Showing papers on "Resonance published in 1985"

The two-dimensional resonance of sediment-filled valleys

Abstract: This paper presents a numerical study of the response of relatively embanked sediment-filled valleys to incident plane SH , SV , and P waves, in the two-dimensional case. The Aki-Larner technique used here is shown to be reliable even for steep interface slopes. Numerical results show the existence and the importance in such valleys of specific two-dimensional resonance patterns, which may be classified in three categories: the antiplane shear modes, corresponding to SH motion; the in-plane shear modes ( SV ); and the in-plane bulk modes ( P ). Each of them is characterized by the consistency of the peak frequencies, and the in-phase motion (modulo 180°) across the whole valley. They induce a very large amplification, even in the case of significant damping (up to 4 times the corresponding one-dimensional prediction), a very long duration of motion, and large differential motion. The characteristics of the fundamental modes are in good qualitative agreement with the relevant experimental observations. The existence of this two-dimensional resonance is controlled by the shape ratio (thickness to half-width ratio) and the velocity contrast: a quantitative relationship is proposed in the SH case. The frequency of these resonance modes, for each pattern, is shown to depend only on two parameters: the one-dimensional resonance frequency at the valley center and the shape ratio. A simple model of a soft rectangular inclusion is shown to provide satisfactory quantitative formulas to estimate the fundamental resonance frequencies of any valley. As to the amplitude of this two-dimensional resonance, the general trends of its dependence on the different valley parameters (shape ratio, velocity contrast, Poisson ratio, damping) and on the incident wave field characteristics (wave type, incidence angle) are indicated. An important result, however, for earthquake engineering purposes is that both the two-dimensional resonant frequencies and amplification values differ a lot from their “classical” one-dimensional estimates.

Resonance Raman scattering by confined LO and TO phonons in GaAs-AlAs superlattices.

Abstract: It is shown that in GaAs-AlAs superlattices the confined longitudinal-optic Raman phonons created via either deformation-potential or Fr\"ohlich electron-phonon interaction are different. This effect is demonstrated by comparison of resonance and off-resonance Raman spectra. Phonons of ${A}_{1}$ symmetry (point group ${D}_{2d}$) dominate in resonance, while ${B}_{2}$ phonons are stronger in the off-resonance case. The resonance profile of the ${A}_{1}$ modes is discussed. We also report the observation of confined transverse-optic phonons under extremely resonant conditions.

Energy calibration of the 500 kV heavy ion implanter ionas

Abstract: Gamma ray yield functions of (p, αγ) and (p, γ) resonance reactions on semi-thick 19F, 23Na, 24,26Mg and 27Al targets were measured and used to calibrate the accelerating voltage and energy resolution of the new 500 kV heavy ion implanter at Gottingen. The energy spread of the proton beam was found to vary linearly with the accelerating voltage from ΔE(200 keV) = 55 eV fwhm to ΔE(500 keV) = 105 eV; it is made up by a 0.012% high voltage ripple and the Doppler broadening of the resonances due to the thermal motion of the target nuclei. A long term stability of the proton energy of Applications of the accelerator for the remeasurement of some resonance energies and widths and for depth profiling of light implanted ions in metals by the resonance broadening method will be briefly discussed.

Populations in the metastable and the resonance levels of argon and stepwise ionization effects in a low‐pressure argon positive column

Abstract: The contribution of the ionization from the two metastable and the two resonance levels of argon to the total ionization rate in a low‐pressure argon positive column is investigated theoretically and experimentally. A simple yet self‐consistent discharge model is developed by coupling the balance between the electron total production and loss rates to the steady‐state rate balance equations for the excited states. The predictions of this model, i.e., the maintenance field for the positive column and the populations in the individual excited states as a function of the gas pressure and the discharge current are compared with the experiment (0.05

Effect of inelastic processes on resonant tunneling in one dimension.

Abstract: We consider the effect of inelastic scattering on tunneling resonances in one dimension using a Breit-Wigner scattering formalism. We show that the peak transmission at resonance is decreases by the ratio of the intrinsic resonance width to the inelastic-scattering rate. For disorder-localized one-dimensional systems this predicts that resonant-tunneling conduction, in addition to variable-range-hopping conduction, will be observable at temperatures below 0.01 K in present experimental systems.

Intermodulation and harmonic distortion in InGaAsP lasers

Abstract: A theoretical and experimental study is presented of intermodulation and harmonic distortion in high-speed 1.3 and 1.5 ?m InGaAsP lasers modulated at frequencies up to 8 GHz. It is found that all lasers measured, including Fabry-Perot and distributed feedback lasers, generate approximately the same distortion levels for a given modulation depth and relaxation resonance frequency. There are minor differences between lasers, which result from differences in the damping of the small-signal resonance peak.

Microwave and infrared characterization of several weakly bound NH3 complexesa)

Abstract: We present the results of microwave and infrared spectroscopic studies of several van der Waals complexes of NH3. These results were obtained with a molecular beam electric resonance spectrometer. The microwave spectroscopy of the complexes (NH3)2 and Ar–NH3 show that both systems are nonrigid. The observed dipole moments for (NH3)2[0.74(2) D] and (ND3)2[0.57(1) D] are not compatible with the presently accepted theoretical structure. Ar–NH3, which has a complicated and currently unassigned microwave spectrum, exhibits Q branch inversion transitions near 19 GHz which indicate that the NH3 subunit is likely to be a near‐free rotor. Infrared studies of the complexes NH3–HCCH, NH3–CO2, (NH3)2, Ar–NH3, NH3–OCS, NH3–N2O, and NH3–HCN have been carried out with a line tunable CO2 laser. Only for NH3–HCN were no infrared resonances discovered. Photodissociative transitions are observed in all of the other systems. Band origins for the photodissociative infrared transitions involving the ν2 umbrella motion of NH3 were determined for NH3–HCCH [984.4(9) cm−1], NH3–CO2 [987.1(2) cm−1]. NH3–OCS [981.5(15) cm−1], and NH3–N2O [980(2) cm−1]. The observation of an infrared transition for Ar–NH3 at 938.69 cm−1, which is 40 cm−1 lower than the band origins in the other NH3 complexes, lends support to the model of Ar–NH3 mentioned above. NH3–HCCH, NH3–CO2, (NH3)2, and Ar–NH3 were studied in microwave‐infrared double resonance experiments in order to eliminate much of the inhomogeneous broadening present in their infrared spectra and to aid in the rotational assignment of the infrared spectra. Linewidths were determined for NH3–HCCH (0.15 GHz) and for NH3–CO2 [14(6) GHz]. An important result of this study is that the dissociation energies of all the complexes studied, except for NH3–HCN, are established to be less than 990 cm−1, i.e., 2.8 kcal/mol.

A sensitive new method for the determination of adhesive bonding between a particle and a substrate

Abstract: We use an AT‐cut quartz resonator with metal electrodes as the substrate. The material properties of the quartz are well characterized, and the resonant frequency can be determined accurately (1 part in 108 or better). When a particle was placed on the electrode, the resonant frequency increased, contrary to mass loading theory. If the particle‐resonator system is modeled mechanically as a coupled oscillator system, indeed the resonant frequency should increase. The increase is determined by the bonding force constant between particle and substrate, which we calculate. Experimental data on the autohesion force constants of Au spheres on etched Au electrodes in air is presented.

Reduction seismic response with heavily-damped vibration absorbers

Abstract: It is shown that two of the damping ratios of certain systems composed of a building and a small attachment in resonance are given by the average of the damping ratios of the two independent components. Based on this fact and the fact that the seismic response of a building can always be reduced by increasing its damping, it is demonstrated that the attachment of a small heavily-damped system in resonance can increase the damping of a building and reduce thus its response to earthquake excitations. Numerical solutions are presented to confirm the demonstration, and recommendations are given to calculate the parameters of such systems.

X-ray resonance magnetic scattering

Abstract: A resonance-type X-ray magnetic scattering at the K -absorption edge was first observed in 220 Bragg reflection of ferromagnetic Ni single crystal. Further a theoretical discussion on the resonance magnetic scattering curve observed was carried out; A difference of the oscillator-strength density for each direction of the spins was also derived from this curve. The oscillator-strength density for minority spin excesses that for the majority spin between the Fermi level and 25 eV above the level. The difference of oscillator-strength density amounts to about 1×10 -4 /Ry at the maximum.

Characterization of the lowest‐lying Π bending state of Ar–HCl by far infrared laser–Stark spectroscopy and molecular beam electric resonance

Abstract: Far infrared laser–Stark spectroscopy is used to populate an excited vibrational state in the van der Waals molecule, ArHCl, in a molecular beam. Microwave–far infrared double resonance allows the identification of this state as the first excited bending state of Π symmetry. Subsequent radio frequency electric resonance of the vibrationally excited molecule combined with far infrared–radio frequency two photon experiments gives the following spectroscopic constants: ν0−B’=33.9248(7) (cm−1), B’=1695.(20) (MHz), μ=0.265(3) (D), eqQaa=12.(7) (MHz), eqQbb−eqQcc=−73.927(23) (MHz), q1=−49.583(2) (MHz). These constants are compared with theoretical predictions obtained using previously suggested potential energy surfaces and are related to the presence of other nearby vibrational states.

Dynamics of hyperspherical and local mode resonance decay studied by time dependent wave packet propagation

Abstract: Time dependent wave packet propagation of resonance states of ABA molecules is used to demonstrate the correlation between the directionality of the lobes of the wave functions and mode selectivity of the unimolecular decay. This correlation was inferred by Hose and Taylor. The molecule is modeled by the Thiele–Wilson coupled Morse oscillators. A near‐degenerate pair of resonances with extreme motions is studied in detail: The local ‘‘bond’’ mode with lobes pointing towards the exit valleys of the potential decays about 30 times faster than the hyperspherical ‘‘restricted precession’’ mode with dominant lobe on the potential ridge. This is in close analogy to mode selectivity in the Henon–Heiles system. The wave function propagation technique also yields detailed insight into the dissociation mechanism. Out of several choices, only a single lobe penetrates into the exit valley. For the local mode resonance vibrational predissociation starts out primarily from extended vibrationally excited diatomic config...

Method of making a piezoelectric shear wave resonator

Abstract: An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/°C.

Pressure broadening of rotational bands. I - A statistical theory

Abstract: Absorption of electromagnetic waves by rotational transitions of molecules is formulated for the case in which the wave frequency is displaced from resonance by an amount large compared to the reciprocal duration of a typical binary collision, and also large compared to the differences between frequencies of the strong resonances of the gas. In this far-wing limit, Fano's relaxation operator is reduced to a scalar parameter which depends on the frequency displacement. This relaxation parameter is not symmetric with respect to reflection about resonance, but becomes symmetric when multiplied by the factor exp (h/2pi) (omega sub d)/2kT where omega sub d is the frequency displacement. The theory applies to dipolar molecules of any shape, in collisions with either dipolar or quadrupolar molecules.

Enhanced quantum efficiency internal photoemission detectors by grating coupling to surface plasma waves

Abstract: Enhanced quantum efficiencies have been obtained for Au‐InP internal photoemission detectors using grating coupling of incident radiation into surface plasma waves confined to the air‐metal interface. Enhancements of over a factor of 30 are observed at the resonance coupling angles. A model calculation of the surface plasma wave coupling is in good qualitative agreement with the experiment. Time‐resolved response measurements show that the present detectors are capacitance limited; picosecond response speeds are attainable with lower carrier concentration materials and smaller active areas.

Resonances of plates and cylinders: Guided waves

Abstract: The study of the normal diffusion of an ultrasonic plane wave by cylinders and plates imbedded in the water shows resonances which are the natural modes of vibration. When a natural mode of an elastic target is excited, the energy which is stored during the forced excitation is emitted after the end of the forced excitation. The observation of backscattered spectra obtained by the Resonance Isolation and Identification Method (RIIM) from an aluminum cylinder shows supplementary resonances. The directivity pattern of the transducer is the cause of these supplementary resonances. The behavior of these resonances is analogous to the resonances of the plate. This leads us to study the natural modes of the cylinder. All the resonances which are experimentally detected may be considered as normal modes of the target. The results obtained on plates and cylinders have a common point: the generation of a guided wave by the excitation of a resonance.

31P spin-lattice relaxation times and resonance linewidths of rat tissue in vivo: dependence upon the static magnetic field strength.

Abstract: Phosphorus-31 NMR spin-lattice relaxation times and resonance linewidths of rat leg muscle, brain, and liver metabolites in vivo have been examined at 1.9-, 4.7-, and 8.5-T static magnetic field strengths. The resonance linewidths expressed in ppm that have been measured are independent of field strength. The spin-lattice relaxation times of muscle and brain phosphorus metabolites decrease linearly with increasing field strength while those of liver are constant over the range of static fields examined.

The spin‐wave spectrum of layered magnetic thin films

Abstract: The ferromagnetic resonance spectrum of a layered magnetic thin film is expected to show a number of standing spin‐wave resonances with a wavelength that matches the thickness of the film. For the case of perpendicular resonance such spectra were calculated for some typical films in which magnetic layers are alternated with weaker magnetic layers. Some useful approximations are discussed. The results of the calculations are compared with experimental perpendicular spectra measured on films in which fifty Permalloy layers alternate with Ni layers.

High-Resolution Nuclear Magnetic Resonance of Inorganic Solids

Abstract: Recent improvements in instrumentation and technique now permit the observation of high-resolution nuclear magnetic resonance spectra of many nuclei in inorganic solids. The application of nuclear magnetic resonance to the study of the structures of materials of interest in chemistry, earth science, and materials science are discussed together with a prognosis for future work.

Tags for identification system

Abstract: Identification tags for identifying objects, for example goods. The tags contain a number of electrical resonance circuits all of which are tuned to different resonance frequencies and each of which consist of an inductance and a capacitance. According to this invention, all identification tags are identical after manufacture and have predetermined resonance frequencies. In these basic tags, the resonance circuits are on the surface of an electrically insulated foil, in the form of a flat coil with one or more condenser plates on each side of the foil. According to this invention, after manufacture, the basic tags have been given their individual characteristics, frequency signatures, by changing the resonance frequencies of one or more of the component resonance circuits, either in the form of a well-defined predetermined reduction in capacitance, or in the form of a drastic reduction in inductance by punching holes or cutting away determined areas in the foil and thereby in the resonance circuits in question.