Elastic Resonance Research Articles

Jost function description of elastic and few-body resonances

We discuss how the analysis of the zeros of the functions introduced by Jost in 1946, acting individually or collectively, provides a comprehensive framework for describing resonances in single and multichannel collisions. In particular, we propose a generalization of the Wigner threshold law that copes with some deviations recently observed in opening reaction channels. We also pay special attention to the appearance of zeros of the s-wave Jost function in the fourth quadrant of the complex momentum plane, as analysed by Nussenzveig in 1959 but erroneously ruled out in following studies.

Scattering by an elastic cylinder embedded in a fluid sediment. Generalized method of images (GMI) approach

An original method is presented for calculating the scattered acoustic field due to a plane wave incident upon an infinitely long elastic cylinder embedded in a sedimentary medium. The sedimentary medium is an half space domain bounded by a fluid. The cylinder is parallel to the plane interface between the sedimentary and fluid media. First, in order to estimate the scattering by a cylinder close to a plane interface, an analytical model that generalizes the method of images, restricted to rigid and soft interfaces, is described. The validity and the accuracy of this new approach are analyzed. Under some assumptions, the transmission, from the sediment to the surrounding fluid, of the acoustic field scattered by the embedded cylinder is evaluated, then the detection from the fluid medium of the buried elastic cylinder resonances is treated.

Nonlinear interactions in elastic resonators

This work is dedicated to nonlinear interactions in elastic resonators. It is supposed that a resonator wall yields locally to the inner pressure. The elastic wall of the resonator induces strong dispersion and dissipation of acoustic energy. The dispersion can significantly influence studied nonlinear interactions which are ineffective because the synchronous conditions are not satisfied and hence a coherence length is too short. In the frame of this work conditions for generation of subharmonics are studied on the basis of topological and numerical analyze. For this reason the method of local stability is applied. For description of nonlinear standing wave is derived modified inhomogeneous Burgers equation and the inhomogeneous Korteweg–de Vries–Burgers equation. These equations take into account thermo-viscous losses of supposed fluids, boundary layer losses, wall losses and dispersion effects caused by both the resonator wall and the acoustic boundary layer. Number of numerical solutions of these model equations is shown and unsteady solitary waves are investigated.

Thermal Phonon Resonance in Solid Glass

Thermal phonon resonance was observed in a stiff solid material of fused silica, from which a lower intensity of scattered light is expected than from liquids. The improved detection sensitivity of the optical beating Brillouin spectroscopy technique enabled us to observe the spontaneous elastic resonance of the solid sample attributable to thermal density fluctuation with a frequency resolution of 1 kHz. The accuracy in determining phonon velocity was then increased up to 10-5. The high frequency resolution also revealed the fine structure of the resonance peak train brought about by the lateral mode vibration, and the eigen frequencies of the compound mode are in good agreement with those theoretically estimated. Volume and shear elasticities were uniquely determined from the resonance spectra of longitudinal and shear phonons. Phonon absorption at about 100 MHz was also determined from the resonance peak width of the Brillouin component.

Oxygen content of La1−xSrxMnO3−y thin films and its relation to electric-magnetic properties

It is known that the electric and magnetic properties of typical double-exchange materials La1−xSrxMnO3−y (LSMO) are strongly affected by oxygen nonstoichiometry y, as well as by divalent ion doping level x. In the present study, we fabricated LSMO (x=0.4) thin films on SrTiO3 (STO) (001) and LaAlO3 (LAO) (001) under various pressures of oxygen ambient pO2, and evaluated their oxygen content 3−y using non-Rutherford elastic resonance spectroscopy. The change of their electric and magnetic properties was also measured and discussed. It was revealed that the oxygen content 3−y does not increase monotonically as pO2 increases. Curie temperature TC and insulator-metal transition temperature TIM were correlated with 3−y for the films on STO. The film on LAO of a quite high pO2 showed ferromagnetism and a metallic conductivity, unlike the films of lower pO2’s. The ferromagnetism is attributed to c∕a axis ratio closer to that of the bulk.

THERMAL STABILITY OF EPITAXIAL SrRuO3 BOTTOM ELECTRODES AND THEIR CONTRIBUTION TO THE CHARACTERISTICS OF (Ba0.5Sr0.5)TiO3 FILMS GROWN ON THEM

ABSTRACT Thermal stability of epitaxial SrRuO3 films grown on (100)SrTiO3 substrates by RF magnetron sputter deposition as a function of the oxygen partial pressure (pO2) was investigated in view of the crystal structure, surface roughness and electrical resistivity. The surface normal lattice parameter and diffraction peak intensity of SrRuO3 films heat-treated at 700°C decreased with the decrease of pO2 below 1.7 Pa, and finally SrRuO3 peak completely disappeared at pO2 below 1.7 × 10−4 Pa. Surface roughness also became high with decreasing the pO2. X-ray diffraction and Non-Rutherford Elastic Resonance Scattering measurements suggest that SrRuO3film most probably decomposes to metal Ru and amorphous SrO after the heat treatment at pO2 below 1.7 × 10−4 Pa. Epitaxial (Ba0.5Sr0.5)TiO3 films were grown on these pre-heat-treated SrRuO3 bottom electrodes by RF magnetron sputter deposition. (Ba0.5Sr0.5)TiO3 film with low crystallinity deposited on SrRuO3 bottom electrode heat-treated under pO2 below 1.7 × 10−4 Pa showed much higher leakage current than the others. This is considered to be due to the high surface roughness of (Ba0.5Sr0.5)TiO3 film inducing the concentration of electric field and/or the diffusion of Ru into (Ba0.5Sr0.5)TiO3 film. This result suggests that the characteristics of capacitors are significantly affected by the heat treatment conditions of SrRuO3 bottom electrodes.

Reexamination of the energy levels ofF15byO14+H1elastic resonance scattering

The energy levels of {sup 15}F have been measured by the p({sup 14}O,p){sup 14}O reaction. The 120 MeV {sup 14}O radioactive ion beam was produced by the BEARS coupled cyclotron system at an intensity averaging 1x10{sup 4} particles/second on target. Energy calibration was obtained using resonances from the p({sup 14}N,p){sup 14}N reaction. The two lowest resonances in {sup 15}F were fitted with an R-matrix calculation. The fit to the ground state had J{sup {pi}}=1/2{sup +} at 1.23 {+-} 0.05 MeV (width 0.5 - 0.84 MeV), and the first excited state was J{sup {pi}}=5/2{sup +} at 2.81 {+-} 0.02 MeV (width 0.30 {+-} 0.06 MeV), both relative to the mass-energy of the proton and {sup 14}O. The {sup 15}F ground state energy supports the disappearance of the Z = 8 proton magic number for odd Z,T{sub z}=-3/2 nuclei.

Multichannel R-matrix analysis of elastic and inelastic resonances in the 20,21Na+p compound systems

Resonant scattering studies were performed using radioactive 20,21 Na beams at ISAC between energies of 0.5 keV/u and 1.5 keV/u. Intensities of up to 1 × 10 8 /sec were used with thick CH 2 targets, and elastic and inelastic proton resonances were observed corresponding to states in 21,22 Mg by detecting recoil protons using the LEDA silicon array. A multichannel R-Matrix formalism was used to fit the excitation functions leading to the deduction of partial widths and spin-parity assignments. In certain cases definite spin-parity assignments could be made without fitting angular distributions due to the constraining nature of Coulomb-interfering resonances. Where possible, analogue assignments are made in the A=22, T=1, system based on the 21 Na+p analysis.

Elastic resonances of a periodic array of fluid-filled cylindrical cavities embedded in an elastic matrix

The resonant scattering by a periodic infinite array of fluid-filled cylindrical cavities in an elastic matrix is studied. The exact reflection and transmission coefficients of the array are calculated by means of a multiple scattering formalism taking into account all the interactions between the cavities. Numerical results are next given for low frequencies for which only the longitudinal and transverse zero modes propagate. A first study based on the analysis of the transmission coefficients clearly shows that the resonances of the array can be classified into two sets: those close to the resonances of a single cavity and those due to a resonant coupling between a cavity and its nearer neighbors. The resonant coupling is due to the interaction between the whispering-gallery surface waves propagating around each cavity. In the case of cavities with very close spacing, it is observed that the dispersion curves of the waves propagating along the array can also be classified into two sets: those with a positive group velocity have cut-off frequencies that correspond to the resonances of a single cavity, those with a negative group velocity have cut-off frequencies that correspond to the resonances resulting from the strong coupling. A new method for the analysis of the resonances is presented. It is based on the properties of the scattering matrix and consists in studying the resonant eigenvalues of the scattering matrix of the array once the background is removed. For the detection of very fine resonances, as well as in the separation of several resonances very close to each other, this method proves to be more efficient than one based on the analysis of the reflection and transmission coefficients.

Monopole and quadrupole polarization effects on the α-particle description ofBe8

We investigate the effect of monopole and quadrupole modes on the elastic alpha-alpha resonance structure of $^{8}$Be. To this end we make a fully microscopic coupled channels calculation with three coupled channels, using the Algebraic Model. The continuum spectrum and wave functions are analyzed in terms of the individual channels to understand the nature of the resonances. It is shown that both monopole and quadrupole modes have a non-negligible effect on the resonances in the alpha-alpha continuum.

Radial vibration characteristics of spherical piezoelectric transducers

This paper presents the vibration characteristics of the radial mode in spherical piezoelectric transducers. The differential equations of piezoelectric radial motion have been derived in terms of radial displacement and electric potential. Applying mechanical and electrical boundary conditions yielded a characteristic equation for radial vibration. Theoretical calculations of the fundamental natural frequency have been compared with numerical and experimental results for transducers of several sizes, and have shown a good agreement. This paper discusses the dependence of natural frequencies on the radius and thickness of the piezoelectric spheres and the difference between piezoelectric and elastic resonances. From the results it has been concluded that the natural frequency was not affected for the first radial mode but was reduced by the piezoelectric phenomenon. It has also been concluded that the natural frequency of the first radial mode depended mostly on the radius rather than on the thickness of the sphere whereas the natural frequency of the second radial mode depended mostly on the thickness rather than the radius.

MultichannelR-matrix analysis of elastic and inelastic resonances in theNa21+pcompound system

A multichannel R-matrix formalism was used to fit $^{21}\mathrm{Na}+$ p resonant elastic and inelastic scattering data taken at the TRIUMF UK detector array facility at TRIUMF-ISAC. Five resonances were observed corresponding to states in $^{22}\mathrm{Mg}$ above the proton threshold. Four of these corresponded to states seen in previous transfer reaction studies where firm spin-parity assignments could not be made. One new resonance, previously unobserved in any reaction, was also seen. Where possible, resonance energies, partial widths, and spin-parity values of these resonances were extracted. The correspondence between these states and possible analogs in the mirror nucleus $^{22}\mathrm{Ne}$ is discussed, as well as the relation to $T=1$ states in the nucleus $^{22}\mathrm{Na}$.

Implications of the present bound on the width of theΘ+(1540)

The recently reported Theta(1540) exotic baryon seems to be very narrow: Gamma(Theta)< 1 MeV according to some analyses. Using methods of low energy scattering theory, we develop expectations for the width of the Theta, an elastic resonance in KN scattering in a theory where the characteristic range of interactions is ~1 Fermi. If the Theta is a potential scattering resonance, generated by the forces in the KN channel, its width is hard to account for unless the KN-channel orbital angular momentum, l, is two or greater. If the Theta is a CDD pole, its coupling to the scattering channel is at least an order of magnitude less than the coupling of the Lambda(1520) unless l is two or greater. Either way, if the Theta proves to be in the KN s- or p-wave, new physics must be responsible for its narrow width.

Properties of the Oxygen Sublattice Structure of YBa[sub 2]Cu[sub 3]O[sub 7 – ][sub x] Crystal Studied by Ion Channeling

Properties of the oxygen sublattice structure of the YBa2Cu3O7 −x crystal are studied using the diffusion model of ion channeling. The angular dependence of the elastic resonance scattering of helium ions on oxygen nuclei along the 〈001〉 direction is measured at an ion energy of 3.055 MeV. Steps are observed in the scattering yield at an angle of about 0.4°. The best fit of the calculated angular dependence of elastic resonance scattering to the experimental data is attained under the assumption that the oxygen rows contain vacancies corresponding to a fraction (not exceeding 20%) of the disordered oxygen atoms, which are randomly distributed in the plane normal to the 〈001〉 direction, and that the oxygen atoms in the rows are displaced from their equilibrium positions in a direction normal to the 〈001〉 axis.

Acoustic intensity measurement of the sound field radiated by a concert harp

An experimental study of the acoustic radiation of a concert harp is presented. Using a stationary mechanical excitation placed at one string location, the acoustic radiation of the complete instrument is investigated. Two main acoustic radiation sources are identified: the soundboard and the soundbox holes. Acoustic intensity vectors are measured in two planes located in the near field of these two sources, making use of a 3D intensity probe. A detailed description of the acoustic intensity field radiated by these two sources is given. Calculations of acoustic power radiated by the soundboard surface and by the soundbox holes allow us to quantify the relative importance of these two sources. In three frequency ranges, it is shown that the soundbox holes radiate more than the soundboard. In the first range, it is suggested that the acoustic radiation of the instrument can be described by two point sources of sound implying that in this range the harp acts as an equivalent elastic Helmholtz resonator.

Correlation between O/Er Content Ratio and Photoluminescence Intensity of (Er, O)-Doped Hydrogenated Amorphous Si Thin Films Prepared by a Catalytic Chemical Vapor Deposition/Laser Ablation Hybrid Process

(Er, O)-doped hydrogenated amorphous Si (a-Si:H) thin films were prepared on Si or SiO2 substrates by a novel catalytic chemical vapor deposition (Cat-CVD)/laser ablation hybrid process which simultaneously performs a Cat-CVD of a-Si:H matrices and a doping of laser-ablated (Er, O) from an Er2O3 sintered target. These (Er, O)-doped a-Si:H films showed excellent photoluminescence (PL) properties in spite of the low temperature of the process (200°C during deposition and no postannealing). The Er and O contents of these films were evaluated by Rutherford backscattering and non-Rutherford elastic resonance scattering (NRERS), respectively. It was clarified that the dependence of the (Er, O) content on ambient pressure was not identical for O and Er. Thus, the O/Er content ratio, correlated to the PL intensity, strongly depended on the ambient pressure.

Oxygen-deficient(La0.6Pr0.4)0.7Ca0.3MnO3−δthin films: Towards a first-order metal-insulator transition

Thin films of (La0 0.6 Pr 0.4 ) 0.7 Ca 0.3 MnO 3 were grown on NdGaO 3 (110) and LaAlO 3 (001) substrates by pulsed laser deposition. The substrate temperature was held at 820 °C, and the oxygen pressure during deposition and cooling was controlled from a few mTorr to 400 mTorr. X-ray diffraction data show an interesting structural evolution with oxygen deficiency, which was estimated by non-Rutherford elastic resonance scattering of He + ions at 3.045 MeV. With increase in oxygen deficiency the insulator-metal transition temperature (T p ) shows a significant shift to lower temperature and the transition becomes much sharper and hysteretic, with a greatly enhanced temperature coefficient of resistance (TCR). Low field magnetotransport also shows peculiar characteristics. These results bring out the tendency towards increasingly first order character with oxygen deficiency, and are in clear contrast to those in oxygen deficient La 0.7 Ca 0.3 MnO 3 films, wherein the TCR is seen to decrease with decreasing T p . The observations are discussed within the framework of the phase separation picture.

Elastic modulus and resonance behavior of boron nitride nanotubes

The effective elastic modulus (E) of boron nitride nanotubes (BNNTs) was measured using the electric-field-induced resonance method inside a transmission electron microscope. The average value of E from the measurements of 18 individually cantilevered BNNTs was 722 GPa, comparable to the theoretical estimate of ∼850 GPa. No strong variation of E with the diameter of the BNNTs, which spanned from 34 to 94 nm, was observed. Low quality factors (&amp;lt;680) obtained from the mechanical resonance is attributed to the layered structural nature of BNNT.

New Analysis of Elastic Wave Resonance Scattering from a Fluid-Filled Cylindrical Cavity

A new method is presented for the isolation of resonances from scattered waves for elastic wave resonance scattering problems. The resonance scattering function consisting purely of resonance information of the scatterer is defined. Elastic wave resonance scattering from a water-filled cylindrical cavity imbedded in an aluminum matrix is numerically analyzed. The classical resonance scattering theory and the new method compute different magnitudes and phases of the resonances from each partial wave, and therefore, their total resonance spectra are quite different. The exact π-radians phase shifts through the resonance and anti-resonance frequencies show that the proposed method properly extracts the vibrational resonance information of the scatterer compared to resonance scattering theory.

First two energy levels in15F

The ground state and first excited state of ${}^{15}\mathrm{F}$ were measured by the method of elastic resonance scattering in inverse kinematics. A secondary beam of 115 MeV/nucleon ${}^{14}\mathrm{O}$ was slowed down to 8 MeV/nucleon and energy bunched before stopping in a ${\mathrm{C}}_{2}{\mathrm{H}}_{4}$ target. The ${}^{15}\mathrm{F}$ excitation energy spectrum was extracted from elastically scattered protons at $0\ifmmode^\circ\else\textdegree\fi{}.$ The ${1/2}^{+}$ ground state resonance of ${}^{15}\mathrm{F}$ was determined to be unbound with respect to single-proton emission by $1.51\ifmmode\pm\else\textpm\fi{}0.11\mathrm{MeV},$ corresponding to a mass excess of $16.81\ifmmode\pm\else\textpm\fi{}0.11\mathrm{MeV}.$ The ${5/2}^{+}$ first excited state resonance is unbound by $2.853\ifmmode\pm\else\textpm\fi{}0.045\mathrm{MeV}$ leading to an excitation energy of $1.34\ifmmode\pm\else\textpm\fi{}0.15\mathrm{MeV}.$ A comparison with systematics of single-nucleon separation energies and theoretical models suggests that ${}^{11}\mathrm{N}$ should be unbound by about $1.5\ifmmode\pm\else\textpm\fi{}0.15\mathrm{MeV}.$