Types Of Vibration Modes Research Articles

Spectral dependence of the amplification factor in surface enhanced Raman scattering

Multi-wavelength SERS measurements on dyes molecules adsorbed on gold evaporated nanoparticles substrates are presented. The spectra are correlated with the Localized Surface Plasmon Resonance (LSPR) profile of the nanostructured substrate before and after the adsorption process. The enhancement of the typical vibrational modes of the methylene blue is investigated for the different excitation wavelengths and we show that its behavior follows properly the LSPR profile of nanoparticles dressed with the dye molecules.

Quantum restricted effects on ballistic thermal conductance associated with six types of vibration modes in nanowire superlattice

We study ballistic phonon transport and thermal conductance associated with six low-lying vibrational modes in a quadrate nanowire superlattice at low temperatures. The results show that the transmission rates of the six vibrational modes display periodic forbidden regions of frequencies and have different relations with geometrical details of the nanowire superlattice. The thermal conductances contributed from different vibrational modes show different characteristics. On the basis of the theoretical analysis and calculated simulation, quantum restricted effects on ballistic thermal conductance in the quadrate nanowire superlattice are revealed.

Excited-State Dynamics of trans,trans-1,3,5,7-Octatetraene: Estimation of Decay Rate Constants of 11Bu ⇝ 21Ag and 21Ag ⇝ 11Ag Internal Conversions

The general expressions we previously derived for calculating internal conversion rate constants between two adiabatic displaced-distorted-rotated potential energy surfaces, by including all vibratinal modes, are applied to estimate the decay rate constants of 1(1)B(u) ⇝ 2(1)A(g) and 2(1)A(g) ⇝ 1(1)A(g) internal conversions in trans,trans-1,3,5,7-octatetraene molecule. The minimal models with respect to the number and types of vibrational modes are determined for these processes. Our calculations show that in the low temperature limit the 1(1)B(u) ⇝ 2(1)A(g) internal conversion takes place on a 232-290 fs time scale in the condensed phase and 2 ps in the gas phase, whereas 2(1)A(g) ⇝ 1(1)A(g) internal conversion takes place on a 2 μs time scale under the isolated conditions.

Capacitive Spring Softening in Single-Walled Carbon Nanotube Nanoelectromechanical Resonators

We report the capacitive spring softening effect observed in single-walled carbon nanotube (SWNT) nanoelectromechanical (NEM) resonators. The nanotube resonators adopt a dual-gate configuration with both bottom-gate and end-gate capable of tuning the resonance frequency through capacitive coupling. Interestingly, downward resonance frequency shifting is observed with increasing end-gate voltage, which can be attributed to the capacitive softening of the spring constant. Furthermore, in-plane vibrational modes exhibit a much stronger spring softening effect than out-of-plan modes. Our dual-gate design should enable the differentiation between these two types of vibrational modes and open up the new possibility for nonlinear operation of nanotube resonators.

On the vibrations of single-walled carbon nanotubes

In this paper, a detailed numerical study on the free and forced vibrations of single walled carbon nanotubes is presented. A simple and straightforward method developed such that the proximity of the mathematical model to the actual atomic structure of the nanotube is significantly retained, is used for this purpose. Both zigzag and armchair chiralities of the carbon nanotubes for clamped–free and clamped–clamped boundary conditions are analyzed and their natural frequencies and corresponding mode shapes are obtained. Results pertaining to axial, bending, and torsional modes of vibration are reported with discussions. These modes of vibration appear in the eigen-values and eigen-vectors without any distinction. The direct integration method by Newmark is used extensively along with the fast Fourier transform to identify different types of vibrational modes. In the case of zigzag nanotubes, the axial, bending, and torsional modes appear to be decoupled, whereas the armchair nanotubes show coupling between such modes.

ChemInform Abstract: Pressure and Temperature Study of the Isotropic Raman Spectra for the Symmetric A1 Vibrational Modes of Liquid Furan.

The Raman bands of the symmetric Ar modes of liquid furan have been measured as a function of temperature (-42.0 to 80.8 o C) and pressure (1 bar to 5 kbar). Line widths and peak frequencies of the isotropic spectra are determined for two C-H bending modes, three ring stretching modes, and two C-H stretching modes. More conclusive evidence concerning these assignments are offered since the three types of vibrational modes have distinctive bandwidth and frequency shift trends in response to increasing temperature and pressure

A Periodic Orbit Bifurcation Analysis of Vibrationally Excited Isotopologues of Sulfur Dioxide and Water Molecules: Symmetry Breaking Substitutions

Theoretical predictions and assignment of highly excited vibrational states and their organization is one of the most important challenges in molecular spectroscopy. A systematic procedure to investigate such problems is locating the principal families of periodic orbits that emanate from the stationary points of the molecule and then following their evolution with the total energy. This results in constructing continuation/bifurcation diagrams that assist in locating the critical bifurcation energies and to discover new types of vibrational modes. Another parameter that may influence the dynamics of a molecule is isotopic mass substitution. In this article, we investigate the effect of symmetry breaking by isotopic mass substitution of triatomic molecules with C(2v) symmetry in classical and quantum dynamics. Sulfur dioxide and water molecules in their ground electronic state are studied by employing accurate potential energy surfaces. Continuation/bifurcation diagrams of periodic orbits are constructed by varying the energy and the mass of one oxygen atom of sulfur dioxide and one hydrogen atom of a water molecule. The transition from normal-to-local mode vibrations is studied in terms of a pitchfork to a center-saddle elementary bifurcation of periodic orbits. The results presented in this article aim to help the assignment of experimentally obtained spectra.

Evaporation and Condensation of SiO and SiO2 Studied by Infrared Spectroscopy

Physical evaporation of SiO and SiO(2) under ultra-high vacuum conditions was monitored in situ with infrared spectroscopy at frequencies between 450 cm(-1) and 5000 cm(-1). The measured vibrational spectra of the condensed films are identical in both cases, for SiO and SiO(2) evaporation, and can be described with four Brendel oscillators located at 380 cm(-1), 713 cm(-1), 982 cm(-1), and 1101 cm(-1), corresponding to typical vibration modes in SiO.

Effects of Anisotropy of Single Crystal Silicon on the Vibration Properties of Disk-Type MEMS Resonators

Disk-type resonators employing in-plane resonant modes have a great impact on the application for high-sensitive mass sensing because of the high quality factor (Q) in atmospheric pressure. In this paper, we had fabricated disk-type resonators for two types of in-plane vibration modes with single crystal silicon (SCS), and the frequency properties were experimentally measured. Furthermore, modal analyses have been performed using finite element method for the structure model of the disk-type resonators under the conditions with different crystal orientations of SCS. We have examined the effects of the crystal orientation of SCS on the frequency properties of disk-type resonators for two types of vibration modes by the experimental and numerical analytical methods.

The optical and vibrational properties of dominant defects in undoped ZnO: A first-principles study

Studying native defects in semiconductors is of crucial importance for understanding the nature of defects as well as for controlling the quality of the as-grown materials. In this work, we present theoretical studies on the electronic structures, optical and vibrational properties of the dominant defects (VO, HO and VZn) in nominally undoped wurtzite ZnO. We find that the imaginary parts of dielectric functions and absorption coefficient arising from these defects show different features. Typically, the existence of VO in bulk ZnO makes it transparent for visible light but not for violet light. For the cases of both HO and VZn, there are strong infrared absorptions. On the other hand, the vibrational frequencies associated with these defects are calculated, from which some typical vibrational modes relevant to the defects are revealed.

Theoretical Study of Internal Conversion Decay Rates Associated with the Three Lowest Singlet Electronic States in Pyrazine

The general expressions we recently derived for calculating internal conversion decay rate constants between two adiabatic and between two diabatic displaced-distorted-rotated harmonic potential energy surfaces (including all vibrational modes) are now applied to determine the decay rate constants of 1B(2u)(pi pi*)-->1B(3u)(n pi*), 1B(2u)(pi pi*)-->1A(g), and 1B(3u)(n pi*)-->1A(g) internal conversions in pyrazine molecule. The minimal models with respect to the number and the types of vibrational modes are investigated for these processes. An exact expression for the adiabatic vibrational frequencies of the coupling modes in terms of interstate coupling constants and the parameters determining the diabatic potential energy surfaces are also derived.

Vibration Mode Analysis of a Rotating Circular Membrane under Transverse Distributed Load

Vibration modes of an extremely thin rotating circular membrane subjected to transverse distributed load are investigated. In the previous paper, the author proposed an analytical method to obtain equilibrium states with large transverse deformations employing the von Karman theory and taking account of buckling under the assumptions of rotationally symmetric deformations. In this paper, transverse vibration equation around the equilibrium state under transverse load is derived and modal equation is formulated. The equation is numerically solved and modal frequencies and modal shapes are obtained. Typical vibration modes are illustrated. In order to confirm the validity of the analysis, eigenvalue analysis of a spring-mass system model for the membrane are performed to obtain vibration modes. A fairly good agreement is found between the theoretical and numerical results. Experiments of thin rotating circular membranes under gravity in vacuum are also conducted and transverse vibration frequencies are measured for a variety of rotation speed and air pressure. Analytical results are compared with the experimental results to verify the validity of the present analysis.

Combined Raman Spectroscopy and Transmission Electron Microscopy Studies of a NanoBud Structure

We succeeded in providing for the first time the evidence of the NanoBud structure (fullerenes attached to the surface of SWCNT) by Raman spectroscopy in combination with TEM. This work was performed on the individual freestanding NanoBud structure. The Raman features corresponding to the typical vibrational modes of fullerenes were observed in the range of 1440-1480 cm(-1). The simultaneous presence of SWCNT and fullerene features in the Raman spectrum is in good agreement with the TEM and ED investigations on the same NanoBud structure, which confirmed the Raman measurement interpretation of the SWCNT chirality assignment (16,11) and the presence of fullerenes on the surface of the SWCNT.

Characteristic vibrational modes of a single vacancy in a zigzag carbon nanotube

We have applied ab initio calculations to studying phonon frequencies and the corresponding eigenmodes for zigzag carbon nanotubes with single vacancies. We find two types of vibrational modes that serve as fingerprints of the single vacancy, which may be detected by Raman spectra technique. Our calculations reveal that these vibrational frequencies exhibit a weak size dependence on the diameters of tubes. Moreover, it is found that the frequencies of radial breathing modes of the defective tubes are quite close to those of the related perfect ones.

엔진 및 프로펠러에 의해 가진되는 소형 위그선 복합재 주날개의 진동 거동 해석

논문에서는 시험선인 소형 위그선의 주날개 구조를 엔진 및 프로펠러에 의해 유발되는 진동을 가진력으로 하여 강제진동 해석을 수행하였다. 대상 위그선은 2행정의 왕복엔진을 날개에 장착하여 프로펠러에 의한 추력으로 비행하며, 미는 형식(Pusher Type)의 엔진 배열을 취하고 있다. 유한요소해석을 위해서 구조해석 상용프로그램인 MSC/NASTRAN을 사용하였으며, 엔진의 주요 진동 특성인 H-mode 와 V-mode 그리고 X-mode를 특정 가진 주파수로 하여 주파수 응답 해석을 수행하였고, 엔진의 횡방향 진동 모드인 L-mode를 프로펠러의 회전에 의해 진동을 수반하는 가진 추력으로 가정하여 과도응답 해석을 수행한 후 날개의 진동 특성을 살펴보았다. this study, forced vibration analysis was performed on the composite main wing structure of a small scale WIG craft which is equipped two-stroke pusher type reciprocating engine. The structural vibration analysis based on the finite element method was performed using a commercial FEM code, MSC/NASTRAN. Excitations for the frequency response analysis were assumed as the H-mode(horizontal mode), the V-mode(vertical mode) and the X-mode(twisted mode) which are typical main vibration modes of engine. And excitations for the transient response analysis were assumed as the L-mode(longitudinal mode) with the oscillating propeller thrust which occurs.

Raman study on the pressure-induced disordered state of polystyrene

The pressure-induced disordered state was first reported for iPS, the polymer showing thermal shrinkage. The low-frequency Raman study showed clearly that pressure introduces irregularity into the polymer backbone of iPS. It has also been revealed that there exist two types of vibrational modes, which show different sensitivities on the regularity of the main chain. These modes indicate two distinctive features of dispersion in the ordered form. In the disordered state, the dispersive modes smear out and the dispersionless one survives to be observed. We conclude that pressure causes the ordered–disordered conversion like thermal shrinkage. This conversion will be a common feature of the polymers showing thermal shrinkage and would be able to take place at relatively low pressure.

Manifestation of interaction effects in Raman spectra of CdTe quantum-dot layers with ZnTe narrow barriers

The Raman spectra of superlattices consisting of layers of CdTe self-assembled quantum dots separated by ZnTe narrow barriers with thicknesses of 10 and 5 monolayers are investigated. It is found that, apart from the bands previously observed at frequencies of ∼120 and ∼140 cm−1 for samples with thicker barriers (25 and 12 monolayers), the Raman spectra exhibit a band at ∼147 cm−1 in the frequency range of CdTe vibrational modes. This band is attributed to a symmetric vibrational mode of a pair of quantum dots with oppositely directed oscillations of the dipole moments. It is this type of vibrational mode in the material surrounding the ZnTe quantum dot that accounts for the shift of the band at ∼200 cm−1 near the LO mode of ZnTe vibrations toward lower frequencies.

Three-dimensional postbuckling and vibration of vertical half-loop under self-weight

The stability and vibration characteristics of a flexible and inextensible half-loop are investigated. The loop is fixed at two base points, which are separated by a specified distance, and is only subjected to gravity loading. If the length of the loop is sufficiently small, the loop stands upright in a vertical plane. If the length is increased past a critical value, the planar equilibrium shape becomes unstable and the loop droops to one side (i.e., laterally). This out-of-plane displacement may occur smoothly (supercritical bifurcation), or the loop may suddenly jump to a severely-drooped configuration (subcritical bifurcation), depending on the constitutive law. Linearly-elastic and softening materials are considered. Prebuckled and postbuckled equilibrium states are determined numerically with the use of a shooting method. Droop caused by an applied torsional moment is also analyzed. Then small vibrations about the prebuckled (planar) states are studied. Three basic types of vibration modes occur: in-plane, out-of-plane (symmetric), and twist about a vertical axis through the center of the loop. Experiments on a fiber-optic rod and a curtain wire are carried out to qualitatively verify the numerical results for both types of constitutive laws.

Theoretical analysis and experimental measurement for resonant vibration of piezoceramic circular plates.

Based on the electroelastic theory for piezoelectric plates, the vibration characteristics of piezoceramic disks with free-boundary conditions are investigated in this work by theoretical analysis, numerical simulation, and experimental measurement. The resonance of thin piezoceramic disks is classified into three types of vibration modes: transverse, tangential, and radial extensional modes. All of these modes are investigated in detail. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are used to validate the theoretical analysis. Because the clear fringe patterns are shown only at resonant frequencies, both the resonant frequencies and the corresponding mode shapes are obtained experimentally at the same time by the proposed AF-ESPI method. Good quality of the interferometric fringe patterns for both the transverse and extensional vibration mode shapes are demonstrated. The resonant frequencies of the piezoceramic disk also are measured by the conventional impedance analysis. Both theoretical and experimental results indicate that the transverse and tangential vibration modes cannot be measured by the impedance analysis, and only the resonant frequencies of extensional vibration modes can be obtained. Numerical calculations based on the finite element method also are performed, and the results are compared with the theoretical analysis and experimental measurements. It is shown that the finite element method (FEM) calculations and the experimental results agree fairly well for the resonant frequencies and mode shapes. The resonant frequencies and mode shapes predicted by theoretical analysis and calculated by finite element method are in good agreement, and the difference of resonant frequencies for both results with the thickness-to-diameter (h/D) ratios, ranging from 0.01 to 0.1, are presented.

Orientation dependence of electromechanical coupling factors in KNbO/sub 3/

This paper is concerned with the electromechanical coupling factors for bulk waves in KNbO(3) crystal. The dependence of coupling factors on the orientation of vibrators for various types of vibration modes has been calculated. As a result, it has been found that most of these coupling factors are very large at certain orientations of vibrators. Especially, the maximum coupling factor of the thickness-extensional mode excited with a perpendicular field, k(t ), is as high as 69% for the rotated X-cut by an angle 49.5 degrees about the Y-axis; that of the thickness-shear mode, k(s), is 88% for the X-cut. To the best of our knowledge, these coupling factors are the highest among those of known piezoelectrics. It has also been found that the coupling factor of the width-extensional mode of a thin finite-width plate with electrodes on its edges, k(ww)', is 82% for the rotated Z-cut by an angle 43.5 degrees about the Y-axis. This vibrator would be promising as elements of phased array ultrasonic probes.