channel flow
Authors: Choi Jung-Il , Yeo Kyongmin , Lee Changhoon
Published: February 2004

The Lagrangian dispersion of fluid particles in inhomogeneous turbulence is investigated by a direct numerical simulation of turbulent channel flow. Lagrangian velocity and acceleration along a particle trajectory are computed by employing several interpolation schemes. Among the schemes tested, the four-point Hermite interpolation in the homogeneous directions combined with Chebyshev polynomials in the wall-normal direction seems to produce most reliable Lagrangian statistics. Inhomogeneity of Lagrangian statistics in turbulent boundary layer is investigated by releasing many particles at several different wall-normal locations and tracking those particles. The fluid particle dispersion and Lagrangian structure function of velocity are investigated for the Kolmogorov similarity. The behavior of the Lagrangian integral time scales, Kolmogorov constants a0 and C0 of the velocity structure function near the wall are discussed. The intermittent behavior of the fluid particle acceleration is also examined by kurtosis of the Lagrangian structure function. Finally, the effect of the initial particle location on the dispersion is analyzed by the probability density function of particle position at several downstream locations.
Ordering parameters of self-organized three-dimensional quantum-dot lattices determined from anomalous x-ray diffraction
Authors: Lechner R. T. , Schülli T. U. , Holý V. , Springholz G. , Stangl J. , Raab A. , Bauer G. , Metzger T. H.
Published: February 2004

Anomalous x-ray diffraction is used to investigate self-organized ordering of PbSe/PbEuTe quantum dot superlattices in which different ordered structures form for different PbSe dot layer spacings. Using a theoretical dot ordering model, the different ordering parameters are determined from the x-ray spectra.
Local vibrational modes of H complexes in Mg-doped GaN grown by molecular beam epitaxy
Authors: Cuscó R. , Artús L. , Pastor D. , Naranjo F. B. , Calleja E.
Published: February 2004

Local vibrational modes (LVM’s) in Mg-doped GaN grown by molecular beam epitaxy have been studied by Raman scattering. Besides Mg local vibrational modes, several local mode peaks associated with hydrogen complexes are observed in the region around 2200 cm−1 and peaks assigned to carbon-hydrogen complexes are also detected in the region around 2900 cm−1. These modes arise from the presence of unintentional carbon and hydrogen impurities in the sample, which was corroborated by secondary ion mass spectroscopy measurements. Raman scattering evidence of local vibrational modes of the C-H complex in GaN is reported. The behavior of the LVM’s associated with the hydrogen and carbon impurity complexes with annealing temperature is also reported.
Tensile strained epitaxial Ge films on Si(100) substrates with potential application in L-band telecommunications
Authors: Cannon Douglas D. , Liu Jifeng , Ishikawa Yasuhiko , Wada Kazumi , Danielson David T. , Jongthammanurak Samerkhae , Michel Jurgen , Kimerling Lionel C.
Published: February 2004

Tensile strained epitaxial Ge films were grown on Si(100) substrates by ultra-high vacuum chemical vapor deposition. The tensile strain was induced by the thermal expansion coefficient mismatch between Si and Ge during the cooling process from elevated growth temperatures, which induces narrowing of the Ge direct band gap, EgΓ, and pushes the absorption spectrum of Ge toward longer wavelengths. The EgΓ versus strain relation was measured experimentally by photoreflectance and x-ray diffraction, and the result agrees well with calculations by deformation potential theory. With an in-plane tensile strain of 0.21%, the EgΓ of the Ge film grown at 800 °C decreased from 32 meV to 0.768 eV compared with 0.80 for bulk Ge, and corresponded to an absorption edge at 1610 nm. The broadened absorption spectrum of tensile strained Ge makes it promising as a Si-compatible photodector material for L-band (1560–1620 nm) optical communications.
Ion irradiation effects on the mechanical stability of compressed metallic thin films
Authors: Goudeau P. , George M. , Coupeau C.
Published: February 2004

Residual stresses in materials and components such as thin films in microelectromechanical systems are developed during the production process and may drastically limit their functionality and lifetime; their minimization is thus of utmost technical importance. Ion beam irradiation in polycrystalline Mo thin films sputter-deposited on (100) silicon wafer at room temperature has been used to reduce the residual stresses present in the layer and thus to improve the mechanical stability of the film/substrate set. Although a strong reduction of residual stresses in the whole film is evidenced, irradiation affects the film-substrate bond strength; defect creation at the film-substrate interface due to ion implantation induces thin-film delamination.
Nonlinear propagation of ultrafast 1.5 μm pulses in high-index-contrast silicon-on-insulator waveguides
Authors: Rieger Georg W. , Virk Kuljit S. , Young Jeff F.
Published: February 2004

Propagation through silicon-on-insulator (SOI) waveguide structures of 1.53 μm, 100 fs laser pulses with peak powers up to 400 W is studied experimentally and theoretically. The dominant nonlinear effects are two-photon absorption and self-phase modulation. The two-photon absorption coefficient and the nonlinear refractive index of Si obtained in this work are β2=0.9 cm/GW and n2=0.7×10−13 cm2/W, respectively. At high intensities, free carriers generated by two-photon absorption are demonstrated to have a significant influence on pulse spectra and transmitted power. The figure of merit for all-optical switching obtained in this work (T=1.8) indicates that a switch based on a SOI waveguide structure might be possible at 1.55 μm.
Influence of strain on the dielectric relaxation of pyrochlore bismuth zinc niobate thin films
Authors: Lu Jiwei , Klenov Dmitri O. , Stemmer Susanne
Published: February 2004

Bi 1.5 Zn 1.0 Nb 1.5 O 7 (BZN) films were deposited by rf magnetron sputtering on different substrates to systematically vary the film stress due the thermal mismatch between BZN and the substrate. Substrates included Pt/SiO2 covered silicon, vycor glass, magnesium oxide, and sapphire. The BZN film microstructures (orientation, grain size, and roughness) were similar on the different substrates. Measurements of the permittivity and dielectric loss tangent were carried out between 80 and 300 K at frequencies between 10 kHz and 10 MHz. Films that were under a moderate tensile stress showed a low-temperature dielectric relaxation, associated with a dielectric loss peak and drop in permittivity, at ∼100 K. In contrast, the dielectric relaxation was shifted to temperatures below 80 K in films on vycor that were under a large tensile stress. This shift reflected a lowering of the activation energy of the dielectric relaxation processes due to tensile stress. It is expected that films under large tensile stress require higher frequencies than bulk BZN to shift the dielectric relaxation to room temperature, which makes these films attractive for low-loss high-frequency applications.
Effect of nitridation on polarity, microstructure, and morphology of AlN films
Authors: Wu Y. , Hanlon A. , Kaeding J. F. , Sharma R. , Fini P. T. , Nakamura S. , Speck J. S.
Published: February 2004

The polarity of AlN epitaxial layers grown on (0001) sapphire, SiC, and nitrided sapphire substrates was examined by convergent beam electron diffraction, and the morphology and microstructure were characterized by atomic force microscopy and scattering contrast transmission electron microscopy (TEM). The AlN films grown on sapphire and SiC without a buffer layer or nitridation of the substrate were flat and had Al polarity. From TEM studies in both cross section and plan view, it was found that the threading dislocation (TD) density was ∼1×108 and 2×1010 cm−2 for screw-component and pure edge component dislocations, respectively. N-face AlN was realized by pregrowth nitridation of sapphire substrates, but these films contained a small volume fraction of Al-face inversion domains which were related to hexagonal pyramids defined by {11̄02} facets. The density of screw-component TDs was significantly reduced due to nitridation. Cross-sectional TEM showed that the film grown on nitrided sapphire was almost free of screw-component TDs and that the density of pure edge TDs was ∼4×109 cm−2.
Digital holographic method for tomography-image reconstruction
Authors: Liu Cheng , Yan Changchun , Gao Shumei
Published: February 2004

A digital holographic method for three-dimensional reconstruction of tomography images is demonstrated theoretically and experimentally. In this proposed method, a numerical hologram is first computed by calculating the total diffraction field of all transect images of a detected organ. Then, the numerical hologram is transferred to the usual recording medium to generate a physical hologram. Last, all the transect images are reconstructed in their original position by illuminating the physical hologram with a laser, thereby forming a three-dimensional transparent image of the organ detected. Due to its true third dimension, the reconstructed image using this method is much more vivid and accurate than that of other methods. Potentially, it may have great prospects for application in medical engineering.
Reduced SnO2 surfaces by first-principles calculations
Authors: Bergermayer Wolfgang , Tanaka Isao
Published: February 2004

SnO 2 (110) and (101) surfaces with eleven different kinds of terminations for each are systematically investigated by a first-principles projector augmented wave method. Surface energies are discussed as a function of temperature and oxygen partial pressure. Atomic relaxations of the surfaces are then compared. In agreement with previous calculations, the stoichiometric (110) surface is the most stable surface at high oxygen chemical potentials (i.e., low temperature or high pressure). At lower oxygen chemical potentials, however, one of the reduced (101) surface terminations becomes energetically preferred. The other surface terminations are found to be less stable. This is consistent with recent thin-film experimental results.
High pressure saturation of hydrogen stored by single-wall carbon nanotubes
Authors: Lawrence Jeremy , Xu Gu
Published: February 2004

Since the early report of adsorption on single-walled carbon nanotubes in 1997, a number of controversial publications have claimed the hydrogen capacity of these materials to be between 0.1 and 10.0 wt %. However, no study has yet demonstrated a plateau of adsorption with pressure that is consistent with monolayer saturation. Others have suggested that the tube bundle structure expand under high pressure to enable higher adsorption on newly uncovered surfaces, but received no confirmation. Using a high-pressure instrument with in situ electrical probes, we found that a plateau is nearly achieved at about 300 atm in the room temperature isotherm. And that nanotube bundles do not expand or swell, shown by the in situ electrical measurements of purified single-walled nanotube (SWNT) bundles. The monolayer saturation plateau was found on bundled SWNT at room temperature corresponding to an adsorption of 0.9 wt %.
INVESTIGATIONS OF COHERENT OSCILLATIONS IN AN ARGON ION LASER PLASMA TUBE
Authors: Galehouse D. C. , Ingard U. , Ryan T. J. , Ezekiel S.
Published: February 2004

Coherent fluctuations in the light of an argon ion laser have been investigated and laser operation free from these fluctuations has been achieved. Oscillations in the kHz range have been identified as anode oscillations and were suppressed by use of an auxiliary cathode. Oscillations related to the longitudinal magnetic field and to striations were eliminated by choice of plasma tube operating conditions. Wideband incoherent noise was less than 0.2%.
THE RESISTIVITY OF EPITAXIAL FILMS OF SILVER WITH CONTROLLED SURFACE ROUGHNESS
Authors: Berman A. , Juretschke H.J.
Published: February 2004

The resistivity of epitaxial silver films on mica in vacuum is studied as a function of temperature, thickness, and surface specularity on a sequence of samples having a common silver-mica interface. Surface roughness is controlled by low-temperature evaporation of very thin silver overlays. Typical size effect behavior is obtained, but the resistivity variation with temperature is less than in bulk and decreases for thinner films and rougher surfaces. Interpretation in terms of a Fuchs-Sondheimer model requires temperature-dependent specularity parameters.
CH FREE RADICALS DETECTED BY INFRARED LASER MAGNETIC RESONANCE
Authors: Evenson K. M. , Radford H. E. , Moran M. M.
Published: February 2004

CH radicals in an oxyacetylene flame have been detected by a magnetic resonance absorption method, with a water-vapor laser as the source oscillator at a frequency of 2.5 THz. The absorption spectrum is identified with the pure rotational transition, J, K=(5/2, 2) → (7/2, 3) at a wavelength of 118. 6 μm.
SECONDARY ELECTRON EMISSION OF AMORPHOUS SEMICONDUCTOR THIN FILMS
Authors: Chen A. C. M. , Norton J. F. , Wang J. M.
Published: February 2004

The secondary electron yields of amorphous and the crystalline phases of thin films of Ge–Te–As are reported. For film which exhibited reversible bistable conductivity, a large change in yield between the amorphous and the crystalline phases was measured. For film which exhibited irreversible bistable conductivity only a small change was found.
SPONTANEOUS PARAMETRIC SCATTERING OF LIGHT IN PROUSTITE
Authors: Hordvik A. , Schlossberg H. R. , Stickley C. M.
Published: February 2004

The spontaneous parametric scattering from ruby-laser-pumped proustite crystals has been investigated. By rotating the crystal, the signal wavelength was tuned from 0.7293 to 1.0875 μ corresponding to an idler wavelength range of 14.6 to 1.93 μ. Frequency tuning by varying the crystal temperature was found to be less efficient than for LiNbO3. Bandwidth and effect of idler absorption were also studied, and the effective nonlinear coefficients of proustite and LiNbO3 were compared.
CURRENT INDUCED SELF-FIELD EFFECT IN Pb–Cu–Pb JOSEPHSON JUNCTIONS
Authors: Mitani M. , Aihara K. , Hara N.
Published: February 2004

A recovery phenomenon from the mixed to the superconducting state was observed in Pb–Cu–Pb junctions even when the tunneling current was increased over the maximum dc Josephson current. This phenomenon is well interpreted from the inclination effect of the Fraunhofer diffraction pattern because of large dc Josephson currents.
DETERMINATION OF THE SECOND-HARMONIC-GENERATION COEFFICIENT AND THE LINEAR ELECTRO-OPTIC COEFFICIENT IN LiIO3 THROUGH OBLIQUE RAMAN PHONON MEASUREMENTS
Authors: Otaguro W. S. , Wiener-Avnear E. , Porto S. P. S.
Published: February 2004

A new method for determing the second-harmonic-generation coefficient dijk and the linear electro-optic term rijk as well as their relative sign from oblique phonon Raman-scattering experiments is introduced. This method is applicable to piezoelectric crystals of orthorhombic or higher symmetry, where the oblique phonon cross section can be measured. The value of d13 and r13 for LiIO3 were determined.
ELECTROREFLECTANCE AND THERMOREFLECTANCE OF ZnSiAs2
Authors: Kwan Clarence C. Y. , Woolley John C.
Published: February 2004

Measurements of electroreflectance as a function of temperature in the range 195–350°K and of thermoreflectance at room temperature have been made on chalcopyrite-type ZnSiAs2 in the energy range 1.9–3.5 eV. The identification of the various peaks in the E0 and E1 complexes is discussed and the temperature coefficient of the various transitions determined.
NEW MODEL FOR LASER DOPPLER VELOCITY MEASUREMENT ON TURBULENT FLOW
Authors: Wang C. P.
Published: February 2004

Using the theory of optical-mixing spectroscopy, a new model is proposed for the laser Doppler velocity measurement on both laminar and turbulent flow, and a system using two incident light beams is described.
RESIDUAL ELECTRICALLY ACTIVE DEFECTS AFTER LATTICE REORDERING IN ION-IMPLANTED SILICON
Authors: Davies D. Eirug , Roosild S.
Published: February 2004

Thermally stimulated current measurements have been conducted on low-dose carbon-implanted silicon. After annealing for lattice reordering, five defect levels are found still present and of energies ranging from 0.27 to 0.40 eV. Since they all show similar annealing to above 500°C, they reveal a major annealing stage in low-dose ion-implanted silicon that occurs at considerably higher temperatures than what is generally ascribed to lattice reordering.
INTERNAL AND SURFACE CONTRIBUTION TO LIGHT DIFFRACTION BY SURFACE-ACOUSTIC WAVES
Authors: Alippi A. , Palma A. , Palmieri L. , Socino G.
Published: February 2004

An analysis is done of depth interaction between polarized light and acoustic-surface waves, which gives account for the actual dependence of the scattered-light intensity vs the angle of incidence, in transmission experiments. Measurements were performed at 11.8 and 18.8 MHz for surface waves propagating in Y direction on X-cut, α-quartz, and Z-polarized light.
FAST MAGNETICALLY CONTROLLED SWITCHING IN IRON OXIDE FILMS
Authors: Balberg I.
Published: February 2004

The application of a magnetic field of 10 kG causes a decrease by more than a factor of 2 in the delay time for switching in iron oxide films. This effect is associated with very short switching time (≲ 20 nsec) and some other characteristic properties. It appears that while initiated thermally, the switching itself is an electric breakdown that follows a buildup of a high electric field.
ENHANCEMENT OF CO2 LASER POWER AND EFFICIENCY BY NEUTRON IRRADIATION
Authors: Ganley T. , Verdeyen J. T. , Miley G. H.
Published: February 2004

Experiments have been performed which show that it is possible to increase the efficiency and power of a CO2 laser by irradiating the discharge with energetic α and Li ions produced by the (n, α) reaction with B10. This effect is explained by a tailoring of the electron-energy distribution towards optimum pumping of the laser.
p-TYPE CONDUCTION IN Li-DOPED ZnSe
Authors: Park Y. S. , Hemenger P. M. , Chung C. H.
Published: February 2004

p-type conduction was observed in ZnSe grown from the vapor phase and from the melt in the presence of lithium dopants. Hall measurements are presented.
NEW PHOTOTECHNOLOGY SUITABLE FOR RECORDING PHASE HOLOGRAMS AND SIMILAR INFORMATION IN HARDENED GELATIN
Authors: Pennington K. S. , Harper J. S. , Laming F. P.
Published: February 2004

Novel phototechniques are described for the formation of phase holograms in hardened gelatin. These techniques result in recordings similar to those produced with the well-known dichromated gelatin process; however, several major advantages arise from these new approaches. Photographic speeds several orders of magnitude (102–105) faster than dichromated gelatin are readily obtained together with panchromatic response characteristics. Moreover, like dichromated gelatin but distinct from bleached silver halides, the stored information is not affected by intense blue or uv irradiation (40 W/cm2 at 4880 Å).
GaAs1−xPx DIODE PUMPED YAG: Nd LASERS
Authors: Ostermayer F. W.
Published: February 2004

Experiments using GaAs1−xPx diodes emitting at 8100 Å to cw pump YAG: Nd laser rods are described. At an electrical input power of 7.6 W to an array of 4% efficient diodes operating at room-temperature threshold was attained for a laser rod, with high-reflectivity mirrors, cooled to 3.5°C. For a laser rod with a 0.4% transmission output mirror threshold was reached at −2.5°C. From threshold-temperature-dependence data for the latter rod, an extrapolation has been made showing that a straightforward increase in the number of diodes by a factor of 3 to 4 will result in threshold being exceeded by 2 to 3 times at a rod temperature of 20°C.
FIELD EFFECT TRANSISTORS ON EPITAXIAL GaAs AS TRANSDUCERS FOR ACOUSTIC SURFACE WAVES
Authors: Bruun M. , Ludvik S. , Quate C. F.
Published: February 2004

Two field effect transistor structures on epitaxial GaAs have been used as input and output transducers on an acoustic delay line. The transducer mechanism is described in terms of a piezoelectric coupling between the current modulation produced in the field effect transistor and the acoustic waves. The conversion loss at 90 MHz was 44 dB which is close to what can be estimated using a simple model.
EFFICIENT PHOTOEMISSION FROM Ge-DOPED GaAs GROWN BY LIQUID-PHASE EPITAXY
Authors: Schade H. , Nelson H. , Kressel H.
Published: February 2004

Efficient photoemission with white light sensitivities as high as 1100 μA/lm has been obtained from Ge-doped GaAs layers grown by liquid-phase epitaxy. The hole concentrations of the samples were relatively low (5×1017–2×1018 cm−3), and the sample surfaces were chemically polished prior to cesium-oxygen activation. Quantum yield data show an unusually high infrared response and suggest long diffusion lengths, between 2 and 7 μ, for the photo-excited Γ-electrons.
DOPPLER JITTER STABILIZATION OF A CO2 LASER
Authors: Goldberg M. W. , Yusek R.
Published: February 2004

A CO2 laser oscillating on the P(18) transition of the 10. 6-μ band was electronically stabilized without internal modulation to an inverted Lamb dip generated in an extra-cavity SF6 absorption cell. Laser modulation was avoided by employing an external moving mirror to Doppler jitter the light entering the absorption cell. The resultant stabilization point was shown to be independent of laser characteristics. The frequency stability so achieved was 1 part in 109 over a 15-min period.
EXCITATION OF ACOUSTIC SURFACE WAVES WITH A GRATING-COUPLED GUNN OSCILLATOR
Authors: Dakss M. L. , Lean E. G. , Schoenwald J.
Published: February 2004

Up to 0.25 mW of acoustic surface wave power at 225 MHz have been generated on LiNbO3 with a Gunn oscillator via periodic piezoelectric coupling of the Gunn domain electric fields across an air gap. The coupling periodicity is produced by a metal or dielectric grating on the LiNbO3 surface. The ratio of generated surface wave power Pac to the electrical pulse power is up to 2.5×10−6 for the metal grating and 10−7 for the dielectric grating. The observed dependence of Pac on the number of grating fingers is explained by the degree of phase matching between Gunn domains and acoustic surface waves.
MAYER ABSORPTION ANOMALY FOR ALKALI METALS
Authors: Marton J. P.
Published: February 2004

An analysis of the optical properties of free-electron metals in the aggregated state shows features with striking similarities to the anomalous absorption behavior of Mayer's alkali metals. It is suggested that the Mayer anomaly is due to rough or contaminated surfaces and that such absorptions may be typical of free metallic surfaces in general.
DIGITAL ELECTRO-OPTIC GRATING DEFLECTOR AND MODULATOR
Authors: Hammer J. M.
Published: February 2004

A new method of laser light deflection and modulation based on diffraction by electro-optic phase gratings has been demonstrated. The method is applicable to thin-film light guides, requires relatively low power for high-speed operation, and is capable of high diffraction efficiency.
PLASMA EXPANSION UNDER HEATING BY A CO2 LASER PULSE
Authors: Tomlinson Richard G.
Published: February 2004

This paper treats the expansion of a gas breakdown plasma produced in argon by the focused radiation from a high-voltage transient-pumped CO2 laser. With the long pulses attainable from such pulsed CO2 lasers, a transition is observed in the mechanism of expansion from a radiation-driven detonation to a thermal expansion. The implications of this observation for CO2 laser heating of plasmas are discussed.
HARMONIC MIXING OF MICROWAVE AND FAR-INFRARED LASER RADIATION USING A JOSEPHSON JUNCTION
Authors: McDonald D. G. , Risley A. S. , Cupp J. D. , Evenson K. M.
Published: February 2004

Simultaneous irradiation of a Josephson junction with ≈ 10 GHz microwave power and 891-GHz laser radiation produces a 60-MHz beat between the fundamental laser frequency and harmonics of the klystron, ranging from the 84th to the 100th as the klystron is tuned. Observation of such high-order harmonic mixing of klystron and laser signals is unprecedented.
SELF-LOCKING OF MODES IN A HIGH-PRESSURE CO2 LASER WITH TRANSVERSE PULSE EXCITATION
Authors: Gilbert J. , Lachambre J. L.
Published: February 2004

An investigation has been made of the spontaneous self-locking of axial modes in a transversely excited atmospheric (TEA) CO2 laser of helical geometry. Laser emission was found to consist of 0.5-μsec bursts of short periodic pulsations typically 5 nsec in duration with peak powers in the megawatt range. Reproducible pulsating patterns have been achieved with the use of SF6 acting as mode selector in the optical resonator.
UNIFORM ELECTRICAL EXCITATION OF LARGE-VOLUME HIGH-PRESSURE NEAR-SONIC CO2–N2–He FLOWSTREAM
Authors: Hill Alan E.
Published: February 2004

Aerodynamic techniques are described whereby continuous electric discharges may be produced uniformly over large volumes in near-sonic CO2–N2–He flowstreams. Experiment shows that discharge input power scales with pressure for the range 30–150 Torr thereby maintaining a fixed specific power load of ≃ 270 kW/lb(mass)/sec, while diffuse discharges at 1-atm pressure have been achieved at much lower specific power levels. Discharges occupying 4.5- and 43-liter volumes with the corresponding flowrates 2700 and 28 000 cfm are each uniform over their entire volumes, indicating that volume-flowrate scaling is not affected by wall diffusion. Using these discharge techniques, a closed cycle 28 000-cfm 5.6 × 76 × 100-cm3 CO2 laser amplifier channel has been designed to produce in excess of 20 kW laser power, continuous. In preliminary experiments small-signal gains reaching 1.9%/cm have been measured transversely across both cold and hot extremities of this device.
ANOMALOUSLY HIGH ``MOBILITY'' IN SEMICONDUCTORS
Authors: Wolfe C. M. , Stillman G. E.
Published: February 2004

In this paper we present a simple model for an inhomogeneous semiconductor which leads to an anomalously high apparent mobility. The model consists of a cylindrically symmetric van der Pauw measurement with a conducting inhomogeneity. This model is analyzed quantitatively and verified experimentally for several measurement configurations. The results cast doubt on the use of a high mobility as an indication of the quality of a semiconductor unless the homogeneity is unambiguously determined or the magnetic field dependence of the Hall constant is carefully examined.
STIMULATED ANTI-STOKES SPIN-FLIP RAMAN SCATTERING IN InSb
Authors: Shaw E. D. , Patel C. K. N.
Published: February 2004

We report the first observation of tunable stimulated anti-Stokes spin-flip Raman (SFR) scattering in InSb. Using a CO2 laser at 10.6μ as the pump, the anti-Stokes SFR laser is tunable from ∼10.0 to ∼9.4μ, and the concurrently appearing Stokes SFR laser is tunable from ∼11.3 to 12.2μ by changing the magnetic field from ∼30 to ∼65 kG.
MEASUREMENTS OF CATHODE SPOT TEMPERATURE IN VACUUM ARCS
Authors: Utsumi Takao
Published: February 2004

The cathode spot temperatures of various metals in vacuum arcs have been measured for the first time on the basis of the Maxwellian portion of velocity distribution of the vapor atoms emanating from the cathode spot region by employing the combined technique of time-of-flight and quadrupole mass analysis.
SEQUENTIAL EXCITATION OF LONGITUDINAL MODES IN GaAs LASERS
Authors: Wieder Harold
Published: February 2004

Experimental evidence is presented which demonstrates that, in the vicinity of threshold, GaAs lasers exhibit longitudinal mode hopping, in agreement with the theory of Popov et al.
DISSOCIATION AND BREAKDOWN OF MOLECULAR GASES BY PULSED CO2 LASER RADIATION
Authors: Isenor N. R. , Richardson M. C.
Published: February 2004

In gases which absorb CO2 laser radiation, luminescence, consisting largely of the molecular spectra of dissociation products, precedes the occurence of breakdown. Temporal, spatial, and spectral characteristics of this radiation and also of the sparks produced in a number of gases have been studied.
ERRATUM: HIGH-PRESSURE LASER ACTION IN 13 GASES WITH TRANSVERSE EXCITATION
Authors: Wood O. R. , Burkhardt E. G. , Pollack M. A. , Bridges T. J.
Published: February 2004

Laser action has been achieved in 13 gases at high pressures using pulsed transverse excitation. A total of 149 wavelengths from 0.8 to 28μ was observed. Pulse lengths were found to lie in the range 0.2–5μsec. Several gases operate at atmospheric pressure and above and promise to give very high power outputs.
HETERODYNE DETECTION AT 10.6 μm WITH THIN-FILM BOLOMETERS
Authors: Contreras B. , Gaddy O.L.
Published: February 2004

Heterodyne detection at 10.6 μm using fast-response-time thin-film bolometer infrared detectors is described. With a local oscillator power of 1 W, the minimum detectable power is found to be 4×10−11 W/Hz. Good agreement is found between experimental results and theory.
LASER PUMPING BY EXCITATION TRANSFER IN DYE MIXTURES
Authors: Moeller C.E. , Verber C.M. , Adelman A.H.
Published: February 2004

The output of a N2-laser-pumped cresyl violet dye laser can be increased by the addition of an intermediary dye which enhances pumping efficiency. This should be a general technique for increasing the utility of the N2 laser for pumping dye lasers.
ANISOTROPIC ULTRASONIC WAVE PROPAGATION IN A NEMATIC LIQUID CRYSTAL PLACED IN A MAGNETIC FIELD
Authors: Lieberman Ernest D. , Lee James D. , Moon Francis C.
Published: February 2004

Ultrasonic longitudinal waves were observed in a nematic liquid crystal (p-azoxyanisole) which was ordered by a magnetic field. Attenuation in the direction of the field-induced nematic axis was 30% greater than that perpendicular to the axis and was independent of field strength. No anisotropy in velocity was observed to an error of ± 0.1%.
STUDY OF FAILURE MECHANISMS IN Al–Cu THIN FILMS BY HIGH-VOLTAGE ELECTRON MICROSCOPY
Authors: Berenbaum L. , Patnaik B.
Published: February 2004

Al-4% Cu thin-film stripes have been examined by high-voltage electron microscopy after being powered to failure. Particular emphasis was given to the study of damage sites in order to get a better understanding of the mechanisms responsible for mass depletion. It was found that these mechanisms were the same as have been reported for pure Al films, namely, structural damage at mixed grain-size interfaces and at triple points in regions having a uniform grain-size distribution.
INFLUENCE OF DEPOSITION TEMPERATURE ON PROPERTIES OF HYDROLYTICALLY GROWN ALUMINUM OXIDE FILMS
Authors: Kamoshida M. , Mitchell I. V. , Mayer J. W.
Published: February 2004

Aluminum oxide films deposited onto silicon substrates by hydrolysis of AlCl3 show marked differences in etch rates, electron diffraction patterns, ir absorption spectra, and chlorine contents between films grown below 700°C and above 800°C. Analysis of the composition from the yield of backscattered MeV He ions indicated that both film types were stoichiometric throughout the layer thickness. These analyses indicated that the Cl was incorporated uniformly in the low-temperature-deposited films to a level of about 2 at. %.
ON THE DIRECTION OF ELECTROMIGRATION IN THIN SILVER, GOLD, AND COPPER FILMS
Authors: Hummel R. E. , Breitling R. M.
Published: February 2004

Migration of ions in thin silver, copper, and gold films under the influence of a direct current has been found to be directed towards the cathode, contrary to observations in bulk metals. This was concluded from resistance and radioactive tracer measurements as well as scanning electron micrographs. The results can be explained by using the concept that electromigration in thin films is confined to grain boundaries, and the electron concentration in the grain boundary is different from that in the bulk.
EFFECT OF BIAS AND CATHODE BOUNDARY CONDITIONS ON GaAs SPACE-CHARGE AMPLIFIERS
Authors: Williamson W. J.
Published: February 2004

A simple one-dimensional model is used to calculate the performance of GaAs traveling-wave space-charge amplifiers. It is shown that an inbuilt field at the cathode boundary can have a controlling effect on the device performance. The model gives good agreement with experimental results and indicates optimum preparation and operating conditions.
BaTiO3 FILMS PREPARED BY RF SPUTTERING ONTO InSb OR GaAs
Authors: Iida Shosan , Kataoka Shoei
Published: February 2004

BaTiO3 films were prepared onto InSb or GaAs semiconductor by RF sputtering with a tetrode apparatus at about 300°C. Analysis by x-ray diffraction patterns shows that the films are of tetragonal structure of BaTiO3. Electrical properties of these films were measured and the Curie point was observed at 120–140°C.
SEMICONDUCTOR LASERS OPERATING CONTINUOUSLY IN THE ``VISIBLE'' AT ROOM TEMPERATURE
Authors: Miller B. I. , Ripper J. E. , Dyment J. C. , Pinkas E. , Panish M. B.
Published: February 2004

Continuous operation of AlxGa1−xAs–Aly Ga1−yAs–AlzGa1−zAs double heterostructure injection lasers at room temperature has been achieved with diodes whose lasing energy was as high as 1.61 eV (7730 Å). This energy was achieved with y = 0.20, and at this energy the far-field radiation pattern was visible. In the pulsed mode, low thresholds have been achieved up to 7450 Å (1.66 eV) using both broad-contact and stripe-geometry lasers. The lasing threshold remains relatively unchanged in the range y = 0 to 0.21.
Thermal Diffusivity of Heterogeneous Materials. II. Limits of the Steady-State Approximation
Authors: Kerrisk Jerry F.
Published: February 2004

In the first paper of this series, the concept of the thermal diffusivity as a characteristic constant of a heterogeneous material was examined by considering the derivation of the heat conduction equation. In this second paper, a specific transient thermal problem with periodic boundary conditions is treated for two model heterogeneous materials: spheres imbedded in a matrix, and a two-phase material composed of roughly spherical particles with neither phase continuous. In the steady-state limit (low frequency or small particle size), it is shown that the material may be considered homogeneous and the proper value of thermal conductivity and heat capacity are those developed from a steady-state development of thermal conductivity and the equilibrium heat capacity. A criterion for determining when a material of this type may be treated as homogeneous for a given transient thermal problem is also developed.
Gain Saturation in Extrinsic Germanium Photoconductors Operating at Low Temperatures
Authors: Blouke M. M. , Harp E. E. , Jeffus C. Ray , Williams R. L.
Published: February 2004

A semiempirical model has been developed for the frequency dependence of the photoconductive response of high-resistivity extrinsic Ge samples operating at cryogenic temperatures. The model predicts that the photoconductive gain saturates to the sweepout-limited value of ½ for frequencies greater than G(0)/πτρ, where G(0) is the dc photoconductive gain and τρ=εε0ρ is the dielectric relaxation time. Measurements of signal as a function of modulation frequency and background for a large Ge : Hg sample at liquid neon (∼ 28°K) show good agreement with the model.
Two-Metal Heat-Pipe Oven: Operation, Dynamics, and Use in Spectroscopic Investigations
Authors: Hessel M. M. , Jankowski P.
Published: February 2004

Two different metals in a heat-pipe oven will form separate metallic-vapor zones. These zones can be moved so that in a crossed heat-pipe oven, spectroscopic studies of intermetallic molecules can be made at the interface between the two zones. We describe the operation and construction of the two-metal heat-pipe oven as well as a laser technique that can be used to study some of the dynamics of the heat pipe.
Breakdown of Thin-Film Emitters
Authors: Ahmed H.
Published: February 2004

The examination of thin-film emitters in the scanning electron microscope has revealed a mechanism by which they break down. The top film is continuous when emission is first obtained from the device but microscopic punctures appear after a short period of operation and the emission becomes unstable. Eventually the device ceases to conduct as the number and size of the micropunctures increase.
Explanation of Light-Intensity Dependence of Photoconductivity in Zinc Phthalocyanine
Authors: Aoyagi Yoshinobu , Masuda Kohzoh , Namba Susumu
Published: February 2004

Photoconductivity of zinc phthalocyanine single crystals was studied over a temperature range from 0 to 120 °C. The photocurrent increased exponentially with an increase of light intensity. The power p in the relation I ∝ Lp (I, photocurrent; L, light intensity) varied with temperature and became smaller than ½ above 320 °K. This value of p less than ½ could not be explained by Rose's theory, in which it was shown that p could vary only between 1 and ½, but an advanced explanation was given in this paper by assuming the diffusion effect of photoexcited carriers and the exponential trap distribution.
Annealing-Induced Mobility Changes in Rare-Earth Orthoferrite
Authors: Shumate P. W.
Published: February 2004

The domain-wall mobility at room temperature, as measured in thin crystal platelets of flux-grown rare-earth orthoferrites, has been found to depend strongly on annealing treatment. Increases of 30% above the as-grown mobility have been achieved by anneals in the 1200–1300°C range, but further annealing at higher temperatures causes the mobility to decrease substantially. For samples of flux-grown YFeO3 and Sm0.55Tb0.45FeO3, peak values of 6500 and 1440 cm sec−1 Oe−1 were attained, respectively, which are higher than any previously published value. Samples of Bridgman-grown YFeO3 were also studied. These samples showed no large increases in mobility; however, a region of abnormally low mobility was observed to increase in value, rising to that of the remainder of the material, ∼5500 cm sec−1 Oe−1, after annealing at 1300°C. This controlled annealing therefore makes possible improvements in domain-wall mobility and removal of variation in mobility from sample to sample.
Field expressions for a circular loop antenna in terms of a new set of functions
Authors: Huerta Manuel A. , Gonzalez Guillermo
Published: February 2004

An exact expression for the fields produced by an electrically small loop antenna is obtained in terms of a series involving a new set of functions, namely en(σ,γ)=(1/2π)∫02πcos(nΦ)sin[σ(1−2γcosΦ)1/2]dΦ and fn(σ,γ)=(1/2π)×∫02πcos(nΦ)cos[σ(1−2γcosΦ)1/2]dΦ, where − ∞<σ<∞ and 0≤γ≤1/2. Series expansion, approximate expressions for γ2σ≪1 and recursion relations for the functions are derived. These functions permit the exact evaluation of the fields in the Fresnel and near-field regions of the loop antenna. In the case that the distance to the point of observation is of the order of a wavelength or greater, but greater than the loop radius, the field expression is given in terms of the function q1(σ,γ) = f1(σ,γ) + ie1(σ,γ). Numerical results describing the behavior of the functions f1(σ,γ) and e1(σ,γ) are given. Field expressions for the electrically large loop antenna are also derived.
Scattering of obliquely incident waves by inhomogeneous fibers
Authors: Yeh C. , Wang P. K. C.
Published: February 2004

The problem of the interaction of obliquely incident electromagnetic waves with a radially inhomogeneous fiber cylinder is treated analytically. By formulating this problem in terms of the two-point boundary-value problem, we eliminate the need to evaluate untabulated functions or to invert large matrices. Numerical results for the differential scattering cross sections are obtained for the case of an inhomogeneous fiber whose radial dielectric variation may be described by the Luneberg profile. It is found that the induced cross-polarized scattered field as well as the characteristics of the total scattered fields are influenced significantly by the inhomogeneity of the dielectric medium.
Helicon resonances in a two-sample geometry
Authors: Giovanielli D.
Published: February 2004

The frequencies of geometric helicon resonances were measured for systems of two similar metal samples separated by known distances. The measured frequencies were found to vary with sample separation in a predictable manner based on the existence of spatially decaying fields external to the samples.
Perturbation solution for growth of nonlinear shock waves in a lattice
Authors: Tasi James
Published: February 2004

A perturbation solution is obtained for the propagation of longitudinal shock waves in a one-dimensional lattice with a velocity step applied to the first mass. The nonlinear part of the elastic interaction force is assumed to be of parabolic form. The growth of particle velocity at the head of the wave and the noticeable high-frequency contributions travelling behind, that arise due to nonlinearity, have been observed previously in numerical studies and are found also in the perturbation solution. Within the range of validity of the solution, the nonlinear growth of maximum particle velocity at the head of the shock wave is shown to increase with distance into the lattice as the two-thirds power.
An acoustic characterization of polymethyl methacrylate and three epoxy formulations
Authors: Sutherland Herbert J. , Lingle Richard
Published: February 2004

This paper presents the results of an experimental study conducted to obtain an acoustic characterization of polymethyl methacrylate (PMMA) and three Epon 828 formulations in their glassy state. By using a pulse-transmission technique, ultrasonic dispersion data were obtained for these polymeric materials as a function of frequency and temperature, and then the principle of time-temperature superposition was used to transform the dispersion data for each material into a linear-viscoelastic ``master-curve'' representation. The master curve for each material contains sufficient information to determine the propagation characteristics of a low-amplitude wave as a function of its frequency (or frequency spectrum) and the temperature of the polymer. This representation is equivalent to the more common stress-relaxation-modulus and complex-moduli representations of linear-viscoelastic behavior and is valid over an extensive frequency range.