Bavigadda, Viswanath; Moothanchery, Mohesh; Pramanik, Manojit; Mihaylova, Emilia; Toal, Vincent
2017-03-01
An out-of-plane sensitive electronic speckle pattern interferometer (ESPI) using holographic optical elements (HOEs) for studying rotations and vibrations is presented. Phase stepping is implemented by modulating the wavelength of the laser diode in a path length imbalanced interferometer. The time average ESPI method is used for vibration measurements. Some factors influencing the measurements accuracy are reported. Some advantages and limitations of the system are discussed.
Energy Technology Data Exchange (ETDEWEB)
Itikawa, Yukikazu [Institute of Space and Astronautical Science, Sagamihara, Kanagawa (Japan)
2001-04-01
A list of papers reporting cross sections for electron-impact excitations of rotational and vibrational states of molecules is presented. The list includes both the theoretical and the experimental papers published in 1980-2000. An index by molecular species is provided at the end of the bibliography. (author)
Translational, rotational, vibrational and electron temperatures of a gliding arc discharge
DEFF Research Database (Denmark)
Zhu, Jiajian; Ehn, Andreas; Gao, Jinlong
2017-01-01
Translational, rotational, vibrational and electron temperatures of a gliding arc discharge in atmospheric pressure air were experimentally investigated using in situ, non-intrusive optical diagnostic techniques. The gliding arc discharge was driven by a 35 kHz alternating current (AC) power source...... and operated in a glow-type regime. The two-dimensional distribution of the translational temperature (Tt) of the gliding arc discharge was determined using planar laser-induced Rayleigh scattering. The rotational and vibrational temperatures were obtained by simulating the experimental spectra. The OH A–X (0......, 0) band was used to simulate the rotational temperature (Tr) of the gliding arc discharge whereas the NO A–X (1, 0) and (0, 1) bands were used to determine its vibrational temperature (Tv). The instantaneous reduced electric field strength E/N was obtained by simultaneously measuring...
Translational, rotational, vibrational and electron temperatures of a gliding arc discharge.
Zhu, Jiajian; Ehn, Andreas; Gao, Jinlong; Kong, Chengdong; Aldén, Marcus; Salewski, Mirko; Leipold, Frank; Kusano, Yukihiro; Li, Zhongshan
2017-08-21
Translational, rotational, vibrational and electron temperatures of a gliding arc discharge in atmospheric pressure air were experimentally investigated using in situ, non-intrusive optical diagnostic techniques. The gliding arc discharge was driven by a 35 kHz alternating current (AC) power source and operated in a glow-type regime. The two-dimensional distribution of the translational temperature (Tt) of the gliding arc discharge was determined using planar laser-induced Rayleigh scattering. The rotational and vibrational temperatures were obtained by simulating the experimental spectra. The OH A-X (0, 0) band was used to simulate the rotational temperature (Tr) of the gliding arc discharge whereas the NO A-X (1, 0) and (0, 1) bands were used to determine its vibrational temperature (Tv). The instantaneous reduced electric field strength E/N was obtained by simultaneously measuring the instantaneous length of the plasma column, the discharge voltage and the translational temperature, from which the electron temperature (Te) of the gliding arc discharge was estimated. The uncertainties of the translational, rotational, vibrational and electron temperatures were analyzed. The relations of these four different temperatures (Te>Tv>Tr >Tt) suggest a high-degree non-equilibrium state of the gliding arc discharge.
Vibrations of rotating machinery
Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick
2017-01-01
This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...
Han, Jiande; Freel, Keith; Heaven, Michael C.
2011-06-01
We have examined state-to-state rotational and vibrational energy transfers for the vibrational levels (1010000) and (0112000) of C2H2 in the ground electronic state at ambient temperature. Measurements were made using a pulsed IR - UV double resonance technique. Total removal rate constants and state-to-state rotational energy transfer rate constants have been characterized for certain even-numbered rotational levels from J = 0 to 12 within the two vibrational modes. The measured state-to-state rotational energy transfer rate constants were fit to some energy-based empirical scaling and fitting laws, and the rate constants were found to be best reproduced by the statistical power-exponential gap law (PEGL). The measured rate constants were then further evaluated by a kinetic model which simulated the experimental spectra by solving simultaneous first order differential rate equations. Some rotationally-resolved vibrational energy transfer channels were also observed following excitation of (1010000). The vibrational relaxation channels were found to contribute less than 30% to the total removal rate constants of the measured rotational levels for both of the studied vibrational states.
Rotationally Vibrating Electric-Field Mill
Kirkham, Harold
2008-01-01
A proposed instrument for measuring a static electric field would be based partly on a conventional rotating-split-cylinder or rotating-split-sphere electric-field mill. However, the design of the proposed instrument would overcome the difficulty, encountered in conventional rotational field mills, of transferring measurement signals and power via either electrical or fiber-optic rotary couplings that must be aligned and installed in conjunction with rotary bearings. Instead of being made to rotate in one direction at a steady speed as in a conventional rotational field mill, a split-cylinder or split-sphere electrode assembly in the proposed instrument would be set into rotational vibration like that of a metronome. The rotational vibration, synchronized with appropriate rapid electronic switching of electrical connections between electric-current-measuring circuitry and the split-cylinder or split-sphere electrodes, would result in an electrical measurement effect equivalent to that of a conventional rotational field mill. A version of the proposed instrument is described.
Zero-point vibrational effects on optical rotation
DEFF Research Database (Denmark)
Ruud, K.; Taylor, P.R.; Åstrand, P.-O.
2001-01-01
We investigate the effects of molecular vibrations on the optical rotation in two chiral molecules, methyloxirane and trans-2,3-dimethylthiirane. It is shown that the magnitude of zero-point vibrational corrections increases as the electronic contribution to the optical rotation increases....... Vibrational effects thus appear to be important for an overall estimate of the molecular optical rotation, amounting to about 20-30% of the electronic counterpart. We also investigate the special case of chirality introduced in a molecule through isotopic substitution. In this case, the zero-point vibrational...
Vibration of imperfect rotating disk
Directory of Open Access Journals (Sweden)
Půst L.
2011-12-01
Full Text Available This study is concerned with the theoretical and numerical calculations of the flexural vibrations of a bladed disk. The main focus of this study is to elaborate the basic background for diagnostic and identification methods for ascertaining the main properties of the real structure or an experimental model of turbine disks. The reduction of undesirable vibrations of blades is proposed by using damping heads, which on the experimental model of turbine disk are applied only on a limited number of blades. This partial setting of damping heads introduces imperfection in mass, stiffness and damping distribution on the periphery and leads to more complicated dynamic properties than those of a perfect disk. Calculation of FEM model and analytic—numerical solution of disk behaviour in the limited (two modes frequency range shows the splitting of resonance with an increasing speed of disk rotation. The spectrum of resonance is twice denser than that of a perfect disk.
Rotational isovector vibrations in titanium nuclei
Energy Technology Data Exchange (ETDEWEB)
Faessler, A.; Nojarov, R.; Taigel, T.
1989-01-30
The strong M1 states with K/sup ..pi../ = 1/sup +/ in /sup 44,46,48,50/Ti are described microscopically with a deformed Woods-Saxon potential plus QRPA using a parameter-free self-consistent quadrupole force and an interaction, which restores the rotational symmetry. The available experimental data (energies, B(M1) values and (e,e') form factors in /sup 46,48/Ti) are well described in terms of isovector quadrupole rotational vibrations. These RPA states correspond to the scissor-type of isovector motion described by the two-rotor model, but they overlap only 20-30% with the collective isovector rotational state of this model since only few quasiparticle configurations take part in the RPA rotational vibration.
Vibrational and Rotational Energy Relaxation in Liquids
DEFF Research Database (Denmark)
Petersen, Jakob
Vibrational and rotational energy relaxation in liquids are studied by means of computer simulations. As a precursor for studying vibrational energy relaxation of a solute molecule subsequent to the formation of a chemical bond, the validity of the classical Bersohn-Zewail model for describing......, the vibrational energy relaxation of I2 subsequent to photodissociation and recombination in CCl4 is studied using classical Molecular Dynamics simulations. The vibrational relaxation times and the time-dependent I-I pair distribution function are compared to new experimental results, and a qualitative agreement...... the intramolecular dynamics during photodissociation is investigated. The apparent agreement with quantum mechanical calculations is shown to be in contrast to the applicability of the individual approximations used in deriving the model from a quantum mechanical treatment. In the spirit of the Bersohn-Zewail model...
Monitoring Vibration of A Model of Rotating Machine
Directory of Open Access Journals (Sweden)
Arko Djajadi
2012-03-01
Full Text Available Mechanical movement or motion of a rotating machine normally causes additional vibration. A vibration sensing device must be added to constantly monitor vibration level of the system having a rotating machine, since the vibration frequency and amplitude cannot be measured quantitatively by only sight or touch. If the vibration signals from the machine have a lot of noise, there are possibilities that the rotating machine has defects that can lead to failure. In this experimental research project, a vibration structure is constructed in a scaled model to simulate vibration and to monitor system performance in term of vibration level in case of rotation with balanced and unbalanced condition. In this scaled model, the output signal of the vibration sensor is processed in a microcontroller and then transferred to a computer via a serial communication medium, and plotted on the screen with data plotter software developed using C language. The signal waveform of the vibration is displayed to allow further analysis of the vibration. Vibration level monitor can be set in the microcontroller to allow shutdown of the rotating machine in case of excessive vibration to protect the rotating machine from further damage. Experiment results show the agreement with theory that unbalance condition on a rotating machine can lead to larger vibration amplitude compared to balance condition. Adding and reducing the mass for balancing can be performed to obtain lower vibration level.
Rotational spectra of vibrationally excited CCH and CCD.
Killian, T C; Gottlieb, C A; Thaddeus, P
2007-09-21
The millimeter-wave rotational spectra of the lowest bending and stretching vibrational levels of CCH and CCD were observed in a low pressure discharge through acetylene and helium. The rotational, centrifugal distortion, and fine structure constants were determined for the (02(0)0) and (02(2)0) bending states, the (100) and (001) stretching levels, and the (011) combination level of CCH. The same pure bending and stretching levels, and the (110) combination level were observed in CCD. Apparent anomalies in the spectroscopic constants in the bending states were shown to be due to l-type resonances. Hyperfine constants, which in CCH are sensitive to the degree of admixture of the A 2Pi excited electronic state, were determined in the excited vibrational levels of both isotopic species. Theoretical Fermi contact and dipole-dipole hyperfine constants calculated by Peric et al. [J. Mol. Spectrosc. 150, 70 (1991)] were found to be in excellent agreement with the measured constants. In CCD, new rotational lines tentatively assigned to the (100) level largely on the basis of the observed hyperfine structure support the assignment of the C-H stretching fundamental (nu1) by Stephens et al. [J. Mol. Struct. 190, 41 (1988)]. Rotational lines in the excited vibrational levels of CCH are fairly intense in our discharge source because the vibrational excitation temperatures of the bending vibrational levels and the (110) and (011) combination levels are only about 100 K higher than the gas kinetic temperature, unlike the higher frequency stretching vibrations, where the excitation temperatures are five to ten times higher.
DEFF Research Database (Denmark)
Sauer, Stephan P. A.; Paidarová, Ivana; Oddershede, Jens
2011-01-01
The vibrational g factor, that is, the nonadiabatic correction to the vibrational reduced mass, of LiH has been calculated for internuclear distances over a wide range. Based on multiconfigurational wave functions with a large complete active space and an extended set of gaussian type basis...... functions, these calculations yielded also the rotational g factor, the electric dipolar moment, and its gradient with internuclear distance for LiH in its electronic ground state X (1)Sigma(+). The vibrational g factor g(v) exhibits a pronounced minimum near internuclear distance R = 3.65 x 10(-10) m...
Communication: creation of molecular vibrational motions via the rotation-vibration coupling
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Henriksen, Niels Engholm
2015-01-01
whereas a fast rotational excitation leads to a non-stationary vibrational motion. As a result, under field-free postpulse conditions, either a stretched stationary bond or a vibrating bond can be created due to the coupling between the rotational and vibrational degrees of freedom. The latter corresponds......Building on recent advances in the rotational excitation of molecules, we show how the effect of rotation-vibration coupling can be switched on in a controlled manner and how this coupling unfolds in real time after a pure rotational excitation. We present the first examination of the vibrational...... motions which can be induced via the rotation-vibration coupling after a pulsed rotational excitation. A time-dependent quantum wave packet calculation for the HF molecule shows how a slow (compared to the vibrational period) rotational excitation leads to a smooth increase in the average bond length...
Purely collective versus RPA rotational vibrations
Energy Technology Data Exchange (ETDEWEB)
Faessler, A.; Nojarov, R.
1988-12-22
The low-lying 1/sup +/ isovector state vertical strokeRPA> in /sup 48/Ti is calculated in RPA removing the spurious state due to rotations. Its excitation energy, the magnetic dipole transition B(M1; 0/sup +/->1/sup +/) and the (e, e') form factors are compared with experiment, with the purely collective scissor vibration of the deformed protons against the deformed neutrons vertical strokeROT>=N(ed /sub n/J/sub x//sup n/-ed /sub p/J/sub x//sup p/)vertical stroke> and with the purely orbital state vertical strokeORB>=N/sub L/(b/sub n/L/sub x//sup n/-b/sub p/L/sub x//sup p/)vertical stroke>. Although the collective state overlap only ty vertical stroke
VIBRATION ANALYSIS OF LOW-ASPECT RATIO ROTATING ...
African Journals Online (AJOL)
vibrations. And the program developed may be used to include other design characteristics by way of refining the blade modeling. REFERENCES. [1] Campbell,W., "Tangential Vibration of Steam. Turbine Buckets." Trans. of ASME, pp. 643 -. 671, 1924. [2] Lo, H.; RenbargerJ.L.; "Bending Vibration of a Rotating Beams." Proc ...
Large electron transfer rate effects from the Duschinsky mixing of vibrations
DEFF Research Database (Denmark)
Sando, Gerald M.; Spears, Kenneth G; Hupp, Joseph T
2001-01-01
vibrations are very important. The Duschinsky effect arises when two electronic states have vibrational normal mode coordinate systems that are rotated and translated relative to each other. We use a conventional quantum rate model for ET, and the examples include 6-8 vibrations, where two vibrational modes...
Resonant vibration control of rotating beams
DEFF Research Database (Denmark)
Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker
2011-01-01
Rotatingstructures,like e.g.wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor–actuator system, governed by a resonant controller. The theory is here demonstrated...... modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency....
Science and Art--Rotating and Vibrating Soap Films.
Ramme, Goran
1993-01-01
Describes activities concerning interference phenomena derived from illuminated rotating soap films. Suggests reflecting incident light off of the soap film onto a projection screen. Discusses several possible experiments, how to make soap solutions, and vibrating soap films. (MVL)
Vibration-rotation-tunneling dynamics in small water clusters
Energy Technology Data Exchange (ETDEWEB)
Pugliano, Nick [Univ. of California, Berkeley, CA (United States)
1992-11-01
The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm^{-1} intermolecular vibration of the water dimer-d_{4}. Each of the VRT subbands originate from K_{a}''=0 and terminate in either K_{a}'=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A' rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K_{a}' quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a' symmetry, and the vibration is assigned as the v_{12} acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D_{2 }
Vibration-rotation-tunneling dynamics in small water clusters
Energy Technology Data Exchange (ETDEWEB)
Pugliano, N.
1992-11-01
The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm[sup [minus]1] intermolecular vibration of the water dimer-d[sub 4]. Each of the VRT subbands originate from K[sub a][double prime]=0 and terminate in either K[sub a][prime]=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A[prime] rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K[sub a][prime] quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a[prime] symmetry, and the vibration is assigned as the [nu][sub 12] acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D[sub 2]O-DOH isotopomer.
Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades
Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas
2012-01-01
Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.
Measuring unbalance-induced vibrations in rotating tools
Directory of Open Access Journals (Sweden)
Kimmelmann Martin
2017-01-01
Full Text Available Unbalances in a tool cause vibrations of the spindle and the machine itself and lead to a waviness of the machined workpiece surface. This paper presents an experimental and analytical procedure for optically measuring the unbalance-induced displacements of the tool centre point (TCP. Therefore, a new method is introduced to determine the dynamic vibrations of a tool by comparing the geometrical profile of the tool with the dynamical profile at a high rotational speed. The necessary steps for measuring the signals and calculating the underlying dynamic vibrations of the tool are presented here. Afterwards, the unbalance-induced vibrations of a milling tool are shown as well as their influence on the eccentricity of the rotation axis. With this newly introduced method it is possible to directly link the displacements of the tool under rotation to the waviness of the workpiece surface and the dynamic stiffness of machine tools.
DEFF Research Database (Denmark)
Pawlowski, F; Jorgensen, P; Olsen, Jeppe
2002-01-01
A detailed study is carried out of the accuracy of molecular equilibrium geometries obtained from least-squares fits involving experimental rotational constants B(0) and sums of ab initio vibration-rotation interaction constants alpha(r)(B). The vibration-rotation interaction constants have been...... calculated for 18 single-configuration dominated molecules containing hydrogen and first-row atoms at various standard levels of ab initio theory. Comparisons with the experimental data and tests for the internal consistency of the calculations show that the equilibrium structures generated using Hartree......-Fock vibration-rotation interaction constants have an accuracy similar to that obtained by a direct minimization of the CCSD(T) energy. The most accurate vibration-rotation interaction constants are those calculated at the CCSD(T)/cc-pVQZ level. The equilibrium bond distances determined from these interaction...
Energy Technology Data Exchange (ETDEWEB)
Hougen, J.T. [NIST, Gaithersburg, MD (United States)
1993-12-01
The goal of this project is to use spectroscopic techniques to investigate in detail phenomena involving the vibrational quasi-continuum in a simple physical system. Acetaldehyde was chosen for the study because: (i) methyl groups have been suggested to be important promotors of intramolecular vibrational relaxation, (ii) the internal rotation of a methyl group is an easily describle large-amplitude motion, which should retain its simple character even at high levels of excitation, and (iii) the aldehyde carbonyl group offers the possibility of both vibrational and electronic probing. The present investigation of the ground electronic state has three parts: (1) understanding the {open_quotes}isolated{close_quotes} internal-rotation motion below, at, and above the top of the torsional barrier, (2) understanding in detail traditional (bond stretching and bending) vibrational fundamental and overtone states, and (3) understanding interactions involving states with multiquantum excitations of at least one of these two kinds of motion.
Vibrational Dynamics of Light Body in Rotating Cavity with Liquid
Kozlov, Nikolai; Subbotin, Stanislav
2014-11-01
Dynamics of a light body of cylindrical or spherical shape in a rotating cavity (cylindrical or spherical) with liquid is studied. The system is set at rotation, the body occupies a steady position near the cavity axis under the action of centrifugal force. Action of an external periodic force excites inertial oscillations of the body and, as consequence, its differential rotation. The mechanism of the latter is the generation of an average mass force in a viscous boundary layer on the oscillating body surface [Fluid Dyn. 43, 9 (2008); 47, 683 (2012)]. In experiments, two types of external action are used. Rotation of a horizontal cavity in the gravity field leads to circular body oscillations with the frequency of rotation; as a result the body rotates slower than the cavity. External vibration, perpendicular to the rotation axis, leads to a resonant excitation of intensive body oscillations; as a result the body spins in the cavity rotation direction (outrunning rotation), or in the opposite (lagging rotation). The eigenfrequency of rotating system is mainly determined by the ratio of vibration and rotation frequencies n =Ωv /Ωr . Body motion intensity is determined by the dimensionless acceleration Γ = g /RsΩr2 or Γv =bvΩv2 /RsΩr2 . The work is supported by Russian Scientific Foundation (Project No. 14-11-00476).
Reactivity, vibrational spectroscopy, internal rotation and thermochemical aspects of methylarsine
Viana, Rommel B.
2017-01-01
The aim of this investigation was to perform a characterization of the spectroscopic and thermodynamic properties of methylarsine (CH3AsH2). Post-Hartree-Fock, 29 DFT methods and eight different composite methodologies were employed in these analyses. A comparison between harmonic and anharmonic frequency accuracies in reproducing the observable frequencies was performed here. In addition, the CH3AsH2 → CH2AsH3 isomerization barrier energy was estimated in 100 kcal mol- 1, whereas the H2-release routes barrier heights were in the 45-107 kcal mol- 1 range. A rate constant of 10- 66 s- 1 was predicted regarding the isomerization route, while the CH2AsH3 hydrogen elimination mechanism is faster than the methylarsine one. The transition state structure of the CH3AsH2 internal rotational barrier energy varied between 1.0 and 1.4 kcal mol- 1. For the CH2AsH3 internal rotation the estimated barrier heights varied 0.6-2.5 kcal mol- 1. The adiabatic ionization energy and the heat of formation each structure was also calculated here. Table S2 Mean absolute error (MAE, in cm- 1) based in the harmonic frequencies calculated for each method in the prediction of the methylarsine experimental vibrational modes. Table S3 Calculated harmonic (ν, in cm- 1) and anharmonic (ω, in cm- 1) vibrational frequencies in reproducing the methylarsine observed frequencies using the cc-pVTZ basis sets. Table S4. Calculated harmonic (ZPVEHARM, in kcal mol- 1) and anharmonic (ZPVEANHARM, in kcal mol- 1) methylarsine zero-point vibrational energy values (ZPVE) and the difference (ΔZPVE) between both values. Table S5. Arsenic-Carbon bond order indexes for each molecule. Table S6 Properties at As-C bond critical points (BCPs) as electronic charge density [ρ(r)] and its Laplacian [∇2ρ(r)], total energy density [H(r)], ellipticity (ε) and the relationship between local potential energy and local energy density [V(r)/G(r)]. Table S7 Carbon [q(C)] and arsenic [q(As)] atomic charge distribution
Vibrational spectroscopy in the electron microscope.
Krivanek, Ondrej L; Lovejoy, Tracy C; Dellby, Niklas; Aoki, Toshihiro; Carpenter, R W; Rez, Peter; Soignard, Emmanuel; Zhu, Jiangtao; Batson, Philip E; Lagos, Maureen J; Egerton, Ray F; Crozier, Peter A
2014-10-09
Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample--that is, for 'aloof' spectroscopy that largely avoids radiation damage.
Numerical analysis of free vibrations of damped rotating structures
Gupta, K. K.
1977-01-01
This paper is concerned with the efficient numerical solution of damped and undamped free vibration problems of rotating structures. While structural discretization is achieved by the finite element method, the associated eigenproblem solution is effected by a combined Sturm sequence and inverse iteration technique that enables the computation of a few required roots only without having to compute any other. For structures of complex configurations, a modal synthesis technique is also presented, which is based on appropriate combinations of eigenproblem solution of various structural components. Such numerical procedures are general in nature, which fully exploit matrix sparsity inherent in finite element discretizations, and prove to be most efficient for the vibration analysis of any damped rotating structure, such as rotating machineries, helicopter and turbine blades, spinning space stations, among others.
Research of rotating machinery vibration parameters - Shaft speed relationship
Kostyukov, V. N.; Kostyukov, A. V.; Zaytsev, A. V.; Teterin, A. O.
2017-08-01
The paper considers the relationship between the parameters of the vibration arising in rotating machinery during operation and the shaft speed. The goal of this paper is to determine the dependence of the vibration parameters on the shaft speed for solving applied engineering problems. To properly evaluate the technical condition of bearing assemblies, we should take into account the pattern of the rotating machinery vibration parameters-shaft speed relationship, which will allow creating new diagnostic features, the totality of which will ensure an increased reliability of diagnosis. We took the check for a correlation between the factor and resultative feature parameters as the correlation analysis method. A high pair linear correlation between the diagnostic features (acceleration, velocity, displacement) and the shaft speed was determined on the basis of the check for correlation between the vibration parameters and the shaft speed, and also the linear correlation coefficients can be used to solve the applied engineering problems of diagnosing the bearing assemblies of the rotating machinery.
Status on the Global Vibration-Rotation Model in Acetylene
Amyay, B.; Herman, M.; Fayt, A.
2009-06-01
We have developed a global model to deal with all vibration-rotation levels in acetylene up to high vibrational excitation energy, typically up to 9000 wavenumbers. It has been applied to a number of isotopologues, considering all known vibration-rotation lines published in the literature, for various purposes such as line assignment and astrophysical applications. Coriolis interaction is now systematically being introduced in the model. Recent results concerning the analysis of hot emission FTIR spectra recorded around 3 microns by R. Georges et al. at the University of Rennes (France) and of CW-CRDS spectra recorded around 1.5 microns by A. Campargue et al. at the University of Grenoble (France) will help illustrate the role of this vibration-rotation coupling in the global polyad scheme. S. Robert, M. Herman, A. Fayt, A. Campargue, S. Kassi, A. Liu, L. Wang, G. Di Lonardo, and L. Fusina, Mol. Phys., 106, 2581 (2008). A. Jolly, Y. Benilan, E. Cané, L. Fusina, F. Tamassia, A. Fayt, S. Robert, and M. Herman, J.Q.S.R.T., 109, 2846 (2008).
Rotational Spectra in 29 Vibrationally Excited States of Interstellar Aminoacetonitrile
Energy Technology Data Exchange (ETDEWEB)
Kolesniková, L.; Alonso, E. R.; Mata, S.; Alonso, J. L. [Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Área de Química-Física, Laboratorios de Espectroscopia y Bioespectroscopia, Parque Científico UVa, Unidad Asociada CSIC, Universidad de Valladolid, E-47011 Valladolid (Spain)
2017-04-01
We report a detailed spectroscopic investigation of the interstellar aminoacetonitrile, a possible precursor molecule of glycine. Using a combination of Stark and frequency-modulation microwave and millimeter wave spectroscopies, we observed and analyzed the room-temperature rotational spectra of 29 excited states with energies up to 1000 cm{sup −1}. We also observed the {sup 13}C isotopologues in the ground vibrational state in natural abundance (1.1%). The extensive data set of more than 2000 new rotational transitions will support further identifications of aminoacetonitrile in the interstellar medium.
Free vibration analysis of a rotating nanoshaft based SWCNT
Belhadj, Abdelkadir; Boukhalfa, Abdelkrim; Belalia, Sid A.
2017-12-01
In this paper, the vibration behaviour of a nanoscale rotating shaft based single-walled carbon nanotube is investigated. The Euler-Bernoulli beam model is used to model the dynamic behaviour of the nanorotor based on Eringen's nonlocal theory of elasticity. The governing equations and boundary conditions are derived according to the Hamilton's principle and the resulted equations system is solved with the aid of the generalized differential quadrature method (GDQM). The effects of the small-scale parameter, angular velocity and boundary conditions are reported. The results can provide useful guidance for the dynamic behaviour and design of the next generation of rotating nanomachinery, such as nanoturbines and nanomotors.
Ab initio potential energy surface and vibration-rotation energy levels of beryllium monohydroxide.
Koput, Jacek
2017-01-05
The accurate potential energy surface of beryllium monohydroxide, BeOH, in its ground electronic state X 2A' has been determined from ab initio calculations using the coupled-cluster approach in conjunction with the correlation-consistent core-valence basis sets up to septuple-zeta quality. The higher-order electron correlation, scalar relativistic, and adiabatic effects were taken into account. The BeOH molecule was confirmed to be bent at equilibrium, with the BeOH angle of 141.2° and the barrier to linearity of 129 cm-1 . The vibration-rotation energy levels of the BeOH and BeOD isotopologues were predicted using a variational approach and compared with recent experimental data. The results can be useful in a further analysis of high-resolution vibration-rotation spectra of these interesting species. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
Peculiar rotation of electron vortex beams.
Schachinger, T; Löffler, S; Stöger-Pollach, M; Schattschneider, P
2015-11-01
Standard electron optics predicts Larmor image rotation in the magnetic lens field of a TEM. Introducing the possibility to produce electron vortex beams with quantized orbital angular momentum brought up the question of their rotational dynamics in the presence of a magnetic field. Recently, it has been shown that electron vortex beams can be prepared as free electron Landau states showing peculiar rotational dynamics, including no and cyclotron (double-Larmor) rotation. Additionally very fast Gouy rotation of electron vortex beams has been observed. In this work a model is developed which reveals that the rotational dynamics of electron vortices are a combination of slow Larmor and fast Gouy rotations and that the Landau states naturally occur in the transition region in between the two regimes. This more general picture is confirmed by experimental data showing an extended set of peculiar rotations, including no, cyclotron, Larmor and rapid Gouy rotations all present in one single convergent electron vortex beam. Copyright © 2015 Elsevier B.V. All rights reserved.
Manipulation of molecular vibrational motions via pure rotational excitations
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Henriksen, Niels Engholm
2015-01-01
The coupling between different molecular degrees of freedom plays a decisive role in many quantum phenomena, including electron transfer and energy redistribution. Here, we demonstrate a quantum-mechanical time-dependent simulation to explore how a vibrational motion in a molecule can be affected...
The Lowest Vibrational States of Urea from the Rotational Spectrum
Kisiel, Zbigniew; Thomas, Jessica; Medvedev, Ivan
2014-06-01
The urea molecule, (NH_2)_2CO, has a complex potential energy surface resulting from a combination of the NH_2 torsion and NH_2 inversion motions. This leads to a distribution of lowest vibrational states that is expected to be significantly different from the more familiar picture from simple inversion or normal mode models. The broadband 207-500 GHz spectrum of urea recorded in Dayton has signal to noise sufficient for assignment of rotational transitions in excited vibrational states up to at least 500 cm-1. In addition to the previously reported analysis of the ground and the lowest excited state we have been able to assign transitions in at least five other excited vibrational states. Strongly perturbed transitions in a close doublet of such states have been fitted to within experimental accuracy with a coupled fit and a splitting in the region of 1 cm-1. These assignments combined with vibrational energy estimates from relative intensity measurements allow for empirical discrimination between different models for the energy level manifestation of the large amplitude motions in urea.^b P.D.Godfrey, R.D.Brown, A.N.Hunter J. Mol. Struct., 413-414, 405-414 (1997). N.Inostroza, M.L.Senent, Chem. Phys. Lett., 524, 25 (2012).
The Astrophysical Weeds: Rotational Transitions in Excited Vibrational States
Alonso, José L.; Kolesniková, Lucie; Alonso, Elena R.; Mata, Santiago
2017-06-01
The number of unidentified lines in the millimeter and submillimeter wave surveys of the interstellar medium has grown rapidly. The major contributions are due to rotational transitions in excited vibrational states of a relatively few molecules that are called the astrophysical weeds. necessary data to deal with spectral lines from astrophysical weeds species can be obtained from detailed laboratory rotational measurements in the microwave and millimeter wave region. A general procedure is being used at Valladolid combining different time and/or frequency domain spectroscopic tools of varying importance for providing the precise set of spectroscopic constants that could be used to search for this species in the ISM. This is illustrated in the present contribution through its application to several significant examples. Fortman, S. M., Medvedev, I. R., Neese, C.F., & De Lucia, F.C. 2010, ApJ,725, 1682 Rotational Spectra in 29 Vibrationally Excited States of Interstellar Aminoacetonitrile, L. Kolesniková, E. R. Alonso, S. Mata, and J. L. Alonso, The Astrophysical Journal Supplement Series 2017, (in press).
High Accuracy ab Initio Calculations of Rotational-Vibrational Levels of the HCN/HNC System.
Makhnev, Vladimir Yu; Kyuberis, Aleksandra A; Zobov, Nikolai F; Lodi, Lorenzo; Tennyson, Jonathan; Polyansky, Oleg L
2018-02-08
Highly accurate ab initio calculations of vibrational and rotational-vibrational energy levels of the HCN/HNC (hydrogen cyanide/hydrogen isocyanide) isomerising system are presented for several isotopologues. All-electron multireference configuration interaction (MRCI) electronic structure calculations were performed using basis sets up to aug-cc-pCV6Z on a grid of 1541 geometries. The ab initio energies were used to produce an analytical potential energy surface (PES) describing the two minima simultaneously. An adiabatic Born-Oppenheimer diagonal correction (BODC) correction surface as well as a relativistic correction surface were also calculated. These surfaces were used to compute vibrational and rotational-vibrational energy levels up to 25 000 cm -1 which reproduce the extensive set of experimentally known HCN/HNC levels with a root-mean-square deviation σ = 1.5 cm -1 . We studied the effect of nonadiabatic effects by introducing opportune radial and angular corrections to the nuclear kinetic energy operator. Empirical determination of two nonadiabatic parameters results in observed energies up to 7000 cm -1 for four HCN isotopologues (HCN, DCN, H 13 CN, and HC 15 N) being reproduced with σ = 0.37 cm -1 . The height of the isomerization barrier, the isomerization energy and the dissociation energy were computed using a number of models; our best results are 16 809.4, 5312.8, and 43 729 cm -1 , respectively.
Rotational Laser Cooling of Vibrationally and Translationally Cold Molecular Ions
DEFF Research Database (Denmark)
Drewsen, Michael
2011-01-01
an excellent alternative to atomic qubits in the realization of a practical ion trap based quantum computer due to favourable internal state decoherence rates. In chemistry, state prepared molecular targets are an ideal starting point for uni-molecular reactions, including coherent control...... by sympathetic cooling with Doppler laser cooled Mg+ ions. Giving the time for the molecules to equilibrate internally to the room temperature blackbody radiation, the vibrational degree of freedom will freeze out, leaving only the rotational degree of freedom to be cooled. We report here on the implementation...
Vibrational motions in rotating nuclei studied by Coulomb excitations
Energy Technology Data Exchange (ETDEWEB)
Shimizu, Yoshifumi R. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics
1998-03-01
As is well-known Coulomb excitation is an excellent tool to study the nuclear collective motions. Especially the vibrational excitations in rotating nuclei, which are rather difficult to access by usual heavy-ion fusion reactions, can be investigated in detail. Combined with the famous 8{pi}-Spectrometer, which was one of the best {gamma}-ray detector and had discovered some of superdeformed bands, such Coulomb excitation experiments had been carried out at Chalk River laboratory just before it`s shutdown of physics division. In this meeting some of the experimental data are presented and compared with the results of theoretical investigations. (author)
Vibrational Suspension of Light Sphere in a Tilted Rotating Cylinder with Liquid
Victor G. Kozlov; Subbotin, Stanislav V.
2014-01-01
The dynamics of a light sphere in a quickly rotating inclined cylinder filled with liquid under transversal vibrations is experimentally investigated. Due to inertial oscillations of the sphere relative to the cavity, its rotation velocity differs from the cavity one. The intensification of the lagging motion of a sphere and the excitation of the outstripping differential rotation are possible under vibrations. It occurs in the resonant areas where the frequency of vibrations coincides with t...
Comparison of methods for separating vibration sources in rotating machinery
Klein, Renata
2017-12-01
Vibro-acoustic signatures are widely used for diagnostics of rotating machinery. Vibration based automatic diagnostics systems need to achieve a good separation between signals generated by different sources. The separation task may be challenging, since the effects of the different vibration sources often overlap. In particular, there is a need to separate between signals related to the natural frequencies of the structure and signals resulting from the rotating components (signal whitening), as well as a need to separate between signals generated by asynchronous components like bearings and signals generated by cyclo-stationary components like gears. Several methods were proposed to achieve the above separation tasks. The present study compares between some of these methods. The paper also presents a new method for whitening, Adaptive Clutter Separation, as well as a new efficient algorithm for dephase, which separates between asynchronous and cyclo-stationary signals. For whitening the study compares between liftering of the high quefrencies and adaptive clutter separation. For separating between the asynchronous and the cyclo-stationary signals the study compares between liftering in the quefrency domain and dephase. The methods are compared using both simulated signals and real data.
Rotational nuclear models and electron scattering
Energy Technology Data Exchange (ETDEWEB)
Moya de Guerra, E.
1986-05-01
A review is made of the basic formalism involved in the application of nuclear rotational models to the problem of electron scattering from axially symmetric deformed nuclei. Emphasis is made on the use of electron scattering to extract information on the nature of the collective rotational model. In this respect, the interest of using polarized beam and target is discussed with the help of illustrative examples. Concerning the nuclear structure four rotational models are considered: Two microscopic models, namely the Projected Hartree-Fock (PHF) and cranking models; and two collective models, the rigid rotor and the irrotational flow models. The problem of current conservation within the different models is also discussed.
Liicg - a New Method for Rotational and Ro-Vibrational Spectroscopy at 4K
Kluge, Lars; Stoffels, Alexander; Bruenken, Sandra; Asvany, Oskar; Schlemmer, Stephan
2014-06-01
Since many years low temperature ion trapping techniques are successfully used in our laboratories in combination with sensitive action spectroscopy schemes (Laser Induced Reactions) to measure high resolution ro-vibrational and rotational spectra of gas-phase molecular ions. Here we present a further development of a LIR method first introduced for recording rotationally resolved electronic spectra of N2+. This new method, called LIICG (Light Induced Inhibition of Complex Growth), makes use of state specific He-attachment rates to stored cold molecular ions. We have recently demonstrated its applicability to rotational and ro-vibrational spectroscopy of C3H+ and CH5+. The measurements were performed in recently completed 4K 22-pole ion trap instruments. Ionic species are produced in a storage ion source and are mass selected before they enter the trap. For spectroscopy normally a few thousand ions are stored at 4K together with He at high number densities (around 1014 cm-3). Under these conditions He attaches to the ions via ternary collision processes. As we will show, this attachement process is hindered by exciting a rotational or ro-vibrational transition, likely because the attachment rates for He are slower for higher rotational or ro-vibrational levels. So by exciting the bare ion the number of ion- He complexes at equilibrium is reduced. In this way the spectrum of the bare ion can be recorded by counting the number of ion-He complexes as a function of frequency. To test the new method we chose well known rotational ground state transitions of CO+, HCO+ and CD+. In particular CD+ appeared to be a good candidate for understanding the new method in detail, due to its strong LIICG signal and its simple rotational spectrum. In this contribution we will explain the LIICG scheme and its underlying kinetics using the example of CD+. We will show effects of different experimental conditions on the signal (e.g. He number density, temperature, radiation power…) to
Can an Electron Rotate a Brick?
Bohren, Craig F.
2009-01-01
In "The Theory of Almost Everything", Robert Oerter asserts the following: "Take a beam of electrons that are all spinning in the same direction and fire it at, say, a brick. If you could keep this up for long enough, and if there were no other forces acting on the brick, the electrons would transfer their rotation to the brick, and it would begin…
Electroexcitation of rotational vibrations in sup 164 Dy
Energy Technology Data Exchange (ETDEWEB)
Scholtz, F.G.; Nojarov, R.; Faessler, A. (Institut fur Theoretische Physik, Universitat Tubingen, Auf der Morgenstelle 14, D-7400 Tubingen 1, Federal Republic of Germany (DE))
1989-09-25
We calculate the {ital M}1 spectrum and the distorted-wave Born-approximation ({ital e},{ital e}{prime}) form factors of the strong {ital K}{sup {pi}}=1{sup +} states in {sup 164}Dy, using a deformed Woods-Saxon potential and the quasiparticle random-phase approximation with quadrupole, spin, and spin-quadrupole interactions. A residual rotation-vibrational coupling ensures the exclusion of the spurious state. We find strongly orbital {ital M}1 states at 3.1 MeV which fit the experimental spectrum very well and exhaust 40% of the collectivity of the 1{sup +} mode. The form factor of the lowest one of these states is also in a good agreement with the experimental form factor.
Orbital rotational vibrations in the A =130 mass region
Energy Technology Data Exchange (ETDEWEB)
Faessler, A.; Nojarov, R. (Institut fuer Theoretische Physik, Universitaet Tuebingen, Auf der Morgenstelle 14, D-7400 Tuebingen, Federal Republic of Germany (DE))
1990-03-01
The rotational vibrations ({ital K}{sup {pi}}=1{sup +} states) in 16 even-even Xe, Ba, and Ce nuclei are studied in the quasiparticle random-phase approximation with a mean field given by a deformed Woods-Saxon potential and residual forces: a self-consistent quadrupole-quadrupole interaction, a spin-spin interaction, and a force that restores the rotational invariance of the Hamiltonian. A shell effect is found which is typical for this mass region: a strong orbital character of almost all low-energy (2.5--5 MeV) excitations, while the higher-energy ones are predominantly spin flip. The comparison of random-phase approximation {ital M}1 transition densities and ({ital e},{ital e}{prime}) form factors with the microscopic realization of the two-rotor model 1{sup +} state allow us to conclude that the strongly orbital low-energy random-phase approximation states perform the scissor-type motion described by the two-rotor model, but only few particles are involved in this motion.
Laporta, V; Tennyson, J; Celiberto, R; 10.1088/0963-0252/21/4/045005
2012-01-01
Resonant vibrational and rotation-vibration excitation cross sections for electron-CO scattering are calculated in the 0-10 eV energy range for all 81 vibrational states of CO, assuming that the excitation occur via the 2{\\Pi} shape resonance. Static exchange plus polarization calculations performed using the R-matrix method are used to estimate resonance positions and widths as functions of internuclear separation. The effects of nuclear motion are considered using a local complex potential model. Good agreement is obtained with available experimental data on excitation from the vibrational ground state. Excitation rates and cross sections are provided as a functions of the initial CO vibrational state for all ground state vibrational levels.
Ab initio potential energy surface and vibration-rotation energy levels of sulfur dioxide.
Koput, Jacek
2017-05-05
An accurate potential energy surface of sulfur dioxide, SO2 , in its ground electronic state X∼ 1A1 has been determined from ab initio calculations using the coupled-cluster approach in conjunction with the correlation-consistent basis sets up to septuple-zeta quality. The results obtained with the conventional and explicitly correlated coupled-cluster methods are compared. The role of the core-electron correlation, higher-order valence-electron correlation, scalar relativistic, and adiabatic effects in determining the structure and dynamics of the SO2 molecule is discussed. The vibration-rotation energy levels of the 32 SO2 and 34 SO2 isotopologues were predicted using a variational approach. It was shown that the inclusion of the aforementioned effects was mandatory to attain the "spectroscopic" accuracy. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
Y. Yoshida
2008-01-01
Full Text Available Asymmetric cavitation is known as one type of the sources of cavitation induced vibration in turbomachinery. Cavity lengths are unequal on each blade under condition of synchronous rotating cavitation, which causes synchronous shaft vibration. To investigate the relationship of the cavity length, fluid force, and shaft vibration in a cavitating inducer with three blades, we observed the unevenness of cavity length at the inception of synchronous rotating cavitation. The fluid force generated by the unevenness of the cavity length was found to grow exponentially, and the amplitude of shaft vibration was observed to increase exponentially. These experimental results indicate that the synchronous shaft vibration due to synchronous rotating cavitation is like selfexcited vibrations arising from the coupling between cavitation instability and rotordynamics.
Khan, Sheraz Ali; Kim, Jong-Myon
2016-04-01
Structural vibrations of bearing housings are used for diagnosing fault conditions in bearings, primarily by searching for characteristic fault frequencies in the envelope power spectrum of the vibration signal. The fault frequencies depend on the non-stationary angular speed of the rotating shaft. This paper explores an imaging-based approach to achieve rotational speed independence. Cycle length segments of the rectified vibration signal are stacked to construct grayscale images which exhibit unique textures for each fault. These textures show insignificant variation with the rotational speed, which is confirmed by the classification results using their local binary pattern histograms.
Bryant, Mark S.; Reeve, Scott W.; Burns, William A.
2008-01-01
The linear molecule N[subscript 2]O is presented as an alternative gas-phase species for the ubiquitous undergraduate physical chemistry rotation-vibration spectroscopy experiment. Utilizing a 0.5 cm[superscript -1] resolution teaching grade FTIR spectrometer, 15 vibrational bands, corresponding to 1229 rotation-vibration transitions, have been…
On gyroscopic effects in vibrating and axially rotating solid and annular discs
CSIR Research Space (South Africa)
Joubert, SV
2007-05-01
Full Text Available , such as cylindrical, hemispherical and planar circular disc rotational sensors. The model of a thin circular disc vibrating in its plane and subjected to inertial rotation is considered. The dynamics of the disc gyroscope are considered in terms of linear elasticity...
Transition densities in the context of the generalized rotation-vibration model
Morales Botero, D. F.; Chamon, L. C.; Carlson, B. V.
2017-10-01
A collective model for the description of heavy-ion nuclear structure, called the generalized rotation-vibration model (GRVM), was proposed in an earlier paper. In the present work, we use this model to study transition densities for the low-lying states of several nuclei. In order to evaluate the accuracy of the model, we test the GRVM transition densities in the description of experimental results corresponding to elastic and inelastic electron-nucleus scattering. We also compare the GRVM densities with those arising from microscopic Dirac-Hartree-Bogoliubov theoretical calculations. The GRVM transition densities can be used in future works to calculate folding-type coupling potentials in coupled-channel data analyses for heavy-ion systems.
High-accuracy calculations of the rotation-vibration spectrum of {{\\rm{H}}}_{3}^{+}
Tennyson, Jonathan; Polyansky, Oleg L.; Zobov, Nikolai F.; Alijah, Alexander; Császár, Attila G.
2017-12-01
Calculation of the rotation-vibration spectrum of {{{H}}}3+, as well as of its deuterated isotopologues, with near-spectroscopic accuracy requires the development of sophisticated theoretical models, methods, and codes. The present paper reviews the state-of-the-art in these fields. Computation of rovibrational states on a given potential energy surface (PES) has now become standard for triatomic molecules, at least up to intermediate energies, due to developments achieved by the present authors and others. However, highly accurate Born–Oppenheimer energies leading to highly accurate PESs are not accessible even for this two-electron system using conventional electronic structure procedures (e.g. configuration-interaction or coupled-cluster techniques with extrapolation to the complete (atom-centered Gaussian) basis set limit). For this purpose, highly specialized techniques must be used, e.g. those employing explicitly correlated Gaussians and nonlinear parameter optimizations. It has also become evident that a very dense grid of ab initio points is required to obtain reliable representations of the computed points extending from the minimum to the asymptotic limits. Furthermore, adiabatic, relativistic, and quantum electrodynamic correction terms need to be considered to achieve near-spectroscopic accuracy during calculation of the rotation-vibration spectrum of {{{H}}}3+. The remaining and most intractable problem is then the treatment of the effects of non-adiabatic coupling on the rovibrational energies, which, in the worst cases, may lead to corrections on the order of several cm‑1. A promising way of handling this difficulty is the further development of effective, motion- or even coordinate-dependent, masses and mass surfaces. Finally, the unresolved challenge of how to describe and elucidate the experimental pre-dissociation spectra of {{{H}}}3+ and its isotopologues is discussed.
Wang, Zhao; Yan, Hong; Li, Qibing; Xu, Kun
2017-12-01
The unified gas-kinetic scheme (UGKS) is a direct modeling method for both continuum and rarefied flow computations. In the previous study, the UGKS was developed for diatomic molecular simulations with translation and rotational motions. In this paper, a UGKS with non-equilibrium translational, rotational, and vibrational degrees of freedom, will be developed. The new scheme is based on the phenomenological gas dynamics model, where the translational, rotational, and vibrational modes get to the equilibrium with different time scales with the introduction of rotational and vibrational collision numbers. This new scheme is tested in a few cases, such as the homogeneous flow relaxation, shock structure, shock tube problem, and flow passing through a circular and semi-circular cylinders. The analytical and DSMC solutions are used for the validation of the UGKS, and reasonable agreements have been achieved.
Ultrafast electronic relaxation and vibrational dynamics in a polyacetylene derivative
Kobayashi, Takayoshi; Iiyama, Tsugumasa; Okamura, Kotaro; Du, Juan; Masuda, Toshio
2013-04-01
Real-time vibrational spectra in a polyacetylene derivative, poly[o-TFMPA([o-(trifluoromethyl) phenyl]acetylene)] in a broad electronic spectral region were observed using a sub-7-fs laser. Using the frequencies and initial phases of vibrational modes obtained by the spectroscopy, the assignment of the wavepackets was made. From the first moment, Huang-Rhys parameters were determined for six most prominent modes, which characterize the potential hypersurface composed of multi-dimensional vibrational mode spaces.
Vibrational Suspension of Light Sphere in a Tilted Rotating Cylinder with Liquid
Directory of Open Access Journals (Sweden)
Victor G. Kozlov
2014-01-01
Full Text Available The dynamics of a light sphere in a quickly rotating inclined cylinder filled with liquid under transversal vibrations is experimentally investigated. Due to inertial oscillations of the sphere relative to the cavity, its rotation velocity differs from the cavity one. The intensification of the lagging motion of a sphere and the excitation of the outstripping differential rotation are possible under vibrations. It occurs in the resonant areas where the frequency of vibrations coincides with the fundamental frequency of the system. The position of the sphere in the center of the cylinder could be unstable. Different velocities of the sphere are matched with its various quasistationary positions on the axis of rotating cavity. In tilted rotating cylinder, the axial component of the gravity force appears; however, the light sphere does not float to the upper end wall but gets the stable position at a definite distance from it. It makes possible to provide a vibrational suspension of the light sphere in filled with liquid cavity rotating around the vertical axis. It is found that in the wide range of the cavity inclination angles the sphere position is determined by the dimensionless velocity of body differential rotation.
Directory of Open Access Journals (Sweden)
Saleem Riaz
2017-02-01
Full Text Available Safety, reliability, efficiency and performance of rotating machinery in all industrial applications are the main concerns. Rotating machines are widely used in various industrial applications. Condition monitoring and fault diagnosis of rotating machinery faults are very important and often complex and labor-intensive. Feature extraction techniques play a vital role for a reliable, effective and efficient feature extraction for the diagnosis of rotating machinery. Therefore, developing effective bearing fault diagnostic method using different fault features at different steps becomes more attractive. Bearings are widely used in medical applications, food processing industries, semi-conductor industries, paper making industries and aircraft components. This paper review has demonstrated that the latest reviews applied to rotating machinery on the available a variety of vibration feature extraction. Generally literature is classified into two main groups: frequency domain, time frequency analysis. However, fault detection and diagnosis of rotating machine vibration signal processing methods to present their own limitations. In practice, most healthy ingredients faulty vibration signal from background noise and mechanical vibration signals are buried. This paper also reviews that how the advanced signal processing methods, empirical mode decomposition and interference cancellation algorithm has been investigated and developed. The condition for rotating machines based rehabilitation, prevent failures increase the availability and reduce the cost of maintenance is becoming necessary too. Rotating machine fault detection and diagnostics in developing algorithms signal processing based on a key problem is the fault feature extraction or quantification. Currently, vibration signal, fault detection and diagnosis of rotating machinery based techniques most widely used techniques. Furthermore, the researchers are widely interested to make automatic
Vibration Analysis of Structures with Rotation and Reflection Symmetry
Directory of Open Access Journals (Sweden)
Baojian Li
1996-01-01
Full Text Available The article applies group representation theory to the vibration analysis of structures with Cnv symmetry, and presents a new structural vibration analysis method. The eigenvalue problem of the whole structure is divided into much smaller subproblems by forming the mass and stiffness matrices of one substructure and than modifying them to form mass and stiffness matrices in each irreducible subspace, resulting in the saving of computer time and memory. The modal characteristics of structures with Cnv symmetry are derived from theoretical analysis. Computation and modal testing are used to verify the validity of the theoretical deductions.
Vibrational and electronic spectroscopic studies of melatonin
Singh, Gurpreet; Abbas, J. M.; Dogra, Sukh Dev; Sachdeva, Ritika; Rai, Bimal; Tripathi, S. K.; Prakash, Satya; Sathe, Vasant; Saini, G. S. S.
2014-01-01
We report the infrared absorption and Raman spectra of melatonin recorded with 488 and 632.8 nm excitations in 3600-2700 and 1700-70 cm-1 regions. Further, we optimized molecular structure of the three conformers of melatonin within density functional theory calculations. Vibrational frequencies of all three conformers have also been calculated. Observed vibrational bands have been assigned to different vibrational motions of the molecules on the basis of potential energy distribution calculations and calculated vibrational frequencies. Observed band positions match well with the calculated values after scaling except Nsbnd H stretching mode frequencies. It is found that the observed and calculated frequencies mismatch of Nsbnd H stretching is due to intermolecular interactions between melatonin molecules.
DEFF Research Database (Denmark)
Zhang, Zili; Nielsen, Søren R. K.; Basu, Biswajit
2015-01-01
Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g. This facilit......Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g...... free-surface elevation equally well, the one-mode model can still be utilized for the design of TLD. Parametric optimization of the TLD is carried out based on the one-mode model, and the optimized damper effectively improves the dynamic response of wind turbine blades....
Vibration-rotation energy pattern in acetylene: 13CH12CH up to 6750 cm-1.
Fayt, A; Robert, S; Di Lonardo, G; Fusina, L; Tamassia, F; Herman, M
2007-03-21
All known vibration-rotation absorption lines of 13CH12CH accessing levels up to 6750 cm-1 were gathered from the literature. They were fitted simultaneously to J-dependent Hamiltonian matrices exploiting the well known vibrational polyad or cluster block diagonalization, in terms of the pseudo-quantum-numbers Ns=v1+v2+v3 and Nr=5v1+3v2+5v3+v4+v5, and accounting also for l parity and ef symmetry properties. The anharmonic interaction coupling terms known to occur from a pure vibrational fit in this acetylene isotopologue [Robert et al., J. Chem. Phys. 123, 174302 (2005)] were included in the model. A total of 12 703 transitions accessing 158 different (v1v2v3v4v5,l4l5) vibrational states was fitted with a dimensionless standard deviation of 0.99, leading to the determination of 216 vibration-rotation parameters. The experimental data included very weak vibration-rotation transitions accessing 18 previously unreported states, some of them forming Q branches with very irregular patterns.
Is the Coupling of C3V Internal Rotation and Normal Vibrations a Tractable Problem?
Pearson, John; Groner, Peter; Daly, Adam M.
2016-06-01
The solution of a C3V internal rotation problem for the torsional manifold of an isolated vibrational state such as the ground state is well established. However, once an interacting small amplitude vibrational state is involved the path to a solution becomes far less clear and there is little guidance in the literature on how to proceed. The fundamental challenge is that the torsional problem and the internal axis system are unique to each torsional manifold of a specific vibrational state. In an asymmetric top molecule vibrational angular momentum can be rotated away, but this sort of rotation changes the angle between the internal rotation axis and the principle axis when there is an internal rotor. This means that there is an angle between the internal axis systems of each torsional manifold of a vibrational state. The net result is that the coupling between the two states must account for the difference in internal axis angle and will have some significant consequences to the selection rules and interactions. Two cases will be discussed, methanol and ethyl cyanide.
DEFF Research Database (Denmark)
Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas
2014-01-01
Gliding arc discharges have generally been used to generate non-equilibrium plasma at atmospheric pressure. Temperature distributions of a gliding arc are of great interest both for fundamental plasma research and for practical applications. In the presented studies, translational, rotational...... and vibrational temperatures of a gliding arc generated at atmospheric pressure air are investigated. Translational temperatures (about 1100 K) were measured by laser-induced Rayleigh scattering, and two-dimensional temperature imaging was performed. Rotational and vibrational temperatures (about 3600 K and 6700...
Rotation in vibration, optimization, and aeroelastic stability problems. Ph.D. Thesis
Kaza, K. R. V.
1974-01-01
The effects of rotation in the areas of vibrations, dynamic stability, optimization, and aeroelasticity were studied. The governing equations of motion for the study of vibration and dynamic stability of a rapidly rotating deformable body were developed starting from the nonlinear theory of elasticity. Some common features such as the limitations of the classical theory of elasticity, the choice of axis system, the property of self-adjointness, the phenomenon of frequency splitting, shortcomings of stability methods as applied to gyroscopic systems, and the effect of internal and external damping on stability in gyroscopic systems are identified and discussed, and are then applied to three specific problems.
Ab initio potential energy surface and vibration-rotation energy levels of silicon dicarbide, SiC2.
Koput, Jacek
2016-10-05
The accurate ground-state potential energy surface of silicon dicarbide, SiC2 , has been determined from ab initio calculations using the coupled-cluster approach. Results obtained with the conventional and explicitly correlated coupled-cluster methods were compared. The core-electron correlation, higher-order valence-electron correlation, and scalar relativistic effects were taken into account. The potential energy barrier to the linear SiCC configuration was predicted to be 1782 cm(-1) . The vibration-rotation energy levels of the SiC2 , (29) SiC2 , (30) SiC2 , and SiC(13) C isotopologues were calculated using a variational method. The experimental vibration-rotation energy levels of the main isotopologue were reproduced to high accuracy. In particular, the experimental energy levels of the highly anharmonic vibrational ν3 mode of SiC2 were reproduced to within 6.7 cm(-1) , up to as high as the v3 = 16 state. © 2016 Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
Daniel Zurita-Millán
2016-01-01
Full Text Available Vibration monitoring plays a key role in the industrial machinery reliability since it allows enhancing the performance of the machinery under supervision through the detection of failure modes. Thus, vibration monitoring schemes that give information regarding future condition, that is, prognosis approaches, are of growing interest for the scientific and industrial communities. This work proposes a vibration signal prognosis methodology, applied to a rotating electromechanical system and its associated kinematic chain. The method combines the adaptability of neurofuzzy modeling with a signal decomposition strategy to model the patterns of the vibrations signal under different fault scenarios. The model tuning is performed by means of Genetic Algorithms along with a correlation based interval selection procedure. The performance and effectiveness of the proposed method are validated experimentally with an electromechanical test bench containing a kinematic chain. The results of the study indicate the suitability of the method for vibration forecasting in complex electromechanical systems and their associated kinematic chains.
Rotational excitation of interstellar molecular ions by electrons
Energy Technology Data Exchange (ETDEWEB)
Faure, A [Laboratoire d' Astrophysique, UMR 5571 CNRS, Universite Joseph-Fourier, B.P. 53, 38041 Grenoble cedex 09 (France); Tennyson, J [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Kokoouline, V [Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States); Greene, Chris H, E-mail: afaure@obs.ujf-grenoble.f [Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)
2009-11-15
Electrons are known to be efficient in rotationally exciting molecular ions in cold ionized media. Rotational effects have also been shown to affect the dissociative recombination (DR) process. Electron collisions are thus expected to play a significant role in the thermalization and dissociation dynamics of molecular ions, both in the laboratory and in space. Using the molecular R-matrix method combined with the Adiabatic-Nuclei-Rotation (ANR) approximation corrected for threshold and closed-channel effects, we have computed new rate coefficients for the rotational excitation of H{sup +}{sub 3} and HCO{sup +} by electrons at temperatures from 10 to 1 000K. At temperatures above rotational thresholds, rotational rates are found to compete or even dominate those of dissociative recombination, suggesting that electron collisions provide a possible source of rotational (de)excitation in DR measurements.
Magnetostrictive Vibration Damper and Energy Harvester for Rotating Machinery
Deng, Zhangxian; Asnani, Vivake M.; Dapino, Marcelo J.
2015-01-01
Vibrations generated by machine driveline components can cause excessive noise and structural damage. Magnetostrictive materials, including Galfenol (iron-gallium alloys) and Terfenol-D (terbium-iron-dysprosium alloys), are able to convert mechanical energy to magnetic energy. A magnetostrictive vibration ring is proposed, which generates electrical energy and dampens vibration, when installed in a machine driveline. A 2D axisymmetric finite element (FE) model incorporating magnetic, mechanical, and electrical dynamics is constructed in COMSOL Multiphysics. Based on the model, a parametric study considering magnetostrictive material geometry, pickup coil size, bias magnet strength, flux path design, and electrical load is conducted to maximize loss factor and average electrical output power. By connecting various resistive loads to the pickup coil, the maximum loss factors for Galfenol and Terfenol-D due to electrical energy loss are identified as 0.14 and 0.34, respectively. The maximum average electrical output power for Galfenol and Terfenol-D is 0.21 W and 0.58 W, respectively. The loss factors for Galfenol and Terfenol-D are increased to 0.59 and 1.83, respectively, by using an L-C resonant circuit.
Vibrational and rotational relaxation times of solvated molecular ions
Li, M.; Owrutsky, J.; Sarisky, M.; Culver, J. P.; Yodh, A.; Hochstrasser, R. M.
1993-04-01
Infrared pump-probe and infrared polarization spectroscopy have been used to measure the vibrational relaxation times (T1) of the antisymmetric stretching mode and the reorientation times (TR) for N3-, NCS-, and NCO- in D2O and/or methanol. For N3-, experiments were also conducted in H2O and hexamethyl-phosphamide (HPMA) solutions. The rapid vibrational relaxation and slow reorientation observed demonstrate strong coupling between the ions and the solvents. Longer vibrational relaxation and shorter reorientation times measured for NCS- reveal weaker solvent interactions that may be due to the importance of the charge distribution and the form of the normal coordinate. A comparison of the T1 and TR times in different solvents permits a determination of the relative interaction strengths for the solvents investigated. The relatively weaker coupling of N3- in the aprotic solvent HMPA demonstrates the importance of hydrogen bonding in strong solvent interactions in ionic solutions. The experimental results are compared with recent molecular dynamics simulations of ionic solutions.
Characteristics of steady vibration in a rotating hub-beam system
Zhao, Zhen; Liu, Caishan; Ma, Wei
2016-02-01
A rotating beam features a puzzling character in which its frequencies and modal shapes may vary with the hub's inertia and its rotating speed. To highlight the essential nature behind the vibration phenomena, we analyze the steady vibration of a rotating Euler-Bernoulli beam with a quasi-steady-state stretch. Newton's law is used to derive the equations governing the beam's elastic motion and the hub's rotation. A combination of these equations results in a nonlinear partial differential equation (PDE) that fully reflects the mutual interaction between the two kinds of motion. Via the Fourier series expansion within a finite interval of time, we reduce the PDE into an infinite system of a nonlinear ordinary differential equation (ODE) in spatial domain. We further nondimensionalize the ODE and discretize it via a difference method. The frequencies and modal shapes of a general rotating beam are then determined numerically. For a low-speed beam where the ignorance of geometric stiffening is feasible, the beam's vibration characteristics are solved analytically. We validate our numerical method and the analytical solutions by comparing with either the past experiments or the past numerical findings reported in existing literature. Finally, systematic simulations are performed to demonstrate how the beam's eigenfrequencies vary with the hub's inertia and rotating speed.
Vibrationally assisted electron transfer mechanism of olfaction: myth or reality?
Solov'yov, Ilia A; Chang, Po-Yao; Schulten, Klaus
2012-10-28
Smell is a vital sense for animals. The mainstream explanation of smell is based on recognition of the odorant molecules through characteristics of their surface, e.g., shape, but certain experiments suggest that such recognition is complemented by recognition of vibrational modes. According to this suggestion an olfactory receptor is activated by electron transfer assisted through odorant vibrational excitation. The hundreds to thousands of different olfactory receptors in an animal recognize odorants over a discriminant landscape with surface properties and vibrational frequencies as the two major dimensions. In the present paper we introduce the vibrationally assisted mechanism of olfaction and demonstrate for several odorants that, indeed, a strong enhancement of an electron tunneling rate due to odorant vibrations can arise. We discuss in this regard the influence of odorant deuteration and explain, thereby, recent experiments performed on Drosophila melanogaster. Our demonstration is based on known physical properties of biological electron transfer and on ab initio calculations on odorants carried out for the purpose of the present study. We identify a range of physical characteristics which olfactory receptors and odorants must obey for the vibrationally assisted electron transfer mechanism to function. We argue that the stated characteristics are feasible for realistic olfactory receptors, noting, though, that the receptor structure presently is still unknown, but can be studied through homology modeling.
Vibrationally coupled electron transport through single-molecule junctions
Energy Technology Data Exchange (ETDEWEB)
Haertle, Rainer
2012-04-26
Single-molecule junctions are among the smallest electric circuits. They consist of a molecule that is bound to a left and a right electrode. With such a molecular nanocontact, the flow of electrical currents through a single molecule can be studied and controlled. Experiments on single-molecule junctions show that a single molecule carries electrical currents that can even be in the microampere regime. Thereby, a number of transport phenomena have been observed, such as, for example, diode- or transistor-like behavior, negative differential resistance and conductance switching. An objective of this field, which is commonly referred to as molecular electronics, is to relate these transport phenomena to the properties of the molecule in the contact. To this end, theoretical model calculations are employed, which facilitate an understanding of the underlying transport processes and mechanisms. Thereby, one has to take into account that molecules are flexible structures, which respond to a change of their charge state by a profound reorganization of their geometrical structure or may even dissociate. It is thus important to understand the interrelation between the vibrational degrees of freedom of a singlemolecule junction and the electrical current flowing through the contact. In this thesis, we investigate vibrational effects in electron transport through singlemolecule junctions. For these studies, we calculate and analyze transport characteristics of both generic and first-principles based model systems of a molecular contact. To this end, we employ a master equation and a nonequilibrium Green's function approach. Both methods are suitable to describe this nonequilibrium transport problem and treat the interactions of the tunneling electrons on the molecular bridge non-perturbatively. This is particularly important with respect to the vibrational degrees of freedom, which may strongly interact with the tunneling electrons. We show in detail that the resulting
Electronic and Vibrational Coherences in Algal Light-Harvesting Proteins
Directory of Open Access Journals (Sweden)
Scholes Gregory D.
2013-03-01
Full Text Available We present broadband two-dimensional electronic spectra of a lightharvesting protein from photosynthetic algae. Analysis of the spectra show that the amplitude of the main cross peak oscillates as a function of the waiting time period. Both electronic coupling and intramolecular vibrational modes, and their mixture, can lead to such oscillations. Using predictions based on models of four-level systems, we describe ways to distinguish electronic from vibrational contributions to the coherence and find that both types of coupling contribute to the measured dynamics.
Investigation of gyroscopic effects in vibrating fluid-filled cylinders subjected to axial rotation
CSIR Research Space (South Africa)
Shatalov, MY
2007-07-01
Full Text Available of the theory of gyroscopic effects in distributed structures. The model of a thick vibrating cylinder filled with a fluid and subjected to inertial rotation is analyzed. The dynamics of the cylinder is considered in terms of linear elasticity and the fluid...
An analysis of vibration-rotation lines of OH in the solar infrared spectrum
Grevesse, N.; Sauval, A.J.; Dishoeck, van E.F.
1984-01-01
High resolution solar spectra have permitted the measurement with great accuracy of equivalent widths of vibration-rotation lines of OH in the X2Pi state near 3-micron wavelength. Using recent theoretical results for the transition probabilities, a solar oxygen abundance of (8.93 + or - 0.02) is
Charge transport in DNA model with vibrational and rotational coupling motions
National Research Council Canada - National Science Library
Ngoubi, H; Ben-Bolie, G H; Kofané, T C
2017-01-01
The dynamics of the Peyrard-Bishop model for vibrational motion of DNA dynamics, which has been extended by taking into account the rotational motion for the nucleotides (Silva et al., J. Biol. Phys. 34, 511–519, 2018) is studied...
Rotation-vibrational spectra of diatomic molecules and nuclei with Davidson interactions
Rowe, D J
1998-01-01
Complete rotation-vibrational spectra and electromagnetic transition rates are obtained for Hamiltonians of diatomic molecules and nuclei with Davidson interactions. Analytical results are derived by dynamical symmetry methods for diatomic molecules and a liquid-drop model of the nucleus. Numerical solutions are obtained for a many-particle nucleus with quadrupole Davidson interactions within the framework of the microscopic symplectic model. (author)
Vibration-rotation bands of CH in the solar infrared spectrum and the solar carbon abundance
Grevesse, N.; Lambert, D.L.; Sauval, A.J.; Dishoeck, van E.F.; Farmer, C.B.; Norton, R.H.
1991-01-01
High resolution solar spectra obtained from the ATMOS Fourier Transform Spectrometer (Spacelab 3 flight on April 29-May 6, 1985) have made it possible to identify and measure a large number of lines of the vibration-rotation fundamental bands of the X2 Pi state of CH. From about 100 lines of the
Active Lubrication: Feasibility and Limitations on Reducing Vibration in Rotating Machinery
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2003-01-01
In the present work, experimental results show the feasibility of reducing the amplitude of resonance peaks in rotor-bearing test rig, in the frequency domain, by using active lubricated bearings. The most important consequence of this vibration reduction in rotating machines is the feasibility...
Self-Tuning Vibration Control of a Rotational Flexible Timoshenko Arm Using Neural Networks
Directory of Open Access Journals (Sweden)
Minoru Sasaki
2012-01-01
Full Text Available A self-tuning vibration control of a rotational flexible arm using neural networks is presented. To the self-tuning control system, the control scheme consists of gain tuning neural networks and a variable-gain feedback controller. The neural networks are trained so as to make the root moment zero. In the process, the neural networks learn the optimal gain of the feedback controller. The feedback controller is designed based on Lyapunov's direct method. The feedback control of the vibration of the flexible system is derived by considering the time rate of change of the total energy of the system. This approach has the advantage over the conventional methods in the respect that it allows one to deal directly with the system's partial differential equations without resorting to approximations. Numerical and experimental results for the vibration control of a rotational flexible arm are discussed. It verifies that the proposed control system is effective at controlling flexible dynamical systems.
Directory of Open Access Journals (Sweden)
Farzad Ebrahimia
Full Text Available AbstractFree vibration analysis of rotating functionally graded (FG thick Timoshenko beams is presented. The material properties of FG beam vary along the thickness direction of the constituents according to power law model. Governing equations are derived through Hamilton's principle and they are solved applying differential transform method. The good agreement between the results of this article and those available in literature validated the presented approach. The emphasis is placed on investigating the effect of several beam parameters such as constituent volume fractions, slenderness ratios, rotational speed and hub radius on natural frequencies and mode shapes of the rotating thick FG beam.
Energy Technology Data Exchange (ETDEWEB)
Wang, Haobin, E-mail: haobin.wang@ucdenver.edu [Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364 (United States); Thoss, Michael [Institut für Theoretische Physik und Interdisziplinäres Zentrum für Molekulare Materialien, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7/B2, D-91058 (Germany)
2016-12-20
The accuracy of the noninteracting electron approximation is examined for a model of vibrationally coupled electron transport in single molecule junction. In the absence of electronic-vibrational coupling, steady state transport in this model is described exactly by Landauer theory. Including coupling, both electronic-vibrational and vibrationally induced electron–electron correlation effects may contribute to the real time quantum dynamics. Using the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) theory to describe nuclear dynamics exactly while maintaining the noninteracting electron approximation for the electronic dynamics, the correlation effects are analyzed in different physical regimes. It is shown that although the noninteracting electron approximation may be reasonable for describing short time dynamics, it does not give the correct long time limit for certain initial conditions.
Directory of Open Access Journals (Sweden)
Ernesto Altshuler
Full Text Available While "vibrational noise" induced by rotating components of machinery is a common problem constantly faced by engineers, the controlled conversion of translational into rotational motion or vice-versa is a desirable goal in many scenarios ranging from internal combustion engines to ultrasonic motors. In this work, we describe the underlying physics after isolating a single degree of freedom, focusing on devices that convert a vibration along the vertical axis into a rotation around this axis. A typical Vibrot (as we label these devices consists of a rigid body with three or more cantilevered elastic legs attached to its bottom at an angle. We show that these legs are capable of transforming vibration into rotation by a "ratchet effect", which is caused by the anisotropic stick-slip-flight motion of the leg tips against the ground. Drawing an analogy with the Froude number used to classify the locomotion dynamics of legged animals, we discuss the walking regime of these robots. We are able to control the rotation frequency of the Vibrot by manipulating the shaking amplitude, frequency or waveform. Furthermore, we have been able to excite Vibrots with acoustic waves, which allows speculating about the possibility of reducing the size of the devices so they can perform tasks into the human body, excited by ultrasound waves from the outside.
An Efficient Method of Vibration Diagnostics For Rotating Machinery Using a Decision Tree
Directory of Open Access Journals (Sweden)
Bo Suk Yang
2000-01-01
Full Text Available This paper describes an efficient method to automatize vibration diagnosis for rotating machinery using a decision tree, which is applicable to vibration diagnosis expert system. Decision tree is a widely known formalism for expressing classification knowledge and has been used successfully in many diverse areas such as character recognition, medical diagnosis, and expert systems, etc. In order to build a decision tree for vibration diagnosis, we have to define classes and attributes. A set of cases based on past experiences is also needed. This training set is inducted using a result-cause matrix newly developed in the present work instead of using a conventionally implemented cause-result matrix. This method was applied to diagnostics for various cases taken from published work. It is found that the present method predicts causes of the abnormal vibration for test cases with high reliability.
Sun, Dongming; Wang, Sheng; Hata, Seiichi; Sakurai, Junpei; Shimokohbe, Akira
2009-03-01
A thin film rotating sputtering system is presented for fabrication of a circular cylindrical shell (CCS). The length, diameter, and thickness of the CCS are 5.0 mm, 1.5 mm, and 25 mum, respectively. To investigate the vibration characteristics, the CCS is fabricated on the outer surface of a piezoelectric ceramic tube (PCT). The vibration of PCT excited by driving voltage signals causes the vibration of the CCS, and the vibration characteristics can be measured using a laser Doppler vibrometer system. Furthermore, a finite element method (FEM) simulation and 2 analytical calculation methods are proposed for comparison with the measurement results. The frequency factor, the key factor that dominates the effective ranges of the 2 analytical methods, is determined as a value of 0.92 through a series of discussions. Combining the results of the 2 analytical calculation methods, good agreement of the analytical, FEM, and measurement results is obtained.
Electronic and vibrational spectroscopy and vibrationally mediated photodissociation of V+(OCO).
Citir, Murat; Altinay, Gokhan; Metz, Ricardo B
2006-04-20
Electronic spectra of gas-phase V+(OCO) are measured in the near-infrared from 6050 to 7420 cm(-1) and in the visible from 15,500 to 16,560 cm(-1), using photofragment spectroscopy. The near-IR band is complex, with a 107 cm(-1) progression in the metal-ligand stretch. The visible band shows clearly resolved vibrational progressions in the metal-ligand stretch and rock, and in the OCO bend, as observed by Brucat and co-workers. A vibrational hot band gives the metal-ligand stretch frequency in the ground electronic state nu3'' = 210 cm(-1). The OCO antisymmetric stretch frequency in the ground electronic state (nu1'') is measured by using vibrationally mediated photodissociation. An IR laser vibrationally excites ions to nu1'' = 1. Vibrationally excited ions selectively dissociate following absorption of a second, visible photon at the nu1' = 1 CO2, due to interaction with the metal. Larger blue shifts observed for complexes with fewer ligands agree with trends seen for larger V+(OCO)n clusters.
Vibrational kinetics of electronically excited states in H2 discharges
Colonna, Gianpiero; Pietanza, Lucia D.; D'Ammando, Giuliano; Celiberto, Roberto; Capitelli, Mario; Laricchiuta, Annarita
2017-11-01
The evolution of atmospheric pressure hydrogen plasma under the action of repetitively ns electrical pulse has been investigated using a 0D state-to-state kinetic model that self-consistently couples the master equation of heavy particles and the Boltzmann equation for free electrons. The kinetic model includes, together with atomic hydrogen states and the vibrational kinetics of H2 ground state, vibrational levels of singlet states, accounting for the collisional quenching, having a relevant role because of the high pressure. The mechanisms of excitations, radiative decay and collisional quenching involving the excited H2 states and the corresponding cross sections, integrated over the non-equilibrium electron energy distribution function (EEDF) to obtain kinetic rates, are discussed in the light of the kinetic simulation results, i.e. the time evolution during the pulse of the plasma composition, of the EEDF and of the vibrational distributions of ground and singlet excited states.
Final Report: Vibrational Dynamics in Photoinduced Electron Transfer
Energy Technology Data Exchange (ETDEWEB)
Kenneth G. Spears
2006-04-19
The objective of this grant was to understand how molecular vibrational states (geometry distortions) are involved in photoinduced electron transfer rates of molecules. This subject is an important component of understanding how molecular absorbers of light convert that energy into charge separation. This is important because the absorption usually excites molecular vibrations in a new electronic state prior to electron transfer to other molecules or semiconductor nanoparticles, as in some types of solar cells. The speeds of charge separation and charge recombination are key parameters that require experiments such as those in this work to test the rules governing electron transfer rates. Major progress was made on this goal. Some of the molecular structures selected for developing experimental data were bimolecular charge transfer complexes that contained metals of cobalt or vanadium. The experiments used the absorption of an ultrafast pulse of light to directly separate charges onto the two different molecular parts of the complex. The charge recombination then proceeds naturally, and one goal was to measure the speed of this recombination for different types of molecular vibrations. We used picosecond and femtosecond duration pulses with tunable colors at infrared wavelengths to directly observe vibrational states and their different rates of charge recombination (also called electron transfer). We discovered that different contact geometries in the complexes had very different electron transfer rates, and that one geometry had a significant dependence on the amount of vibration in the complex. This is the first and only measurement of such rates, and it allowed us to confirm our interpretation with a number of molecular models and test the sensitivity of electron transfer to vibrational states. This led us to develop a general theory, where we point out how molecular distortions can change the electron transfer rates to be much faster than prior theories
Subrahmanyam, K. B.; Kaza, K. R. V.
1985-01-01
Theoretical natural frequencies of the first three modes of torsional vibration of pretwisted, rotating cantilever beams are determined for various thickness and aspect ratios. Conclusions concerning individual and collective effects of warping, pretwist, tension-torsion coupling and tennis racket effect (twist-rotational coupling) terms on the natural frequencies are drawn from numerical results obtained by using a finite difference procedure with first order central differences. The relative importance of structural warping, inertial warping, pretwist, tension-torsion and twist-rotational coupling terms is discussed for various rotational speeds. The accuracy of results obtained by using the finite difference approach is verified by a comparison with the exact solution for specialized simple cases of the equation of motion used in this paper.
Low energy electron impact vibrational excitation of acetylene
Patra, Sigma; Hargreaves, Leigh; Khakoo, Murtadha
2016-05-01
Experimental differential cross sections for the vibration excitation of the four fundamental modes of acetylene at low incident electron energies from 1 eV to 20 eV and scattering angles of 10o to 130o will be presented. The results will be compared to results available in the literature. Funded by NSF-AMOP-RUI Grant.
Inelastic vibrational signals in electron transport across graphene nanoconstrictions
DEFF Research Database (Denmark)
Gunst, Tue; Markussen, Troels; Stokbro, Kurt
2016-01-01
We present calculations of the inelastic vibrational signals in the electrical current through a graphene nanoconstriction. We find that the inelastic signals are only present when the Fermi-level position is tuned to electron transmission resonances, thus, providing a fingerprint which can link ...
DEFF Research Database (Denmark)
Kuznetsov, A.M.; Ulstrup, Jens
2002-01-01
, corresponding to the fully diabatic limit. The rectification process then reduces to a sequence of vibrationally relaxed single-electron transfer steps. In the limits where the interactions are strong, denoted as the partially and fully adiabatic limits, the character of the rectification process is different......, and electron flow proceeds coherently, without vibrational relaxation. In still another class of mechanisms the electronic level broadening of either donor or acceptor from the adjacent electrode is so strong that it is comparable to the vibrational broadening. The process then reduces to a three...
Huo, Winifred M.; Langhoff, Stephen R. (Technical Monitor)
1995-01-01
At high altitudes and velocities equal to or greater than the geosynchronous return velocity (10 kilometers per second), the shock layer of a hypersonic flight will be in thermochemical nonequilibrium and partially ionized. The amount of ionization is determined by the velocity. For a trans atmospheric flight of 10 kilometers per second and at an altitude of 80 kilometers, a maximum of 1% ionization is expected. At a velocity of 12 - 17 kilometer per second, such as a Mars return mission, up to 30% of the atoms and molecules in the flow field will be ionized. Under those circumstances, electrons play an important role in determining the internal states of atoms and molecules in the flow field and hence the amount of radiative heat load and the distance it takes for the flow field to re-establish equilibrium. Electron collisions provide an effective means of transferring energy even when the electron number density is as low as 1%. Because the mass of an electron is 12,760 times smaller than the reduced mass of N2, its average speed, and hence its average collision frequency, is more than 100 times larger. Even in the slightly ionized regime with only 1% electrons, the frequency of electron-molecule collisions is equal to or larger than that of molecule-molecule collisions, an important consideration in the low density part of the atmosphere. Three electron-molecule collision processes relevant to hypersonic flows will be considered: (1) vibrational excitation/de-excitation of a diatomic molecule by electron impact, (2) electronic excitation/de-excitation, and (3) dissociative recombination in electron-diatomic ion collisions. A review of available data, both theory and experiment, will be given. Particular attention will be paid to tailoring the molecular physics to the condition of hypersonic flows. For example, the high rotational temperatures in a hypersonic flow field means that most experimental data carried out under room temperatures are not applicable. Also
Tuned liquid column dampers for mitigation of edgewise vibrations in rotating wind turbine blades
DEFF Research Database (Denmark)
Zhang, Zili; Basu, Biswajit; Nielsen, Søren R.K.
2015-01-01
Edgewise vibrations in wind turbine blades are lightly damped, and large amplitude vibrations induced by the turbulence may significantly shorten the fatigue life of the blade. This paper investigates the performance of tuned liquid column dampers (TLCDs) for mitigating edgewise vibrations...... are the mounting position, the mass ratio, the geometries, and the head loss coefficient of the damper. Based on a reduced 2-DOF nonlinear model developed by the authors, the optimization of these parameters are carried out by minimizing the standard deviation of the edgewise tip displacement...... and the aerodynamic damping presented in different modes. Various turbulence intensities and rotational speeds of the rotor have been considered to evaluate the performance of the TLCD. Further, the optimized damper is incorporated into the 13-DOF model to verify the application of the decoupled optimization...
Molecular rotation-vibration dynamics of low-symmetric hydrate crystal in the terahertz region.
Fu, Xiaojian; Wu, Hongya; Xi, Xiaoqing; Zhou, Ji
2014-01-16
The rotational and vibrational dynamics of molecules in copper sulfate pentahydrate crystal are investigated with terahertz dielectric spectra. It is shown that the relaxation-like dielectric dispersion in the low frequency region is related to the reorientation of water molecules under the driving of terahertz electric field, whereas the resonant dispersion can be ascribed to lattice vibration. It is also found that, due to the hydrogen-bond effect, the vibrational mode at about 1.83 THz along [-111] direction softens with decreasing temperature, that is, the crystal expands in this direction when cooled. On the contrary, the mode hardens in the direction perpendicular to [-111] during the cooling process. This contributes to the further understanding of the molecular structure and bonding features of hydrate crystals.
Femtochemistry in the electronic ground state: Dynamic Stark control of vibrational dynamics
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Thomas, Esben Folger; Henriksen, Niels Engholm
2017-01-01
We study the interplay of vibrational and rotational excitation in a diatomic molecule due to the non-resonant dynamic Stark effect. With a fixed peak intensity, optimal Gaussian pulse durations for maximizing vibrational or rotational transitions are obtained analytically and confirmed numerically...
Li, Chuan; Sánchez, René-Vinicio; Zurita, Grover; Cerrada, Mariela; Cabrera, Diego
2016-06-17
Fault diagnosis is important for the maintenance of rotating machinery. The detection of faults and fault patterns is a challenging part of machinery fault diagnosis. To tackle this problem, a model for deep statistical feature learning from vibration measurements of rotating machinery is presented in this paper. Vibration sensor signals collected from rotating mechanical systems are represented in the time, frequency, and time-frequency domains, each of which is then used to produce a statistical feature set. For learning statistical features, real-value Gaussian-Bernoulli restricted Boltzmann machines (GRBMs) are stacked to develop a Gaussian-Bernoulli deep Boltzmann machine (GDBM). The suggested approach is applied as a deep statistical feature learning tool for both gearbox and bearing systems. The fault classification performances in experiments using this approach are 95.17% for the gearbox, and 91.75% for the bearing system. The proposed approach is compared to such standard methods as a support vector machine, GRBM and a combination model. In experiments, the best fault classification rate was detected using the proposed model. The results show that deep learning with statistical feature extraction has an essential improvement potential for diagnosing rotating machinery faults.
Fault Diagnosis for Rotating Machinery Using Vibration Measurement Deep Statistical Feature Learning
Li, Chuan; Sánchez, René-Vinicio; Zurita, Grover; Cerrada, Mariela; Cabrera, Diego
2016-01-01
Fault diagnosis is important for the maintenance of rotating machinery. The detection of faults and fault patterns is a challenging part of machinery fault diagnosis. To tackle this problem, a model for deep statistical feature learning from vibration measurements of rotating machinery is presented in this paper. Vibration sensor signals collected from rotating mechanical systems are represented in the time, frequency, and time-frequency domains, each of which is then used to produce a statistical feature set. For learning statistical features, real-value Gaussian-Bernoulli restricted Boltzmann machines (GRBMs) are stacked to develop a Gaussian-Bernoulli deep Boltzmann machine (GDBM). The suggested approach is applied as a deep statistical feature learning tool for both gearbox and bearing systems. The fault classification performances in experiments using this approach are 95.17% for the gearbox, and 91.75% for the bearing system. The proposed approach is compared to such standard methods as a support vector machine, GRBM and a combination model. In experiments, the best fault classification rate was detected using the proposed model. The results show that deep learning with statistical feature extraction has an essential improvement potential for diagnosing rotating machinery faults. PMID:27322273
Rotation of the apparent vibration plane of a swinging spring at the 1:1:2 resonance
Petrov, A. G.
2017-05-01
Nonlinear spatial vibrations of a mass point on a weightless elastic suspension (pendulum on a spring) are considered. The frequency of vertical vibrations is assumed to be equal to the doubled swinging frequency (the 1:1:2 resonance). In this case, as numerical calculations and experiments show, the vertical vibrations are unstable, which leads to the vertical vibration energy transfer to the pendulum swinging energy. The vertical vibrations of the mass point decay and, after a certain time period, the pendulum starts swinging in a certain vertical plane. This swinging is also unstable, which results in the reverse energy transfer into the vertical vibration mode. The vertical vibrations are again repeated. But after the second transfer of the vertical vibration energy to the pendulum swinging energy, the apparent plane of vibrations rotates by a certain angle. These effects are described analytically; namely, the energy transfer period, the time variations in the amplitudes of both modes, and the variations in the angle of the apparent vibration plane are determined. An asymptotic solution is also constructed for the mass point trajectory in the orbit elements. In projection on the horizonal plane, the mass point moves in a nearly elliptic trajectory. The ellipse semiaxes slowly vary with time, so that their product remains constant, and the major semiaxis slowly rotates at a constant sectorial velocity. The obtained analytic time dependence of the ellipse semiaxes and the precession angle agree well with the results of numerical calculations.
Amplifying vibrational circular dichroism by manipulation of the electronic manifold.
Domingos, Sérgio R; Panman, Matthijs R; Bakker, Bert H; Hartl, Frantisek; Buma, Wybren J; Woutersen, Sander
2012-01-11
Vibrational circular dichroism is a powerful technique to study the stereochemistry of chiral molecules, but often suffers from small signal intensities. Electrochemical modulation of the energies of the electronically excited state manifold is now demonstrated to lead to an order of magnitude enhancement of the differential absorption. Quantum-chemical calculations show that increased mixing between ground and excited states is at the origin of this amplification. This journal is © The Royal Society of Chemistry 2012
Johnson, Jeremy A; Kim, Kilyoung; Mayhew, Maurine; Mitchell, Deborah G; Sevy, Eric T
2008-03-27
Relaxation of highly vibrationally excited pyridine (C5NH5) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot pyridine (E' = 40,660 cm(-1)) was prepared by 248 nm excimer laser excitation followed by rapid radiationless relaxation to the ground electronic state. Pyridine then collides with CO2, populating the high rotational CO2 states with large amounts of translational energy. The CO2 nascent rotational population distribution of the high-J (J = 58-80) tail of the 00(0)0 state was probed at short times following the excimer laser pulse to measure rate constants and probabilities for collisions populating these CO2 rotational states. Doppler spectroscopy was used to measure the CO2 recoil velocity distribution for J = 58-80 of the 00(0)0 state. The energy-transfer distribution function, P(E,E'), from E' - E approximately 1300-7000 cm(-1) was obtained by re-sorting the state-indexed energy-transfer probabilities as a function of DeltaE. P(E,E') is fit to an exponential or biexponential function to determine the average energy transferred in a single collision between pyridine and CO2. Also obtained are fit parameters that can be compared to previously studied systems (pyrazine, C6F6, methylpyrazine, and pyrimidine/CO2). Although the rotational and translational temperatures that describe pyridine/CO2 energy transfer are similar to previous systems, the energy-transfer probabilities are much smaller. P(E,E') fit parameters for pyridine/CO2 and the four previously studied systems are compared to various donor molecular properties. Finally, P(E,E') is analyzed in the context of two models, one indicating that P(E,E') shape is primarily determined by the low-frequency out-of-plane donor vibrational modes, and the other that indicates that P(E,E') shape can be determined from how the donor molecule final density of states changes with DeltaE.
Hierarchies of intramolecular vibration-rotation dynamical processes in acetylene up to 13,000 cm-1
Perry, David S.; Martens, Jonathan; Amyay, Badr; Herman, Michel
2012-11-01
The vibration-rotation dynamics of ? acetylene are computed from a spectroscopic Hamiltonian with 468 parameters fit to 19,582 vibration-rotation transitions up to 13,000 cm-1 of vibrational energy. In this energy range, both the bending and the CH stretching vibrations can reach large amplitudes, but the maximum energy remains below the threshold for isomerization to vinylidene. In contrast to the behavior at energies below 5000 cm-1 [Mol. Phys. 108, 1115 (2010)], excitation of single bright states leads, in almost all cases, to computed intramolecular vibrational redistribution (IVR) that is irreversible on the timescales investigated. Hierarchies of IVR processes on timescales ranging from 20 fs to 20 ps result when different bright states are excited. Different parts of the vibrational quantum number space are explored as a result of the four different classes of coupling terms: vibrational l-type resonance, anharmonic resonances, the rotational l-type resonance, and Coriolis couplings. The initial IVR rates are very different depending on whether the bright states are bending states or stretching states, normal modes or local modes, edge states or interior states. However, the rates of the rotationally mediated couplings do not depend substantially on these distinctions.
Evangelisti, Luca; Holdren, Martin S.; Mayer, Kevin J.; Smart, Taylor; West, Channing; Pate, Brooks
2017-06-01
The absolute configuration of 3-methylcyclohexanone was established by chiral tag rotational spectroscopy measurements using 3-butyn-2-ol as the tag partner. This molecule was chosen because it is a benchmark measurement for vibrational circular dichroism (VCD). A comparison of the analysis approaches of chiral tag rotational spectroscopy and VCD will be presented. One important issue in chiral analysis by both methods is the conformational flexibility of the molecule being analyzed. The analysis of conformational composition of samples will be illustrated. In this case, the high spectral resolution of molecular rotational spectroscopy and potential for spectral simplification by conformational cooling in the pulsed jet expansion are advantages for chiral tag spectroscopy. The computational chemistry requirements for the two methods will also be discussed. In this case, the need to perform conformer searches for weakly bound complexes and to perform reasonably high level quantum chemistry geometry optimizations on these complexes makes the computational time requirements less favorable for chiral tag rotational spectroscopy. Finally, the issue of reliability of the determination of the absolute configuration will be considered. In this case, rotational spectroscopy offers a "gold standard" analysis method through the determination of the ^{13}C-subsitution structure of the complex between 3-methylcyclohexanone and an enantiopure sample of the 3-butyn-2-ol tag.
A nonlinear circular ring model with rotating effects for tire vibrations
Vu, Trong Dai; Duhamel, Denis; Abbadi, Zouhir; Yin, Hai-Ping; Gaudin, Arnaud
2017-02-01
Rolling noise contributes significantly to the noise inside cars. This noise comes from the tire/road contact and for low frequencies (0-400 Hz), it is mainly transmitted into the cabin through structural vibrations. Thus estimating this noise requires modelling the tire vibrations by taking into account the rotating effects and the contact with rough surfaces. Concerning the model of rolling tire, a formulation of a deformable solid is constructed by using an Arbitrary Lagrangian Eulerian approach. This formulation is applied on a new simplified tire model which is a circular ring including shear stresses and nonlinear effects due to the vehicle load. This model is successfully validated by comparison with FEM results.
Directory of Open Access Journals (Sweden)
S. Khajehpour
Full Text Available AbstractIn this study, the governing equations of a rotating cantilever pipe conveying fluid are derived and the longitudinal and lateral induced vibrations are controlled. The pipe considered as an Euler Bernoulli beam with tip mass which piezoelectric layers attached both side of it as sensors and actuators. The follower force due to the fluid discharge causes both conservative and non-conservative work. For mathematical modeling, the Lagrange-Rayleigh-Ritz technique is utilized. An adaptive-robust control scheme is applied to suppress the vibration of the pipe. The adaptive-robust control method is robust against parameter uncertainties and disturbances. Finally, the system is simulated and the effects of varying parameters are studied. The simulation results show the excellent performance of the controller.
Rotational total skin electron irradiation with a linear accelerator.
Reynard, Eric P; Evans, Michael D C; Devic, Slobodan; Parker, William; Freeman, Carolyn R; Roberge, David; Podgorsak, Ervin B
2008-11-03
The rotational total skin electron irradiation (RTSEI) technique at our institution has undergone several developments over the past few years. Replacement of the formerly used linear accelerator has prompted many modifications to the previous technique. With the current technique, the patient is treated with a single large field while standing on a rotating platform, at a source-to-surface distance of 380 cm. The electron field is produced by a Varian 21EX linear accelerator using the commercially available 6 MeV high dose rate total skin electron mode, along with a custom-built flattening filter. Ionization chambers, radiochromic film, and MOSFET (metal oxide semiconductor field effect transistor) detectors have been used to determine the dosimetric properties of this technique. Measurements investigating the stationary beam properties, the effects of full rotation, and the dose distributions to a humanoid phantom are reported. The current treatment technique and dose regimen are also described.
Ab initio vibration rotation spectra of triterated isotopologues of H3+
Amin, Amit; Nazareth, Jude; Tennyson, Jonathan
2008-11-01
Vibration-rotation energy levels for T3+, H 2T +, T 2H +, D 2T + and T 2D + are reported. These were calculated using the high accuracy model of Polyansky and Tennyson (J. Chem. Phys. 110 (1999) 5056) which explicitly allows for both adiabatic and non-adiabatic corrections to the Born-Oppenheimer approximation. These levels should be reliable to better than 0.05 cm -1 and can thus be used to make reliable predictions of infrared spectra for the triterated H3+ species.
On a Self-Tuning Impact Vibration Damper for Rotating Turbomachinery
Duffy, Kirsten P.; Bagley, Ronald L.; Mehmed, Oral; Choi, Ben (Technical Monitor)
2000-01-01
A self-tuning impact damper is investigated analytically and experimentally as a device to inhibit vibration and increase the fatigue life of rotating components in turbomachinery. High centrifugal loads in rotors can inactivate traditional impact dampers because of friction or misalignment of the damper in the g-field. Giving an impact damper characteristics of an acceleration tuned-mass damper enables the resulting device to maintain damper mass motion and effectiveness during high-g loading. Experimental results presented here verify that this self-tuning impact damper can be designed to follow an engine order line. damping rotor component resonance crossings.
The vibration of a layered rotating planet and Bryan’s effect
CSIR Research Space (South Africa)
Shatalov, MY
2011-12-01
Full Text Available to distinguish between spheroidal and torsional modes. For the spheroidal mode we assume that ?i = 0. In this case the stress components of the 413The Vibration of a Layered Rotating Planet and Bryan?s Effect 10 Will-be-set-by-IN-TECH solids are ?i,rr = [ 2...?. For the investigation of the torsional modes we assume that ?i = 0 and ?i = 0 and hence the corresponding stress components are ?i,r? = ?i a sin ? ? ?? ( ??i ?r ? ?i r ) , (53a) ?i,r? = ? ?i a ? ?? ( ??i ?r ? ?i r ) . (53b) Let us model a...
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Lutao Yan
2013-01-01
Full Text Available This paper presents a new vibration based electromagnetic power generator to transfer energy from stationary to rotating equipment, which can be a new attempt to substitute slip ring in rotational systems. The natural frequencies and modes are simulated in order to have a maximum and steady power output from the device. Parameters such as piezoelectric disk location and relative motion direction of the magnet are theoretically and experimentally analyzed. The results show that the position that is close to the fixed end of the cantilever and the relative motion along the long side gives higher power output. Moreover, the capability of the energy harvester to extract power from lower energy environment is experimentally validated. The voltage and power output are measured at different excitation frequencies.
Electronic and vibrational circular dichroism spectra of (R)-(-)-apomorphine
Energy Technology Data Exchange (ETDEWEB)
Abbate, Sergio, E-mail: abbate@med.unibs.it [Dipartimento di Scienze Biomediche e Biotecnologie, Universita di Brescia, Viale Europa 11, 25123 Brescia (Italy); CNISM, Consorzio Interuniversitario Scienze Fisiche della Materia, Via della Vasca Navale 84, 00146 Roma (Italy); Longhi, Giovanna; Lebon, France [Dipartimento di Scienze Biomediche e Biotecnologie, Universita di Brescia, Viale Europa 11, 25123 Brescia (Italy); CNISM, Consorzio Interuniversitario Scienze Fisiche della Materia, Via della Vasca Navale 84, 00146 Roma (Italy); Tommasini, Matteo [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' G. Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Consorzio Interuniversitario per la Scienza e Tecnologia dei Materiali (INSTM), Unita di Ricerca del Politecnico di Milano (Dip. CMIC), Piazza Leonardo da Vinci 32, 20133 Milano (Italy)
2012-09-11
Highlights: Black-Right-Pointing-Pointer ECD and VCD Spectra of (R)-(-)-apomorphine measured in various solvents. Black-Right-Pointing-Pointer DFT calculations allow to study the protonation state and conformations. Black-Right-Pointing-Pointer Contributions from catechol OH vibrations to the VCD spectra is studied. -- Abstract: Apomorphine is a chiral drug molecule; notwithstanding its extraordinary importance, little attention has been paid to the characterization of its chiroptical properties. Here we report on its electronic circular dichroism (ECD) spectra, recorded in methanol and water, and vibrational circular dichroism (VCD) in methanol and dimethyl sulfoxide (DMSO) solutions. Density functional theory (DFT) calculations have allowed us to interpret the spectra and to evaluate the role of possible conformations, charge-states and interactions with counter ions.
Dosimetry of rotational partial-skin electron irradiation.
Müller-Sievers, K; Ertan, E; Kober, B
2001-02-01
Often, the most appropriate treatment for superficially and extensively spreading tumors of the skin is to use electron irradiation at enlarged distances. Rotational skin electron irradiation is a proven method for the treatment of the entire skin surface. We here report modifications of this technique in the set-up of partial-skin electron irradiation and the results of dosimetric examinations with regard to optimal shielding, dose profiles and depth dose curves under various irradiation conditions. Irradiation was performed using electron beams with nominal energies of 6 MeV from a linear accelerator. The phantom was located on a rotating platform at a source-surface distance SSD=300 cm. A horizontal slit aperture (height: 32 cm) within a 2 cm thick polymethylmethacrylate (PMMA) shielding plate near the phantom was used to define the size of the irradiated region. Influences on dose distributions due to scattering processes on the PMMA edges were investigated using a flat ionization chamber and films. Absolute dose measurements and film calibration were made with the flat chamber. The quality of bremsstrahlung radiation behind the shielding was determined with a thimble ionization chamber in the phantom. The results of rotational partial-skin electron irradiation reveal some of the investigated shielding geometries to be optimal. Depth dose distributions and dose rates correspond to the results obtained in total skin electron rotational irradiation. It is possible to apply the dose superficially in the first millimeters of the skin; the dose maximum is located at a depth of 0-2 mm, the 80% isodose at 9 mm. The amount of bremsstrahlung contamination is 2.5%. The local amount of absorbed dose per monitor unit depends strongly on patient/phantom cross-section geometry. At our institute, rotational partial-skin electron irradiation was implemented into clinical routine in 1997.
Kosov, Daniel S.
2017-09-01
Quantum transport of electrons through a molecule is a series of individual electron tunneling events separated by stochastic waiting time intervals. We study the emergence of temporal correlations between successive waiting times for the electron transport in a vibrating molecular junction. Using the master equation approach, we compute the joint probability distribution for waiting times of two successive tunneling events. We show that the probability distribution is completely reset after each tunneling event if molecular vibrations are thermally equilibrated. If we treat vibrational dynamics exactly without imposing the equilibration constraint, the statistics of electron tunneling events become non-renewal. Non-renewal statistics between two waiting times τ1 and τ2 means that the density matrix of the molecule is not fully renewed after time τ1 and the probability of observing waiting time τ2 for the second electron transfer depends on the previous electron waiting time τ1. The strong electron-vibration coupling is required for the emergence of the non-renewal statistics. We show that in the Franck-Condon blockade regime, extremely rare tunneling events become positively correlated.
Phase influence of combined rotational and transverse vibrations on the structural response
Habtour, Ed; Sridharan, Raman; Dasgupta, Abhijit; Robeson, Mark; Vantadori, Sabrina
2018-02-01
The planar dynamic response of a cantilever metallic beam structure under combined harmonic base excitations (consisting of in-plane transverse and rotation about the out-of-plane transverse axis) was investigated experimentally. The important effect of the phase angle between the two simultaneous biaxial excitations on the beam tip displacement was demonstrated. The experiments were performed using a unique six degree-of-freedom (6-DoF) electrodynamic shaker with high control accuracy. The results showed that the beam tip displacement at the first flexural mode was amplified when the phase angle between the rotational and translational base excitations was increased. The beam nonlinear stiffness, on the other hand, simultaneously: (i) decreased due to fatigue damage accumulation, and (ii) increased due to an increase in the phase angle. The results were compared to the uniaxial excitation technique, where the principle of superposition was applied (mathematical addition of the structural response for each uniaxial excitation). The principle of superposition was shown to overestimate the structural response for low phase angles. Thus, the application of the superposition vibration testing as a substitute for multiaxial vibration testing may lead to over-conservatism and erroneous dynamic and reliability predictions.
Oliver, Thomas A A; Lewis, Nicholas H C; Fleming, Graham R
2014-07-15
Multidimensional nonlinear spectroscopy, in the electronic and vibrational regimes, has reached maturity. To date, no experimental technique has combined the advantages of 2D electronic spectroscopy and 2D infrared spectroscopy, monitoring the evolution of the electronic and nuclear degrees of freedom simultaneously. The interplay and coupling between the electronic state and vibrational manifold is fundamental to understanding ensuing nonradiative pathways, especially those that involve conical intersections. We have developed a new experimental technique that is capable of correlating the electronic and vibrational degrees of freedom: 2D electronic-vibrational spectroscopy (2D-EV). We apply this new technique to the study of the 4-(di-cyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H-pyran (DCM) laser dye in deuterated dimethyl sulfoxide and its excited state relaxation pathways. From 2D-EV spectra, we elucidate a ballistic mechanism on the excited state potential energy surface whereby molecules are almost instantaneously projected uphill in energy toward a transition state between locally excited and charge-transfer states, as evidenced by a rapid blue shift on the electronic axis of our 2D-EV spectra. The change in minimum energy structure in this excited state nonradiative crossing is evident as the central frequency of a specific vibrational mode changes on a many-picoseconds timescale. The underlying electronic dynamics, which occur on the hundreds of femtoseconds timescale, drive the far slower ensuing nuclear motions on the excited state potential surface, and serve as a excellent illustration for the unprecedented detail that 2D-EV will afford to photochemical reaction dynamics.
Perry, David S.; Miller, Anthony; Amyay, Badr; Fayt, André; Herman, Michel
2010-04-01
The link between energy-resolved spectra and time-resolved dynamics is explored quantitatively for acetylene (12C2H2), ? with up to 8600 cm-1 of vibrational energy. This comparison is based on the extensive and reliable knowledge of the vibration-rotation energy levels and on the model Hamiltonian used to fit them to high precision [B. Amyay, S. Robert, M. Herman, A. Fayt, B. Raghavendra, A. Moudens, J. Thiévin, B. Rowe, and R. Georges, J. Chem. Phys. 131, 114301 (2009)]. Simulated intensity borrowing features in high resolution absorption spectra and predicted survival probabilities in intramolecular vibrational redistribution (IVR) are first investigated for the v 4 + v 5 and v 3 bright states, for J = 2, 30 and 100. The dependence of the results on the rotational quantum number and on the choice of vibrational bright state reflects the interplay of three kinds of off-diagonal resonances: anharmonic, rotational l-type, and Coriolis. The dynamical quantities used to characterize the calculated time-dependent dynamics are the dilution factor φ d, the IVR lifetime τ IVR , and the recurrence time τ rec. For the two bright states v 3 + 2v 4 and 7v 4, the collisionless dynamics for thermally averaged rotational distributions at T = 27, 270 and 500 K were calculated from the available spectroscopic data. For the 7v 4 bright state, an apparent irreversible decay of is found. In all cases, the model Hamiltonian allows a detailed calculation of the energy flow among all of the coupled zeroth-order vibration-rotation states.
The effects of electron beam rotation upon electron beam welded copper-304 couples
Zysk, Kevin Tacy
The United States Air Force, Arnold Engineering Development Center, has been using copper to 304 stainless steel couples made using the electron beam welding process during the fabrication of intrusive gas-path diagnostic probes for over five years. Only a limited physical analysis of the resulting welds had been done. The purpose of this investigation was to determine the effects that varying the rotation frequency of the electron beam had upon the mechanical characteristics of the copper to 304 stainless steel couples. All controllable weld process parameters were held constant with the exception of the electron beam rotation frequency; the rotation frequency was varied from 20 Hz to 180 Hz in steps of 20 Hz. Samples welded without electron beam rotation provided a baseline for comparison. Microhardness distributions showed that weld region homogeneity as evidenced by microhardness maps and optical microscopy was a function of the electron beam rotation frequency. There was no correlation between electron beam rotation frequency and weld tensile strength since each test coupon failed in the Cu base material outside of the weld region. The welds made at all electron beam rotation frequencies used for this study contained cracks within the weld region, heat affected zone (HAZ), or both. The relative number, length, and location of the individual cracks changed with electron beam rotation frequency. Cracking in the HAZ due to liquid metal embrittlement (LME) was not evident in those samples welded with the electron beam rotation frequencies below 100 Hz, Cracking due to LME outside of the weld region in the HAZ was observed to increase with the electron beam rotation frequency above 80 Hz. The relationship between weld region cracking and residual stress within the weld region was shown to be dependent on the electron beam rotation frequency. Cracking in the weld region was not observed in samples welded with the electron beam rotation frequency above 80 Hz
Energy Technology Data Exchange (ETDEWEB)
Tarana, Michal [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440 (United States); Houfek, Karel; Horacek, Jiri [Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University in Prague, V Holesovickach 2, Prague (Czech Republic); Fabrikant, Ilya I. [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)
2011-11-15
We present a study of dissociative electron attachment and vibrational excitation processes in electron collisions with the CF{sub 3}Cl molecule. The calculations are based on the two-dimensional nuclear dynamics including the C-Cl symmetric stretch coordinate and the CF{sub 3} symmetric deformation (umbrella) coordinate. The complex potential energy surfaces are calculated using the ab initio R-matrix method. The results for dissociative attachment and vibrational excitation of the umbrella mode agree quite well with experiment whereas the cross section for excitation of the C-Cl symmetric stretch vibrations is about a factor-of-three too low in comparison with experimental data.
Directory of Open Access Journals (Sweden)
Liang Yonggang
2013-01-01
Full Text Available Classical Amplitude Spectrum analysis and Full Amplitude Spectrum analysis exhibit deficiencies in analyzing the two perpendicular directional vibration displacement signals of a rotating rotor. The shape of Classical Amplitude Spectrum is influenced by the installing position of its sensor. Neither Classical Amplitude Spectrum nor Full Amplitude Spectrum can indicate the actual radial rotor vibration amplitude on every frequency. Therefore, the previous two methods are not convenient to be used in rotating machine diagnoses. To solve these problems, this paper proposes a new rotor vibration analyzing tool here called Synthetic Amplitude Spectrum (SAS. The paper discusses the principle of SAS analysis, provides the specific making process of SAS, and applies it to two other current important analyzing methods in rotating machine diagnoses, resulting in two SAS extensions. The two extensions include a short-time SAS array tool for rotor vibration time-frequency analysis and a SAS waterfall plot tool for analyzing rotor vibration during machine startup or shutdown. The experiments and theoretical analysis showed that SAS and its two extension methods are not influenced by the installation position of the two sensors, and each amplitude of the spectrums can represent the actual radial rotor vibration amplitude on the frequency.
A 3D finite element model for the vibration analysis of asymmetric rotating machines
Lazarus, A.; Prabel, B.; Combescure, D.
2010-08-01
This paper suggests a 3D finite element method based on the modal theory in order to analyse linear periodically time-varying systems. Presentation of the method is given through the particular case of asymmetric rotating machines. First, Hill governing equations of asymmetric rotating oscillators with two degrees of freedom are investigated. These differential equations with periodic coefficients are solved with classic Floquet theory leading to parametric quasimodes. These mathematical entities are found to have the same fundamental properties as classic eigenmodes, but contain several harmonics possibly responsible for parametric instabilities. Extension to the vibration analysis (stability, frequency spectrum) of asymmetric rotating machines with multiple degrees of freedom is achieved with a fully 3D finite element model including stator and rotor coupling. Due to Hill expansion, the usual degrees of freedom are duplicated and associated with the relevant harmonic of the Floquet solutions in the frequency domain. Parametric quasimodes as well as steady-state response of the whole system are ingeniously computed with a component-mode synthesis method. Finally, experimental investigations are performed on a test rig composed of an asymmetric rotor running on nonisotropic supports. Numerical and experimental results are compared to highlight the potential of the numerical method.
Directory of Open Access Journals (Sweden)
MIHAIL PRICOP
2016-06-01
Full Text Available Vulnerable and critical mechanical systems are bearings and drive belts. Signal analysis of vibration highlights the changes in root mean square, the frequency spectrum (frequencies and amplitudes in the time- frequency (Short Time Fourier Transform and Wavelet Transform, are the most used method for faults diagnosis and location of rotating machinery. This article presents the results of an experimental study applied on a di agnostic platform of rotating machinery through three Wavelet methods: (Discrete Wavelet Transform -DWT, Continuous Wavelet Transform -CWT, Wavelet Packet Transform -WPT with different mother wavelet. Wavelet Transform is used to decompose the original sig nal into sub -frequency band signals in order to obtain multiple data series at different resolutions and to identify faults appearing in the complex rotation systems. This paper investigates the use of different mother wavelet functions for drive belts and bearing fault diagnosis. The results demonstrate the possibility of using different mother wavelets in rotary systems diagnosis detecting and locating in this way the faults in bearings and drive belts.
Vibration isolation techniques suitable for portable electronic speckle pattern interferometry
Findeis, Dirk M.; Gryzagoridis, Jasson; Rowland, David R.
2002-06-01
Electronic Speckle Pattern Interferometry (ESPI) and Digital Shearography are optical interference techniques, suitable for non-destructive inspection procedures. Due to the stringent vibration isolation conditions required for ESPI, the technique is mainly suited for laboratory based inspection procedures, which cannot be said for Digital Shearography. On the other hand, the interference patterns obtained using ESPI exhibit better fringe definition and contrast than those obtained using Digital Shearography. The image quality of Digital Shearography can be improved by introducing phase stepping and unwrapping techniques, but these methods add a level of complexity to the inspection system and reduce the image refresh rate of the overall process. As part of a project to produce a low cost portable ESPI system suitable for industrial applications, this paper investigates various methods of minimizing the impact of environmental vibration on the ESPI technique. This can be achieved by effectively 'freezing' the object movement during the image acquisition process. The methods employed include using a high-powered infra-red laser, which is continuously pulsed using an electronic signal generator as well as a mechanical chopper. The effect of using a variable shutter speed camera in conjunction with custom written software acquisition routines is also studied. The techniques employed are described and are applied to selected samples. The initial results are presented and analyzed. Conclusions are drawn and their impact on the feasibility of a portable ESPI system discussed.
Kim, Dongkyu; Khalil, Hossam; Jo, Youngjoon; Park, Kyihwan
2016-06-01
An image-based tracking system using laser scanning vibrometer is developed for vibration measurement of a rotating object. The proposed system unlike a conventional one can be used where the position or velocity sensor such as an encoder cannot be attached to an object. An image processing algorithm is introduced to detect a landmark and laser beam based on their colors. Then, through using feedback control system, the laser beam can track a rotating object.
Energy Technology Data Exchange (ETDEWEB)
Kim, Dongkyu, E-mail: akein@gist.ac.kr; Khalil, Hossam; Jo, Youngjoon; Park, Kyihwan, E-mail: khpark@gist.ac.kr [School of Mechatronics, Gwangju Institute of Science and Technology, Buk-gu, Gwangju, South Korea, 500-712 (Korea, Republic of)
2016-06-28
An image-based tracking system using laser scanning vibrometer is developed for vibration measurement of a rotating object. The proposed system unlike a conventional one can be used where the position or velocity sensor such as an encoder cannot be attached to an object. An image processing algorithm is introduced to detect a landmark and laser beam based on their colors. Then, through using feedback control system, the laser beam can track a rotating object.
Perry, David; Miller, Anthony; AMYAY, Badr; Fayt, André; Herman, Michel
2010-01-01
Abstract The link between energy-resolved spectra and time-resolved dynamics is explored quantitatively for acetylene (12C2H2), with up to 8,600 cm-1 of vibrational energy This comparison is based on the extensive and reliable knowledge of the vibration-rotation energy levels and on the model Hamiltonian used to fit them to high precision (B. Amyay, S. Robert, M. Herman, A. Fayt, B. Raghavendra, A. Moudens, J. Thievin, B. Rowe, and R. Georges, J. Chem. Phys. 131 (2009) 114301-11431...
FAULT DIAGNOSIS IN ROTATING MACHINE USING FULL SPECTRUM OF VIBRATION AND FUZZY LOGIC
Directory of Open Access Journals (Sweden)
ROGER R. DA SILVA
2017-11-01
Full Text Available Industries are always looking for more efficient maintenance systems to minimize machine downtime and productivity liabilities. Among several approaches, artificial intelligence techniques have been increasingly applied to machine diagnosis. Current paper forwards the development of a system for the diagnosis of mechanical faults in the rotating structures of machines, based on fuzzy logic, using rules foregrounded on the full spectrum of the machine´s complex vibration signal. The diagnostic system was developed in Matlab and it was applied to a rotor test rig where different faults were introduced. Results showed that the diagnostic system based on full spectra and fuzzy logic is capable of identifying with precision different types of faults, which have similar half spectrum. The methodology has a great potential to be implemented in predictive maintenance programs in industries and may be expanded to include the identification of other types of faults not covered in the case study under analysis.
Electron beam machining using rotating and shaped beam power distribution
Elmer, J.W.; O`Brien, D.W.
1996-07-09
An apparatus and method are disclosed for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: (1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and (2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1,000 {micro}m (1 mm or larger), compared to the 250 {micro}m diameter of laser drilling. 5 figs.
Electron beam machining using rotating and shaped beam power distribution
Elmer, John W.; O'Brien, Dennis W.
1996-01-01
An apparatus and method for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: 1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and 2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1000 .mu.m (1 mm or larger), compared to the 250 .mu.m diameter of laser drilling.
Global modeling of vibration-rotation spectra of the acetylene molecule
Lyulin, O. M.; Perevalov, V. I.
2016-07-01
The global modeling of both line positions and intensities of the acetylene molecule in the 50-9900 cm-1 region has been performed using the effective operators approach. The parameters of the polyad model of effective Hamiltonian have been fitted to the line positions collected from the literature. The used polyad model of effective Hamiltonian takes into account the centrifugal distortion, rotational and vibrational ℓ-doubling terms and both anharmonic and Coriolis resonance interaction operators arising due to the approximate relations between the harmonic frequencies: ω1≈ω3≈5ω4≈5ω5 and ω2≈3ω4≈3ω5. The dimensionless weighted standard deviation of the fit is 2.8. The fitted set of 237 effective Hamiltonian parameters allowed reproducing 24,991 measured line positions of 494 bands with a root mean squares deviation 0.0037 cm-1. The eigenfunctions of the effective Hamiltonian corresponding to the fitted set of parameters were used to fit the observed line intensities collected from the literature for 15 series of transitions: ΔP = 0-13,15, where P=5V1+5V3 +3V2+V4+V5 is the polyad number (Vi are the principal vibrational quantum numbers). The fitted sets of the effective dipole moment parameters reproduce the observed line intensities within their experimental uncertainties 2-20%.
ExoMol molecular line lists - XVII. The rotation-vibration spectrum of hot SO_{3}
DEFF Research Database (Denmark)
Underwood, Daniel S.; Yurchenko, Sergei N.; Tennyson, Jonathan
2016-01-01
Sulphur trioxide (SO3) is a trace species in the atmospheres of the Earth and Venus, as well as being an industrial product and an environmental pollutant. A variational line list for 32S16O3, named UYT2, is presented containing 21 billion vibration-rotation transitions. UYT2 can be used to model...
ExoMol molecular line lists - XIV. The rotation-vibration spectrum of hot SO_{2}
DEFF Research Database (Denmark)
Underwood, Daniel S.; Tennyson, Jonathan; Yurchenko, Sergei N.
2016-01-01
Sulphur dioxide is well-known in the atmospheres of planets and satellites, where its presence is often associated with volcanism, and in circumstellar envelopes of young and evolved stars as well as the interstellar medium. This work presents a line list of 1.3 billion 32S16O2 vibration-rotation...
Rogowski, R. S.; Bair, C. H.; Wade, W. R.; Hoell, J. M.; Copeland, G. E.
1978-01-01
Tunable diode laser spectroscopy is used to measure the infrared vibration-rotation spectra of the ClO radical. The radical is generated in a flow system where a Cl2-He mixture passes through a microwave discharge to dissociate the Cl2. An O3-O2 mixture from an ozone generator is injected into the system downstream of the microwave discharge where O3 combines with Cl to form ClO. By adjusting the gas flow rates to yield an excess of Cl atoms, all the ozone is combined. ClO concentration is measured with UV absorption at 2577 and 2772 A and a deuterium lamp as a continuous source. Total cell pressure is 5.5 torr. The diode laser spectrometer is calibrated with ammonia lines as a reference where possible. The frequency of vibration-rotation lines is expressed as a function of rotational quantum number, fundamental vibrational frequency, and the rotational constants of the upper and lower vibrational states.
Vibration-rotation spectroscopic database on acetylene, X ˜ 1 Σg + (12C2H2)
Amyay, B.; Fayt, A.; Herman, M.; Vander Auwera, J.
2016-06-01
A complete set of calculated vibration-rotation energies of 12C2H2 ( X ˜ 1 Σg + ) is provided for all vibrational states up to 13 000 cm-1 and some at higher energies, with rotational (J) and vibrational angular momentum (l) quantum numbers such that 0 ≤ J ≤ 100 and 0 ≤ |l| ≤ 20, respectively. The calculation is performed using a global effective Hamiltonian and related spectroscopic constants from the literature [B. Amyay et al., J. Mol. Spectrosc. 267, 80 (2011)], based on the polyad model. The numerical values of all related polyad matrix elements are also provided. The model and equations for the Hamiltonian matrix elements are gathered. The experimental acetylene database used for determining the parameters is listed.
Perry, David S.; Miller, Anthony; Amyay, B.; Fayt, A.; Herman, M.
2010-06-01
The link between energy-resolved spectra and time-resolved dynamics is explored quantitatively for acetylene (12C2H2), X1Σg+ with up to 8,600 wn of vibrational energy. This comparison is based on the extensive knowledge of the vibration-rotation energy levels and on the model Hamiltonian used to fit them to high precision. Simulated intensity borrowing features in high resolution absorption spectra and predicted survival probabilities for intramolecular vibrational redistribution (IVR) are first investigated for the ν4+ν5 and ν3 bright states, for J = 2, 30 and 100. The dependence of the results on the rotational quantum number and on the choice of vibrational bright state reflects the interplay of three kinds of off-diagonal resonances: anharmonic, rotational l-type, and Coriolis. The dynamical quantities used to characterize the calculated time-dependent dynamics are the dilution factor φd, the IVR lifetime τIVR, and the recurrence time τrec. For the two bright states ν3+2ν4 and 7ν4, the collisionless dynamics for thermally averaged rotational distributions at T = 27, 270 and 500 K were calculated from the available spectroscopic data. For the 7ν4 bright state, an apparent irreversible decay of is found. In all cases, the model Hamiltonian allows a detailed calculation of the energy flow among all of the coupled zeroth-order vibration-rotation states. B. Amyay, S. Robert, M. Herman, A. Fayt, B. Raghavendra, A. Moudens, J. Thiévin, B. Rowe, and R. Georges, J. Chem. Phys., 131, 114301 (2009).
Symmetry-broken effects on electron momentum spectroscopy caused by adiabatic vibration
Zhu, Yinghao; Ma, Xiaoguang; Lou, Wenhua; Wang, Meishan; Yang, Chuanlu
2017-11-01
The vibronic coupling effect is usually studied by invoking the breakdown of Born-Oppenheimer approximation. The present study shows that the symmetry-broken effect induced by nuclei vibrations can also lead strong impact on the electronic states under the framework of Born-Oppenheimer approximation. This adiabatic-invoking vibrational effect on electron momentum spectroscopy of ethylene (C2H4), ethane (C2H6) and methanol (CH3OH) was studied with quantum mechanical method. The results show that electron momentum spectroscopy of localized electrons, especially core electrons in axial symmetric geometry molecules can be affected unusually and strongly by several asymmetric vibrational modes.
Directory of Open Access Journals (Sweden)
Ying Chen
2016-01-01
Full Text Available Prognostic of electronic device under vibration condition can help to get information to assist in condition-based maintenance and reduce life-cycle cost. A prognostic and remaining life prediction method for electronic devices under random vibration condition is proposed. Vibration response is measured and monitored with acceleration sensor and OMA parameters, including vibration resonance frequency, especially first-order resonance frequency, and damping ratio is calculated with cross-power spectrum density (CPSD method and modal parameter identification (MPI algorithm. Steinberg vibration fatigue model which considers transmissibility factor is used to predict the remaining life of electronic component. Case study with a test board is carried out and remaining life is predicted. Results show that with this method the vibration response characteristic can be monitored and predicted.
DEFF Research Database (Denmark)
Højbjerre, Klaus; Hansen, Anders Kragh; Skyt, Peter Sandegaard
2009-01-01
The first steps toward the implementation of a simple scheme for rotational cooling of MgH+ ions based on rotational state optical pumping is considered. The various aspects of such an experiment are described in detail, and the rotational state-selective dissociation spectra of translationally...
Vibration-rotation energy pattern in acetylene: (13)CH(12)CH up to 10 120 cm(-1).
Robert, S; Amyay, B; Fayt, A; Di Lonardo, G; Fusina, L; Tamassia, F; Herman, M
2009-11-26
All 18,219 vibration-rotation absorption lines of (13)CH(12)CH published in the literature, accessing substates up to 9400 cm(-1) and including some newly assigned, were simultaneously fitted to J-dependent Hamiltonian matrices exploiting the well-known vibrational polyad or cluster block-diagonalization, in terms of the pseudo quantum numbers N(s) = v(1) + v(2) + v(3) and N(r) = 5v(1) + 3v(2) + 5v(3) + v(4) + v(5), also accounting for k = l(4) + l(5) parity and e/f symmetry properties. Some 1761 of these lines were excluded from the fit, corresponding either to blended lines, for about 30% of them, or probably to lines perturbed by Coriolis for the remaining ones. The dimensionless standard deviation of the fit is 1.10, and 317 vibration-rotation parameters are determined. These results significantly extend those of a previous report considering levels below only 6750 cm(-1) [Fayt, A.; et al. J. Chem. Phys. 2007, 126, 114303]. Unexpected problems are reported when inserting in the global fit the information available on higher-energy polyads, extending from 9300 to 10 120 cm(-1). They are tentatively interpreted as resulting from a combination of the relative evolution of the two effective bending frequencies and long-range interpolyad low-order anharmonic resonances. The complete database, made of 18,865 vibration-rotation lines accessing levels up to 10 120 cm(-1), is made available as Supporting Information.
[Vibrational and rotational excitation of CO2 in the collisional quenching of H2(v = 1)].
Zhang, Wen-jun; Feng, Li; Li, Jia-ling; Liu, Jing; Dai, Kang; Shen, Yi-fan
2014-06-01
Energy transfer in H2 (1,1) +CO2 collisions was investigated using high resolution transient laser spectroscopy. Rotational state selective excitation of v = 1 for rotational level J = 1 was achieved by stimulated Raman pumping. Energy gain into CO2 resulting from collisions with H2 (1,1) was probed using transient absorption techniques, Distributions of nascent CO2 rotational populations in both the ground (00 degrees 0) state and the vibrationally excited (00 degrees 1) state were determined from overtone absorption measurements. Translational energy distributions of the recoiling CO2 in individual rovibrational states were determined through measurement of Doppler-broadened transient line shapes. A kinetic model was developed to describe rates for appearance of CO2 states resulting from collisions with H2(1,1). From scanned CARS (coherent anti-stokes Raman scattering) the spectral peaks population ratio n0/n1 was obtained, where n0 and n1 represent the number densities of H2 at the levels (0,1) and (1,1), respectively. Using rotational Boltzmann distribution of H2 (v = 0) at 300 K, n1 was yielded. Values for rate coefficients were obtained using data for CO2 (00 degrees 0) J = 48 to 76 and CO2 (00 degrees 1) J = 5 to 33. The rate coefficients derived from appearance of the (00 degrees 0) state have values of K(tr) = (3.9 ± 0.8) x 10(-11) cm3 x molecule(-1) x s(-1) for J = 48 and k(tr) = (1.4 ± 0.3) x 10(-10) cm3 x molecule(-1) x s(-1) for J = 76, with a monotonic increase for the higher J states. For the (00 degrees 1) state, values of k(tr) remain fairly constant at k(tr) = (4.3 ± 0.9) x 10(-12) cm3 x molecule(-1) x s(-1). Rotational populations for the nascent CO2 states were measured at 0. 5 μs following excitation of H2. The transient population for each state was fit using a Boltzmann rotational distribution. The CO2 (00 degrees 0) J = 48-76 rotational states were populated substantially relative to the initial 300 K CO2 distributions, and the
DFT studies on the vibrational and electronic spectra of acetylsalicylic acid
Ye, Yunfeng; Tang, Guodong; Han, Yonghong; Culnane, Lance F.; Zhao, Jianyin; Zhang, Yu
2016-05-01
The following is a theoretical and experimental study on the vibrational and electronic properties of acetylsalicylic acid (ASA). Vibrational information was obtained by FT-IR and Raman spectroscopy which agree well with harmonic vibrational frequency calculations. The calculations were carried out using density functional theory B3LYP methods with 6-311G** and LANL2DZ basis sets. The vibrational assignments were calculated by Gaussview. Absorption UV-Vis experiments of ASA reveal three maximum peaks at 203, 224 and 277 nm, which are in agreement with calculated electronic transitions using TD-B3LYP/6-311G**.
Petit, Andrew S.; Wellen, Bethany A.; McCoy, Anne B.
2012-06-01
Our group has developed a fixed-node Diffusion Monte Carlo (DMC) methodology that can be used to describe rotationally excited states of highly fluxional symmetric top molecules. This technique has been thoroughly benchmarked using rotationally excited states of H_3^+, H_3O^+, and NH_3 with J≤12. Here, we report a recently developed extension of this methodology to asymmetric top molecules which undergo large amplitude, zero-point vibrational motion. The nodal surfaces used in the fixed-node DMC calculations are obtained from rigid-rotor wave functions calculated using the system's ground state vibrationally averaged rotational constants. The algorithms used to evaluate node crossing and re-crossing are generalized to account for the pronounced curvature exhibited by the nodal surfaces of asymmetric top molecules with κ ≈ 0 due to the strong mixing of two or more symmetric top basis functions. Finally, the insight that can be obtained from these calculations into the nature and strength of the vibration-rotation coupling present in highly fluxional asymmetric top molecules will be briefly discussed and further elaborated on in the following talk. A. S. Petit and A. B. McCoy, J. Phys. Chem. A 113, 12706 (2009). A. S. Petit, B. A. Wellen, and A. B. McCoy, J. Chem. Phys. 136, 074101 (2012).
Acetylene, 12C2H2: new CRDS data and global vibration-rotation analysis up to 8600 cm-1
Herman, Michel
2008-01-01
Abstract The absorption spectrum of 12C2H2 has been recorded using cavity ring downringdown spectroscopy and analyzed in the ranges 60006356 cm and 66677015 cm. Fourteen new bands have been identified and additional J-lines were assigned in 10 already known bands. These new data, together with the published vibration-rotation absorption lines of 12C2H2 accessing vibrational states up to 8600 cm have been gathered in a ...
Mihaylova, Emilia; Naydenova, Izabela; Martin, Suzanne; Toal, Vincent
2004-01-01
Electronic speckle pattern shearing interferometry (ESPSI) is superior to Electronic speckle pattern interferometry (ESPI) when strain distribution, arising from object deformation or vibration, need to be measured. This is because shearography provides data directly related to the spatial derivatives of the displacement. Further development of ESPSI systems could be beneficial for wider application to the measurement of mechanical characteristics of vibrating objects. Two electronic speckle ...
DEFF Research Database (Denmark)
Olsen, Thomas; Schiøtz, Jakob
2010-01-01
We propose a mechanism which allows one to control the transmission of single electrons through a molecular junction. The principle utilizes the emergence of transmission sidebands when molecular vibrational modes are coupled to the electronic state mediating the transmission. We will show that i....... As an example we perform a density-functional theory analysis of a benzene molecule between two Au(111) contacts and show that exciting a particular vibrational mode can give rise to transmission of a single electron....
Free-Vibration Analysis of Rotating Beams by a Variable-Order Finite-Element Method
Hodges, Dewey H.; Rutkowski, Michael J.
1981-01-01
The free vibration of rotating beams is analyzed by means of a finite-element method of variable order. This method entails displacement functions that are a complete power series of a variable number of terms. The terms are arranged so that the generalized coordinates are composed of displacements and slopes at the element extremities and, additionally, displacements at certain points within the element. The displacement is assumed to be analytic within an element and thus can be approximated to any degree of accuracy desired by a complete power series. Numerical results are presented for uniform beams with zero and nonzero hub radii, tapered beams, and a nonuniform beam with discontinuities. Since the present method reduces to a conventional beam finite-element method for a cubic displacement function, the results are compared and found to be superior to the conventional results in terms of accuracy for a given number of degrees of freedom. Indeed, essentially exact eigenvalues and eigenvectors are obtained with this technique, which is far more rapidly convergent than other approaches in the literature.
Jiang, Chi-Lun
2015-01-01
With a 600mk homebuilt UHV STM system, we studied molecular vibration at the solid surface with inelastic electron tunneling spectroscopy (IETS) of Acetylene single molecules adsorbed on Cu(100) surface and revealed five new vibrational modes that were previously inaccessible to STM-IETS at 8K temperature. The identification of vibrational IETS features with normalized conductance change (Δσ/σ) as low as 0.24% was demonstrated. Facilitated by the high energy resolution, we also revealed the a...
Calculated low-energy electron-impact vibrational excitation cross sections for CO2 molecule
Laporta, V; Celiberto, R
2016-01-01
Vibrational-excitation cross sections of ground electronic state of carbon dioxide molecule by electron-impact through the CO2-(2\\Pi) shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume decoupling between normal modes and employ the local complex potential model for the treatment of the nuclear dynamics, usually adopted for the electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and comparison with data present in the literature is discussed.
Electron-Beam Mapping of Vibrational Modes with Nanometer Spatial Resolution.
Dwyer, C; Aoki, T; Rez, P; Chang, S L Y; Lovejoy, T C; Krivanek, O L
2016-12-16
We demonstrate that a focused beam of high-energy electrons can be used to map the vibrational modes of a material with a spatial resolution of the order of one nanometer. Our demonstration is performed on boron nitride, a polar dielectric which gives rise to both localized and delocalized electron-vibrational scattering, either of which can be selected in our off-axial experimental geometry. Our experimental results are well supported by our calculations, and should reconcile current controversy regarding the spatial resolution achievable in vibrational mapping with focused electron beams.
Zou, Luyao; Widicus Weaver, Susanna L.
2016-06-01
Three new weak bands of the Ar-H2O vibration-rotation-tunneling spectrum have been measured in the millimeter wavelength range. These bands were predicted from combination differences based on previously measured bands in the submillimeter region. Two previously reported submillimeter bands were also remeasured with higher frequency resolution. These new measurements allow us to obtain accurate information on the Coriolis interaction between the 101 and 110 states. Here we report these results and the associated improved molecular constants.
Energy Technology Data Exchange (ETDEWEB)
Herbert, John M. [Kansas State Univ., Manhattan, KS (United States). Dept. of Chemistry
1997-01-01
Rayleigh-Schroedinger perturbation theory is an effective and popular tool for describing low-lying vibrational and rotational states of molecules. This method, in conjunction with ab initio techniques for computation of electronic potential energy surfaces, can be used to calculate first-principles molecular vibrational-rotational energies to successive orders of approximation. Because of mathematical complexities, however, such perturbation calculations are rarely extended beyond the second order of approximation, although recent work by Herbert has provided a formula for the nth-order energy correction. This report extends that work and furnishes the remaining theoretical details (including a general formula for the Rayleigh-Schroedinger expansion coefficients) necessary for calculation of energy corrections to arbitrary order. The commercial computer algebra software Mathematica is employed to perform the prohibitively tedious symbolic manipulations necessary for derivation of generalized energy formulae in terms of universal constants, molecular constants, and quantum numbers. As a pedagogical example, a Hamiltonian operator tailored specifically to diatomic molecules is derived, and the perturbation formulae obtained from this Hamiltonian are evaluated for a number of such molecules. This work provides a foundation for future analyses of polyatomic molecules, since it demonstrates that arbitrary-order perturbation theory can successfully be applied with the aid of commercially available computer algebra software.
Disentangling electronic and vibrational coherence in the Phycocyanin-645 light-harvesting complex
Richards, Gethin H; Curmi, Paul M G; Davis, Jeffrey A
2013-01-01
Energy transfer between chromophores in photosynthesis proceeds with near unity quantum efficiency. Understanding the precise mechanisms of these processes is made difficult by the complexity of the electronic structure and interactions with different vibrational modes. Two-dimensional spectroscopy has helped resolve some of the ambiguities and identified quantum effects that may be important for highly efficient energy transfer. Many questions remain, however, including whether the coherences observed are electronic and/or vibrational in nature and what role they play. We utilise a two-colour four-wave mixing experiment with control of the wavelength and polarization to selectively excite specific coherence pathways. For the light-harvesting complex PC645, from cryptophyte algae, we reveal and identify specific contributions from both electronic and vibrational coherences and determine an excited state structure based on two strongly-coupled electronic states and two vibrational modes. Separation of the cohe...
Acoustic vibration modes and electron-lattice coupling in self-assembled silver nanocolumns.
Burgin, J; Langot, P; Arbouet, A; Margueritat, J; Gonzalo, J; Afonso, C N; Vallée, F; Mlayah, A; Rossell, M D; Van Tendeloo, G
2008-05-01
Using ultrafast spectroscopy, we investigated electron-lattice coupling and acoustic vibrations in self-assembled silver nanocolumns embedded in an amorphous Al2O3 matrix. The measured electron-lattice energy exchange time is smaller in the nanocolumns than in bulk silver, with a value very close to that of isolated nanospheres with comparable surface to volume ratio. Two vibration modes were detected and ascribed to the breathing and extensional mode of the nanocolumns, in agreement with numerical simulations.
Nonequilibrium electron-vibration coupling and conductance fluctuations in a C-60 junction
DEFF Research Database (Denmark)
Ulstrup, Soren; Frederiksen, Thomas; Brandbyge, Mads
2012-01-01
displacement. Combined with a vibrational heating mechanism we construct a model from our results that explain the polarity-dependent two-level conductance fluctuations observed in recent scanning tunneling microscopy (STM) experiments [N. Neel et al., Nano Lett. 11, 3593 (2011)]. These findings highlight...... the significance of nonequilibrium effects in chemical bond formation/breaking and in electron-vibration coupling in molecular electronics....
Hong, Liu; Qu, Yongzhi; Dhupia, Jaspreet Singh; Sheng, Shuangwen; Tan, Yuegang; Zhou, Zude
2017-09-01
The localized failures of gears introduce cyclic-transient impulses in the measured gearbox vibration signals. These impulses are usually identified from the sidebands around gear-mesh harmonics through the spectral analysis of cyclo-stationary signals. However, in practice, several high-powered applications of gearboxes like wind turbines are intrinsically characterized by nonstationary processes that blur the measured vibration spectra of a gearbox and deteriorate the efficacy of spectral diagnostic methods. Although order-tracking techniques have been proposed to improve the performance of spectral diagnosis for nonstationary signals measured in such applications, the required hardware for the measurement of rotational speed of these machines is often unavailable in industrial settings. Moreover, existing tacho-less order-tracking approaches are usually limited by the high time-frequency resolution requirement, which is a prerequisite for the precise estimation of the instantaneous frequency. To address such issues, a novel fault-signature enhancement algorithm is proposed that can alleviate the spectral smearing without the need of rotational speed measurement. This proposed tacho-less diagnostic technique resamples the measured acceleration signal of the gearbox based on the optimal warping path evaluated from the fast dynamic time-warping algorithm, which aligns a filtered shaft rotational harmonic signal with respect to a reference signal assuming a constant shaft rotational speed estimated from the approximation of operational speed. The effectiveness of this method is validated using both simulated signals from a fixed-axis gear pair under nonstationary conditions and experimental measurements from a 750-kW planetary wind turbine gearbox on a dynamometer test rig. The results demonstrate that the proposed algorithm can identify fault information from typical gearbox vibration measurements carried out in a resource-constrained industrial environment.
Vibration Control of Novel Passive Multi-joints Rotational Friction Dampers
DEFF Research Database (Denmark)
Mualla, Imad H.; Koss, Holger
2017-01-01
This work presents a novel passive friction damper for vibration control of structures. The device is designed to dissipate input energy and protect buildings, especially large and tall buildings from structural and non-structural damage during moderate and severe vibration caused by earthquakes...
Delor, Milan; Archer, Stuart A.; Keane, Theo; Meijer, Anthony J. H. M.; Sazanovich, Igor V.; Greetham, Gregory M.; Towrie, Michael; Weinstein, Julia A.
2017-11-01
Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer donor-bridge-acceptor-bridge-donor 'fork' system: asymmetric 13C isotopic labelling of one of the two -C≡C- bridges makes the two parallel and otherwise identical donor→acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UVpump(excitation)-IRpump(perturbation)-IRprobe(monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices.
Damage-free vibrational spectroscopy of biological materials in the electron microscope.
Rez, Peter; Aoki, Toshihiro; March, Katia; Gur, Dvir; Krivanek, Ondrej L; Dellby, Niklas; Lovejoy, Tracy C; Wolf, Sharon G; Cohen, Hagai
2016-03-10
Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an 'aloof' electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies <1 eV can be 'safely' investigated. To demonstrate the potential of aloof spectroscopy, we record electron energy loss spectra from biogenic guanine crystals in their native state, resolving their characteristic C-H, N-H and C=O vibrational signatures with no observable radiation damage. The technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ∼10 nm, simultaneously combined with imaging in the electron microscope.
Fujihashi, Yuta; Ishizaki, Akihito
2015-01-01
In 2D electronic spectroscopy studies, long-lived quantum beats have recently been observed in photosynthetic systems, and it has been suggested that the beats are produced by quantum mechanically mixed electronic and vibrational states. Concerning the electronic-vibrational quantum mixtures, the impact of protein-induced fluctuations was examined by calculating the 2D electronic spectra of a weakly coupled dimer with vibrational modes in the resonant condition [J. Chem. Phys. 142, 212403 (2015)]. This analysis demonstrated that quantum mixtures of the vibronic resonance are rather robust under the influence of the fluctuations at cryogenic temperatures, whereas the mixtures are eradicated by the fluctuations at physiological temperatures. However, this conclusion cannot be generalized because the magnitude of the coupling inducing the quantum mixtures is proportional to the inter-pigment coupling. In this study, we explore the impact of the fluctuations on electronic-vibrational quantum mixtures in a strongl...
Wu, Jizhou; Liu, Wenliang; Li, Yuqing; Ma, Jie; Xiao, Liantuan; Jia, Suotang
2017-04-01
We report an accurate experimental determination of rotational constants of the lowest vibrational levels in the purely long-range state of ultracold cesium molecules (Cs2). We engineer a precise reference of the frequency difference through double photoassociation spectroscopy (PAS). The PAS for the lowest vibrational levels, v=0-3, has been obtained with an enhanced sensitivity and accuracy, according to which the binding energies have been corrected. As deduced from the reference, the frequency intervals between neighboring rotational levels are fitted to a non-rigid rotor model, thus the rotational constants are precisely obtained. The experimental results show good agreement with theoretical expectations.
Vibrationally Assisted Electron Transfer Mechanism of Olfaction: Myth or Reality?
DEFF Research Database (Denmark)
Solov'yov, Ilia; Chang, Po-Yao; Schulten, Klaus
2012-01-01
Smell is a vital sense for animals. The mainstream explanation of smell is based on recognition of the odorant molecules through characteristics of their surface, e.g., shape, but certain experiments suggest that such recognition is complemented by recognition of vibrational modes. According to t...
Van Dyke, Michael B.
2013-01-01
Present preliminary work using lumped parameter models to approximate dynamic response of electronic units to random vibration; Derive a general N-DOF model for application to electronic units; Illustrate parametric influence of model parameters; Implication of coupled dynamics for unit/board design; Demonstrate use of model to infer printed wiring board (PWB) dynamics from external chassis test measurement.
Selfconsistent vibrational and free electron kinetics for CO2 dissociation in cold plasmas
Capitelli, Mario
2016-09-01
The activation of CO2 by cold plasmas is receiving new theoretical interest thanks to two European groups. The Bogaerts group developed a global model for the activation of CO2 trying to reproduce the experimental values for DBD and microwave discharges. The approach of Pietanza et al was devoted to understand the dependence of electron energy distribution function (eedf) of pure CO2 on the presence of concentrations of electronically and vibrationally excited states taken as parameter. To understand the importance of the vibrational excitation in the dissociation process Pietanza et al compared an upper limit to the dissociation process from a pure vibrational mechanism (PVM) with the corresponding electron impact dissociation rate, the prevalence of the two models depending on the reduced electric field and on the choice of the electron molecule cross section database. Improvement of the Pietanza et al model is being considered by coupling the time dependent Boltzmann solver with the non equilibrium vibrational kinetics of asymmetric mode and with simplified plasma chemistry kinetics describing the ionization/recombination process and the excitation-deexcitation of a metastable level at 10.5eV. A new PVM mechanism is also considered. Preliminary results, for both discharge and post discharge conditions, emphasize the action of superelastic collisions involving both vibrationally and electronically excited states in affecting the eedf. The new results can be used to plan a road map for future developments of numerical codes for rationalizing existing experimental values, as well as, for indicating new experimental situations.
Smart Woven Fabrics With Portable And Wearable Vibrating Electronics
Directory of Open Access Journals (Sweden)
Özdemir Hakan
2015-06-01
Full Text Available The portable and wearable instrumented fabrics capable of measuring biothermal variable is essential for drivers, especially long-distance drivers. Here we report on portable and wearable devices that are able to read the temperature of human body within the woven fabric. The sensory function of the fabric is achieved by temperature sensors, soldered on conductive threads coated with cotton. The presence of stainless steel wires gives these materials conductive properties, enabling the detection of human body temperature and transmitting the signal form sensors to the motors on the fabric. When body temperature decreases, hardware/software platforms send a signal to the vibration motors in order to stimulate the driver. The ‘smart woven fabric’-sensing architecture can be divided into two parts: a textile platform, where portable and wearable devices acquire thermal signals, and hardware/software platforms, to which a sensor sends the acquired data, which send the signals to the vibration motors.
Mode-selective vibrational modulation of charge transport in organic electronic devices
Bakulin, Artem A.
2015-08-06
The soft character of organic materials leads to strong coupling between molecular, nuclear and electronic dynamics. This coupling opens the way to influence charge transport in organic electronic devices by exciting molecular vibrational motions. However, despite encouraging theoretical predictions, experimental realization of such approach has remained elusive. Here we demonstrate experimentally that photoconductivity in a model organic optoelectronic device can be modulated by the selective excitation of molecular vibrations. Using an ultrafast infrared laser source to create a coherent superposition of vibrational motions in a pentacene/C60 photoresistor, we observe that excitation of certain modes in the 1,500–1,700 cm−1 region leads to photocurrent enhancement. Excited vibrations affect predominantly trapped carriers. The effect depends on the nature of the vibration and its mode-specific character can be well described by the vibrational modulation of intermolecular electronic couplings. This presents a new tool for studying electron–phonon coupling and charge dynamics in (bio)molecular materials.
Tennyson, Jonathan; Bernath, Peter F.; Brown, Linda R.; Campargue, Alain; Császár, Attila G.; Daumont, Ludovic; Gamache, Robert R.; Hodges, Joseph T.; Naumenko, Olga V.; Polyansky, Oleg L.; Rothman, Laurence S.; Vandaele, Ann Carine; Zobov, Nikolai F.; Al Derzi, Afaf R.; Fábri, Csaba; Fazliev, Alexander Z.; Furtenbacher, Tibor; Gordon, Iouli E.; Lodi, Lorenzo; Mizus, Irina I.
2013-03-01
This is the third of a series of articles reporting critically evaluated rotational-vibrational line positions, transition intensities, and energy levels, with associated critically reviewed labels and uncertainties, for all the main isotopologues of water. This paper presents experimental line positions, experimental-quality energy levels, and validated labels for rotational-vibrational transitions of the most abundant isotopologue of water, H216O. The latest version of the MARVEL (Measured Active Rotational-Vibrational Energy Levels) line-inversion procedure is used to determine the rovibrational energy levels of the electronic ground state of H216O from experimentally measured lines, together with their self-consistent uncertainties, for the spectral region up to the first dissociation limit. The spectroscopic network of H216O containstwo components, an ortho (o) and a para (p) one. For o-H216O and p-H216O, experimentally measured, assigned, and labeled transitions were analyzed from more than 100 sources. The measured lines come from one-photon spectra recorded at room temperature in absorption, from hot samples with temperatures up to 3000 K recorded in emission, and from multiresonance excitation spectra which sample levels up to dissociation. The total number of transitions considered is 184 667 of which 182 156 are validated: 68 027 between para states and 114 129 ortho ones. These transitions give rise to 18 486 validated energy levels, of which 10 446 and 8040 belong to o-H216O and p-H216O, respectively. The energy levels, including their labeling with approximate normal-mode and rigid-rotor quantum numbers, have been checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators as well as against previous compilations of energy levels. The extensive list of MARVEL lines and levels obtained are deposited in the supplementary data of this paper, as well as in a distributed information system
MARVEL analysis of the rotational-vibrational states of the molecular ions H2D+ and D2H+.
Furtenbacher, Tibor; Szidarovszky, Tamás; Fábri, Csaba; Császár, Attila G
2013-07-07
Critically evaluated rotational-vibrational line positions and energy levels, with associated critically reviewed labels and uncertainties, are reported for two deuterated isotopologues of the H3(+) molecular ion: H2D(+) and D2H(+). The procedure MARVEL, standing for Measured Active Rotational-Vibrational Energy Levels, is used to determine the validated levels and lines and their self-consistent uncertainties based on the experimentally available information. The spectral ranges covered for the isotopologues H2D(+) and D2H(+) are 5.2-7105.5 and 23.0-6581.1 cm(-1), respectively. The MARVEL energy levels of the ortho and para forms of the ions are checked against ones determined from accurate variational nuclear motion computations employing the best available adiabatic ab initio potential energy surfaces of these isotopologues. The number of critically evaluated, validated and recommended experimental (levels, lines) are (109, 185) and (104, 136) for H2D(+) and D2H(+), respectively. The lists of assigned MARVEL lines and levels and variational levels obtained for H2D(+) and D2H(+) as part of this study are deposited in the ESI to this paper.
Energy Technology Data Exchange (ETDEWEB)
Albert, Julian; Falge, Mirjam; Hildenbrand, Heiko; Engel, Volker [Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Emil-Fischer-Str. 42, Campus Nord, Am Hubland, 97074 Würzburg (Germany); Gomez, Sandra; Sola, Ignacio R. [Departamento de Quimica Fisica, Universidad Complutense, 28040 Madrid (Spain)
2015-07-28
We theoretically investigate the photon-echo spectroscopy of coupled electron-nuclear quantum dynamics. Two situations are treated. In the first case, the Born-Oppenheimer (adiabatic) approximation holds. It is then possible to interpret the two-dimensional (2D) spectra in terms of vibrational motion taking place in different electronic states. In particular, pure vibrational coherences which are related to oscillations in the time-dependent third-order polarization can be identified. This concept fails in the second case, where strong non-adiabatic coupling leads to the breakdown of the Born-Oppenheimer-approximation. Then, the 2D-spectra reveal a complicated vibronic structure and vibrational coherences cannot be disentangled from the electronic motion.
[Vibrational to rotational energy transfer between CsH (Chi1 Sigma+, nu > or = 15) and CO2].
Dai, Kang; Wang, Shu-Ying; Liu, Jing; Shen, Yi-Fan
2012-11-01
The quenching of highly vibrational excited CsH through collisions with a 500 K bath of CO2 was investigated using the laser spectroscopy technique. CsH was formed by the Cs(7P)+H2 reaction. The pulse laser prepared CsH in the highly vibrational levels. Laser induced fluorescence was used to detect collisionally relaxed CsH. The relaxation rate coefficient of CsH (nu" = 21) with CO2 is 10 times larger than that of CsH(nu" = 15). Relaxation of CsH(nu") with H2 was also investigated. The mass effect on the collisional relaxation rate coefficients is strong. The observed collisional relaxation rate coefficients of H2 are bigger than those of CO2. Energy gain into CO2 resulting from collisions with excited CsH was probed using laser overtone spectroscopy technique. Distributions of nascent CO2 rotational population in the ground (00(0)0) state were determined. For CsH excited at nu" = 15, the scattered CO2 molecules have a rotational temperature of T(rot) = (605 +/- 50) K. For excitation at nu" = 21, the CO2 rotational temperature is T(rot) = (780 +/- 70) K. Based on the rotational temperatures, the average change in the CO2 rotational energy has a stronger dependence on the CsH initial energy. Using the ambient cell temperature, nu = 21 -2. 7 nu" = 15 was found. The nascent distributions of recoil velocities for collisions were determined from stimulated absorption line profiles of individual CO2 rotational states. For nu" = 15, scattered CO2 molecules with J = 36-48 have center of mass translational energy of = 600-972 cm(-1). For nu" = 21, the values increase to = 972-1 351 cm(-1). Based on propensity rules for collisions that favor small changes in energy and angular momentum, it is reasonable that low-J CO2 states will have lower translational energy than the high-J states. Extrapolating nu" = 15 and 21 data to the initial relative translational energy of E0 = 520 cm(-1) gives an estimate of the threshold states J(th) = 34 and 24, respectively. The onset of large
Valduga de Almeida Camargo, Franco; Anderson, Harry; Meech, Steve; Heisler, Ismael
2015-01-01
In this work we present experimental and calculated two-dimensional electronic spectra for a 5,15-bisalkynyl porphyrin chromophore. The lowest energy electronic Qy transition couples mainly to a single 380 cm–1 vibrational mode. The two-dimensional electronic spectra reveal diagonal and cross peaks which oscillate as a function of population time. We analyze both the amplitude and phase distribution of this main vibronic transition as a function of excitation and detection frequencies. Even t...
DEFF Research Database (Denmark)
Johannessen, Christian; Thulstrup, Peter W.
2007-01-01
Vibrational absorption (VA) and vibrational circular dichroism (VCD) spectroscopy was applied in the analysis of vibrational and low lying electronic transitions of a triplet ground state cobalt(III) coordination compound. The spectroscopic measurements were performed on the tetrabutylammonium salt...
Single-molecule electronics: Cooling individual vibrational modes by the tunneling current.
Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C
2016-03-21
Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.
Mielke, Steven L; Truhlar, Donald G
2009-04-23
We present two enhancements to our methods for calculating vibrational-rotational free energies by Feynman path integrals, namely, a sequential sectioning scheme for efficiently generating random free-particle paths and a stratified sampling scheme that uses the energy of the path centroids. These improved methods are used with three interaction potentials to calculate equilibrium constants for the fractionation behavior of Cl(-) hydration in the presence of a gas-phase mixture of H(2)O, D(2)O, and HDO. Ion cyclotron resonance experiments indicate that the equilibrium constant, K(eq), for the reaction Cl(H(2)O)(-) + D(2)O right harpoon over left harpoon Cl(D(2)O)(-) + H(2)O is 0.76, whereas the three theoretical predictions are 0.946, 0.979, and 1.20. Similarly, the experimental K(eq) for the Cl(H(2)O)(-) + HDO right harpoon over left harpoon Cl(HDO)(-) + H(2)O reaction is 0.64 as compared to theoretical values of 0.972, 0.998, and 1.10. Although Cl(H(2)O)(-) has a large degree of anharmonicity, K(eq) values calculated with the harmonic oscillator rigid rotator (HORR) approximation agree with the accurate treatment to within better than 2% in all cases. Results of a variety of electronic structure calculations, including coupled cluster and multireference configuration interaction calculations, with either the HORR approximation or with anharmonicity estimated via second-order vibrational perturbation theory, all agree well with the equilibrium constants obtained from the analytical surfaces.
Kim, In-Ho; Jang, Seon-Jun; Jung, Hyung-Jo
2013-07-01
In this paper, an innovative strategy for improving the performance of a recently developed rotational energy harvester is proposed. Its performance can be considerably enhanced by replacing the electromagnetic induction part, consisting of moving permanent magnets and a fixed solenoid coil, with a moving mass and a rotational generator (i.e., an electric motor). The proposed system is easily tuned to the natural frequency of a target structure using the position change of a proof mass. Owing to the high efficiency of the rotational generator, the device can more effectively harness electrical energy from the wind-induced vibration of a stay cable. Also, this new configuration makes the device more compact and geometrically tunable. In order to validate the effectiveness of the new configuration, a series of laboratory and field tests are carried out with the prototype of the proposed device, which is designed and fabricated based on the dynamic characteristics of the vibration of a stay cable installed in an in-service cable-stayed bridge. From the field test, it is observed that the normalized output power of the proposed system is 35.67 mW (m s-2)-2, while that of the original device is just 5.47 mW (m s-2)-2. These results show that the proposed device generates much more electrical energy than the original device. Moreover, it is verified that the proposed device can generate sufficient electricity to power a wireless sensor node placed on a cable under gentle-moderate wind conditions.
Ab initio prediction of the rotation-vibration spectrum of H/sub 3//sup +/ and D/sub 3//sup +/
Energy Technology Data Exchange (ETDEWEB)
Carney, G.D.; Porter, R.N.
1980-08-18
the first few lines in the P, Q, and R branches of the rotation-vibration spectra of the equilateral-triangle molecular ions H/sub 3//sup +/ and D/sub 3//sup +/, obtained by ab initio nonperturbative calculations, are reported. Comparison with observations indicates an accuracy better than 1% was obtained for both the infrared-active fundamental vibration frequency and the equilibrium internuclear distances.
Vibration analysis of low-aspect ratio rotating blade modeled as a ...
African Journals Online (AJOL)
Vibration analysis of a low-aspect ratio blade modeled as a plate is presented which uses MATLAB coded computer program. The analysis presented employs an accurate strain-displacement relationship based on the thin plate theory, known as the Kirchhoff - Lava hypothesis. The equation of motion of the blade is derived ...
CSIR Research Space (South Africa)
Joubert, S
2006-05-01
Full Text Available and calculation of the corresponding proportionality factors. In the present paper radial and torsional vibrational modes are considered on the basis of an exact solution of 3-D equations of motion of an isotropic body in spherical coordinates. The solutions...
Energy Technology Data Exchange (ETDEWEB)
Cobut, V.; Frongillo, Y.; Jay-Gerin, J.-P. (Sherbrooke Univ., PQ (Canada). Faculte de Medecine); Patau, J.-P. (Toulouse-3 Univ., 31 (France))
1992-12-01
An energy spectrum of ''subexcitation electrons'' produced in liquid water by electrons with initial energies of a few keV is obtained by using a Monte Carlo transport simulation calculation. It is found that the introduction of vibrational-excitation cross sections leads to the appearance of a sharp peak in the probability density function near the electronic-excitation threshold. Electrons contributing to this peak are shown to be more naturally described if a novel energy spectrum, that we propose to name ''vibrationally-relaxing electron'' spectrum, is introduced. The corresponding distribution function is presented, and an empirical expression of it is given. (author).
An approximate solution for the free vibrations of rotating uniform cantilever beams
Peters, D. A.
1973-01-01
Approximate solutions are obtained for the uncoupled frequencies and modes of rotating uniform cantilever beams. The frequency approximations for flab bending, lead-lag bending, and torsion are simple expressions having errors of less than a few percent over the entire frequency range. These expressions provide a simple way of determining the relations between mass and stiffness parameters and the resultant frequencies and mode shapes of rotating uniform beams.
Rotation of a Single Acetylene Molecule on Cu(001) by Tunneling Electrons in STM
Shchadilova, Yulia E.; Tikhodeev, Sergei G.; Paulsson, Magnus; Ueba, Hiromu
2013-11-01
We study the elementary processes behind one of the pioneering works on scanning tunneling microscope controlled reactions of single molecules [Stipe et al., Phys. Rev. Lett. 81, 1263 (1998)]. Using the Keldysh-Green function approach for the vibrational generation rate in combination with density functional theory calculations to obtain realistic parameters we reproduce the experimental rotation rate of an acetylene molecule on a Cu(100) surface as a function of bias voltage and tunneling current. This combined approach allows us to identify the reaction coordinate mode of the acetylene rotation and its anharmonic coupling with the C-H stretch mode. We show that three different elementary processes, the excitation of C-H stretch, the overtone ladder climbing of the hindered rotational mode, and the combination band excitation together explain the rotation of the acetylene molecule on Cu(100).
Rotational and translational effects in collisions of electronically excited diatomic hydrides
Crosley, David R.
1988-01-01
Collisional quenching and vibrational energy proceed competitively with rotational energy transfer for several excited states of the diatomic radicals OH, NH, and CH. This occurs for a wide variety of molecular collision partners. This phenomenon permits the examination of the influence of rotational motion on the collision dynamics of these theoretically tractable species. Measurements can also be made as a function of temperature, i.e., collision velocity. In OH (sup 2 sigma +), both vibrational transfer and quenching are found to decrease with an increase in rotational level, while quenching decreases with increasing temperature. This behavior indicates that for OH, anisotropic attractive forces govern the entrance channel dynamics for these collisions. The quenching of NH (sup 3 pi sub i) by many (although not all) collision partners also decreases with increasing rotational and translational energy, and NH (sup 1 pi) behaves much like OH (sup 2 sigma +). However, the quenching of CH (sup 2 delta) appears to decrease with increasing rotation but increases with increasing temperature, suggesting in this case anisotropic forces involving a barrier or repulsive wall. Such similarities and differences should furnish useful comparisons with both simple and detailed theoretical pictures of the appropriate collision dynamics.
Mellouki, Abdeloihid; Vander Auwera, Jean; Herman, Michel
1999-01-01
We have recorded the infrared absorption spectrum of pyrrole at 0.005 cm-1spectral resolution using a Fourier transform interferometer. The rotational analysis of the symmetric out-of-plane C-H bend 2210fundamental band at 722.132993(5) cm-1was performed, allowing 6760 lines to be assigned. These lines were fitted simultaneously to literature data on ν1[A. Mellouki, R. Georges, M. Herman, D. L. Snavely, and S. Leytner,Chem. Phys.220, 311-322 (1997)] and microwave lines [G. Wlodarczak, L. Martinache, J. Demaison, and B. P. Van Eijck,J. Mol. Spectrosc.127, 200-208 (1988)]. A set of rotation parameters was determined for the ground state in Irand IIIrrepresentations, together with vibration-rotation constants for thev1= 1 andv22= 1 vibrational states. The fine structure in the strongest of the hot bands in that range was highlighted by division, from the experimental data, of the spectrum of the 2210band, computed using the vibration-rotation parameters. The rotational assignment of 930 lines in the strongest hot band was performed. The 22102411vibrational assignment is proposed, leading tox22,24= 1.90 cm-1. The transition dipole matrix element for the 2210band is estimated to ‖‖ = 2 × 10-4D.
Mellouki; Vander Auwera J; Herman
1999-01-01
We have recorded the infrared absorption spectrum of pyrrole at 0.005 cm-1 spectral resolution using a Fourier transform interferometer. The rotational analysis of the symmetric out-of-plane C-H bend 22(1)0 fundamental band at 722.132993(5) cm-1 was performed, allowing 6760 lines to be assigned. These lines were fitted simultaneously to literature data on nu1 [A. Mellouki, R. Georges, M. Herman, D. L. Snavely, and S. Leytner, Chem. Phys. 220, 311-322 (1997)] and microwave lines [G. Wlodarczak, L. Martinache, J. Demaison, and B. P. Van Eijck, J. Mol. Spectrosc. 127, 200-208 (1988)]. A set of rotation parameters was determined for the ground state in Ir and IIIr representations, together with vibration-rotation constants for the v1 = 1 and v22 = 1 vibrational states. The fine structure in the strongest of the hot bands in that range was highlighted by division, from the experimental data, of the spectrum of the 22(1)0 band, computed using the vibration-rotation parameters. The rotational assignment of 930 lines in the strongest hot band was performed. The 22(1)024(1)1 vibrational assignment is proposed, leading to x22,24 = 1.90 cm-1. The transition dipole matrix element for the 22(1)0 band is estimated to || || = 2 x 10(-4) D. Copyright 1999 Academic Press.
Observations of rotation in JET plasmas with electron heating by ion cyclotron resonance heating
DEFF Research Database (Denmark)
Hellsten, T.; Johnson, T. J.; Van Eester, D.
2012-01-01
is better than with coupled power, indicating that for these types of discharges the dominating mechanism for the rotation is related to indirect effects of electron heat transport, rather than to direct effects of ICRF heating. There is no conclusive evidence that mode conversion in itself affects rotation...
Energy Technology Data Exchange (ETDEWEB)
Laporta, V. [Istituto di Metodologie Inorganiche e dei Plasmi, CNR, Bari, Italy and Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Celiberto, R. [Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica, Politecnico di Bari, Italy and Istituto di Metodologie Inorganiche e dei Plasmi, CNR, Bari (Italy); Tennyson, J. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)
2014-12-09
Rate coefficients for dissociative electron attachment and electron-impact dissociation processes, involving vibrationally excited molecular oxygen, are presented. Analytical fits of the calculated numerical data, useful in the applications, are also provided.
Using consumer electronic devices to estimate whole-body vibration exposure.
Wolfgang, Rebecca; Burgess-Limerick, Robin
2014-01-01
The cost and complexity of commercially available devices for measuring whole-body vibration is a barrier to the systematic collection of the information required to manage this hazard at workplaces. The potential for a consumer electronic device to be used to estimate whole-body vibration was assessed by use of an accelerometer calibrator, and by collecting 42 simultaneous pairs of measurements from a fifth-generation iPod Touch and one of two gold standard vibration measurement devices (Svantech SV111 [Svantech, Warsaw, Poland] or Brüel & Kjær 4447 [Brüel & Kjær Sound & Vibration Measurement A/S, Nærum, Denmark]) while driving light vehicles on a variety of different roadway surfaces. While sampling rate limitations make the accelerometer data collected from the iPod Touch unsuitable for frequency analysis, the vibration amplitudes recorded are sufficiently accurate (errors less than 0.1 m/s(2)) to assist workplaces manage whole-body vibration exposures.
Vibrational excitation resulting from electron capture in LUMO of F 2 ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Chemical Sciences; Volume 124; Issue 1. Vibrational excitation resulting from electron capture in LUMO of F2 and HCl - A treatment using the time-dependent wave packet approach. Bhavesh K Shandilya Manabendra Sarma Satrajit Adhikari Manoj K Mishra. Volume 124 Issue 1 January 2012 ...
Zhang, Y.; Zheng, R.; Kaizuka, T.; Su, D.; Nakano, K.; Cartmell, M. P.
2015-11-01
A model for energy harvesting from a rotating automotive tyre is suggested in which the principle of stochastic resonance is advantageously exploited. A bistable response characteristic is obtained by recourse a small harvester comprising a magnetically repellant configuration in which an instrumented cantilever beam can flip between two physical response states when suitably excited by the rotation of a car wheel into which it is fitted. The rotation of the wheel creates a periodic modulation which enables stochastic resonance to take place and as a consequence of this for energy to be harvested from road noise transmitted through the tyre. An optimised mathematical model of the system is presented based on a series of experimental tests and it is shown that a ten-fold increase in harvested energy over a comparable monostable case is feasible. The suggested application for this harvester is to provide electrical power for a tyre pressure monitoring system.
A New Vibration Measurement Procedure for On-Line Quality Control of Electronic Devices
Directory of Open Access Journals (Sweden)
Gian Marco Revel
2002-01-01
Full Text Available In this paper the problem of experimentally testing the mechanical reliability of electronic components for quality control is approached. In general, many tests are performed on electronic devices (personal computers, power supply units, lamps, etc., according to the relevant international standards (IEC, in order to verify their resistance to shock and vibrations, but these are mainly “go no-go” experiments, performed on few samples taken from the production batches.
McBride, William R.; McBride, Daniel R.
2016-08-01
The Daniel K. Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, with a 4-meter off-axis primary mirror and 16 meter rotating Coudé laboratory within the telescope pier. The off-axis design requires a mount similar to an 8-meter on-axis telescope. Both the telescope mount and the Coudé laboratory utilize a roller bearing technology in place of the more commonly used hydrostatic bearings. The telescope enclosure utilizes a crawler mechanism for the altitude axis. As these mechanisms have not previously been used in a telescope, understanding the vibration characteristics and the potential impact on the telescope image is important. This paper presents the methodology used to perform jitter measurements of the enclosure and the mount bearings and servo system in a high-noise environment utilizing seismic accelerometers and high dynamic-range data acquisition equipment, along with digital signal processing (DSP) techniques. Data acquisition and signal processing were implemented in MATLAB. In the factory acceptance testing of the telescope mount, multiple accelerometers were strategically located to capture the six axes-of-motion of the primary and secondary mirror dummies. The optical sensitivity analysis was used to map these mirror mount displacements and rotations into units of image motion on the focal plane. Similarly, tests were done with the Coudé rotator, treating the entire rotating instrument lab as a rigid body. Testing was performed by recording accelerometer data while the telescope control system performed tracking operations typical of various observing scenarios. The analysis of the accelerometer data utilized noise-averaging fast Fourier transform (FFT) routines, spectrograms, and periodograms. To achieve adequate dynamic range at frequencies as low as 3Hz, the use of special filters and advanced windowing functions were necessary. Numerous identical automated tests were compared to identify and select the data sets
Hunter, William F.
1967-01-01
A numerical method is Presented for determining the natural vibration frequencies, and the corresponding mode shapes, of a rotating cantilever beam which has a nonuniform, unsymmetrical cross section. Two coupled fourth-order differential equations of motion with variable coefficients are derived which govern the motion of such a beam having deformations in two directions. Through the development and utilization of the integrating matrix, the solution of the differential equations is obtained in the form of an eigenvalue problem. The solutions to the eigenvalue problem are determined by an iteration method based upon a special orthogonality relationship which is derived. Numerical examples, including an application to a twisted propeller blade, are presented with the results of the integrating matrix solutions being compared to exact solutions and experimental data.
Possible interaction between thermal electrons and vibrationally excited N2 in the lower E-region
Directory of Open Access Journals (Sweden)
K.-I. Oyama
2011-03-01
Full Text Available As one of the tasks to find the energy source(s of thermal electrons, which elevate(s electron temperature higher than neutral temperature in the lower ionosphere E-region, energy distribution function of thermal electron was measured with a sounding rocket at the heights of 93–131 km by the applying second harmonic method. The energy distribution function showed a clear hump at the energy of ~0.4 eV. In order to find the reason of the hump, we conducted laboratory experiment. We studied difference of the energy distribution functions of electrons in thermal energy range, which were measured with and without EUV radiation to plasma of N2/Ar and N2/O2 gas mixture respectively. For N2/Ar gas mixture plasma, the hump is not clearly identified in the energy distribution of thermal electrons. On the other hand for N2/O2 gas mixture, which contains vibrationally excited N2, a clear hump is found when irradiated by EUV. The laboratory experiment seems to suggest that the hump is produced as a result of interaction between vibrationally excited N2 and thermal electrons, and this interaction is the most probable heating source for the electrons of thermal energy range in the lower E-region. It is also suggested that energy distribution of the electrons in high energy part may not be Maxwellian, and DC probe measures the electrons which are non Maxwellian, and therefore "electron temperature" is calculated higher.
The separation of vibrational coherence from ground- and excited-electronic states in P3HT film
Song, Yin
2015-06-07
© 2015 AIP Publishing LLC. Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S (λ 1, T∼ 2, λ 3)) along the population time (T∼ 2) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S (λ 1, ν∼ 2, λ 3)). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ ν∼ 2) in the rephasing beating map and at negative frequency (- ν∼ 2) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems.
John R. Jones; Wayne D. Shepperd
1985-01-01
The rotation, in forestry, is the planned number of years between formation of a crop or stand and its final harvest at a specified stage of maturity (Ford-Robertson 1971). The rotation used for many species is the age of culmination of mean usable volume growth [net mean annual increment (MAI)]. At that age, usable volume divided by age reaches its highest level. That...
Energy Technology Data Exchange (ETDEWEB)
Picher, Matthieu; Mazzucco, Stefano [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899-6203 (United States); Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20740 (United States); Blankenship, Steve [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899-6203 (United States); Sharma, Renu, E-mail: renu.sharma@nist.gov [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899-6203 (United States)
2015-03-15
Here, we present a measurement platform for collecting multiple types of spectroscopy data during high-resolution environmental transmission electron microscopy observations of dynamic processes. Such coupled measurements are made possible by a broadband, high-efficiency, free-space optical system. The critical element of the system is a parabolic mirror, inserted using an independent hollow rod and placed below the sample holder which can focus a light on the sample and/or collect the optical response. We demonstrate the versatility of this optical setup by using it to combine in situ atomic-scale electron microscopy observations with Raman spectroscopy. The Raman data is also used to measure the local temperature of the observed sample area. Other applications include, but are not limited to: cathodo- and photoluminescence spectroscopy, and use of the laser as a local, high-rate heating source. - Highlights: • Broadband, high-efficiency design adaptable to other electron microscopes. • Raman spectroscopy integrated with environmental transmission electron microscopy. • Raman spectra peak frequency shifts enable measurement of local sample temperature. • Multiple types of optical spectroscopy enabled, e.g. cathodoluminescence.
Correlating electronic and vibrational motions in charge transfer systems
Energy Technology Data Exchange (ETDEWEB)
Khalil, Munira [Univ. of Washington, Seattle, WA (United States)
2014-06-27
The goal of this research program was to measure coupled electronic and nuclear motions during photoinduced charge transfer processes in transition metal complexes by developing and using novel femtosecond spectroscopies. The scientific highlights and the resulting scientific publications from the DOE supported work are outlined in the technical report.
Pearson, J. C.; Pickett, Herbert M.; Sastry, K. V. L. N.
2000-01-01
C2H5CN (Propionitrile or ethyl cyanide) is a well known interstellar species abundantly observed in hot cores during the onset of star formation. The onset of star formation generally results in elevated temperature, which thermally populates may low lying vibrational states such as the 206/cm in-plane bend and the 212/cm first excited torsional state in C2H5CN. Unfortunately, these two states are strongly coupled through a complex series of torsion-vibration-rotation interactions, which dominate the spectrum. In order to understand the details of these interactions and develop models capable of predicting unmeasured transitions for astronomical observations in C2H5CN and similar molecules, several thousand rotational transitions in the lowest excited in-plane bend and first excited torsional state have been recorded, assigned and analyzed. The analysis reveals very strong a- and b-type Coriolis interactions and a number of other smaller interactions and has a number of important implications for other C3V torsion-rotation-vibration systems. The relative importance and the physical origins of the coupling among the rotational, vibrational and torsional motions will be presented along with a full spectroscopic analysis and supporting astronomical observations.
Electron scattering from the octupole band in /sup 238/U
Energy Technology Data Exchange (ETDEWEB)
Hirsch, A.; Creswell, C.; Bertozzi, W.; Heisenberg, J.; Hynes, M.V.; Kowalski, S.; Miska, H.; Norum, B.; Rad, F.N.; Sargent, C.P.; Sasanuma, T.; Turchinetz, W.
1978-03-06
A simple model for nuclear surface vibrations in permanently deformed nuclei does well in reproducing electron scattering cross sections of rotational levels built on a K/sup ..pi../= 0/sup -/ intrinsic octupole vibration in /sup 238/U.
Mihaylova, Emilia M.; Naydenova, Izabela; Martin, Suzanne; Toal, Vincent
2004-06-01
Electronic speckle pattern shearing interferometry (ESPSI) is superior to Electronic speckle pattern interferometry (ESPI) when strain distribution, arising from object deformation or vibration, need to be measured. This is because shearography provides data directly related to the spatial derivatives of the displacement. Further development of ESPSI systems could be beneficial for wider application to the measurement of mechanical characteristics of vibrating objects. Two electronic speckle pattern shearing interferometers (ESPSI) suitable for vibration measurements are presented. In both ESPSI systems photopolymer holographic gratings are used to shear the images and to control the size of the shear. The holographic gratings are recorded using an acrylamide-based photopolymer material. Since the polymerization process occurs during recording, the holograms are produced without any development or processing. The ESPSI systems with photopolymer holographic gratings are simple and compact. Introducing photopolymer holographic gratings in ESPSI gives the advantage of using high aperture optical elements at relatively low cost. It is demonstrated that both ESPSI system can be used for vibration measurements. The results obtained are promising for future applications of the systems for modal analysis.
Pitsevich, G.; Doroshenko, I.; Malevich, A..; Shalamberidze, E.; Sapeshko, V.; Pogorelov, V.; Pettersson, L. G. M.
2017-02-01
Using two sets of effective rotational constants for the ground (000) and the excited bending (010) vibrational states the calculation of frequencies and intensities of vibration-rotational transitions for J″ = 0 - 2; and J‧ = 0 - 3; was carried out in frame of the model of a rigid asymmetric top for temperatures from 0 to 40 K. The calculation of the intensities of vibration-rotational absorption bands of H2O in an Ar matrix was carried out both for thermodynamic equilibrium and for the case of non-equilibrium population of para- and ortho-states. For the analysis of possible interaction of vibration-rotational and translational motions of a water molecule in an Ar matrix by 3D Schrödinger equation solving using discrete variable representation (DVR) method, calculations of translational frequencies of H2O in a cage formed after one argon atom deleting were carried out. The results of theoretical calculations were compared to experimental data taken from literature.
Excitation of vibrational quanta in furfural by intermediate-energy electrons
Energy Technology Data Exchange (ETDEWEB)
Jones, D. B. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Neves, R. F. C. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Instituto Federal do Sul de Minas Gerais, Campus Poços de Caldas, Minas Gerais (Brazil); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, MG (Brazil); Lopes, M. C. A. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, MG (Brazil); Costa, R. F. da [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, Campinas, 13083-859 São Paulo (Brazil); Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, 09210-580 São Paulo (Brazil); Varella, M. T. do N. [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, São Paulo (Brazil); Bettega, M. H. F. [Departamento de Física, Universidade Federal do Paraná, CP 19044, 81531-990 Curitiba, Paraná (Brazil); Lima, M. A. P. [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, Campinas, 13083-859 São Paulo (Brazil); García, G. [Instituto de Física Fundamental, CSIC, Serrano 113-bis, 28006 Madrid (Spain); and others
2015-12-14
We report cross sections for electron-impact excitation of vibrational quanta in furfural, at intermediate incident electron energies (20, 30, and 40 eV). The present differential cross sections are measured over the scattered electron angular range 10°–90°, with corresponding integral cross sections subsequently being determined. Furfural is a viable plant-derived alternative to petrochemicals, being produced via low-temperature plasma treatment of biomass. Current yields, however, need to be significantly improved, possibly through modelling, with the present cross sections being an important component of such simulations. To the best of our knowledge, there are no other cross sections for vibrational excitation of furfural available in the literature, so the present data are valuable for this important molecule.
Gongbo Zhou; Houlian Wang; Zhencai Zhu; Linghua Huang; Wei Li
2015-01-01
Harvesting the energy contained in the running environment of rotating machinery would be a good way to supplement energy to the wireless sensor. In this paper, we take piezoelectric bimorph cantilever beam with parallel connection mode as energy collector and analyze the factors which can influence the generation performance. First, a modal response theory model is built. Second, the static analysis, modal analysis, and piezoelectric harmonic response analysis of the wind-induced piezoelectr...
Invernizzi, Davide; Dozio, Lorenzo
2016-05-01
The equations of motions governing the free vibrations of prismatic slender beams rotating in a plane at constant angular velocity are derived according to a geometrically exact approach. Compared to other modeling methods, additional stiffening terms induced by pre-stress are found in the dynamic equations after fully consistent linearization about the deformed equilibrium configuration. These terms include axial, bending and torsional stiffening effects which arise when second-order generalized strains are retained. It is shown that their contribution becomes relevant at moderate to high angular speeds, where high means that the equilibrium state is subject to strains close to the limit where a physically linear constitutive law still applies. In particular, the importance of the axial stiffening is specifically investigated. The natural frequencies as a function of the angular velocity and other system parameters are computed and compared with benchmark cases available in the literature. Finally, the error on the modal characteristics of the rotating beam is evaluated when the linearization is carried out about the undeformed configuration.
Li, L.; Zhang, D. G.; Zhu, W. D.
2014-02-01
A comprehensive dynamic model of a rotating hub-functionally graded material (FGM) beam system is developed based on a rigid-flexible coupled dynamics theory to study its free vibration characteristics. The rigid-flexible coupled dynamic equations of the system are derived using the method of assumed modes and Lagrange's equations of the second kind. The dynamic stiffening effect of the rotating hub-FGM beam system is captured by a second-order coupling term that represents longitudinal shrinking of the beam caused by the transverse displacement. The natural frequencies and mode shapes of the system with the chordwise bending and stretching (B-S) coupling effect are calculated and compared with those with the coupling effect neglected. When the B-S coupling effect is included, interesting frequency veering and mode shift phenomena are observed. A two-mode model is introduced to accurately predict the most obvious frequency veering behavior between two adjacent modes associated with a chordwise bending and a stretching mode. The critical veering angular velocities of the FGM beam that are analytically determined from the two-mode model are in excellent agreement with those from the comprehensive dynamic model. The effects of material inhomogeneity and graded properties of FGM beams on their dynamic characteristics are investigated. The comprehensive dynamic model developed here can be used in graded material design of FGM beams for achieving specified dynamic characteristics.
Ryder, Matthew R.; Van de Voorde, Ben; Civalleri, Bartolomeo; Bennett, Thomas D.; Mukhopadhyay, Sanghamitra; Cinque, Gianfelice; Fernandez-Alonso, Felix; De Vos, Dirk; Rudić, Svemir; Tan, Jin-Chong
2017-06-01
We show clear experimental evidence of cooperative terahertz (THz) dynamics observed below 3 THz (˜100 cm-1 ), for a low-symmetry Zr-based metal-organic framework structure, termed MIL-140A [ZrO (O2C-C 6H4-CO2) ]. Utilizing a combination of high-resolution inelastic neutron scattering and synchrotron radiation far-infrared spectroscopy, we measured low-energy vibrations originating from the hindered rotations of organic linkers, whose energy barriers and detailed dynamics have been elucidated via ab initio density functional theory calculations. The complex pore architecture caused by the THz rotations has been characterized. We discovered an array of soft modes with trampolinelike motions, which could potentially be the source of anomalous mechanical phenomena such as negative thermal expansion. Our results demonstrate coordinated shear dynamics (2.47 THz), a mechanism which we have shown to destabilize the framework structure, in the exact crystallographic direction of the minimum shear modulus (Gmin ).
Ghadiri, Majid; Shafiei, Navvab; Alireza Mousavi, S.
2016-09-01
Due to having difficulty in solving governing nonlinear differential equations of a non-uniform microbeam, a few numbers of authors have studied such fields. In the present study, for the first time, the size-dependent vibration behavior of a rotating functionally graded (FG) tapered microbeam based on the modified couple stress theory is investigated using differential quadrature element method (DQEM). It is assumed that physical and mechanical properties of the FG microbeam are varying along the thickness that will be defined as a power law equation. The governing equations are determined using Hamilton's principle, and DQEM is presented to obtain the results for cantilever and propped cantilever boundary conditions. The accuracy and validity of the results are shown in several numerical examples. In order to display the influence of size on the first two natural frequencies and consequently changing of some important microbeam parameters such as material length scale, rate of cross section, angular velocity and gradient index of the FG material, several diagrams and tables are represented. The results of this article can be used in designing and optimizing elastic and rotary-type micro-electro-mechanical systems like micro-motors and micro-robots including rotating parts.
Electronic Properties of Si-Hx Vibrational Modes at Si Waveguide Interface.
Bashouti, Muhammad Y; Yousefi, Peyman; Ristein, Jürgen; Christiansen, Silke H
2015-10-01
Attenuated total reflectance (ATR) and X-ray photoelectron spectroscopy in suite with Kelvin probe were conjugated to explore the electronic properties of Si-Hx vibrational modes by developing Si waveguide with large dynamic detection range compared with conventional IR. The Si 2p emission and work-function related to the formation and elimination of Si-Hx bonds at Si surfaces are monitored based on the detection of vibrational mode frequencies. A transition between various Si-Hx bonds and thus related vibrational modes is monitored for which effective momentum transfer could be demonstrated. The combination of the aforementioned methods provides for results that permit a model for the kinetics of hydrogen termination of Si surfaces with time and advanced surface characterizing of hybrid-terminated semiconducting solids.
Jiang, Chi-Lun
2015-01-01
With a 600mk homebuilt UHV STM system, we studied molecular vibration at the solid surface with inelastic electron tunneling spectroscopy (IETS) of Acetylene single molecules adsorbed on Cu(100) surface. The identification of vibrational IETS features with normalized conductance change (Δσ/σ) as low as 0.24% in dI2/d2V spectra was demonstrated. Five vibrational modes with energy level at 117.70meV (Δσ/σ =0.42%), 84.07meV (Δσ/σ =0.24%), 58.46meV (Δσ/σ =1.18%), 34.80meV (Δσ/σ =0.65% ) and 22.1...
Trapping of an electron due to molecular vibrations
Narevicius; Moiseyev
2000-02-21
Here we first show that the nuclear motion of H-2 generates a continuum of autoionization resonance states. The interference between them increases the lifetime of the trapped electron in the e(-)/H(2) scattering experiments and leads to asymmetric oscillations in the phase of the excitation probability amplitude. This collective coherent interference resonance phenomenon is very different from any known mechanism in quantum mechanics which reveals the fingerprints of overlapping resonances in scattering cross section and results from the non-Hermitian properties of the H-2 Hamiltonian.
Directory of Open Access Journals (Sweden)
Bingfeng Ju
2011-03-01
Full Text Available In this paper, a feedback control mechanism and its optimization for rotating disk vibration/flutter via changes of air-coupled pressure generated using piezoelectric patch actuators are studied. A thin disk rotates in an enclosure, which is equipped with a feedback control loop consisting of a micro-sensor, a signal processor, a power amplifier, and several piezoelectric (PZT actuator patches distributed on the cover of the enclosure. The actuator patches are mounted on the inner or the outer surfaces of the enclosure to produce necessary control force required through the airflow around the disk. The control mechanism for rotating disk flutter using enclosure surfaces bonded with sensors and piezoelectric actuators is thoroughly studied through analytical simulations. The sensor output is used to determine the amount of input to the actuator for controlling the response of the disk in a closed loop configuration. The dynamic stability of the disk-enclosure system, together with the feedback control loop, is analyzed as a complex eigenvalue problem, which is solved using Galerkin’s discretization procedure. The results show that the disk flutter can be reduced effectively with proper configurations of the control gain and the phase shift through the actuations of PZT patches. The effectiveness of different feedback control methods in altering system characteristics and system response has been investigated. The control capability, in terms of control gain, phase shift, and especially the physical configuration of actuator patches, are also evaluated by calculating the complex eigenvalues and the maximum displacement produced by the actuators. To achieve a optimal control performance, sizes, positions and shapes of PZT patches used need to be optimized and such optimization has been achieved through numerical simulations.
Graus, M; Grimm, M; Metzger, C; Dauth, M; Tusche, C; Kirschner, J; Kümmel, S; Schöll, A; Reinert, F
2016-04-08
Electron-phonon coupling is one of the most fundamental effects in condensed matter physics. We here demonstrate that photoelectron momentum mapping can reveal and visualize the coupling between specific vibrational modes and electronic excitations. When imaging molecular orbitals with high energy resolution, the intensity patterns of photoelectrons of the vibronic sidebands of molecular states show characteristic changes due to the distortion of the molecular frame in the vibronically excited state. By comparison to simulations, an assignment of specific vibronic modes is possible, thus providing unique information on the coupling between electronic and vibronic excitation.
First-Principles Vibrational Electron Energy Loss Spectroscopy of β -Guanine
Radtke, G.; Taverna, D.; Lazzeri, M.; Balan, E.
2017-07-01
A general approach to model vibrational electron energy loss spectra obtained using an electron beam positioned away from the specimen is presented. The energy-loss probability of the fast electron is evaluated using first-principles quantum mechanical calculations (density functional theory) of the dielectric response of the specimen. The validity of the method is assessed using recently measured anhydrous β -guanine, an important molecular solid used by animals to produce structural colors. The good agreement between theory and experiments lays the basis for a quantitative interpretation of this spectroscopy in complex systems.
The absorption spectrum of D2O in the region of 0.97 μm: the 3ν1 + ν3 vibrational-rotational band
Serdyukov, V. I.; Sinitsa, L. N.
2017-08-01
The vibrational-rotational absorption spectrum of D2O in the range from 10 120 to 10 450 cm-1 is recorded on a Fourier transform spectrometer with a resolution of 0.05 cm-1. The measurements were performed using a multipass White cell with an optical path length of 24 m. A light-emitting diode with brightness higher than that of other devices was used as a radiation source. The signal-to-noise ratio was about 104. The spectrum is interpreted as consisting of lines of more than 400 transitions. The spectral characteristics of lines (centers, intensities, and half widths) are determined by fitting the Voigt profile parameters to experimental data by the least-squares method. The intensities of lines and the experimental rotational energy levels of the (301) vibrational state of the D2 16O molecule with high rotational quantum numbers are determined for the first time.
Ceacero-Vega, Antonio A; Ruiz, Tomas Peña; Gómez, Manuel Fernández; Roldán, José M Granadino; Navarro, Amparo; Fernández-Liencres, M Paz; Jayasooriya, Upali A
2007-07-19
The molecular structure of 2,6-dichlorostyrene has been analyzed at MP2 and DFT levels using different basis sets concluding in a nonplanar geometry. The influence of either the level of theory or the nature of the substituent has been assessed. The vinyl-phenyl torsion barrier has also been investigated as a function of level of theory. The ultimate factors responsible for the torsion barrier have been studied using two different partitioning schemes, i.e., the total electronic potential energy and the natural bond orbital, NBO. A topological analysis of the electron density within the atom-in-molecule, AIM, theory predicts soft intramolecular chlorine (ring)-hydrogen (vinyl) contacts when the system becomes planar. A first complete vibrational study has been performed using theoretical data and experimental vibrational frequencies from IR, Raman and, for the first time, inelastic neutron scattering, INS, spectra. The new assignment proposed is based on a scaled quantum mechanical, SQM, force field and the wavenumber linear scaling, WLS, approach.
Excitation of the lowest CO2 vibrational states by electrons in hypersonic boundary layers
Armenise, I.
2017-07-01
The state-to-state vibrational kinetics of a CO2/O2/CO/C/O/e- mixture in a hypersonic boundary layer under conditions compatible with the Mars re-entry is studied. The model adopted treats three CO2 modes (the two degenerated bending modes are approximated as a unique one) as not independent ones. Vibrational-translational transitions in the bending mode, inter-mode exchanges within CO2 molecule and between molecules of different chemical species as well as dissociation-recombination reactions are considered. Attention is paid to the electron-CO2 collisions that cause transitions from the ground vibrational state, CO2(0,0,0), to the first excited ones, CO2(1,0,0), CO2(0,1,0) and CO2(0,0,1). The corresponding processes rate coefficients are obtained starting from the electron energy distribution function, calculated either as an equilibrium Boltzmann distribution at the local temperature or by solving the Boltzmann equation. Results obtained either neglecting or including in the kinetic scheme the electron-CO2 collisions are compared and explained by analysing the rate coefficients of the electron-CO2 collisions.
Baiardi, A; Paoloni, L; Barone, V; Zakrzewski, V G; Ortiz, J V
2017-07-11
The analysis of photoelectron spectra is usually facilitated by quantum mechanical simulations. Because of the recent improvement of experimental techniques, the resolution of experimental spectra is rapidly increasing, and the inclusion of vibrational effects is usually mandatory to obtain a reliable reproduction of the spectra. With the aim of defining a robust computational protocol, a general time-independent formulation to compute different kinds of vibrationally resolved electronic spectra has been generalized to also support photoelectron spectroscopy. The electronic structure data underlying the simulation are computed using different electron propagator approaches. In addition to the more standard approaches, a new and robust implementation of the second-order self-energy approximation of the electron propagator based on a transition operator reference (TOEP2) is presented. To validate our implementation, a series of molecules has been used as test cases. The result of the simulations shows that, for ultraviolet photoionization spectra, the more accurate nondiagonal approaches are needed to obtain a reliable reproduction of vertical ionization energies but that diagonal approaches are sufficient for energy gradients and pole strengths. For X-ray photoelectron spectroscopy, the TOEP2 approach, besides being more efficient, is also the most accurate in the reproduction of both vertical ionization energies and vibrationally resolved bandshapes.
Ultrafast Control of the electronic phase of a manganite viamode-selective vibrational excitation
Energy Technology Data Exchange (ETDEWEB)
Rini, Matteo; Tobey, Ra' anan I.; Dean, Nicky; Tokura, Yoshinori; Schoenlein, Robert W.; Cavalleri, Andrea
2007-05-01
Controlling a phase of matter by coherently manipulatingspecific vibrational modes has long been an attractive (yet elusive) goalfor ultrafast science. Solids with strongly correlated electrons, inwhich even subtle crystallographic distortions can result in colossalchanges of the electronic and magnetic properties, could be directedbetween competing phases by such selective vibrational excitation. Inthis way, the dynamics of the electronic ground state of the systembecome accessible, and new insight into the underlying physics might begained. Here we report the ultrafast switching of the electronic phase ofa magnetoresistive manganite via direct excitation of a phonon mode at 71meV (17 THz). A prompt, five-order-of-magnitude drop in resistivity isobserved, associated with a non-equilibrium transition from the stableinsulating phase to a metastable metallic phase. In contrast withlight-induced, and current-driven phase transitions, the vibrationallydriven bandgap collapse observed here is not related to hot-carrierinjection and is uniquely attributed to a large-amplitude Mn-Odistortion. This corresponds to a perturbation of theperovskite-structure tolerance factor, which in turn controls theelectronic bandwidth via inter-site orbital overlap. Phase control bycoherent manipulation of selected metal--oxygen phonons should findextensive application in other complex solids--notably in copper oxidesuperconductors, in which the role of Cu-O vibrations on the electronicproperties is currently controversial.
Najib, Hamid
2015-06-01
Several accurate experimental values of the rovibrational interaction constants αC and αB, the harmonic wave-number parameters ωij, and the anharmonicity xij and gij constants have been extracted from the most recent high-resolution Fourier transform infrared (FTIR), centimeter-wave (CMW) and millimeter-wave (MMW) measurements in the spectra of the oblate symmetric top molecule 14NF3. The data used are those of the four fundamental, the overtone, the combination and the hot bands identified and analyzed in the range between 400 cm-1 and 2000 cm-1. Combining the recent experimental values of the constants αC and αB, with the accurate experimental ground state rotational constants C0 and B0, new equilibrium rotational constants have been evaluated: Ce = 0.1968006 (26) cm-1 and Be = 0.358981442 (43) cm-1 for the pyramidal molecule NF3, from which the following equilibrium structure is obtained: re(F-N) = 1.36757 (58) Å; θe(FNF) = 101.8513 (10)°. This experimental equilibrium geometry is in excellent agreement with the recent structure determined by ab initio calculations at the CCSD(T)/aug-cc-pVQZ level of theory.
Structural, electronic, vibrational and optical properties of Bin clusters
Liang, Dan; Shen, Wanting; Zhang, Chunfang; Lu, Pengfei; Wang, Shumin
2017-10-01
The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bin (n = 2-14) clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even-odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster.
Prasad, O.; Sinha, L.; Misra, N.; Narayan, V.; Kumar, N.; Kumar, A.
2010-09-01
The present work deals with the structural, electronic, and vibrational analysis of rivastigmine. Rivastigmine, an antidementia medicament, is credited with significant therapeutic effects on the cognitive, functional, and behavioural problems that are commonly associated with Alzheimer’s dementia. For rivastigmine, a number of minimum energy conformations are possible. The geometry of twelve possible conformers has been analyzed and the most stable conformer was further optimized at a higher basis set. The electronic properties and vibrational frequencies were then calculated using a density functional theory at the B3LYP level with the 6-311+G(d, p) basis set. The different molecular surfaces have also been drawn to understand the activity of the molecule. A narrower frontier orbital energy gap in rivastigmine makes it softer and more reactive than water and dimethylfuran. The calculated value of the dipole moment is 2.58 debye.
Pietanza, L. D.; Colonna, G.; Capitelli, M.
2017-12-01
Nanopulse atmospheric carbon monoxide discharges and corresponding afterglows have been investigated in a wide range of applied reduced electric field (130 kinetics of vibrational and electronic excited states as well as to a simplified plasma chemistry for the different species formed during the activation of CO. The molar fraction of electronically excited states generated in the discharge is sufficient to create structures in the EEDF in the afterglow regime. On the other hand, only for long duration pulses (i.e. 50 ns), non-equilibrium vibrational distributions can be observed especially in the afterglow. The trend of the results for the case study E/N = 200 Td, \\text{pulse}=2$ ns is qualitatively and quantitatively similar to the corresponding case for CO2 implying that the activation of CO2 by cold plasmas should take into account the kinetics of formed CO with the same accuracy as the CO2 itself.
Poloidal rotation driven by electron cyclotron resonance wave in tokamak plasmas
Directory of Open Access Journals (Sweden)
Qing Zhou
2017-10-01
Full Text Available The poloidal electric filed, which is the drive field of poloidal rotation, has been observed and increases obviously after the injection of electron cyclotron resonance wave in HL-2A experiment, and the amplitude of the poloidal electric field is in the order of 103 V/m. Through theoretical analysis using Stringer rotation model, the observed poloidal electric field is of the same order as the theoretical calculation value. In addition, the magnetic pump damping which would damp the poloidal rotation is calculated numerically and the calculation results show that the closer to the core plasmas, the stronger the magnetic pump damping will be. Meanwhile, according to the value of the calculated magnetic pump damping, the threshold of the poloidal electric field which could overcome magnetic pump damping and drive poloidal rotation in tokamak plasmas is given out. Finally, the poloidal rotation velocity over time at different minor radius is studied theoretically.
Alling, B.; Kormann, F.H.W.; Grabowski, B; Glensk, A; Abrikosov, I.A.
2016-01-01
We study the impact of lattice vibrations on magnetic and electronic properties of paramagnetic bcc and fcc iron at finite temperature, employing the disordered local moments molecular dynamics (DLM-MD) method. Vibrations strongly affect the distribution of local magnetic moments at finite
Cross Sections and Rate Coefficients for Vibrational Excitation of HeH+ Molecule by Electron Impact
Directory of Open Access Journals (Sweden)
Mehdi Ayouz
2016-12-01
Full Text Available Cross sections and thermally-averaged rate coefficients for vibration (de-excitation of HeH + by an electron impact are computed using a theoretical approach that combines the multi-channel quantum defect theory and the UK R-matrix code. Fitting formulas with a few numerical parameters are derived for the obtained rate coefficients. The interval of applicability of the formulas is from 40 to 10,000 K.
Resonant electron-impact excitation of vibrational modes in polyatomic molecules
Cartwright, David C.; Trajmar, Sandor
1996-04-01
Measured differential cross sections (DCSs) for electron-impact excitation of bending vibrational modes involving an odd number of vibrational quanta in 0953-4075/29/8/018/img5 by 4 eV incident energy electrons display a strong trend to zero for forward and backward scattering which is characteristic of `symmetry-forbidden' transitions. This DCS behaviour is postulated here to be produced by a Feshbach resonant mechanism involving a low-lying bent excited state of 0953-4075/29/8/018/img5. The model described here identifies three additional low-lying bent excited states of 0953-4075/29/8/018/img5 which could also be parent states for core-excited Feshbach resonances, one of which may play a role in dissociative attachment in this 3.5 - 5.0 eV energy region. The resonant vibrational excitation mechanism proposed here is also believed to be operative in other polyatomic molecules and could be investigated by performing selected electron energy-loss measurements within the lowest energy resonance regions of the molecules 0953-4075/29/8/018/img8 and 0953-4075/29/8/018/img9.
Vibrational and electronic properties of 4‧-halomethyl-2-biphenylcarbonitrile compounds
Shankar Rao, Y. B.; Veeraiah, V.; Sundius, Tom; Chaitanya, Kadali
2017-09-01
In this paper we studied the structural, vibrational and electronic properties of the 4‧-bromomethyl-2-biphenylcarbonitrile (BMBP) 4‧-chloromethyl-2-biphenylcarbonitrile (CMBP) and 4‧-fluoromethyl-2-biphenylcarbonitrile (FMBP) compounds using experimental and theoretical methods. The FT-IR and FT-Raman spectra of BMBP in solid phase were recorded in the region 4000-400 cm-1 and 4000-50 cm-1, respectively. The UV absorption spectrum of BMBP was recorded in dichloromethane and methanol solvents in the range 180-400 nm. The theoretical spectral properties of title compounds were simulated using density functional theory (DFT) and time dependent DFT methods. Scaling of the vibrational frequencies was carried out with the MOLVIB program using multiple scaling factors and assignment to each vibrational frequency was consigned on the basis of potential energy distribution (PED). The electronic spectrum of BMBP in two different solvents (methanol and dichloromethane), calculated at the CAM-B3LYP/6-31G(d,p) level compares well with the experimental data and validates the current method for predicting the absorption spectrum of CMBP and FMBP. Furthermore, the electronic, nonlinear optical and thermodynamics properties of the three compounds were discussed in detailed.
Faure, Géraldine
1997-01-01
This work deals with vibrational and rotational temperatures of molecules in thermal plasmas.This thesis had two main parts : the first is devoted to the molecular spectra calculation and the second part is devoted to the spectra comparison in four different experimental conditions.A code of calculation has been created to simulate spectra of diatomic molecules. It has been essentially applied on the radicals C2, CN, the molecule N2 and the molecular ion N2+ for variable parameter vibration a...
Zapoměl, J.; Ferfecki, P.
2016-09-01
A frequently used technological solution for minimization of undesirable effects caused by vibration of rotating machines consists in placing damping devices in the rotor supports. The application of magnetorheological squeeze film dampers enables their optimum performance to be achieved in a wide range of rotating speeds by adapting their damping effect to the current operating conditions. The damping force, which is produced by squeezing the layer of magnetorheological oil, can be controlled by changing magnetic flux passing through the lubricant. The force acting between the rotor and its frame is transmitted through the rolling element bearing, the lubricating layer and the squirrel spring. The loading of the bearing produces a time variable friction moment, energy losses, uneven rotor running, and has an influence on the rotor service life and the current fluctuation in electric circuits. The carried out research consisted in the development of a mathematical model of a magnetorheological squeeze film damper, its implementation into the computational models of rotor systems, and in performing the study on the dependence of the energy losses and variation of the friction moment on the damping force and its control. The new and computationally stable mathematical model of a magnetorheological squeeze film damper, its implementation in the computational models of rigid rotors and learning more on the energy losses generated in the rotor supports in dependence on the damping effect are the principal contributions of this paper. The results of the computational simulations prove that a suitable control of the damping force enables the energy losses to be reduced in a wide velocity range.
Electronic and Vibrational Spectra of InP Quantum Dots Formed by Sequential Ion Implantation
Hall, C.; Mu, R.; Tung, Y. S.; Ueda, A.; Henderson, D. O.; White, C. W.
1997-01-01
We have performed sequential ion implantation of indium and phosphorus into silica combined with controlled thermal annealing to fabricate InP quantum dots in a dielectric host. Electronic and vibrational spectra were measured for the as-implanted and annealed samples. The annealed samples show a peak in the infrared spectra near 320/cm which is attributed to a surface phonon mode and is in good agreement with the value calculated from Frolich's theory of surface phonon polaritons. The electronic spectra show the development of a band near 390 nm that is attributed to quantum confined InP.
Neural-Net Processing of Characteristic Patterns From Electronic Holograms of Vibrating Blades
Decker, Arthur J.
1999-01-01
Finite-element-model-trained artificial neural networks can be used to process efficiently the characteristic patterns or mode shapes from electronic holograms of vibrating blades. The models used for routine design may not yet be sufficiently accurate for this application. This document discusses the creation of characteristic patterns; compares model generated and experimental characteristic patterns; and discusses the neural networks that transform the characteristic patterns into strain or damage information. The current potential to adapt electronic holography to spin rigs, wind tunnels and engines provides an incentive to have accurate finite element models lor training neural networks.
CSIR Research Space (South Africa)
de Clercq, L
2010-09-01
Full Text Available Coherent control of the upper vibrational level populations in the electronic ground state of a polyatomic molecule was simulated. Results indicate that selective excitation of a specific upper state level is possible...
CSIR Research Space (South Africa)
De Clercq, L
2010-09-01
Full Text Available Coherent control of the upper vibrational level populations in the electronic ground state of a polyatomic molecule was simulated. Results indicate that selective excitation of a specific upper state level is possible....
Directory of Open Access Journals (Sweden)
Gongbo Zhou
2015-01-01
Full Text Available Harvesting the energy contained in the running environment of rotating machinery would be a good way to supplement energy to the wireless sensor. In this paper, we take piezoelectric bimorph cantilever beam with parallel connection mode as energy collector and analyze the factors which can influence the generation performance. First, a modal response theory model is built. Second, the static analysis, modal analysis, and piezoelectric harmonic response analysis of the wind-induced piezoelectric bimorph cantilever beam are given in detail. Finally, an experiment is also conducted. The results show that wind-induced piezoelectric bimorph cantilever beam has low resonant frequency and stable output under the first modal mode and can achieve the maximum output voltage under the resonant condition. The output voltage increases with the increase of the length and width of wind-induced piezoelectric bimorph cantilever beam, but the latter increasing amplitude is relatively smaller. In addition, the output voltage decreases with the increase of the thickness and the ratio of metal substrate to piezoelectric patches thickness. The experiment showed that the voltage amplitude generated by the piezoelectric bimorph cantilever beam can reach the value simulated in ANSYS, which is suitable for actual working conditions.
Zakharenko, Olena; Motiyenko, R. A.; Aviles Moreno, Juan-Ramon; Huet, T. R.
2016-06-01
Methacrolein and methyl vinyl ketone are the two major oxidation products of isoprene emitted in the troposphere. New spectroscopic information is provided with the aim to allow unambiguous identification of these molecules, characterized by a large amplitude motion associated with the methyl top. State-of-the-art millimeter-wave spectroscopy experiments coupled to quantum chemical calculations have been performed. Comprehensive sets of molecular parameters have been obtained. The torsion-rotation-vibration effects will be discussed in detail. From the atmospheric application point of view the results provide precise ground state molecular constants essential as a foundation (by using the Ground State Combination Differences method) for the analysis of high resolution spectrum, recorded from 600 to 1600 wn. The infrared range can be then refitted using appropriate Hamiltonian parameters. The present work is funded by the French ANR through the PIA under contract ANR-11-LABX-0005-01 (Labex CaPPA), by the Regional Council Nord-Pas de Calais and by the European Funds for Regional Economic Development (FEDER).
Császár, Attila G.; Furtenbacher, T.; Tennyson, Jonathan; Bernath, Peter F.; Brown, Linda R.; Campargue, Alain; Daumont, Ludovic; Gamache, Robert R.; Hodges, Joseph T.; Naumenko, Olga V.; Polyansky, Oleg L.; Rothman, Laurence S.; Vandaele, Ann Carine; Zobov, Nikolai F.
2014-06-01
The results of an IUPAC Task Group formed in 2004 on "A Database of Water Transitions from Experiment and Theory" (Project No. 2004-035-1-100) are presented. Energy levels and recommended labels involving exact and approximate quantum numbers for the main isotopologues of water in the gas phase, H216O, H218O, H217O, HD16O, HD18O, HD17O, D216O, D218O, and D217O, are determined from measured transition wavenumbers. The transition wavenumbers and energy levels are validated using the MARVEL (measured active rotational-vibrational energy levels) approach and first-principles nuclear motion computations. The extensive data, e.g., more than 200,000 transitions have been handled for H216O, including lines and levels that are required for analysis and synthesis of spectra, thermochemical applications, the construction of theoretical models, and the removal of spectral contamination by ubiquitous water lines. These datasets can also be used to assess where measurements are lacking for each isotopologue and to provide accurate frequencies for many yet-to-be measured transitions. The lack of high-quality frequency calibration standards in the near infrared is identified as an issue that has hindered the determination of high-accuracy energy levels at higher frequencies. The generation of spectra using the MARVEL energy levels combined with transition intensities computed using high accuracy ab initio dipole moment surfaces are discussed.
Yang, Fujun; Ma, Yinhang; Tao, Nan; He, Xiaoyuan
2017-06-01
Due to its multi properties, including excellent stiffness-to-weight and strength-to-weight ratios, closed-cell aluminum and its alloy foams become candidate materials for use in many high-technology industries, such as the automotive and aerospace industries. For the efficient use of closed-cell foams in structural applications, it is necessary and important to detailly understand their mechanical characteristics. In this paper, the nonlinear vibration responses of the cantilever beams of closed-cell aluminum foams were investigated by use of electronic speckle pattern interferometry (ESPI). The nonlinear resonant mode shapes of testing specimens under harmonic excitation were measured. It is first time to obtain from the experimental results that there exist super-harmonic responses when the cantilever beams of closed-cell aluminum foam were forced to vibrate, which was caused by its specific cellular structures.
Nightmare from which you will never awake: Electronic to vibrational spectra!
Energy Technology Data Exchange (ETDEWEB)
De Silva, Nuwon [Iowa State Univ., Ames, IA (United States)
2013-01-01
The theoretical background of ab initio methods and density functional theory is provided. The anharmonicity associated with weakly bound metal cation dihydrogen complexes is examined using the vibrational self-consistent field (VSCF) method and the interaction between a hydrogen molecule and a metal cation is characterized. A study of molecular hydrogen clustering around the lithium cation and their accompanied vibrational anharmonicity employing VSCF is illustrated. A qualitative interpretation is provided of solvent-induced shifts of amides and simulated electronic absorption spectra using the combined time-dependent density functional theory/effective fragment potential method (TDDFT/EFP). An excited-state solvent assisted quadruple hydrogen atom transfer reaction of a coumarin derivative is elucidated using micro solvated quantum mechanical (QM) water and macro solvated EFP water. A dispersion correction to the QM-EFP1 interaction energy is presented.
Kaloni, Thaneshwor P.
2013-11-01
This thesis covers the structural, electronic, magnetic, and vibrational properties of graphene and silicene. In Chapter I, we will start with an introduction to graphene and silicene. In Chapter II, we will briefly discuss about the methodology (i. e. density functional theory)In Chapter III, we will introduce band gap opening in graphene either by introducing defects/doping or by creating superlattices with h-BN substrate. In Chapter IV, we will focus on the structural and electronic properties of K and Ge-intercalated graphene on SiC(0001). In addition, the enhancement of the superconducting transition temperature in Li-decorated graphene supported by h-BN substrate will be discussed. In Chapter V, we will discuss the vibrational properties of free-standing silicene. In addition, superlattices of silicene with h-BN as well as the phase transition in silicene by applying an external electric field will be discussed. The electronic and magnetic properties transition metal decorated silicene will be discussed, in particular the realization of the quantum anomalous Hall effect will be addressed. Furthermore, the structural, electronic, and magnetic properties of Mn decorated silicene supported by h-BN substrate will be discussed. The conclusion is included in Chapters VI. Finally, we will end with references and a list of publications for this thesis.
Amyay, Badr; Robert, Séverine; Herman, Michel; Fayt, André; Raghavendra, Balakrishna; Moudens, Audrey; Thiévin, Jonathan; Rowe, Bertrand; Georges, Robert
2009-09-01
A high temperature source has been developed and coupled to a high resolution Fourier transform spectrometer to record emission spectra of acetylene around 3 μm up to 1455 K under Doppler limited resolution (0.015 cm-1). The ν3-ground state (GS) and ν2+ν4+ν5 (Σu+ and Δu)-GS bands and 76 related hot bands, counting e and f parities separately, are assigned using semiautomatic methods based on a global model to reproduce all related vibration-rotation states. Significantly higher J-values than previously reported are observed for 40 known substates while 37 new e or f vibrational substates, up to about 6000 cm-1, are identified and characterized by vibration-rotation parameters. The 3 811 new or improved data resulting from the analysis are merged into the database presented by Robert et al. [Mol. Phys. 106, 2581 (2008)], now including 15 562 lines accessing vibrational states up to 8600 cm-1. A global model, updated as compared to the one in the previous paper, allows all lines in the database to be simultaneously fitted, successfully. The updates are discussed taking into account, in particular, the systematic inclusion of Coriolis interaction.
Amyay, Badr; Robert, Séverine; Herman, Michel; Fayt, André; Raghavendra, Balakrishna; Moudens, Audrey; Thiévin, Jonathan; Rowe, Bertrand; Georges, Robert
2009-09-21
A high temperature source has been developed and coupled to a high resolution Fourier transform spectrometer to record emission spectra of acetylene around 3 mum up to 1455 K under Doppler limited resolution (0.015 cm(-1)). The nu(3)-ground state (GS) and nu(2)+nu(4)+nu(5) (Sigma(u) (+) and Delta(u))-GS bands and 76 related hot bands, counting e and f parities separately, are assigned using semiautomatic methods based on a global model to reproduce all related vibration-rotation states. Significantly higher J-values than previously reported are observed for 40 known substates while 37 new e or f vibrational substates, up to about 6000 cm(-1), are identified and characterized by vibration-rotation parameters. The 3 811 new or improved data resulting from the analysis are merged into the database presented by Robert et al. [Mol. Phys. 106, 2581 (2008)], now including 15 562 lines accessing vibrational states up to 8600 cm(-1). A global model, updated as compared to the one in the previous paper, allows all lines in the database to be simultaneously fitted, successfully. The updates are discussed taking into account, in particular, the systematic inclusion of Coriolis interaction.
Directory of Open Access Journals (Sweden)
Dao Van Dung
Full Text Available Abstract In this research work, an exact analytical solution for frequency characteristics of the free vibration of rotating functionally graded material (FGM truncated conical shells reinforced by eccentric FGM stringers and rings has been investigated by the displacement function method. Material properties of shell and stiffeners are assumed to be graded in the thickness direction according to a simple power law distribution. The change of spacing between stringers is considered. Using the Donnell shell theory, Leckhnisky smeared stiffeners technique and taking into account the influences of centrifugal force and Coriolis acceleration the governing equations are derived. For stiffened FGM conical shells, it is difficult that free vibration equations are a couple set of three variable coefficient partial differential equations. By suitable transformations and applying Galerkin method, this difficulty is overcome in the paper. The sixth order polynomial equation for w is obtained and it is used to analyze the frequency characteristics of rotating ES-FGM conical shells. Effects of stiffener, geometrics parameters, cone angle, vibration modes and rotating speed on frequency characteristics of the shell forward and backward wave are discussed in detail. The present approach proves to be reliable and accurate by comparing with published results available in the literature.
Brekke, Stewart
2017-09-01
Einstein calculated the total energy at low speeds in the Special Theory of Relativity to be Etotal =m0c2 + 1 / 2m0v2 . However, the total energy must include the rotational and vibrational kinetic energies as well as the linear kinetic energies. If 1 / 2 Iω2 is the expression for the rotational kinetic energy of mass and 1 / 2 kx02 is the vibrational kinetic energy expression of a typical mass, the expression for the total energy of a mass at low speeds must be Etotal =m0c2 + 1 / 2m0v2 + 1 / 2 Iω2 + 1 / 2 kx02 . If this expression is correct, the relativistic kinetic energy of a mass. at low speeds must include the rotational and vibrational kinetic energies as well as the linear kinetic energies since according to Einstein K = (m -m0) c2 and therefore, K = 1 / 2m0v2 + 1 / 2 Iω2 + 1 / 2 kx02 .
Elastic scattering and vibrational excitation for electron impact on para-benzoquinone
Jones, D. B.; Blanco, F.; García, G.; da Costa, R. F.; Kossoski, F.; Varella, M. T. do N.; Bettega, M. H. F.; Lima, M. A. P.; White, R. D.; Brunger, M. J.
2017-12-01
We report on theoretical elastic and experimental vibrational-excitation differential cross sections (DCSs) for electron scattering from para-benzoquinone (C6H4O2), in the intermediate energy range 15-50 eV. The calculations were conducted with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that also now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (Nopen) at the static-exchange-plus-polarisation (Nopench-SEP) level was used to calculate the scattering amplitudes using a channel coupling scheme that ranges from 1ch-SE up to the 89ch-SEP level of approximation. We found that in going from the 38ch-SEP to the 89ch-SEP, at all energies considered here, the elastic DCSs did not change significantly in terms of both their shapes and magnitudes. This is a good indication that our SMCPP 89ch-SEP elastic DCSs are converged with respect to the multichannel coupling effect for the investigated intermediate energies. While agreement between our IAM-SCAR+I and SMCPP 89ch-SEP computations improves as the incident electron energy increases from 15 eV, overall the level of accord is only marginal. This is particularly true at middle scattering angles, suggesting that our SCAR and interference corrections are failing somewhat for this molecule below 50 eV. We also report experimental DCS results, using a crossed-beam apparatus, for excitation of some of the unresolved ("hybrid") vibrational quanta (bands I-III) of para-benzoquinone. Those data were derived from electron energy loss spectra that were measured over a scattered electron angular range of 10°-90° and put on an absolute scale using our elastic SMCPP 89ch-SEP DCS results. The energy resolution of our measurements was ˜80 meV, which is why, at least in part, the observed vibrational features were only partially resolved. To
Agnes, Gregory Stephen
Linear vibration absorbers are a valuable tool used to suppress vibrations due to harmonic excitation in structural systems. Limited evaluation of the performance of nonlinear vibration absorbers for nonlinear structures exists in the current literature. The state of the art is extended in this work to vibration absorbers in their three major physical implementations: the mechanical vibration absorber, the inductive-resistive shunted piezoelectric vibration absorber, and the electronic vibration absorber (also denoted a positive position feedback controller). A single, consistent, physically similar model capable of examining the response of all three devices is developed. The performance of vibration absorbers attached to single-degree-of-freedom structures is next examined for performance, robustness, and stability. Perturbation techniques and numerical analysis combine to yield insight into the tuning of nonlinear vibration absorbers for both linear and nonlinear structures. The results both clarify and validate the existing literature on mechanical vibration absorbers. Several new results, including an analytical expression for the suppression region's location and bandwidth and requirements for its robust performance, are derived. Nonlinear multiple-degree-of-freedom structures are next evaluated. The theory of Non-linear Normal Modes is extended to include consideration of modal damping, excitation, and small linear coupling, allowing estimation of vibration absorber performance. The dynamics of the N+1-degree-of-freedom system reduce to those of a two-degree-of-freedom system on a four-dimensional nonlinear modal manifold, thereby simplifying the analysis. Quantitative agreement is shown to require a higher order model which is recommended for future investigation. Finally, experimental investigation on both single and multi-degree-of-freedom systems is performed since few experiments on this topic are reported in the literature. The experimental results
Nagy, Péter R.; Surján, Péter R.; Szabados, Ágnes
2014-01-01
Cross sections of inelastic light scattering accompanied by vibronic excitation in large conjugated carbon structures is assessed at the π-electron level. Intensities of Raman and vibrational Raman optical activity (VROA) spectra of fullerenes are computed, relying on a single electron per atom. When considering only first neighbor terms in the Hamiltonian (a tight-binding (TB) type or Hückel-model), Raman intensities are captured remarkably well, based on comparison with frequency-dependent linear response of the self-consistent field (SCF) method. Resorting to π-electron levels when computing spectral intensities brings a beneficial reduction in computational cost as compared to linear response SCF. At difference with total intensities, the first neighbor TB model is found inadequate for giving the left and right circularly polarized components of the scattered light, especially when the molecular surface is highly curved. To step beyond first neighbor approximation, an effective π-electron Hamiltonian, including interaction of all sites is derived from the all-electron Fockian, in the spirit of the Bloch-equation. Chiroptical cross-sections computed by this novel π-electron method improve upon first-neighbor TB considerably, with no increase in computational cost. Computed VROA spectra of chiral fullerenes, such as C76 and C28, are reported for the first time, both by conventional linear response SCF and effective π-electron models.
Gunasekaran, Sethu; Rajalakshmi, K.; Kumaresan, Subramanian
2013-08-01
The Fourier transform (FT-IR) spectrum of Levofloxacin was recorded in the region 4000-400 cm-1 and a complete vibrational assignment of fundamental vibrational modes of the molecule was carried out using density functional method. The observed fundamental modes have been compared with the harmonic vibrational frequencies computed using DFT (B3LYP) method by employing 6-31 G (d, p) basis sets. The most stable geometry of the molecule under investigation has been determined from the potential energy scan. The first-order hyperpolarizability (βo) and other related properties (μ, αo) of Levofloxacin are calculated using density functional theory (DFT) on a finite field approach. UV-vis spectrum of the molecule was recorded and the electronic properties, such as HOMO and LUMO energies were performed by DFT using 6-31 G (d, p) basis sets. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that, the charge transfer occurs within the molecule. The other molecular properties like molecular electrostatic potential (MESP), Mulliken population analysis and thermodynamic properties of the title molecule have been calculated.
Marinică, Oana; Susan-Resiga, Daniela; Bălănean, Florica; Vizman, Daniel; Socoliuc, Vlad; Vékás, Ladislau
2016-05-01
In this paper, static magnetic properties and magnetorheological behavior of a set of 12 nano-micro composite magnetic fluids (CMFs) were studied. The samples with a ferromagnetic particle volume fraction ranging in a large interval φFe = (1 ÷ 44) % were prepared by adding carbonyl iron powder in a highly concentrated transformer oil-based ferrofluid (FF). The ferrofluid has the magnetite volume fraction of φFe3O4 = 22.90 % and saturation magnetization of Ms = 74 kA / m (930 Gs). No further additives were used in order to prevent sedimentation. It was noticed an increase of the static yield stress, of about 3 orders of magnitude, with the increase of the total solid volume fraction of samples and with the increase of the magnetic field, which varied between 0 kA/m and 950 kA/m. The dynamic yield stress (Herschel-Bulkley model) τHB of the samples strongly increases with the magnetic field and shows a slight tendency of saturation for higher intensities of the magnetic field. There is a less pronounced increase of τHB, about an order of magnitude with the increasing volume fraction of the iron particles. The relative viscosity increase induced by the magnetic field reaches a maximum for both considered shear rates: γ ṡ = 7.85s-1 and γ ṡ = 88.41s-1 and it was revealed an optimal volume fraction of Fe particles, φFe = 20 % , corresponding to a total volume fraction of φtot ≈ 38 % , at which the magnetoviscous effect has its maximum value. The magnetic properties and also the magnetorheological and the magnetoviscous behavior of highly concentrated ferrofluid-based CMFs can be controlled by the addition of iron microparticles in order to attain the optimal concentration for the envisaged engineering applications, rotating seals and magnetorheological vibration dampers.
Threshold vibrational excitation of CO{sub 2} by slow electrons
Energy Technology Data Exchange (ETDEWEB)
Vanroose, Wim; Zhang, Zhiyong; McCurdy, C.W.; Rescigno, T.N.
2003-07-08
Threshold structures, reminiscent of those seen in the polar hydrogen halides, have recently been observed in the cross sections for electron impact excitation of certain vibrational levels of the non-polar CO2 molecule. These structures occur at energies outside the range where shape resonances dominate the dynamics. We propose a virtual state model that describes the multi-dimensional nuclear dynamics during the collision and explains quantitatively the selectivity observed in the excitation of the Fermi dyad, as well as the pattern of threshold peaks and oscillations seen in the upper levels of the higher polyads.
Dai, Peng; Jiang, Nan; Tan, Ren-Xiang
2016-01-01
Elucidation of absolute configuration of chiral molecules including structurally complex natural products remains a challenging problem in organic chemistry. A reliable method for assigning the absolute stereostructure is to combine the experimental circular dichroism (CD) techniques such as electronic and vibrational CD (ECD and VCD), with quantum mechanics (QM) ECD and VCD calculations. The traditional QM methods as well as their continuing developments make them more applicable with accuracy. Taking some chiral natural products with diverse conformations as examples, this review describes the basic concepts and new developments of QM approaches for ECD and VCD calculations in solution and solid states.
Chebodayev, M. I.
2017-10-01
Within the framework of the linear thermal elasticity theory a dynamic thermoelastic bending of a whisker crystal is considered under conditions of its irradiation with a high-current electron beam of nanosecond duration. It is shown that the characteristic time of leveling the temperature of superthin pin-type rod nonuniformely heated over its thickness is comparable with the period of the fundamental wave of flexural vibrations. This gives rise to a considerable decrease in the bending amplitude, which is concurrent with the heat conduction processes.
NASA-DoD Lead-Free Electronics Project: Vibration Test
Woodrow, Thomas A.
2010-01-01
Vibration testing was conducted by Boeing Research and Technology (Seattle) for the NASA-DoD Lead-Free Electronics Solder Project. This project is a follow-on to the Joint Council on Aging Aircraft/Joint Group on Pollution Prevention (JCAA/JG-PP) Lead-Free Solder Project which was the first group to test the reliability of lead-free solder joints against the requirements of the aerospace/miLItary community. Twenty seven test vehicles were subjected to the vibration test conditions (in two batches). The random vibration Power Spectral Density (PSD) input was increased during the test every 60 minutes in an effort to fail as many components as possible within the time allotted for the test. The solder joints on the components were electrically monitored using event detectors and any solder joint failures were recorded on a Labview-based data collection system. The number of test minutes required to fail a given component attached with SnPb solder was then compared to the number of test minutes required to fail the same component attached with lead-free solder. A complete modal analysis was conducted on one test vehicle using a laser vibrometer system which measured velocities, accelerations, and displacements at one . hundred points. The laser vibrometer data was used to determine the frequencies of the major modes of the test vehicle and the shapes of the modes. In addition, laser vibrometer data collected during the vibration test was used to calculate the strains generated by the first mode (using custom software). After completion of the testing, all of the test vehicles were visually inspected and cross sections were made. Broken component leads and other unwanted failure modes were documented.
Malik, Naveed ur Rehman
2012-01-01
This thesis deals with the steady-state, dynamic and control aspects of new type of brushless configuration of a doubly-fed induction machine in which the slip rings and carbon brushes are replaced by rotating power electronics and a rotating exciter. The aim is to study the stability of this novel configuration of the generator under mechanical and grid disturbances for wind power applications. The derivation, development and analysis of the steady-state model of the brushless doubly-fed ind...
Energy Technology Data Exchange (ETDEWEB)
Stoschus, Henning
2011-10-13
Small three-dimensional (3D) magnetic perturbations can be used as a tool to control the edge plasma parameters in magnetically confined plasmas in high confinement mode (''H-mode'') to suppress edge instabilities inherent to this regime, the Edge Localized Modes (ELMs). In this work, the impact of rotating 3D resonant magnetic perturbation (RMP) fields on the edge plasma structure characterized by electron density and temperature fields is investigated. We study a low confinement (L-mode) edge plasma (r/a>0.9) with high resistivity (edge electron collisionality {nu}{sup *}{sub e}>4) at the TEXTOR tokamak. The plasma structure in the plasma edge is measured by a set of high resolution diagnostics: a fast CCD camera ({delta}t=20 {mu}s) is set up in order to visualize the plasma structure in terms of electron density variations. A supersonic helium beam diagnostic is established as standard diagnostic at TEXTOR to measure electron density n{sub e} and temperature T{sub e} with high spatial ({delta}r=2 mm) and temporal resolution ({delta}t=20 {mu}s). The measured plasma structure is compared to modeling results from the fluid plasma and kinetic neutral transport code EMC3-EIRENE. A sequence of five new observations is discussed: (1) Imaging of electron density variations in the plasma edge shows that a fast rotating RMP field imposes an edge plasma structure, which rotates with the external RMP rotation frequency of vertical stroke {nu}{sub RMP} vertical stroke =1 kHz. (2) Measurements of the electron density and temperature provide strong experimental evidence that in the far edge a rotating 3D scrape-off layer (SOL) exists with helical exhaust channels to the plasma wall components. (3) Radially inward, the plasma structure at the next rational flux surface is found to depend on the relative rotation between external RMP field and intrinsic plasma rotation. For low relative rotation the plasma structure is dominated by a particle and energy loss
Pireaux, J.J.; Gregoire, Ch.; Caudano, R.; Rei Vilar, M.; Brinkhuis, R.; Schouten, A.J.
1991-01-01
Among the surface-sensitive spectroscopies used to characterize clean and surface-modified polymers, one technique has rather recently emerged as a very promising complementary tool. High-resolution electron energy loss spectroscopy, or electron-induced vibrational spectroscopy, has potentially all
Exploring the vibrational fingerprint of the electronic excitation energy via molecular dynamics
Energy Technology Data Exchange (ETDEWEB)
Deyne, Andy Van Yperen-De; Pauwels, Ewald; Ghysels, An; Waroquier, Michel; Van Speybroeck, Veronique; Hemelsoet, Karen, E-mail: karen.hemelsoet@ugent.be [Center for Molecular Modeling (CMM), Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium); De Meyer, Thierry [Center for Molecular Modeling (CMM), Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium); Department of Textiles, Ghent University, Technologiepark 907, 9052 Zwijnaarde (Belgium); De Clerck, Karen [Department of Textiles, Ghent University, Technologiepark 907, 9052 Zwijnaarde (Belgium)
2014-04-07
A Fourier-based method is presented to relate changes of the molecular structure during a molecular dynamics simulation with fluctuations in the electronic excitation energy. The method implies sampling of the ground state potential energy surface. Subsequently, the power spectrum of the velocities is compared with the power spectrum of the excitation energy computed using time-dependent density functional theory. Peaks in both spectra are compared, and motions exhibiting a linear or quadratic behavior can be distinguished. The quadratically active motions are mainly responsible for the changes in the excitation energy and hence cause shifts between the dynamic and static values of the spectral property. Moreover, information about the potential energy surface of various excited states can be obtained. The procedure is illustrated with three case studies. The first electronic excitation is explored in detail and dominant vibrational motions responsible for changes in the excitation energy are identified for ethylene, biphenyl, and hexamethylbenzene. The proposed method is also extended to other low-energy excitations. Finally, the vibrational fingerprint of the excitation energy of a more complex molecule, in particular the azo dye ethyl orange in a water environment, is analyzed.
Quantum entanglement between electronic and vibrational degrees of freedom in molecules.
McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S; Reimers, Jeffrey R
2011-12-28
We consider the quantum entanglement of the electronic and vibrational degrees of freedom in molecules with tendencies towards double welled potentials. In these bipartite systems, the von Neumann entropy of the reduced density matrix is used to quantify the electron-vibration entanglement for the lowest two vibronic wavefunctions obtained from a model Hamiltonian based on coupled harmonic diabatic potential-energy surfaces. Significant entanglement is found only in the region in which the ground vibronic state contains a density profile that is bimodal (i.e., contains two separate local maxima). However, in this region two distinct types of density and entanglement profiles are found: one type arises purely from the degeneracy of energy levels in the two potential wells and is destroyed by slight asymmetry, while the other arises through strong interactions between the diabatic levels of each well and is relatively insensitive to asymmetry. These two distinct types are termed fragile degeneracy-induced entanglement and persistent entanglement, respectively. Six classic molecular systems describable by two diabatic states are considered: ammonia, benzene, BNB, pyridine excited triplet states, the Creutz-Taube ion, and the radical cation of the "special pair" of chlorophylls involved in photosynthesis. These chemically diverse systems are all treated using the same general formalism and the nature of the entanglement that they embody is elucidated.
Structural, electronic and vibrational properties of lanthanide monophosphide at high pressure
Energy Technology Data Exchange (ETDEWEB)
Panchal, J. M., E-mail: amitjignesh@yahoo.co.in [Government Engineering College, Gandhinagar382028, Gujarat (India); Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat (India); Joshi, Mitesh [Government Polytechnic for Girls, Athwagate, Surat395001, Gujarat (India); Gajjar, P. N., E-mail: pngajjar@rediffmail.com [Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat (India)
2016-05-06
A first-principles plane wave self-consistent method with the ultra-soft-pseudopotential scheme in the framework of the density functional theory (DFT) is performed to study structural, electronic and vibrational properties of LaP for Rock-salt (NaCl/Bl) and Cesium-chloride (CsCl/B2) phases. The instability of Rock-salt (NaCl/Bl) phases around the transition is discussed. Conclusions based on electronic energy band structure, density of state, phonon dispersion and phonon density of states in both phases are outlined. The calculated results are consistence and confirm the successful applicability of quasi-harmonic phonon theory for structural instability studies for the alloys.
Chen, Jun; Hu, Ruiji; Lyu, Bo; Wang, Fudi; Wang, Xiaojie; Xu, Handong; Li, Yingying; Fu, Jia; Yin, Xianghui; Wu, Dajun; Liu, Fukun; Zang, Qing; Liu, Haiqing; Shi, Yuejiang; Mao, Shifeng; Yu, Yi; Wang, Baonian; Ye, Minyou; Shen, Yongcai; EAST Team
2017-10-01
The change in the toroidal rotation of plasma caused by electron cyclotron wave (ECW) injection has been observed in EAST. It is found that the response of the rotation is similar for all possible ECW toroidal injection angles. The core toroidal rotation velocity increases in the co-current direction along with a rise in the plasma temperature and stored energy. The profile of the electron temperature, ion temperature and toroidal rotation velocity gradually become peaked. The change in toroidal rotation in the core increases with the ECW injection power. Different behavior is observed when the ECWs are injected into low hybrid current drive (LHCD) target plasmas, where the electron temperature and rotation profile become peaked, while the ion temperature profile flattens after ECW injection, suggesting different transport characteristics in energy and momentum.
Magnetic vector rotation in response to the energetic electron beam during a flare
Xu, Yan; Cao, Wenda; Kwangsu, Ahn; Jing, Ju; Liu, Chang; Chae, Jongchul; Huang, Nengyi; Deng, Na; Gary, Dale E.; Wang, Haimin
2017-08-01
As one of the most violent forms of eruption on the Sun, flares are believed to be powered by magnetic reconnection, by which stored magnetic energy is released. The fundamental physical processes involving the release, transfer and deposition of energy in multiple layers of the solar atmosphere have been studied extensively with significant progress. Taking advantage of recent developments in observing facilities, new phenomena are continually revealed, bringing new understanding of solar flares. Here we report the discovery of a transient rotation of vector magnetic fields associated with a flare observed by the 1.6-m New Solar Telescope at Big Bear Solar Observatory. After ruling out the possibility that the rotation is caused by line profile changes due to flare heating, our observation shows that the transverse field rotateded by about 12-20 degrees counterclockwise, and returned quickly to previous values after the flare ribbons swept through. More importantly, as a consequence of the rotation, the flare loops untwisted and became more potential. The vector magnetograms were obtained in the near infrared at 1560 nm, which is minimally affected by flare emission and no intensity profile change was detected. Therefore, we believe that these transient changes are real, and conclude the high energy electron beams play an crucial role in the field changes. A straightforward and instructive explanation is that the induced magnetic field of the electron beam superimposed on the pre-flare field leads to a transient rotation of the overall field.
Kim, Hongjip; Che Tai, Wei; Zhou, Shengxi; Zuo, Lei
2017-11-01
Stochastic resonance is referred to as a physical phenomenon that is manifest in nonlinear systems whereby a weak periodic signal can be significantly amplified with the aid of inherent noise or vice versa. In this paper, stochastic resonance is considered to harvest energy from two typical vibrations in rotating shafts: random whirl vibration and periodic stick-slip vibration. Stick-slip vibrations impose a constant offset in centrifugal force and distort the potential function of the harvester, leading to potential function asymmetry. A numerical analysis based on a finite element method was conducted to investigate stochastic resonance with potential function asymmetry. Simulation results revealed that a harvester with symmetric potential function generates seven times higher power than that with asymmetric potential function. Furthermore, a frequency-sweep analysis also showed that stochastic resonance has hysteretic behavior, resulting in frequency difference between up-sweep and down-sweep excitations. An electromagnetic energy harvesting system was constructed to experimentally verify the numerical analysis. In contrast to traditional stochastic resonance harvesters, the proposed harvester uses magnetic force to compensate the offset in the centrifugal force. System identification was performed to obtain the parameters needed in the numerical analysis. With the identified parameters, the numerical simulations showed good agreement with the experiment results with around 10% error, which verified the effect of potential function asymmetry and frequency sweep excitation condition on stochastic resonance. Finally, attributed to compensating the centrifugal force offset, the proposed harvester generated nearly three times more open-circuit output voltage than its traditional counterpart.
Malik, Naveed ur Rehman
2015-01-01
This thesis deals with the modeling, analysis and control of a novel brushlessgenerator for wind power application. The generator is named as rotatingpower electronic brushless doubly-fed induction machine/generator (RPEBDFIM/G). A great advantage of the RPE-BDFIG is that the slip power recoveryis realized in a brushless manner. This is achieved by introducing an additionalmachine termed as exciter together with the rotating power electronicconverters, which are mounted on the shaft of a DFIG...
2015-01-30
effect near zero magnetic field, preprint available at arXiv:1412.3189. This paper reports nearly-ideal edge transport in a topological insulator film...demonstrates the power of using sample rotation in magnetic fields to separate orbital and spin behavior, albeit performed at the NHMFL before we...progress: Transport signatures of spin polarization in quantum spin Hall effect edge modes In the quantum spin Hall effect, all electron transport
{100} or 45.degree.-rotated {100}, semiconductor-based, large-area, flexible, electronic devices
Goyal, Amit [Knoxville, TN
2012-05-15
Novel articles and methods to fabricate the same resulting in flexible, {100} or 45.degree.-rotated {100} oriented, semiconductor-based, electronic devices are disclosed. Potential applications of resulting articles are in areas of photovoltaic devices, flat-panel displays, thermophotovoltaic devices, ferroelectric devices, light emitting diode devices, computer hard disc drive devices, magnetoresistance based devices, photoluminescence based devices, non-volatile memory devices, dielectric devices, thermoelectric devices and quantum dot laser devices.
Etude détaillée et modélisation globale du spectre de vibration-rotation de 12C2H2
AMYAY, Badr
2012-01-01
Nous avons contribué à l’amélioration du modèle global de 12C2H2. Ce modèle, exploitant la notion de polyade, a pris en compte l’ensemble des données spectrales de vibration-rotation de la littérature concernant des niveaux de vibration jusqu’à 8900 cm-1. Au terme de notre travail, les 18415 raies publiées dans la littérature sont reproduites par le modèle endéans 3 fois leur incertitude expérimentale qui est typiquement de l’ordre voire meilleure que 0,001 cm-1. L’introduction des interactio...
Energy Technology Data Exchange (ETDEWEB)
Lazarus, A. [CEA Saclay, Dept. Modelisation de Systemes et Structures (DEN/DANS/DM2S/SEMT), 91 - Gif sur Yvette (France)
2008-07-01
For high rotation speeds, the imperfections (cracks, anisotropy...) of rotating machinery of the energy sector lead to a specific vibratory behavior which can damage the machine. The simulation of rotating machinery are usually realized for systems without defect. The aim of this thesis is to understand the influence of defects and to propose an algorithm to predict the dynamical behavior. In a first part the author studies the simplified rotating oscillators to propose a numerical method in order to taking into account the dynamic of these systems. This method is then applied to real rotating machinery with the Cast3m software. The numerical results are validated with experiments. (A.L.B.)
Energy Technology Data Exchange (ETDEWEB)
Lewis, NHC; Gruenke, NL; Oliver, TAA; Ballottari, M; Bassi, R; Fleming, GR
2016-10-05
Light-harvesting complex II (LHCII) serves a central role in light harvesting for oxygenic photosynthesis and is arguably the most important photosynthetic antenna complex. In this article, we present two-dimensional electronic–vibrational (2DEV) spectra of LHCII isolated from spinach, demonstrating the possibility of using this technique to track the transfer of electronic excitation energy between specific pigments within the complex. We assign the spectral bands via comparison with the 2DEV spectra of the isolated chromophores, chlorophyll a and b, and present evidence that excitation energy between the pigments of the complex are observed in these spectra. Lastly, we analyze the essential components of the 2DEV spectra using singular value decomposition, which makes it possible to reveal the relaxation pathways within this complex.
Cole, Milton W; Crespi, Vincent H; Dresselhaus, Mildred S; Dresselhaus, Gene; Fischer, John E; Gutierrez, Humberto R; Kojima, K; Mahan, Gerald D; Rao, Apparao M; Sofo, Jorge O; Tachibana, M; Wako, K; Xiong, Qihua
2010-08-25
This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C(60) and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature
Cole, Milton W.; Crespi, Vincent H.; Dresselhaus, Mildred S.; Dresselhaus, Gene; Fischer, John E.; Gutierrez, Humberto R.; Kojima, K.; Mahan, Gerald D.; Rao, Apparao M.; Sofo, Jorge O.; Tachibana, M.; Wako, K.; Xiong, Qihua
2010-08-01
This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C60 and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature
Energy Technology Data Exchange (ETDEWEB)
Monahan, Daniele M.; Whaley-Mayda, Lukas; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720 (United States); Ishizaki, Akihito [Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki 444-8585 (Japan)
2015-08-14
Coherence oscillations measured in two-dimensional (2D) electronic spectra of pigment-protein complexes may have electronic, vibrational, or mixed-character vibronic origins, which depend on the degree of electronic-vibrational mixing. Oscillations from intrapigment vibrations can obscure the inter-site coherence lifetime of interest in elucidating the mechanisms of energy transfer in photosynthetic light-harvesting. Huang-Rhys factors (S) for low-frequency vibrations in Chlorophyll and Bacteriochlorophyll are quite small (S ≤ 0.05), so it is often assumed that these vibrations influence neither 2D spectra nor inter-site coherence dynamics. In this work, we explore the influence of S within this range on the oscillatory signatures in simulated 2D spectra of a pigment heterodimer. To visualize the inter-site coherence dynamics underlying the 2D spectra, we introduce a formalism which we call the “site-probe response.” By comparing the calculated 2D spectra with the site-probe response, we show that an on-resonance vibration with Huang-Rhys factor as small as S = 0.005 and the most strongly coupled off-resonance vibrations (S = 0.05) give rise to long-lived, purely vibrational coherences at 77 K. We moreover calculate the correlation between optical pump interactions and subsequent entanglement between sites, as measured by the concurrence. At 77 K, greater long-lived inter-site coherence and entanglement appear with increasing S. This dependence all but vanishes at physiological temperature, as environmentally induced fluctuations destroy the vibronic mixing.
Srivastava, Anubha; Joshi, B. D.; Tandon, Poonam; Ayala, A. P.; Bansal, A. K.; Grillo, Damián
2013-02-01
Imatinib mesylate, 4-(4-methyl-piperazin-1-ylmethyl)-N-u[4-methyl-3-(4-pyridin-3-yl)pyrimidine-2-ylamino)phenyl]benzamide methanesulfonate is a therapeutic drug that is approved for the treatment of chronic myelogeneous leukemia (CML) and gastrointestinal stromal tumors (GIST). It is known that imatinib mesylate exists in two polymorphic forms α and β. However, β-form is more stable than the α-form. In this work, we present a detailed vibrational spectroscopic investigation of β-form by using FT-IR and FT-Raman spectra. These data are supported by quantum mechanical calculations using DFT employing 6-311G(d,p) basis set, which allow us to characterize completely the vibrational spectra of this compound. The FT-IR spectrum of α-form has also been discussed. The importance of hydrogen-bond formation in the molecular packing arrangements of both forms has been examined with the vibrational shifts observed due to polymorphic changes. The red shift of the NH stretching bands in the infrared spectrum from the computed wavenumber indicates the weakening of the NH bond. The UV-vis spectroscopic studies along with the HOMO-LUMO analysis of both polymorphs (α and β) were performed and their chemical activity has been discussed. The TD-DFT method was used to calculate the electronic absorption spectra in the gas phase as well as in the solvent environment using IEF-PCM model and 6-31G basis set. Finally, the results obtained complements to the experimental findings.
Excitonic, vibrational, and van der Waals interactions in electron energy loss spectroscopy.
Mizoguchi, T; Miyata, T; Olovsson, W
2017-09-01
The pioneer, Ondrej L. Krivanek, and his collaborators have opened up many frontiers for the electron energy loss spectroscopy (EELS), and they have demonstrated new potentials of the EELS method for investigating materials. Here, inspired by those achievements, we show further potentials of EELS based on the results of theoretical calculations, that is excitonic and van der Waals (vdW) interactions, as well as vibrational information of materials. Concerning the excitonic interactions, we highlight the importance of the two-particle calculation to reproduce the low energy-loss near-edge structure (ELNES), the Na-L 2,3 edge of NaI and the Li-K edge of LiCl and LiFePO 4 . Furthermore, an unusually strong excitonic interaction at the O-K edge of perovskite oxides, SrTiO 3 and LaAlO 3 , is shown. The effect of the vdW interaction in the ELNES is also investigated, and we observe that the magnitude of the vdW effect is approximately 0.1eV in the case of the ELNES from a solid and liquid, whereas its effect is almost negligible in the case of the ELNES from the gaseous phase owing to the long inter-molecular distance. In addition to the "static" information, the influence of the "dynamic" behavior of atoms in materials to EELS is also investigated. We show that measurements of the infrared spectrum are possible by using a modern monochromator system. Furthermore, an estimation of the atomic vibration in core-loss ELNES is also presented. We show the acquisition of vibrational information using the ELNES of liquid methanol and acetic acid, solid Al 2 O 3 , and oxygen gas. Copyright © 2017 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Wang, Huan; Fenton, J. C.; Chiatti, O. [London Centre for Nanotechnology, University College London, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Warburton, P. A. [London Centre for Nanotechnology, University College London, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)
2013-07-15
Nanoscale mechanical resonators are highly sensitive devices and, therefore, for application as highly sensitive mass balances, they are potentially superior to micromachined cantilevers. The absolute measurement of nanoscale displacements of such resonators remains a challenge, however, since the optical signal reflected from a cantilever whose dimensions are sub-wavelength is at best very weak. We describe a technique for quantitative analysis and fitting of scanning-electron microscope (SEM) linescans across a cantilever resonator, involving deconvolution from the vibrating resonator profile using the stationary resonator profile. This enables determination of the absolute amplitude of nanomechanical cantilever oscillations even when the oscillation amplitude is much smaller than the cantilever width. This technique is independent of any model of secondary-electron emission from the resonator and is, therefore, applicable to resonators with arbitrary geometry and material inhomogeneity. We demonstrate the technique using focussed-ion-beam–deposited tungsten cantilevers of radius ∼60–170 nm inside a field-emission SEM, with excitation of the cantilever by a piezoelectric actuator allowing measurement of the full frequency response. Oscillation amplitudes approaching the size of the primary electron-beam can be resolved. We further show that the optimum electron-beam scan speed is determined by a compromise between deflection of the cantilever at low scan speeds and limited spatial resolution at high scan speeds. Our technique will be an important tool for use in precise characterization of nanomechanical resonator devices.
Electronic, vibrational, superconducting and thermodynamic properties of cubic antiperovskite ZnNNi3
Tütüncü, H. M.; Srivastava, G. P.
2013-12-01
We present results of ab initio theoretical investigations of the structural and electronic properties of the cubic superconductor ZnNNi? by employing the plane wave pseudopotential method within the generalized gradient approximation. The density of states at the Fermi level is found to be governed by the Ni 3d electrons. A linear-response approach to the density functional theory is used to derive the phonon dispersion curves, vibrational density of states and the electron-phonon coupling parameter. The calculated electron-phonon coupling constant ? and the logarithmically averaged phonon frequency are calculated to be 0.654 and 169.89 K, respectively, giving the superconducting transition temperature T?=2.925 K according to the Allen-Dynes formula. Our calculated value of T? is in excellent accord with the corresponding experimental value of 3 K. Using the phonon dispersion results, we further present an assessment of important thermodynamical properties such as internal energy (E), Helmholtz free energy (F), constant-volume specific heat (C?), entropy (S) and Debye temperature (?) in the framework of quasi harmonic approximation theory.
A conceptual design of rotating board technique for delivering total skin electron therapy.
Wu, Jia-Ming; Yeh, Shyh-An; Hsiao, Kuan-Yin; Chao, Max Min; Hargrove, Ishiuan
2010-04-01
This study presents a novel technique in which a uniform radiation dose to the whole body, soles, and scalp vertex can be achieved in one electron beam treatment fraction. The patient was treated at a machine with a home-made rotating board. The patients were treated in two groups in the prone and supine positions by leaning onto an inner rotational board in the prone and supine positions. Each group can further be separated into two subgroups using tilting and rotational positions for treatment. One of the beams was directed 15.5 degrees upward and 15.5 degrees downward from the horizontal axis to provide a field size of as large as 200 cm in height and 140 cm in width. An incline angle of 31.5 degrees anteriorly (forward) or posteriorly (backward) of the outer frame at an angle rotated 60 degrees clockwise or counterclockwise to the inner frame was found to be most appropriate. The output for the rotating board total skin electron therapy (RB-TSET) was 0.046 cGy/MU at ISD of 350 cm. The beam characteristics of the RB-TSET depth dose curves were R50 = 2.48 cm, dmax = 0.7 cm, E0 = 5.78 MeV, and Rp = 3.4 cm. The RB-TSET technique presented in this study is able to deliver a uniform radiation dose to the patient's skin surface, the scalp vertex, and soles of the feet all at one time, eliminating the trouble of having to further irradiate these two regions separately when using the Stanford six field technique.
Electron cryomicroscopy observation of rotational states in a eukaryotic V-ATPase.
Zhao, Jianhua; Benlekbir, Samir; Rubinstein, John L
2015-05-14
Eukaryotic vacuolar H(+)-ATPases (V-ATPases) are rotary enzymes that use energy from hydrolysis of ATP to ADP to pump protons across membranes and control the pH of many intracellular compartments. ATP hydrolysis in the soluble catalytic region of the enzyme is coupled to proton translocation through the membrane-bound region by rotation of a central rotor subcomplex, with peripheral stalks preventing the entire membrane-bound region from turning with the rotor. The eukaryotic V-ATPase is the most complex rotary ATPase: it has three peripheral stalks, a hetero-oligomeric proton-conducting proteolipid ring, several subunits not found in other rotary ATPases, and is regulated by reversible dissociation of its catalytic and proton-conducting regions. Studies of ATP synthases, V-ATPases, and bacterial/archaeal V/A-ATPases have suggested that flexibility is necessary for the catalytic mechanism of rotary ATPases, but the structures of different rotational states have never been observed experimentally. Here we use electron cryomicroscopy to obtain structures for three rotational states of the V-ATPase from the yeast Saccharomyces cerevisiae. The resulting series of structures shows ten proteolipid subunits in the c-ring, setting the ATP:H(+) ratio for proton pumping by the V-ATPase at 3:10, and reveals long and highly tilted transmembrane α-helices in the a-subunit that interact with the c-ring. The three different maps reveal the conformational changes that occur to couple rotation in the symmetry-mismatched soluble catalytic region to the membrane-bound proton-translocating region. Almost all of the subunits of the enzyme undergo conformational changes during the transitions between these three rotational states. The structures of these states provide direct evidence that deformation during rotation enables the smooth transmission of power through rotary ATPases.
Biczysko, Malgorzata; Bloino, Julien; Barone, Vincenzo
2013-06-01
Moving from the common practice of extracting numerical data from experiment to be compared with quantum mechanical (QM) results toward a direct vis-à-vis} comparison of experimental and simulated spectra would strongly reduce any arbitrariness in analysis of complex experimental outcomes and allow a proper account of the information connected to both position and shape of spectral bands. The development of such ``virtual ab initio spectrometers'' for a wide range of wavelengths has been one of our major research goals in the last years [1,2]. Recent methodological advances from our group allow simulation of optical (IR, Raman, UV-vis, etc.) spectra line-shapes for medium-to-large closed- and open-shell molecular systems. Vibrational spectra are computed including anharmonicities through perturbative corrections while electronic spectra line-shapes are simulated accounting for the vibrational structure. Well resolved and accurate theoretical spectra provide data as close as possible to the results directly available from experiment allowing to avoid ambiguities in analysis of the latter. Several examples illustrating interpretation, assignment or revision of experimental spectra for prototypes of bio-molecular systems (phenyl radical, glycine, thymine, pyrimidine, anisole dimer) will be presented. 1. V. Barone, A. Baiardi, M. Biczysko, J. Bloino, C. Cappelli, F. Lipparini Phys. Chem. Chem. Phys, 14, 12404, 2012 2. M. Biczysko, J. Bloino, G. Brancato, et al. Theor. Chem. Acc. 113, 1201, 2012
Fernández, David; Parlak, Cemal; Bilge, Metin; Kaya, Mehmet Fatih; Tursun, Mahir; Keşan, Gürkan; Rhyman, Lydia; Ramasami, Ponnadurai; Şenyel, Mustafa
2017-09-01
The halogen and solvent effects on the structure of 4-bromo-2-halogenobenzaldehydes [C7H4BrXO; X = F (BFB), Cl (BCB) or Br (BBB)] were investigated by the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The B3LYP functional and HF and MP2 levels of theory were used with the 6-311+G(3df,p) or aug-cc-pVDZ basis sets. Computations were focused on the cis and trans conformers of the investigated compounds in the gas phase and solutions of 18 different polar or non-polar organic solvents. The computed frequencies of the C=O stretching vibration of the compounds were correlated with some empirical solvent parameters such as the Kirkwood-Bauer-Magat (KBM) equation, solvent acceptor number (AN), Swain parameters and linear solvation energy relationships (LSERs). The electronic properties of the compounds were also examined. The present work explores the effects of the medium and halogen on the conformation, geometrical parameters, dipole moment, ν(C=O) vibration, UV data, frontier orbitals and density-of-states diagram of the compounds. The findings of this research can be useful for studies on benzaldehydes.
Singh, Poorva; Bala, Anu; Nautiyal, Tashi; Auluck, Sushil
2013-07-01
We have studied evolution of the electronic, magnetic, optical, and vibrational properties of Pd nanowires (NWs) as we go from linear chains (LCs) (the ideal one-dimensional structure) to zigzag (ZZ) structure to 2 × 2 NWs. The 2 × 2 structure is found to be more stable and stiff, as compared to the LCs and ZZ NWs, with promising and versatile optical and vibrational properties. This 2 × 2 structure, built from the stacking of face-centered cubic (110) planes, has already been observed experimentally for silver NWs. Our calculations, which include relaxation of atomic positions, show that on stretching 2 × 2 NWs undergo a structural change from (110) stacking to a more symmetric (001) stacking, which culminates into a metastable state with stable magnetism. Furthermore, inclusion of spin orbit coupling beautifully illustrates its impact on the atomic magnetic moments in 2 × 2 NWs. Structure dependence of the axial anisotropy and azimuthal anisotropy is nicely brought out on comparison for the three structures. The charge density plots show charge accumulation transverse to NW axis for 2 × 2 NWs, consistent with their one-dimensional nature. A late start of the optical response, to the electric field perpendicular to the wire axis, indicates that well-aligned ultrathin Pd wires can effectively be used as polarizers of the light. Our systematic study also resolves discrepancies in the previous reports on Pd ZZ NWs.
Kofsky, I. L.; Barrett, J. L.
1985-01-01
Laboratory experiments in which recombined CO, CO2, D2O, OH, N2, H2, and O2 molecules desorb from surfaces in excited internal and translational states are briefly reviewed. Unequilibrated distributions predominate from the principally catalytic metal substrates so far investigated. Mean kinetic energies have been observed up to approx. 3x, and in some cases less than, wall-thermal; the velocity distributions generally vary with emission angle, with non-Lambertian particle fluxes. The excitation state populations are found to depend on surface impurities, in an as yet unexplained way.
Scherrer, Arne; Sebastiani, Daniel; Gross, E K U; Vuilleumier, Rodolphe
2015-01-01
The nuclear velocity perturbation current-density theory (NVPT) for vibrational circular dichroism (VCD) is derived from the exact factorization of the electron-nuclear wave function. This new formalism offers an exact starting point to include correction terms to the Born-Oppenheimer (BO) form of the molecular wave function, similarly to the complete-adiabatic approximation. The corrections depend on a small parameter that, in a classical treatment of the nuclei, is identified as the nuclear velocity. Apart from proposing a rigorous basis for the NVPT, we show that the rotational strength, related to the intensity of the VCD signal, contain a new contribution beyond-BO that can be evaluated with the NVPT and that only arises when the exact factorization approach is employed. Numerical results are presented for chiral and non-chiral systems to test the validity of the approach.
Kose, Etem; Karabacak, Mehmet; Bardak, Fehmi; Atac, Ahmet
2016-11-01
One of the most significant aromatic amines is aniline, a primary aromatic amine replacing one hydrogen atom of a benzene molecule with an amino group (NH2). This study reports experimental and theoretical investigation of 2,5-difluoroaniline molecule (2,5-DFA) by using mass, ultraviolet-visible (UV-vis), 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared and Raman (FT-IR and FT-Raman) spectra, and supported with theoretical calculations. Mass spectrum (MS) of 2,5-DFA is presented with their stabilities. The UV-vis spectra of the molecule are recorded in the range of 190-400 nm in water and ethanol solvents. The 1H and 13C NMR chemical shifts are recorded in CDCl3 solution. The vibrational spectra are recorded in the region 4000-400 cm-1 (FT-IR) and 4000-10 cm-1 (FT-Raman), respectively. Theoretical studies are underpinned the experimental results as described below; 2,5-DFA molecule is optimized by using B3LYP/6-311++G(d,p) basis set. The mass spectrum is evaluated and possible fragmentations are proposed based on the stable structure. The electronic properties, such as excitation energies, oscillator strengths, wavelengths, frontier molecular orbitals (FMO), HOMO and LUMO energies, are determined by time-dependent density functional theory (TD-DFT). The electrostatic potential surface (ESPs), density of state (DOS) diagrams are also prepared and evaluated. In addition to these, reduced density gradient (RDG) analysis is performed, and thermodynamic features are carried out theoretically. The NMR spectra (1H and 13C) are calculated by using the gauge-invariant atomic orbital (GIAO) method. The vibrational spectra of 2,5-DFA molecule are obtained by using DFT/B3LYP method with 6-311++G(d,p) basis set. Fundamental vibrations are assigned based on the potential energy distribution (PED) of the vibrational modes. The nonlinear optical properties (NLO) are also investigated. The theoretical and experimental results give a detailed description of
Lee, William H K.
2016-01-01
Rotational seismology is an emerging study of all aspects of rotational motions induced by earthquakes, explosions, and ambient vibrations. It is of interest to several disciplines, including seismology, earthquake engineering, geodesy, and earth-based detection of Einstein’s gravitation waves.Rotational effects of seismic waves, together with rotations caused by soil–structure interaction, have been observed for centuries (e.g., rotated chimneys, monuments, and tombstones). Figure 1a shows the rotated monument to George Inglis observed after the 1897 Great Shillong earthquake. This monument had the form of an obelisk rising over 19 metres high from a 4 metre base. During the earthquake, the top part broke off and the remnant of some 6 metres rotated about 15° relative to the base. The study of rotational seismology began only recently when sensitive rotational sensors became available due to advances in aeronautical and astronomical instrumentations.
Energy Technology Data Exchange (ETDEWEB)
David R. Farley
2010-08-19
A model has been developed to calculate the ground-state rotational populations of homonuclear diatomic molecules in kinetic gases, including the effects of electron-impact excitation, wall collisions, and gas feed rate. The equations are exact within the accuracy of the cross sections used and of the assumed equilibrating effect of wall collisions. It is found that the inflow of feed gas and equilibrating wall collisions can significantly affect the rotational distribution in competition with non-equilibrating electron-impact effects. The resulting steady-state rotational distributions are generally Boltzmann for N≥3, with a rotational temperature between the wall and feed gas temperatures. The N=0,1,2 rotational level populations depend sensitively on the relative rates of electron-impact excitation versus wall collision and gas feed rates.
Electronic and vibrational spectroscopy of intermediates in methane-to-methanol conversion by CoO+
Altinay, Gokhan; Kocak, Abdulkadir; Silva Daluz, Jennifer; Metz, Ricardo B.
2011-08-01
At room temperature, cobalt oxide cations directly convert methane to methanol with high selectivity but very low efficiency. Two potential intermediates of this reaction, the [HO-Co-CH3]+ insertion intermediate and [H2O-Co=CH2]+ aquo-carbene complex are produced in a laser ablation source and characterized by electronic and vibrational spectroscopy. Reaction of laser-ablated cobalt cations with different organic precursors seeded in a carrier gas produces the intermediates, which subsequently expand into vacuum and cool. Ions are extracted into a time-of-flight mass spectrometer and spectra are measured via photofragment spectroscopy. Photodissociation of [HO-Co-CH3]+ in the visible and via infrared multiple photon dissociation (IRMPD) makes only Co+ + CH3OH, while photodissociation of [H2O-Co=CH2]+ produces CoCH2+ + H2O. The electronic spectrum of [HO-Co-CH3]+ shows progressions in the excited state Co-C stretch (335 cm-1) and O-Co-C bend (90 cm-1); the IRMPD spectrum gives νOH = 3630 cm-1. The [HO-Co-CH3]+(Ar) complex has been synthesized and its vibrational spectrum measured in the O-H stretching region. The resulting spectrum is sharper than that obtained via IRMPD and gives νOH = 3642 cm-1. Also, an improved potential energy surface for the reaction of CoO+ with methane has been developed using single point energies calculated by the CBS-QB3 method for reactants, intermediates, transition states and products.
Camargo, Franco V A; Anderson, Harry L; Meech, Stephen R; Heisler, Ismael A
2015-01-08
In this work we present experimental and calculated two-dimensional electronic spectra for a 5,15-bisalkynyl porphyrin chromophore. The lowest energy electronic Qy transition couples mainly to a single 380 cm(-1) vibrational mode. The two-dimensional electronic spectra reveal diagonal and cross peaks which oscillate as a function of population time. We analyze both the amplitude and phase distribution of this main vibronic transition as a function of excitation and detection frequencies. Even though Feynman diagrams provide a good indication of where the amplitude of the oscillating components are located in the excitation-detection plane, other factors also affect this distribution. Specifically, the oscillation corresponding to each Feynman diagram is expected to have a phase that is a function of excitation and detection frequencies. Therefore, the overall phase of the experimentally observed oscillation will reflect this phase dependence. Another consequence is that the overall oscillation amplitude can show interference patterns resulting from overlapping contributions from neighboring Feynman diagrams. These observations are consistently reproduced through simulations based on third order perturbation theory coupled to a spectral density described by a Brownian oscillator model.
Chen, Long; Liu, Jinyuan; Duan, Ping; Liu, Guangrui; Bian, Xingyu
2017-02-01
In this work, physical models of neoclassical tearing modes (NTMs) including bootstrap current and multiple modulated electron cyclotron current drive model are applied. Based on the specific physical problems during the suppression of NTMs by driven current, this work compares the efficiency of continuous and modulated driven currents, and simulates the physical processes of multiple modulated driven currents on suppressing rotating magnetic island. It is found that when island rotates along the poloidal direction, the suppression ability of continuous driven current can be massively reduced due to current deposition outside the island separatrix and reverse deposition direction at the X point, which can be avoided by current drive modulation. Multiple current drive has a better suppressing effect than single current drive. This work gives realistic numerical simulations by optimizing the model and parameters based on the experiments, which could provide references for successful suppression of NTMs in future advanced tokamak such as international thermonuclear experimental reactor.
Energy Technology Data Exchange (ETDEWEB)
Plenio, M. B.; Almeida, J.; Huelga, S. F. [Institute for Theoretical Physics, Albert-Einstein-Allee 11, University Ulm, D-89069 Ulm (Germany)
2013-12-21
We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in nonlinear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the nonlinear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of oscillatory behaviour using 2D photon echo techniques to corroborate the fundamental importance of the interplay of electronic and vibrational degrees of freedom in the dynamics of light harvesting aggregates.
Plenio, M B; Almeida, J; Huelga, S F
2013-12-21
We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in nonlinear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the nonlinear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of oscillatory behaviour using 2D photon echo techniques to corroborate the fundamental importance of the interplay of electronic and vibrational degrees of freedom in the dynamics of light harvesting aggregates.
Energy Technology Data Exchange (ETDEWEB)
Li, D.W. [Hitachi, Ltd., Tokyo (Japan); Kaneko, S. [The University of Tokyo, Tokyo (Japan); Hayama, S. [Toyama Prefectural University, Toyama (Japan)
1999-07-25
This study reports the stability of annular leakage-flow-induced vibrations. The pressure distribution of fluid between a fixed outer cylinder and a vibrating inner cylinder was obtained in the case of a translationally and rotationally coupled motion of the inner cylinder. The unsteady fluid force acting on the inner cylinder in the case of translational and rotational single-degree-of-freedom vibrations was then expressed in terms proportional to the acceleration, velocity, and displacement. Then the critical flow rate (at which stability was lost) was determined for an annular leakage-flow-induced vibration. Finally, the stability was investigated theoretically. It is known that instability will occur in the case of a divergent passage, but the critical flow rate depends on the passage increment in a limited range: the eccentricity of the passage and the pressure loss factor at the inlet of the passage lower the stability. (author)
A first principles study of the mechanical, electronic, and vibrational properties of lead oxide
Zhuravlev, Yu. N.; Korabel'nikov, D. V.
2017-11-01
The first principles study of the crystal structure, chemical bonds, elastic and mechanical properties, electron energy band structure and density, and normal long-wave vibrations of nine phases of lead monoxide, dioxide, and tetraoxide has been performed under normal and external pressure within the framework of density functional theory (DFT) with the Perdew-Becke-Ernzerhof (PBE) gradient exchange-correlation functional and its hybrid version with a 25-% Hartree-Fock (HF) exchange contribution in the basis of localized atom orbitals. The behavior of physical parameters has been studied using the cold four- and threeparameter equations of state. The parameters of the crystal structures are in satisfactory agreement with experimental data, and elastic constants indicate their mechanical stability and anisotropy in the elastic properties. The elasticity, shear, and Young moduli, hardness, acoustic velocities, and Debye temperature of dioxide on the one hand and monoxide and tetraoxide on the other hand appreciably differ from each other. The difference between electron properties may be explained by the character of hybridization in the upper filled and lower empty energy bands as evident from the density of states. In monoxide, the indirect band gap width decreases with increasing pressure at a rate of 0.16 eV/GPa, and the direct band gap width increases at a rate of 0.13 eV/GPa. To identify crystalline phases, the frequencies and intensities of long-wave modes active in IR and Raman spectra have been calculated.
Vibrational Surface Electron-Energy-Loss Spectroscopy Probes Confined Surface-Phonon Modes
Directory of Open Access Journals (Sweden)
Hugo Lourenço-Martins
2017-12-01
Full Text Available Recently, two reports [Krivanek et al. Nature (London 514, 209 (2014NATUAS0028-083610.1038/nature13870, Lagos et al. Nature (London 543, 529 (2017NATUAS0028-083610.1038/nature21699] have demonstrated the amazing possibility to probe vibrational excitations from nanoparticles with a spatial resolution much smaller than the corresponding free-space phonon wavelength using electron-energy-loss spectroscopy (EELS. While Lagos et al. evidenced a strong spatial and spectral modulation of the EELS signal over a nanoparticle, Krivanek et al. did not. Here, we show that discrepancies among different EELS experiments as well as their relation to optical near- and far-field optical experiments [Dai et al. Science 343, 1125 (2014SCIEAS0036-807510.1126/science.1246833] can be understood by introducing the concept of confined bright and dark surface phonon modes, whose density of states is probed by EELS. Such a concise formalism is the vibrational counterpart of the broadly used formalism for localized surface plasmons [Ouyang and Isaacson Philos. Mag. B 60, 481 (1989PMABDJ1364-281210.1080/13642818908205921, García de Abajo and Aizpurua Phys. Rev. B 56, 15873 (1997PRBMDO0163-182910.1103/PhysRevB.56.15873, García de Abajo and Kociak Phys. Rev. Lett. 100, 106804 (2008PRLTAO0031-900710.1103/PhysRevLett.100.106804, Boudarham and Kociak Phys. Rev. B 85, 245447 (2012PRBMDO1098-012110.1103/PhysRevB.85.245447]; it makes it straightforward to predict or interpret phenomena already known for localized surface plasmons such as environment-related energy shifts or the possibility of 3D mapping of the related surface charge densities [Collins et al. ACS Photonics 2, 1628 (2015APCHD52330-402210.1021/acsphotonics.5b00421].
Egidi, Franco; Giovannini, Tommaso; Piccardo, Matteo; Bloino, Julien; Cappelli, Chiara; Barone, Vincenzo
2014-06-10
Reliable computations of linear and non-linear optical properties of molecular systems in condensed phases require a proper account of stereo-electronic, vibrational, and environmental effects. In the framework of density functional theory, these effects can be accurately introduced using second-order vibrational perturbation theory in conjunction with polarizable continuum models. We illustrate the combination of an anharmonic description of the ground-state potential energy surface with solvation effects treated with the polarizable continuum model (PCM) in the calculation of the electronic, zero-point, and pure vibrational polarizabilities of selected systems. The description of the solvation environment is enriched by taking into account the dynamical aspects of the solute-solvent interactions through the inclusion of both electronic and vibrational non-equilbrium effects, as well as the direct effect of the solvent on the electric field that generates the molecular response (local field effect). This treatment yields accurate results which can be directly compared with experimental findings without the need of empirical corrections.
On the interplay of morphology and electronic conductivity of rotationally spun carbon fiber mats
Opitz, Martin; Go, Dennis; Lott, Philipp; Müller, Sandra; Stollenwerk, Jochen; Kuehne, Alexander J. C.; Roling, Bernhard
2017-09-01
Carbon-based materials are used as electrode materials in a wide range of electrochemical applications, e.g., in batteries, supercapacitors, and fuel cells. For these applications, the electronic conductivity of the materials plays an important role. Currently, porous carbon materials with complex morphologies and hierarchical pore structures are in the focus of research. The complex morphologies influence the electronic transport and may lead to an anisotropic electronic conductivity. In this paper, we unravel the influence of the morphology of rotationally spun carbon fiber mats on their electronic conductivity. By combining experiments with finite-element simulations, we compare and evaluate different electrode setups for conductivity measurements. While the "bar-type method" with two parallel electrodes on the same face of the sample yields information about the intrinsic conductivity of the carbon fibers, the "parallel-plate method" with two electrodes on opposite faces gives information about the electronic transport orthogonal to the faces. Results obtained for the van-der-Pauw method suggest that this method is not well suited for understanding morphology-transport relations in these materials.
Rotational coherence as an alternative to coincidence techniques at x-ray free electron lasers
Coffee, Ryan; Hegazy, Kareem; Hartmann, Nick; Walter, Peter; Osipov, Timur; Lindahl, Anton; Helml, Wolfram; Ilchen, Markus; Galler, Andreas; Liu, Jia; Buck, Jens; Shevchuk, Ivan; Viefhaus, Jens; Hartmann, Gregor; Knie, Andre; Demekhin, Philipp; Inhester, Ludger; Li, Zheng; Ziaja-Motyka, Beata; Medvedev, Nikita; Bostedt, Christoph; Guillemin, Renaud; Simon, Marc; Novella-Piancastelli, Maria; Miron, Catalin; LCLS-AMOI0314 Team
2017-04-01
We demonstrate an alternative approach to coincidence particle detection, based on impulsive rotational Raman excitation, for molecular frame measurements at x-ray FELs. A train of 8 infrared laser pulses induces the lab-frame observable coherence. At a field-free alignment revival, we register the angle-resolved laboratory frame Auger and photo-electron spectral feature variations with the tumbling molecular body frame. The time and angle dependence of the electron emission patterns that constrain theory are amenable to large numbers of interactions per pulse and, more importantly, has no axial recoil requirement for kinematic reconstruction. We see this as a method to bypass experimental challenges at XFELs by accepting The Linac Coherent Light Source (LCLS) is supported by the U.S. DoE-BES Contract No. DE-AC02-76SF0051.
Chau, Jorge L.; Röttger, Jürgen; Rapp, Markus
2014-10-01
In this paper we study the effects of absorption and Faraday rotation on measurements of polar mesosphere summer echoes (PMSE). We found that such effects can produce significant reduction of signal-to-noise ratio (SNR) when the D region electron densities (Ne) are enhanced, and VHF radar systems with linearly polarized antennas are used. In particular we study the expected effects during the strong solar proton event (SPE) of July 2000, also known as the Bastille day flare event. During this event, a strong anti-correlation between the PMSE SNR and the D-region Ne was found over three VHF radar sites at high latitudes: Andøya, Kiruna, and Svalbard. This anti-correlation has been explained (a) in terms of transport effects due to strong electric fields associated to the SPE and (b) due to a limited amount of aerosol particles as compared to the amount of D-region electrons. Our calculations using the Ne profiles used by previous researchers explain most, if not all, of the observed SNR reduction in both time (around the SPE peak) and altitude. This systematic effect, particularly the Faraday rotation, should be recognized and tested, and possibly avoided (e.g., using circular polarization), in future observations during the incoming solar maximum period, to contribute to the understanding of PMSE during enhanced D region Ne.
Habib, Muddasar; Miles, Nicholas J; Hall, Philip
2013-03-01
The need to recover and recycle valuable resources from Waste Electrical and Electronic Equipment (WEEE) is of growing importance as increasing amounts are generated due to shorter product life cycles, market expansions, new product developments and, higher consumption and production rates. The European Commission (EC) directive, 2002/96/EC, on WEEE became law in UK in January 2007 setting targets to recover up to 80% of all WEEE generated. Printed Wire Board (PWB) and/or Printed Circuit Board (PCB) is an important component of WEEE with an ever increasing tonnage being generated. However, the lack of an accurate estimate for PCB production, future supply and uncertain demands of its recycled materials in international markets has provided the motivation to explore different approaches to recycle PCBs. The work contained in this paper focuses on a novel, dry separation methodology in which vertical vibration is used to separate the metallic and non-metallic fractions of PCBs. When PCBs were comminuted to less than 1mm in size, metallic grades as high as 95% (measured by heavy liquid analysis) could be achieved in the recovered products. Copyright © 2012 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Lewis, Nicholas H. C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Dong, Hui [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Oliver, Thomas A. A. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Fleming, Graham R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2015-09-28
Two dimensional electronic spectroscopy has proven to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale.
Energy Technology Data Exchange (ETDEWEB)
Lewis, Nicholas H. C.; Dong, Hui; Oliver, Thomas A. A.; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720 (United States)
2015-09-28
Two dimensional electronic spectroscopy has proved to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale.
Champagne, Benoît; Spassova, Milena; Jadin, Jean-Benoit; Kirtman, Bernard
2002-03-01
The effect of charging on the longitudinal second hyperpolarizability of polyacetylene (PA) chains containing up to nearly 70 carbon atoms has been investigated ab initio by characterizing chains with and without an explicit alkali atom (Li, Na, K) as dopant. Whereas charging dramatically enhances the static electronic and vibrational hyperpolarizabilities, γLe(0) and γLv, of an isolated chain at intermediate chain lengths, the presence of an alkali atom counterion substantially reduces this effect. As the size of the alkali atom increases, most properties, including the hyperpolarizabilities, approach those of the isolated chain. Detailed analysis shows that the behavior of γLe(0) is most simply explained in terms of a reduced electrostatic pinning potential due to increased distance between chain and counterion. At all chain lengths studied γLe(0) of PA is enhanced by alkali doping. For chains containing 50 carbon atoms (NC=50), the increase due to K doping is about 9×107a.u., which more than doubles the value for an undoped chain of similar length. The normalized quantity γLe(0)/NC exhibits a maximum for the isolated soliton (at about NC=61) that is over four times that of the infinite undoped (and unbent) chain. When the alkali dopant is taken into account this maximum diminishes considerably and shifts to larger NC than we have considered. In comparison with the maximum for the undoped species (at NC=∞) there is a small enhancement of γLe(0)/NC for K doping, but none for either Li or Na doping at the coupled-perturbed Hartree-Fock (CPHF)/6-31G level of theory. Intermediate length isolated chains bearing a charged soliton show order of magnitude increases in γv for the degenerate four-wave mixing (DFWM) and, especially, electric field-induced second harmonic generation (dc-SHG) processes compared to undoped PA. As in the case of γLe(0) this enhancement persists, but is significantly reduced when the dopant atom is included. Vibrational anharmonicity
Energy Technology Data Exchange (ETDEWEB)
Celiberto, R., E-mail: r.celiberto@poliba.it [Department of Water Engineering and Chemistry, Polytechnic of Bari, 70125 Bari (Italy); Institute of Inorganic Methodologies and Plasmas, CNR, 70125 Bari (Italy); Janev, R.K., E-mail: r.janev@fz-juelich.de [Macedonian Academy of Sciences and Arts, P.O.B 428, 1000 Skopje (Macedonia, The Former Yugoslav Republic of); Institute of Energy and Climate Research - Plasma Physics, Forschungszentrum Juelich GmbH Association EURATOM-FZJ, Partner in Trilateral Euregio Cluster, 52425 Juelich (Germany); Wadehra, J.M., E-mail: wadehra@wayne.edu [Physics Department, Wayne State University, Detroit, MI 48202 (United States); Tennyson, J., E-mail: j.tennyson@ucl.ac.uk [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)
2012-04-04
Graphical abstract: Dissociative electron attachment cross sections as a function of the incident electron energy and for the initial vibration levels v{sub i} = 0-5, 10 of the H{sub 2} molecule. Highlights: Black-Right-Pointing-Pointer We calculated electron-hydrogen dissociative attachment cross sections and rates coefficients. Black-Right-Pointing-Pointer Collision processes occurring through a resonant Rydberg state are considered. Black-Right-Pointing-Pointer Cross sections and rates were obtained for vibrationally excited hydrogen molecules. Black-Right-Pointing-Pointer The cross sections exhibit pronounced oscillatory structures. Black-Right-Pointing-Pointer A comparison with the process involving the electron-hydrogen resonant ground state is discussed. - Abstract: Dissociative electron attachment cross sections (DEA) on vibrationally excited H{sub 2} molecule taking place via the {sup 2}{Sigma}{sub g}{sup +} Rydberg-excited resonant state are studied using the local complex potential (LCP) model for resonant collisions. The cross sections are calculated for all initial vibrational levels (v{sub i} = 0-14) of the neutral molecule. In contrast to the previously noted dramatic increase in the DEA cross sections with increasing v{sub i}, when the process proceeds via the X {sup 2}{Sigma}{sub u}{sup +} shape resonance of H{sub 2}, for the {sup 2}{Sigma}{sub g}{sup +} Rydberg resonance the cross sections increase only gradually up to v{sub i} = 3 and then decrease. Moreover, the cross sections for v{sub i} Greater-Than-Or-Slanted-Equal-To 6 exhibit pronounced oscillatory structures. A discussion of the origin of the observed behavior of calculated cross sections is given. The DEA rate coefficients for all v{sub i} levels are also calculated in the 0.5-1000 eV temperature range.
Evans, Michael D.C.; Hudon, Christine; Podgorsak, Ervin B.; Freeman, Carolyn R
2013-01-01
Total skin electron irradiation (TSEI) for patients with cutaneous lymphomas is technically challenging, and numerous approaches have been developed to overcome the many field matching problems associated with such a large and complex treatment volume. Since 1981 we have delivered TSEI using a rotational total skin electron irradiation (RTSEI) technique in conjunction with patch, treat and boost fields in order to provide complete skin and dose coverage. Initially we used a 6 MeV electron bea...
Gaynor, James D; Courtney, Trevor L; Balasubramanian, Madhumitha; Khalil, Munira
2016-06-15
The development of coherent Fourier transform two-dimensional electronic-vibrational (2D EV) spectroscopy with acousto-optic pulse-shaper-generated near-UV pump pulses and an octave-spanning broadband mid-IR probe pulse is detailed. A 2D EV spectrum of a silicon wafer demonstrates the full experimental capability of this experiment, and a 2D EV spectrum of dissolved hexacyanoferrate establishes the viability of our 2D EV experiment for studying condensed phase molecular ensembles.
Design and fabrication of self-powered micro-harvesters rotating and vibrated micro-power systems
Pan, C T; Lin, Liwei; Chen, Ying-Chung
2013-01-01
Presents the latest methods for designing and fabricating self-powered micro-generators and energy harvester systems Design and Fabrication of Self-Powered Micro-Harvesters introduces the latest trends of self-powered generators and energy harvester systems, including the design, analysis and fabrication of micro power systems. Presented in four distinct parts, the authors explore the design and fabrication of: vibration-induced electromagnetic micro-generators; rotary electromagnetic micro-generators; flexible piezo-micro-generator with various widths; and PVDF electrospunpiezo-energy with
Richter, Nils; Hernandez, Yenny R.; Schweitzer, Sebastian; Kim, June-Seo; Patra, Ajit Kumar; Englert, Jan; Lieberwirth, Ingo; Liscio, Andrea; Palermo, Vincenzo; Feng, Xinliang; Hirsch, Andreas; Müllen, Klaus; Kläui, Mathias
2017-02-01
We report on the electronic properties of turbostratic graphitic microdisks, rotationally stacked systems of graphene layers, where interlayer twisting leads to electronic decoupling resulting in charge-transport properties that retain the two dimensionality of graphene, despite the presence of a large number of layers. A key fingerprint of this reduced dimensionality is the effect of weak charge-carrier localization that we observe at low temperatures. The disks' resistivity measured as a function of magnetic field changes its shape from parabolic at room temperature to linear at a temperature of 2.7 K indicating further this type of two-dimensional transport. Compared to Bernal stacked graphite, turbostratic graphene is mechanically much more robust, and it exhibits almost negligible variations of the electrical properties between samples. We demonstrate a reproducible resistivity of (3.52 ±0.11 ) ×10-6 Ω m , which is a particularly low value for graphitic systems. Combined with large charge-carrier mobilities demonstrated at low temperatures of up to 7 ×104 cm2/V s , typical for carbon-based crystalline conductors, such disks are highly interesting from a scientific point of view and, in particular, for applications where robust electronic properties are required.
Measurement of plasma conductivity using faraday rotation of submillimeter waves
Energy Technology Data Exchange (ETDEWEB)
Kuzmenko, P.J.; Self, S.A.
1983-03-01
This paper examines the application of Faraday rotation to the measurement of electron combustion MHD plasmas. Details on the design of a working system are given, including the selection of operating wavelength. A theoretical comparison between the Faraday rotation technique and two-path interferometry shows Faraday rotation in its simplest form to be somewhat less sensitive to changes in electron concentration. This deficit can be balanced against greater immunity to vibration and thermal drift. Improved techniques of measuring the rotation angle promise greater sensitivity. A preliminary experiment has verified the technique.
Lin, Janice B; Jin, Yu; Lopez, Steven A; Druckerman, Nathaniel; Wheeler, Steven E; Houk, K N
2017-11-14
In order to understand the conformational behavior of organic components in organic electronic devices, we have computed the torsional potentials for a library of thiophene-based heterodimers. The accuracy and efficiencies of computational methods for these organic materials were benchmarked for 11 common density functionals with three Pople basis sets against a Focal Point Analysis (FPA) on a model oligothiophene 2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]-thiophene (BTTT) system. This study establishes a set of general trends in regards to conformational preferences, as well as planarization and rotational barriers for a library comprised of common fragments found in organic materials. These gas phase structures are compared to experimental crystal structures to determine the effect of crystal packing on geometry. Finally, we analyze the structure of hole-transporting material DERDTS-TBDT and design a new oligomer likely to be planar in the solid state.
Kinner, Nancy E.; Balkwill, David L.; Bishop, Paul L.
1983-01-01
The biofilms growing in the first compartments of two rotating biological contactors used to treat municipal wastewater were examined by light and electron microscopy. The biofilms were found to contain a complex and varied microbial community that included filamentous and unicellular bacteria, protozoa, metazoa, and (possibly) bacteriophage. The predominant microorganism among these appeared to be a filamentous bacterium that was identical to Sphaerotilus in both morphological and ultrastructural characteristics. It was possible to isolate a Sphaerotilus-like bacterium from each contactor. Both the Sphaerotilus filaments and the wide variety of unicellular bacteria present tended to contain poly-β-hydroxybutyrate inclusions, a probable indication that these organisms were removing carbon from the wastewater and storing it. The microbial population of the biofilms appeared to be metabolically active, as evidenced by the presence of microcolonies and dividing cells. Images PMID:16346299
Inter-ring rotations of AAA ATPase p97 revealed by electron cryomicroscopy.
Yeung, Heidi O; Förster, Andreas; Bebeacua, Cecilia; Niwa, Hajime; Ewens, Caroline; McKeown, Ciarán; Zhang, Xiaodong; Freemont, Paul S
2014-03-05
The type II AAA+ protein p97 is involved in numerous cellular activities, including endoplasmic reticulum-associated degradation, transcription activation, membrane fusion and cell-cycle control. These activities are at least in part regulated by the ubiquitin system, in which p97 is thought to target ubiquitylated protein substrates within macromolecular complexes and assist in their extraction or disassembly. Although ATPase activity is essential for p97 function, little is known about how ATP binding or hydrolysis is coupled with p97 conformational changes and substrate remodelling. Here, we have used single-particle electron cryomicroscopy (cryo-EM) to study the effect of nucleotides on p97 conformation. We have identified conformational heterogeneity within the cryo-EM datasets from which we have resolved two major p97 conformations. A comparison of conformations reveals inter-ring rotations upon nucleotide binding and hydrolysis that may be linked to the remodelling of target protein complexes.
Local analysis of strains and rotations for macromolecular electron microscopy maps
Energy Technology Data Exchange (ETDEWEB)
Martin-Ramos, A.; Prieto, F.; Melero, R.; Martin-Benito, J.; Jonic, S.; Navas-Calvente, J.; Vargas, J.; Oton, J.; Abrishami, V.; Rosa-Trevin, J.L. de la; Gomez-Blanco, J.; Vilas, J.L.; Marabini, R.; Carazo, R.; Sorzano, C.O.S.
2016-07-01
Macromolecular complexes can be considered as molecular nano-machines that must have mobile parts in order to perform their physiological functions. The reordering of their parts is essential to execute their task. These rearrangements induce local strains and rotations which, after analyzing them, may provide relevant information about how the proteins perform their function. In this project these deformations of the macromolecular complexes are characterized, translating into a “mathematical language” the conformational changes of the complexes when they perform their function. Electron Microscopy (EM) volumes are analyzed using a method that uses B-splines as its basis functions. It is shown that the results obtained are consistent with the conformational changes described in their corresponding reference publications. (Author)
Ab initio study of (Fe, Ni) doped GaAs: Magnetic, electronic properties and Faraday rotation
Sbai, Y.; Ait Raiss, A.; Bahmad, L.; Benyoussef, A.
2017-06-01
The interesting diluted magnetic semiconductor (DMS), Gallium Arsenide (GaAs), was doped with the transition metals magnetic impurities: iron (Fe) and Nickel (Ni), in one hand to study the magnetic and magneto-optical properties of the material Ga(Fe, Ni) As, in the other hand to investigate the effect of the doping on the properties of this material, the calculations were performed within the spin polarized density functional theory (DFT) and generalized gradient approximation (GGA) with AKAI KKR-CPA method, the density of states (DOS) for different doping concentrations were calculated, giving the electronical properties, as well as the magnetic state and magnetic states energy, also the effect of these magnetic impurities on the Faraday rotation as magneto-optical property. Furthermore, we found the stable magnetic state for our doped material GaAs.
Svalbonas, V.
1973-01-01
The User's manual for the shell theory automated for rotational structures (STARS) 2B and 2V (buckling, vibrations) is presented. Several features of the program are: (1) arbitrary branching of the shell meridians, (2) arbitrary boundary conditions, (3) minimum input requirements to describe a complex, practical shell of revolution structure, and (4) accurate analysis capability using a minimum number of degrees of freedom.
Crystalline indole at high pressure: chemical stability, electronic, and vibrational properties.
Citroni, Margherita; Costantini, Barbara; Bini, Roberto; Schettino, Vincenzo
2009-10-15
Vibrational and electronic spectra of crystalline indole were measured up to 25.5 GPa at room temperature in a diamond anvil cell. In particular, Fourier transform infrared (FTIR) spectra in the mid-infrared region and two-photon excitation profiles and fluorescence spectra in the region of the HOMO-LUMO transitions were obtained. The analysis of the FTIR spectra revealed a large red-shift of the N-H stretching mode with increasing pressure, indicating the strengthening of the H-bond between the NH group and the pi electron density of nearest neighbor molecules. The frequencies of four vibronic bands belonging to the (1)L(a) and (1)L(b) systems were obtained as a function of pressure. Comparison with literature data shows that the crystal acts as a highly polar environment with regard to the position of the (1)L(b) origin and of the fluorescence maximum, which are largely red-shifted with respect to the gas phase or to solutions in apolar solvents. A large, and increasing with pressure, frequency difference between the (1)L(b) origin and the blue edge of the fluorescence spectrum suggests that the emitting state is (1)L(a), that is known to be more stabilized than (1)L(b) by dipolar relaxation. Crystalline indole was found to be very stable with respect to pressure-induced reactivity. Only traces of a reaction product, containing saturated C-H bonds, are detected after a full compression-decompression cycle. In addition, differently from many unsaturated compounds at high pressure, irradiation with light matching a two-photon absorption for a HOMO-LUMO transition has no enhancing effect on reactivity. The chemical stability of indole at high pressure is ascribed to the crystal structure, where nearest neighbor molecules, formig H-bonds, are not in a favorable position to react, while reaction between equivalent molecules, for which a superposition of the pi electron clouds would be possible, is hindered by H-bonded molecules. Consistently, no excimer emission was
Vibration Sensitivity of a Wide-Temperature Electronically Scanned Pressure Measurement (ESP) Module
Zuckerwar, Allan J.; Garza, Frederico R.
2001-01-01
A vibration sensitivity test was conducted on a Wide-Temperature ESP module. The test object was Module "M4," a 16-channel, 4 psi unit scheduled for installation in the Arc Sector of NTF. The module was installed on a vibration exciter and loaded to positive then negative full-scale pressures (+/-2.5 psid). Test variables were the following: Vibration frequencies: 20, 55, 75 Hz. Vibration level: 1 g. Vibration axes: X, Y, Z. The pressure response was measured on each channel, first without and then with the vibration turned on, and the difference analyzed by means of the statistical t-test. The results show that the vibration sensitivity does not exceed 0.01% Full Scale Output per g (with the exception of one channel on one axis) to a 95 percent confidence level. This specification, limited by the resolution of the pressure source, lies well below the total uncertainty specification of 0.1 percent Full Scale Output.
Directory of Open Access Journals (Sweden)
Apoorva Dwivedi
2015-01-01
Full Text Available The spectroscopic, optical, and electronic properties of tetrahydrofuran and its derivatives were investigated by FTIR techniques. We have done a comparative study of tetrahydrofuran and its derivatives with B3LYP with 6-311 G (d, p as the basis set. Here we have done a relative study of their structures, vibrational assignments, and thermal, electronic, and optical properties of ttetrahydrofuran and its derivatives. We have plotted frontier orbital HOMO-LUMO surfaces and molecular electrostatic potential surfaces to explain the reactive nature of tetrahydrofuran and its derivatives.
Energy Technology Data Exchange (ETDEWEB)
Habib, Muddasar, E-mail: muddasar77@hotmail.com [Department of Chemical Engineering, University of Engineering and Technology, Peshawar (Pakistan); Miles, Nicholas J.; Hall, Philip [Faculty of Science and Engineering, University of Nottingham Ningbo China, Taikang East Road, Ningbo 315100 (China)
2013-03-15
Highlights: ► This work focuses on demonstrating a new scaled up technology to separate the metallic and non-metallic fractions of PCBs. ► PCBs comminuted to <1 mm in size resulted in metallic grade concentration of 95% in some of the recovered products. ► Good separation was observed at 40 mm particle bed height due to the formation of well-structured global convection currents. ► The work reported here contributes to the development of a new approach to dry, fine particle separation. - Abstract: The need to recover and recycle valuable resources from Waste Electrical and Electronic Equipment (WEEE) is of growing importance as increasing amounts are generated due to shorter product life cycles, market expansions, new product developments and, higher consumption and production rates. The European Commission (EC) directive, 2002/96/EC, on WEEE became law in UK in January 2007 setting targets to recover up to 80% of all WEEE generated. Printed Wire Board (PWB) and/or Printed Circuit Board (PCB) is an important component of WEEE with an ever increasing tonnage being generated. However, the lack of an accurate estimate for PCB production, future supply and uncertain demands of its recycled materials in international markets has provided the motivation to explore different approaches to recycle PCBs. The work contained in this paper focuses on a novel, dry separation methodology in which vertical vibration is used to separate the metallic and non-metallic fractions of PCBs. When PCBs were comminuted to less than 1 mm in size, metallic grades as high as 95% (measured by heavy liquid analysis) could be achieved in the recovered products.
Goncharova, Iryna; Urbanová, Marie
2009-09-01
Complexation of bilirubin (BR) and biliverdin (BV) with biogenic and toxic metals (Mn, Cu, Cd, Co, Fe, Ni, Zn, and Ag) has been studied by means of electronic circular dichroism (ECD) and vibrational circular dichroism (VCD). Poly-L-lysine and beta-cyclodextrin in water were chosen as matrices capable of recognizing the single stereoconformer of the pigments with defined M-helicity. Such systems allow structural changes caused by complexation of pigments with metals in aqueous solution at pH 10-11 to be followed using chiroptical methods, which are intrinsically sensitive to spatial structure. These and other spectroscopic techniques have revealed that BV and BR form monomeric complexes with Cd, Cu, and Zn and dimeric complexes with Mn. The stabilities of the complexes with Fe, Ni, Co, and Ag are remarkably lower. The sign of the ECD and VCD patterns of the complexed BV does not change for the chelates of any of the studied metals other than Zn, this exception being interpreted in terms of manifestation of the opposite helicity of BV in its chelate with Zn. In the case of BR, the observed inversion of ECD signal after complexation, together with the analysis of VCD spectra, reveals that a flattening of the molecule takes place, i.e., an increase in the angle between the pyrrinone chromophores without an inversion of helicity. This chiral stereoselectivity, which is very specific in the case of the Zn chelates, is discussed in connection with the specific inhibition of Zn-required enzymes by bile pigments.
Vibration-based Energy Harvesting Systems Characterization Using Automated Electronic Equipment
Directory of Open Access Journals (Sweden)
Ioannis KOSMADAKIS
2015-04-01
Full Text Available A measurement bench has been developed to fully automate the procedure for the characterization of a vibration-based energy scavenging system. The measurement system is capable of monitoring all important characteristics of a vibration harvesting system (input and output voltage, current, and other parameters, frequency and acceleration values, etc.. It is composed of a PC, typical digital measuring instruments (oscilloscope, waveform generator, etc., certain sensors and actuators, along with a microcontroller based automation module. The automation of the procedure and the manipulation of the acquired data are performed by LabVIEW software. Typical measurements of a system consisting of a vibrating source, a vibration transducer and an active rectifier are presented.
Mazanoglu, Kemal; Guler, Serkan
2017-05-01
This paper presents flap-wise and chord-wise flexural vibration analyses for centrifugally stiffened tapered beams made of functionally graded material in axial direction. Functions of material properties varying along beam are defined in terms of the power law distribution. Calculations are conducted by simple computation technique of the Rayleigh-Ritz method that uses simple shape functions and energy expressions written for centrifugally stiffened Euler-Bernoulli beams. Effects of taper ratio, hub radius, angular velocity and non-homogeneity are inspected for the thin beams with several classical boundary conditions. Results given as non-dimensional natural frequencies are validated by the results given in existing literature and/or the outputs of finite element analyses performed for axially functionally graded solid beam. Achievements and limitations of the method are discussed and clearly reflected.
Mineo, Hirobumi; Yamaki, Masahiro; Teranishi, Yoshiaki; Hayashi, Michitoshi; Lin, Sheng Hsien; Fujimura, Yuichi
2012-09-05
Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems.
Faizan, Mohd; Alam, Mohammad Jane; Ahmad, Shabbir
2017-11-01
In the present investigation, spectroscopic techniques (FTIR, FT-Raman and UV-Vis) and quantum chemical calculations are employed for exploring vibrational and electronic spectra of sulindac compound. The calculations are performed on most stable conformer of the sulindac molecule using density functional theory (DFT). Anharmonic corrections are made to frequencies using vibrational second-order perturbation theory (VPT2). The effect of intermolecular interactions on the vibrational dynamics has been analyzed using dimeric structure of sulindac molecule. Hirshfeld surface analysis and 2D fingerprint plots are utilized to investigate the nature of interaction present in the crystal system. To account for electronic spectra in different solvents, an integral equation formalism of polarizable continuum model (IEFPCM) at TD-DFT/B3LYP/6-31G(d,p) level of theory has been employed. An excellent agreement between the theoretical and experimental data over the entire spectral region is observed. In addition, natural bond orbital (NBO) analysis, frontier molecular orbitals, nonlinear optical properties (NLO) and molecular electrostatic potential (MEP) analysis are also reported.
Farooq, M.; Ahmad, Mushtaq
2017-12-01
Dust ion acoustic waves are investigated in four component magneto-rotating dusty plasma comprising opposite polarity dust grains, ions, and nonthermal electrons using the concept of one fluid and two fluid models. The Zakharov-Kuznetsov equation is derived using the reductive perturbation technique to study the nonlinear solitary wave structures. The numerical results show that the superthermality of electrons affects both amplitude and width of the solitary waves while the rotational frequency has a small impression on the width. It is shown that the solitary wave changes its potential from positive to negative at a critical value of the superthermal parameter. It is also observed that the inertial role of dust grains flourishes the effect of rotational frequency and also changes the critical value of the superthermal parameter where the positive/negative potential solitary waves exist.
Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef
2014-10-01
The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.
Mielke, Steven L; Truhlar, Donald G
2015-01-28
We present an improved version of our "path-by-path" enhanced same path extrapolation scheme for Feynman path integral (FPI) calculations that permits rapid convergence with discretization errors ranging from O(P(-6)) to O(P(-12)), where P is the number of path discretization points. We also present two extensions of our importance sampling and stratified sampling schemes for calculating vibrational-rotational partition functions by the FPI method. The first is the use of importance functions for dihedral angles between sets of generalized Jacobi coordinate vectors. The second is an extension of our stratification scheme to allow some strata to be defined based only on coordinate information while other strata are defined based on both the geometry and the energy of the centroid of the Feynman path. These enhanced methods are applied to calculate converged partition functions by FPI methods, and these results are compared to ones obtained earlier by vibrational configuration interaction (VCI) calculations, both calculations being for the Jordan-Gilbert potential energy surface. The earlier VCI calculations are found to agree well (within ∼1.5%) with the new benchmarks. The FPI partition functions presented here are estimated to be converged to within a 2σ statistical uncertainty of between 0.04% and 0.07% for the given potential energy surface for temperatures in the range 300-3000 K and are the most accurately converged partition functions for a given potential energy surface for any molecule with five or more atoms. We also tabulate free energies, enthalpies, entropies, and heat capacities.
Directory of Open Access Journals (Sweden)
Ruben Ruiz-Gonzalez
2014-11-01
Full Text Available The goal of this article is to assess the feasibility of estimating the state of various rotating components in agro-industrial machinery by employing just one vibration signal acquired from a single point on the machine chassis. To do so, a Support Vector Machine (SVM-based system is employed. Experimental tests evaluated this system by acquiring vibration data from a single point of an agricultural harvester, while varying several of its working conditions. The whole process included two major steps. Initially, the vibration data were preprocessed through twelve feature extraction algorithms, after which the Exhaustive Search method selected the most suitable features. Secondly, the SVM-based system accuracy was evaluated by using Leave-One-Out cross-validation, with the selected features as the input data. The results of this study provide evidence that (i accurate estimation of the status of various rotating components in agro-industrial machinery is possible by processing the vibration signal acquired from a single point on the machine structure; (ii the vibration signal can be acquired with a uniaxial accelerometer, the orientation of which does not significantly affect the classification accuracy; and, (iii when using an SVM classifier, an 85% mean cross-validation accuracy can be reached, which only requires a maximum of seven features as its input, and no significant improvements are noted between the use of either nonlinear or linear kernels.
Zentel, Tobias; Overbeck, Viviane; Michalik, Dirk; Kühn, Oliver; Ludwig, Ralf
2018-02-01
The properties of the hydrogen bonds in ethylammonium nitrate (EAN) are analyzed by using molecular dynamics simulations and infrared as well as nuclear magnetic resonance experiments. EAN features a flexible three-dimensional network of hydrogen bonds with moderate strengths, which makes it distinct from related triethylammonium-based ionic liquids. First, the network’s flexibility is manifested in a not very pronounced correlation of the hydrogen bond geometries, which is caused by rapid interchanges of bonding partners. The large flexibility of the network also leads to a substantial broadening of the mid-IR absorption band, with the contributions due to N–H stretching motions ranging from 2800 to 3250 cm‑1. Finally, the different dynamics are also seen in the rotational correlation of the N–H bond vector, where a correlation time as short as 16.1 ps is observed.
Rotational analysis of the A(2)Sigma(+)((nu=1,2))-X-2 Pi((nu=0)) electronic bands of (NO)-N-15-O-18
Ityaksov, D.; Stolte, S.; Linnartz, H.V.J.; Ubachs, W.M.G.
2009-01-01
Deep-UV spectra of (NO)-N-15-O-18 have been recorded using cavity ring-down spectroscopy in the 205-216 nm egion. The rotationally resolved spectra have been assigned for a first time as originating from the nu '' = 0 X-2 Pi(r) states toward nu' = 1 and 2 vibrationally excited levels in the upper
Ishizeki, Keisuke; Sasaoka, Kenji; Konabe, Satoru; Souma, Satofumi; Yamamoto, Takahiro
2017-07-01
We develop a powerful simulation method that can treat electronic transport in a super-micron-scale open system with atomic vibration at finite temperature. As an application of the developed method to realistic materials, we simulate electronic transport in metallic single-walled carbon nanotubes from nanometer scale to micrometer scale at room temperature. Based on the simulation results, we successfully identify two different crossovers, namely, ballistic to diffusive crossover and coherent to incoherent crossover, simultaneously and with equal footing, from which the mean free path and the phase coherence length can be extracted clearly. Moreover, we clarify the scaling behavior of the electrical resistance and the electronic current in the crossover regime.
Magnetic pseudo-fields in a rotating electron-nuclear spin system
Wood, A. A.; Lilette, E.; Fein, Y. Y.; Perunicic, V. S.; Hollenberg, L. C. L.; Scholten, R. E.; Martin, A. M.
2017-11-01
Analogous to the precession of a Foucault pendulum observed on the rotating Earth, a precessing spin observed in a rotating frame of reference appears frequency-shifted. This can be understood as arising from a magnetic pseudo-field in the rotating frame that nevertheless has physically significant consequences, such as the Barnett effect. To detect these pseudo-fields, a rotating-frame sensor is required. Here we use quantum sensors, nitrogen-vacancy (NV) centres, in a rapidly rotating diamond to detect pseudo-fields in the rotating frame. Whereas conventional magnetic fields induce precession at a rate proportional to the gyromagnetic ratio, rotation shifts the precession of all spins equally, and thus primarily affect 13C nuclear spins in the sample. We are thus able to explore these effects via quantum sensing in a rapidly rotating frame, and define a new approach to quantum control using rotationally induced nuclear spin-selective magnetic fields. This work provides an integral step towards realizing precision rotation sensing and quantum spin gyroscopes.
Berg, Christopher J; LaFountain, Amy M; Prum, Richard O; Frank, Harry A; Tauber, Michael J
2013-11-15
Rhodoxanthin is one of few retro-carotenoids in nature. These chromophores are defined by a pattern of single and double bond alternation that is reversed relative to most carotenoids. Rhodoxanthin is found in the plumage of several families of birds, including fruit doves (Ptilinopus, Columbidae) and the red cotingas (Phoenicircus, Cotingidae). The coloration associated with the rhodoxanthin-containing plumage of these fruit dove and cotinga species ranges from brilliant red to magenta or purple. In the present study, rhodoxanthin is characterized in situ by UV-Vis reflectance and resonance Raman spectroscopy to gain insights into the mechanisms of color-tuning. The spectra are compared with those of the isolated pigment in solution and in thin solid films. Key vibrational signatures are identified for three isomers of rhodoxanthin, primarily in the fingerprint region. Electronic structure (DFT) calculations are employed to describe the normal modes of vibration, and determine characteristic modes of retro-carotenoids. These results are discussed in the context of various mechanisms that change the electronic absorption, including structural distortion of the chromophore or enhanced delocalization of π-electrons in the ground-state. From the spectroscopic evidence, we suggest that the shift in absorption is likely a consequence of perturbations that primarily affect the excited state of the chromophore. Copyright © 2013 Elsevier Inc. All rights reserved.
Vibrational excitation resulting from electron capture in LUMO of F2 ...
Indian Academy of Sciences (India)
resonance anionic Hamiltonian HAB- (AB=F2/HCl) is effected using Lanczos reduction technique followed by fast Fourier transform and the target (AB) vibrational eigenfunctions φνi (R) and φν f (R) are calculated using Fourier grid Hamiltonian method applied to potential energy (PE) curve of the neutral target. The result-.
Energy Technology Data Exchange (ETDEWEB)
Tuan, H.P.; Larsson, C.; Huehnerfuss, H. [Hamburg Univ. (Germany). Inst. fuer Organische Chemie; Hoffmann, F.; Froeba, M. [Giessen Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Bergmann, Aa. [Stockholm Univ. (Sweden). Dept. of Environmental Chemistry
2004-09-15
The present paper represents a first result of an ongoing systematic study of atropisomeric methylsulfonyl, methylthionyl, hydroxy, and methoxy metabolites of environmentally most relevant PCBs. This involves semi-preparative enantioselective HPLC separation to obtain pure atropisomers from synthesized PCB metabolite standards, their configuration estimation using the electronic circular dichroism (UV-CD) method and the determination / confirmation of these absolute configurations applying the combined vibrational circular dichroism (VCD) / ab initio approach. The following substances have been investigated: 4-HO-, 4-MeO-, 4-MeS-, 4-MeSO2-, 3-MeS- and 3-MeSO{sub 2}-CB149.
Semenov, Alexander; Babikov, Dmitri
2013-11-07
We formulated the mixed quantum/classical theory for rotationally and vibrationally inelastic scattering process in the diatomic molecule + atom system. Two versions of theory are presented, first in the space-fixed and second in the body-fixed reference frame. First version is easy to derive and the resultant equations of motion are transparent, but the state-to-state transition matrix is complex-valued and dense. Such calculations may be computationally demanding for heavier molecules and/or higher temperatures, when the number of accessible channels becomes large. In contrast, the second version of theory requires some tedious derivations and the final equations of motion are rather complicated (not particularly intuitive). However, the state-to-state transitions are driven by real-valued sparse matrixes of much smaller size. Thus, this formulation is the method of choice from the computational point of view, while the space-fixed formulation can serve as a test of the body-fixed equations of motion, and the code. Rigorous numerical tests were carried out for a model system to ensure that all equations, matrixes, and computer codes in both formulations are correct.
Vibrational effects on UV/Vis laser-driven π-electron ring currents in aromatic ring molecules
Mineo, H.; Lin, S. H.; Fujimura, Y.
2014-10-01
We present the results of a theoretical study of vibrational effects on UV/Vis laser-driven π-electron ring currents in aromatic ring molecules. We consider vibrational effects on both coherent and non-coherent (single quantum state) ring currents. The coherent ring current originates from an excitation of a pair of quasi-degenerate electronic states by an ultrashort linearly polarized UV/Vis laser pulse, while the non-coherent ring current originates from by an excitation of a degenerated electronic state of an aromatic ring molecule with high symmetry by a circularly polarized electric field of a UV/Vis laser pulse. The magnitude of a generated ring current can be expressed as an average of those of the bond currents for both the coherent and non-coherent cases. We derive an analytical expression for the magnitude of the bond currents in the adiabatic approximation. Using the expression, we performed calculations of a non-coherent ring current generated in the optically allowed excited state (1E1U) of benzene and the time evolution of coherent ring current of (P)-2,2-biphenol. Vibrational effects on the non-coherent ring current of benzene were found to be negligibly small. We paid particular attention to the vibrational effects induced by the torsion mode on time evolution of the coherent ring current along the bond bridging between the two aromatic rings of (P)-2,2-biphenol. By comparing the time evolution of the coherent ring current with that in the frozen-nuclear approximation, we found that inclusion of the low-frequency torsion mode brings about modulations in the beating in the ring current. The modulations in the time evolution of the coherent ring current were brought about by contribution of several pairs of the coherently excited vibronic states. Coherent vibronic ring currents generated from pairs of the coherently excited vibronic states interfere each other. The existence of the pairs originates from relatively large potential displacement of the
Sajan, D.; Devi, T. Uma; Safakath, K.; Philip, Reji; Němec, Ivan; Karabacak, M.
2013-05-01
FT-IR, FT-Raman and UV-Vis spectra of the nonlinear optical molecule ninhydrin have been recorded and analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of B3LYP density functional theory method. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Solvent effects have been calculated using time-dependent density functional theory in combination with the polarized continuum model. Natural bond orbital analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule. Employing the open-aperture z-scan technique, nonlinear optical absorption of the sample has been studied in the ultrafast and short-pulse excitation regimes, using 100 fs and 5 ns laser pulses respectively. It is found that ninhydrin exhibits optical limiting for both excitations, indicating potential photonic applications.
Baiardi, Alberto; Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien
2014-06-01
Two parallel theories including Franck-Condon, Herzberg-Teller and Duschinsky (i.e., mode mixing) effects, allowing different approximations for the description of excited state PES have been developed in order to simulate realistic, asymmetric, electronic spectra line-shapes taking into account the vibrational structure: the so-called sum-over-states or time-independent (TI) method and the alternative time-dependent (TD) approach, which exploits the properties of the Fourier transform. The integrated TI-TD procedure included within a general purpose QM code [1,2], allows to compute one photon absorption, fluorescence, phosphorescence, electronic circular dichroism, circularly polarized luminescence and resonance Raman spectra. Combining both approaches, which use a single set of starting data, permits to profit from their respective advantages and minimize their respective limits: the time-dependent route automatically includes all vibrational states and, possibly, temperature effects, while the time-independent route allows to identify and assign single vibronic transitions. Interpretation, analysis and assignment of experimental spectra based on integrated TI-TD vibronic computations will be illustrated for challenging cases of medium-sized open-shell systems in the gas and condensed phases with inclusion of leading anharmonic effects. 1. V. Barone, A. Baiardi, M. Biczysko, J. Bloino, C. Cappelli, F. Lipparini Phys. Chem. Chem. Phys, 14, 12404, (2012) 2. A. Baiardi, V. Barone, J. Bloino J. Chem. Theory Comput., 9, 4097-4115 (2013)
Red shift of the SF6 vibration spectrum induced by the electron absorption: An ab initio study
Directory of Open Access Journals (Sweden)
Bin Tang
2018-01-01
Full Text Available As a widely used gas insulator, sulfur hexafluoride (SF6 has a large cross section for electron absorption, which may make the molecule ionized to the -1 charge state in the high-voltage environment. Using ab initio calculations, we show that the absorbed electron is located averagely on the six F atoms, occupying the antibonding level of the s-p σ bonds and increasing the S-F bond length. The ionized SF6- molecule decreases its decomposition energy to only 1.5 eV, much lower than that of the neutral molecule (4.8 eV, which can be understood according to the occupying of the antibonding orbital and thus weakening of the s-p σ bonds. The weakening of the bonds results in an obvious red shift in the vibrational modes of the ionized SF6- molecule by 120-270 cm-1, compared to those of the neutral molecule. The detailed origin of these vibrational modes is analyzed. Since the appearance of the ionized SF6- molecules is before the decomposition reaction of the SF6- molecule into low-fluoride sulfides, this method may improve the sensitivity of the defection of the partial discharge and save more time for the prevention of the insulation failure in advance.
CD30+ Cutaneous T Cell Lymphoma: Response to Rotational Total Skin Electron Irradiation.
Danish, Hasan H; Heumann, Thatcher R; Bradley, Kyle T; Switchenko, Jeffrey; Esiashvili, Natia; Lechowicz, Mary Jo; Flowers, Christopher R; Khan, Mohammad K
2016-06-01
Rotational total skin electron irradiation (RTSEI) is an effective therapy for cutaneous T cell lymphoma (CTCL). CD30 expression has been identified as a prognostic factor in CTCL. Therefore, we investigated CD30 status, treatment response, and survival in our cohort of patients with CTCL treated with RTSEI. Patients with CTCL treated with RTSEI (≥30 Gy) between 2000 and 2013 at our institution were identified, and clinical and pathologic data were retrospectively reviewed. Primary outcomes were complete clinical response (CCR; >90% reduction of skin disease burden), relapse-free survival (RFS), and overall survival (OS). Sixty-eight patients with CTCL treated with RTSEI were identified. Median age at diagnosis was 51 years with median follow-up of 61 months. Median OS was 76 months and median RFS was 11 months. Thirteen patients (19%) had CD30+ lymphocytes on initial pathology. In the CD30+ cohort, there were no T2, eight T3, and five T4 cases. In comparison, in the CD30- cohort, there were 18 T2, 29 T3, and 8 T4 cases (P = 0.01). Six weeks post-RTSEI, CCR was 85% in CD30+ and 81% in CD30- cases (P = 1). Six months post-RTSEI, CCR was 23% in CD30+ and 50% in CD30- cases (P = 0.083). RTSEI resulted in excellent CCR at 6 weeks in our cohort of patients with CTCL, with a median RFS of 11 months. We found CD30+ patients presented with significantly higher T stage at time of RTSEI and trended towards decreased CCR at 6 months post-RTSEI compared with the CD30- group.
Two-Dimensional Electronic-Vibrational Spectroscopy of Chlorophyll a and b
Energy Technology Data Exchange (ETDEWEB)
Lewis, Nicholas H. C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Div.; Kavli Energy Nanoscience Institute at Berkeley, CA (United States); Fleming, Graham R. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Div.; Kavli Energy Nanoscience Institute at Berkeley, CA (United States)
2016-03-03
Presented are two-dimensional electronic-vibrational (2DEV) spectra of isolated chlorophyll a and b in deuterated ethanol. We excite the Q-band electronic transitions and measure the effects on the carbonyl and C=C double-bond stretch region of the infrared spectrum. With the aid of density functional theory calculations, we provide assignments for the major features of the spectrum. We show how the 2DEV spectra can be used to readily distinguish different solvation states of the chlorophyll, with features corresponding to the minority pentacoordinate magnesium (Mg) species being resolved along each dimension of the 2DEV spectra from the dominant hexacoordinate Mg species. These assignments represent a crucial first step toward the application of 2DEV spectroscopy to chlorophyll-containing pigment-protein complexes.
Govind, Chinju; Karunakaran, Venugopal
2017-04-13
Hemin is a unique model compound of heme proteins carrying out variable biological functions. Here, the excited state relaxation dynamics of heme model compounds in the ferric form are systematically investigated by changing the axial ligand (Cl/Br), the peripheral substituent (vinyl/ethyl-meso), and the solvent (methanol/DMSO) using femtosecond pump-probe spectroscopy upon excitation at 380 nm. The relaxation time constants of these model compounds are obtained by global analysis. Excited state deactivation pathway of the model compounds comprising the decay of the porphyrin excited state (S*) to ligand to metal charge transfer state (LMCT, τ 1 ), back electron transfer from metal to ligand (MLCT, τ 2 ), and relaxation to the ground state through different electronic spin states of iron (τ 3 and τ 4 ) are proposed along with the vibrational cooling processes. This is based on the excited state absorption spectral evolution, similarities between the transient absorption spectra of the ferric form and steady state absorption spectra of the low-spin ferrous form, and the data analysis. The observation of an increase of all the relaxation time constants in DMSO compared to the methanol reflects the stabilization of intermediate states involved in the electronic relaxation. The transient absorption spectra of met-myoglobin are also measured for comparison. Thus, the transient absorption spectra of these model compounds reveal the involvement of multiple iron spin states in the electronic relaxation dynamics, which could be an alternative pathway to the ground state beside the vibrational cooling processes and associated with the inherent features of the heme b type.
Sparta, Manuel; Hansen, Mikkel B; Matito, Eduard; Toffoli, Daniele; Christiansen, Ove
2010-10-12
The availability of an accurate representation of the potential energy surface (PES) is an essential prerequisite in an anharmonic vibrational calculation. At the same time, the high dimensionality of the fully coupled PES and the adverse scaling properties with respect to the molecular size make the construction of an accurate PES a computationally demanding task. In the past few years, our group tested and developed a series of tools and techniques aimed at defining computationally efficient, black-box protocols for the construction of PESs for use in vibrational calculations. This includes the definition of an adaptive density-guided approach (ADGA) for the construction of PESs from an automatically generated set of evaluation points. Another separate aspect has been the exploration of the use of derivative information through modified Shepard (MS) interpolation/extrapolation procedures. With this article, we present an assembled machinery where these methods are embedded in an efficient way to provide both a general machinery as well as concrete computational protocols. In this framework we introduce and discuss the accuracy and computational efficiency of two methods, called ADGA[2gx3M] and ADGA[2hx3M], where the ADGA recipe is used (with MS interpolation) to automatically define modest sized grids for up to two-mode couplings, while MS extrapolation based on, respectively, gradients only and gradients and Hessians from the ADGA determined points provides access to sufficiently accurate three-mode couplings. The performance of the resulting potentials is investigated in vibrational coupled cluster (VCC) calculations. Three molecular systems serve as benchmarks: a trisubstituted methane (CHFClBr), methanimine (CH2NH), and oxazole (C3H3NO). Furthermore, methanimine and oxazole are addressed in accurate calculations aiming to reproduce experimental results.
Nonequilibrium electron-vibration coupling and conductance fluctuations in a C60 junction
DEFF Research Database (Denmark)
Ulstrup, Søren; Frederiksen, Thomas; Brandbyge, Mads
2012-01-01
We investigate chemical bond formation and conductance in a molecular C60 junction under finite bias voltage using first-principles calculations based on density functional theory and nonequilibrium Green's functions (DFT-NEGF). At the point of contact formation we identify a remarkably strong...... displacement. Combined with a vibrational heating mechanism we construct a model from our results that explain the polarity-dependent two-level conductance fluctuations observed in recent scanning tunneling microscopy (STM) experiments [N. Ne´el et al., Nano Lett. 11, 3593 (2011)]. These findings highlight...
Evans, Michael D C; Hudon, Christine; Podgorsak, Ervin B; Freeman, Carolyn R
2014-03-01
Total skin electron irradiation (TSEI) for patients with cutaneous lymphomas is technically challenging, and numerous approaches have been developed to overcome the many field matching problems associated with such a large and complex treatment volume. Since 1981 we have delivered TSEI using a rotational total skin electron irradiation (RTSEI) technique in conjunction with patch, treat and boost fields in order to provide complete skin and dose coverage. Initially we used a 6 MeV electron beam at an extended source-skin distance (SSD) on a modified linear accelerator. More recently we began using a high dose rate electron mode on a commercially available linear accelerator. The RTSEI technique allows the delivery of a seamless surface dose to the majority of the patient's skin surface in a single treatment. In this review paper we present our three-decade experience with the technical development, dosimetry, treatment delivery and clinical outcomes of our RTSEI technique.
Evans, Michael D.C.; Hudon, Christine; Podgorsak, Ervin B.; Freeman, Carolyn R.
2013-01-01
Total skin electron irradiation (TSEI) for patients with cutaneous lymphomas is technically challenging, and numerous approaches have been developed to overcome the many field matching problems associated with such a large and complex treatment volume. Since 1981 we have delivered TSEI using a rotational total skin electron irradiation (RTSEI) technique in conjunction with patch, treat and boost fields in order to provide complete skin and dose coverage. Initially we used a 6 MeV electron beam at an extended source-skin distance (SSD) on a modified linear accelerator. More recently we began using a high dose rate electron mode on a commercially available linear accelerator. The RTSEI technique allows the delivery of a seamless surface dose to the majority of the patient's skin surface in a single treatment. In this review paper we present our three-decade experience with the technical development, dosimetry, treatment delivery and clinical outcomes of our RTSEI technique. PMID:24936331
Tyuterev, Vladimir G; Kochanov, Roman V; Tashkun, Sergey A; Holka, Filip; Szalay, Péter G
2013-10-07
An accurate description of the complicated shape of the potential energy surface (PES) and that of the highly excited vibration states is of crucial importance for various unsolved issues in the spectroscopy and dynamics of ozone and remains a challenge for the theory. In this work a new analytical representation is proposed for the PES of the ground electronic state of the ozone molecule in the range covering the main potential well and the transition state towards the dissociation. This model accounts for particular features specific to the ozone PES for large variations of nuclear displacements along the minimum energy path. The impact of the shape of the PES near the transition state (existence of the "reef structure") on vibration energy levels was studied for the first time. The major purpose of this work was to provide accurate theoretical predictions for ozone vibrational band centres at the energy range near the dissociation threshold, which would be helpful for understanding the very complicated high-resolution spectra and its analyses currently in progress. Extended ab initio electronic structure calculations were carried out enabling the determination of the parameters of a minimum energy path PES model resulting in a new set of theoretical vibrational levels of ozone. A comparison with recent high-resolution spectroscopic data on the vibrational levels gives the root-mean-square deviations below 1 cm(-1) for ozone band centres up to 90% of the dissociation energy. New ab initio vibrational predictions represent a significant improvement with respect to all previously available calculations.
Arun Sasi, B. S.; Jebin, R. P.; Suthan, T.; James, C.
2017-10-01
An organic nonlinear optical material 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline (DMBDNA) has been grown by slow evaporation technique. Vibrational spectral analysis has been carried out using FT Raman, FT-IR and UV-Vis spectroscopic techniques. The influence of intramolecular charge transfer within the molecule has been studied on the basis of NBO analysis. Vibrational frequencies have been calculated and scaled, which has been compared with the experimental FT-IR and FT Raman spectra. The effect of electronic localization and delocalization within the molecule is conceded on the basis of electron density partitioning paradigm.
Hodecker, Manuel; Biczysko, Malgorzata; Dreuw, Andreas; Barone, Vincenzo
2017-01-01
Vibrationally resolved one-photon absorption and electronic circular dichroism spectra of (R)-methyl oxirane were calculated with different electronic and vibronic models selecting, through an analysis of the convergence of the results, the best compromise between reliability and computational cost. Linear-response TD-DFT/CAM-B3LYP/SNST electronic computations in conjunction with the simple vertical gradient vibronic model were chosen and employed for systematic comparison with the available experimental data. Remarkable agreement between simulated and experimental spectra was achieved for both one photon absorption and circular dichroism concerning peak positions, relative intensities, and general spectral shapes considering the computational efficiency of the chosen theoretical approach. The significant improvement of the results with respect to smearing of vertical electronic transitions by phenomenological Gaussian functions and the possible inclusion of solvent effects by polarizable continuum models at a negligible additional cost paves the route toward the simulation and analysis of spectral shapes of complex molecular systems in their natural environment. PMID:27159495
Energy Technology Data Exchange (ETDEWEB)
Gornyi, I. V. [Karlsruhe Institute of Technology, Institut für Nanotechnologie (Germany); Dmitriev, A. P., E-mail: apd1812@hotmail.com [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Mirlin, A. D.; Protopopov, I. V. [Karlsruhe Institute of Technology, Institut für Nanotechnologie (Germany)
2016-08-15
We have studied the motion of an electron in a membrane under the influence of flexural vibrations with a correlator that decreases upon an increase in the distance in accordance with the law r–{sup 2η}. We have conducted a detailed consideration of the case with η < 1/2, in which the perturbation theory is inapplicable, even for an arbitrarily weak interaction. It is shown that, in this case, reciprocal quantum time 1/τ{sub q} is proportional to g{sup 1/(1–η)}T{sup (2–η)/(2–2η)}, where g is the electron–phonon interaction constant and T is the temperature. The method developed here is applied for calculating the electron density of states in a magnetic field perpendicular to the membrane. In particular, it is shown that the Landau levels in the regime with ω{sub c}τ{sub q} » 1 have a Gaussian shape with a width that depends on the magnetic field as B{sup η}. In addition, we calculate the time τ{sub φ} of dephasing of the electron wave function that emerges due to the interaction with flexural phonons for η < 1/2. It has been shown that, in several temperature intervals, quantity 1/τ{sub φ} can be expressed by various power functions of the electron–phonon interaction constant, temperature, and electron energy.
Mineo, Hirobumi; Fujimura, Yuichi
2015-06-01
We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.
Directory of Open Access Journals (Sweden)
Ambrish Kumar Srivastava
2016-12-01
Full Text Available The present study deals with a non-native amino acid, cis-4-hydroxy-d-proline (CHDP using density functional theory at B3LYP/6-31+G(d,p level. The potential energy surface scan reveals the global minimum structure of CHDP along with two potential conformers. Highest occupied molecular orbital, lowest unoccupied molecular orbital, and molecular electrostatic potential surfaces are used to explain the chemical reactivity of title molecule. The atomic charge analysis has been carried out using Mulliken and natural population schemes. The equilibrium geometry of CHDP dimer has been obtained and inter-molecular interactions are explored using QTAIM and Natural bonding orbital analyses. Vibrational spectroscopic analysis has been performed on CHDP monomer and dimer at the same level of theory. Assignments to all vibrational modes up to 400 cm−1 have been offered along with their potential energy distribution to the maximum possible accuracy. The calculated frequencies are scaled by an equation, rather than by a constant factor and then compared with experimental FT-IR frequencies obtained by KBr disc and Nujol mull techniques. A number of electronic and thermodynamic parameters have also been evaluated for CHDP monomer and dimer.
Rotor Vibration Reduction via Active Hybrid Bearings
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2002-01-01
The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... with experiment, and simulations show the feasibility of controlling shaft vibration through this active device....
Ivanco, Thomas G. (Inventor)
2014-01-01
A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.
Pinjari, Rahul V; Joshi, Kaustubh A; Gejji, Shridhar P
2008-12-01
Electronic structure and the vibrational spectra of CH(3)(OCH(2)CH(2))(2)OCH(3)-M(+)-AsF(6)(-) (M=Li, Na, K) have been obtained using the density functional theory. Lithium ion exhibits a pentavalent coordination via 3 oxygens from diglyme and two fluorines of AsF(6)(-) whereas Na(+) and K(+) exhibit coordinate number 6 with 3 fluorines of the anion binding to alkali metal in these complexes. Analysis of calculated spectra reveal that the CH(2) wag (840-1120 cm(-1)) vibrations in the complex are sensitive to metal ion coordination. A frequency downshift relative to the free anion has been predicted for the vibrations of AsF(6)(-) anion when the fluorines are directly bonded (denoted by F) to metal ion. Consequent reorganization of electron density in the complex engenders a frequency shift in the opposite direction for As-F vibrations wherein the fluorine atoms are not coordinating to the alkali metal ion. An approach based on the molecular electron density topography coupled with the difference electron density map explains the direction of the frequency shifts of C-O-C and the As-F stretchings compared to those of free diglyme or AsF(6) anion. A new method, which includes the color-mapping function for the difference molecular electron density (MED), superimposed on the bond critical points in MED topography has been suggested to explain the direction of the frequency shifts in a single attempt.
Recent results on measurement of plasma conductivity using Faraday rotation of submillimeter waves
Energy Technology Data Exchange (ETDEWEB)
Kuzmenko, P.J.; Self, S.A.
1982-01-01
This paper examines the application of Faraday rotation to the measurement of electron concentration in combustion MHD plasmas. Details on the design of a working system are given including the selection of operating wavelength. A theoretical comparison between the Faraday rotation technique and two path interferometry shows Faraday rotation in its simplest form to be somewhat less sensitive to changes in electron concentration. This deficit can be balanced against greater immunity to vibration and thermal drift. Improved techniques of measuring the rotation angle promise greater sensitivity. A preliminary experiment has verified the technique.
Energy Technology Data Exchange (ETDEWEB)
Preciado, Jorge Sanchez; Lopez, Carlos Perez; Santoyo, Fernando Mendoza [Grupo de Metrología Optica, Centro de Investigaciones en Óptica, A. C. Loma del Bosque 115, Col. Lomas del Campestre, León, Guanajuato, 37150 (Mexico)
2014-05-27
Implementing a hybrid arrangement of Laser Doppler Vibrometry (LDV) and high speed Electronic Speckle Pattern Interferometry (ESPI) we were able to measure the dynamic patterns of a flat rectangular elastic membrane clamped at its edges stimulated with the sum of two resonance frequencies. ESPI is a versatile technique to analyze in real-time the deformation of a membrane since its low computational cost and easy implementation of the optical setup. Elastic membranes present nonlinear behaviors when stimulated with low amplitude signals. The elastic membrane under test, with several non rational related vibrating modals below the 200 Hz, was stimulated with two consecutives resonant frequencies. The ESPI patterns, acquired at high speed rates, shown a similar behavior for the dual frequency stimulation as in the case of patterns formed with the entrainment frequency. We think this may be related to the effects observed in the application of dual frequency stimulation in ultrasound.
Ferré, A.; Boguslavskiy, A. E.; Dagan, M.; Blanchet, V.; Bruner, B. D.; Burgy, F.; Camper, A.; Descamps, D.; Fabre, B.; Fedorov, N.; Gaudin, J.; Geoffroy, G.; Mikosch, J.; Patchkovskii, S.; Petit, S.; Ruchon, T.; Soifer, H.; Staedter, D.; Wilkinson, I.; Stolow, A.; Dudovich, N.; Mairesse, Y.
2015-01-01
High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20–26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected. PMID:25608712
Rotational Laser Cooling of MgH^{+} Ions and Rotational Rate Measurements
DEFF Research Database (Denmark)
Hansen, Anders Kragh; Staanum, Peter; Højbjerre, Klaus
blackbody radiation field. To undertake such modelling, we will carry out measurements of a series of transition rates between rotational states in the vibronic ground state at room temperature. The measurements will be performed by the same Resonance Enhanced Multi-Photon Dissociation (REMPD) process used......A method of laser cooling vibrationally and translationally cold trapped MgH+ ions to the rotational ground state using optical pumping was recently demonstrated in our group [1]. This method relies on the 293 K blackbody radiation to redistribute population among the rotational states, while...... exciting a single rovibrational transition within the X1Σ+ electronic ground state for optical pumping into the rovibrational ground state. To model the expected rotational state distributions after the application of the laser beam, one has to know the various rotational transitions rates in the present...
Yang, Pan; Shen, Wei; Li, Ming; He, Rongxing
2017-01-01
The vibrationally resolved electronic spectra of five metal-free NKX-2587 derivatives containing heteroatom with different atomic sizes and electronegativity, were simulated within the Franck-Condon approximation including the Herzberg-Teller and Duschinsky effects, aimed at exploring the correlation of vibronic structure associated with the spectrum and efficiency of dye sensitized solar cells (DSSCs). The parameters of short-circuit current density (Jsc) and open circuit voltage (Voc) involving efficiency of DSSCs, such as total dipole moments (μnormal), the light harvesting efficiency (LHE), injection driving force (Δ Ginject), and the number of electrons in the conduction band (nc), were calculated and discussed in detail. Results showed that the heteroatoms in the same period with large size and weak electronegativity and the ones in the same main group with large size and weak electronegativity are beneficial to Voc. The sizes and electronegativity of the heteroatoms have a weak effect on Jsc. The low-frequency modes play important roles in enhancing the intensities of the electronic spectra and structures can affect light harvesting efficiency (LHE). In this sense, our results provided guidance for understanding the sources of spectral intensities of dye molecules, and a valuable help for rational design of new molecules to improve the energy conversion efficiency (η) of DSSCs.
Varga, Zoltán; Groen, Cornelis Petrus; Kolonits, Mária; Hargittai, Magdolna
2010-07-21
The molecular and electronic structure of dysprosium triiodide, DyI(3), and its dimer, Dy(2)I(6), was determined by high level computations, gas-phase electron diffraction, and gas-phase infrared and matrix-isolation infrared and Raman spectroscopy. The free monomeric molecule is planar from all methods with an equilibrium bond length of 2.808(9) A; the thermal average bond length from electron diffraction is 2.828(6) A. The molecule forms complexes in the matrix-isolation experiments causing pyramidalisation of planar monomeric molecules. The likelihood of having both pyramidal and planar DyI(3) molecules in the matrix is discussed in order to explain certain features of the spectra. Our computations suggest that the dimer geometry depends on the occupation of the partially filled 4f orbitals. As this is the third molecule in the dysprosium trihalide series studied, trends in their electronic and molecular structures are presented and discussed.
Alling, BjöRn
We report the impact of lattice vibrations on magnetic and electronic properties of paramagnetic bcc and fcc iron employing the disordered local moments molecular dynamics (DLM-MD). Vibrations strongly affect the distribution of local magnetic moments and the electronic density of states in the paramagnetic regime. When the coupling between vibrations and magnetism is taken into account at the γ- δ transition temperature (1662 K), the lattice distortions cause very similar mean magnetic moments and total electronic density of states of both bcc and fcc structures. Consequently, our simulations suggest that at the γ- δ transition temperature, electronic and magnetic contributions to the Gibbs free energy are extremely similar in bcc and fcc Fe. In the next step, going beyond the approximation of magnetism as an adiabatically fast degree of freedom, we study paramagnetic CrN using a combination of atomistic spin dynamics and ab-initio molecular dynamics. We demonstrate how the relaxation time scales of the transverse spin dynamics and atomic vibrations are rather similar and study the impact of their explicit coupling on properties such as pair-correlation functions, potential energies, and trajectories.
Cross sections for electron collisions with nitric oxide
Energy Technology Data Exchange (ETDEWEB)
Itikawa, Yukikazu, E-mail: yukitikawa@nifty.com [Institute of Space and Astronautical Science, Sagamihara 252-5210 (Japan)
2016-09-15
Cross section data are reviewed for electron collisions with nitric oxide. Collision processes considered are total scattering, elastic scattering, momentum transfer, excitations of rotational, vibrational, and electronic states, ionization, and dissociative electron attachment. After a survey of the literature (up to the end of 2015), recommended values of the cross section are determined, as far as possible.
Struts, A. V.; Barmasov, A. V.; Brown, M. F.
2015-05-01
Here we review the application of modern spectral methods for the study of G-protein-coupled receptors (GPCRs) using rhodopsin as a prototype. Because X-ray analysis gives us immobile snapshots of protein conformations, it is imperative to apply spectroscopic methods for elucidating their function: vibrational (Raman, FTIR), electronic (UV-visible absorption, fluorescence) spectroscopies, and magnetic resonance (electron paramagnetic resonance, EPR), and nuclear magnetic resonance (NMR). In the first of the two companion articles, we discuss the application of optical spectroscopy for studying rhodopsin in a membrane environment. Information is obtained regarding the time-ordered sequence of events in rhodopsin activation. Isomerization of the chromophore and deprotonation of the retinal Schiff base leads to a structural change of the protein involving the motion of helices H5 and H6 in a pH-dependent process. Information is obtained that is unavailable from X-ray crystallography, which can be combined with spectroscopic studies to achieve a more complete understanding of GPCR function.
Singh, Swapnil; Singh, Harshita; Srivastava, Anubha; Tandon, Poonam; Sinha, Kirti; Bharti, Purnima; Kumar, Sudhir; Kumar, Padam; Maurya, Rakesh
2014-11-11
In the present work, a detailed conformational study of cladrin (3-(3,4-dimethoxy phenyl)-7-hydroxychromen-4-one) has been done by using spectroscopic techniques (FT-IR/FT-Raman/UV-Vis/NMR) and quantum chemical calculations. The optimized geometry, wavenumber and intensity of the vibrational bands of the cladrin in ground state were calculated by density functional theory (DFT) employing 6-311++G(d,p) basis sets. The study has been focused on the two most stable conformers that are selected after the full geometry optimization of the molecule. A detailed assignment of the FT-IR and FT-Raman spectra has been done for both the conformers along with potential energy distribution for each vibrational mode. The observed and scaled wavenumber of most of the bands has been found to be in good agreement. The UV-Vis spectrum has been recorded and compared with calculated spectrum. In addition, 1H and 13C nuclear magnetic resonance spectra have been also recorded and compared with the calculated data that shows the inter or intramolecular hydrogen bonding. The electronic properties such as HOMO-LUMO energies were calculated by using time-dependent density functional theory. Molecular electrostatic potential has been plotted to elucidate the reactive part of the molecule. Natural bond orbital analysis was performed to investigate the molecular stability. Non linear optical property of the molecule have been studied by calculating the electric dipole moment (μ) and the first hyperpolarizability (β) that results in the nonlinearity of the molecule. Copyright © 2014 Elsevier B.V. All rights reserved.
National Research Council Canada - National Science Library
Alfano, R. R
2000-01-01
.... The nonequilibrium population of a local mode of 765 cm(sup -1) in Cr(sup 4+):Mg2SiO4 was found to build up during the transition through an electronic bottleneck and decay by interaction with a restricted number of phonon modes...
Kurzych, Anna; Jaroszewicz, Leszek R.; Kowalski, Jerzy K.
2017-05-01
A relatively young field of study named Rotational Seismology caused a highly interest in an investigation of rotational movements generated by earthquakes, explosions, and ambient vibrations. It includes a wide range of scientific branches. However, this field needs to apply appropriate rotational sensors which should fulfill restrict technical requirements. The presented in this work system FOSREM (Fibre-Optic System for Rotational Events and Phenomena Monitoring) seems to be a promising rotational sensor for such investigation. FOSREM works by measuring the Sagnac effect and generally consists of two basic elements: optical sensor and electronic part. Regarding to its theoretical sensitivity equals 2·10-8 rad/s/Hz1/2, it enables to measure rotation in a wide range of signal amplitude (10-8 rad/s ÷ 10 rad/s) and frequency (DC ÷ 328.12 Hz). Moreover, FOSREM is mobile and remotely controlled via Internet using a special designed software.
Zhang, Wei; Wu, Tongyu; Ding, Baogang; Li, Yonggao; Zhou, Yan; Yin, Zejie
2017-07-01
The precision of plasma electron density and Faraday rotation angle measurement is a key indicator for far-infrared laser interferometer/polarimeter plasma diagnosis. To improve the precision, a new multi-channel high signal-to-noise ratio HCOOH interferometer/polarimeter has been developed on the HL-2A tokamak. It has a higher level requirement for phase demodulation precision. This paper introduces an improved real-time fast Fourier transform algorithm based on the field programmable gate array, which significantly improves the precision. We also apply a real-time error monitoring module (REMM) and a stable error inhibiting module (SEIM) for precision control to deal with the weak signal. We test the interferometer/polarimeter system with this improved precision control method in plasma discharge experiments and simulation experiments. The experimental results confirm that the plasma electron density precision is better than 1/3600 fringe and the Faraday rotation angle measurement precision is better than 1/900 fringe, while the temporal resolution is 80 ns. This performance can fully meet the requirements of HL-2A.
Shin, Hee Won; Ocola, Esther J; Kim, Sunghwan; Laane, Jaan
2014-01-21
The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S1(π,π(*)) electronic excited state. Theoretical calculations at the CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S0 and S1(π,π(*)) electronic states. In each case the decreased π bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similar molecules. The vibrational levels in both S0 and S1(π,π(*)) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S1(π,π(*)) excited state.
Energy Technology Data Exchange (ETDEWEB)
Shin, Hee Won; Ocola, Esther J.; Laane, Jaan, E-mail: laane@mail.chem.tamu.edu [Department of Chemistry, Texas A and M University, College Station, Texas 77843-3255 (United States); Kim, Sunghwan [National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, 8600 Rockville Pike, Bethesda, Maryland 20894 (United States)
2014-01-21
The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S{sub 1}(π,π{sup *}) electronic excited state. Theoretical calculations at the CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S{sub 0} and S{sub 1}(π,π{sup *}) electronic states. In each case the decreased π bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similar molecules. The vibrational levels in both S{sub 0} and S{sub 1}(π,π{sup *}) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S{sub 1}(π,π{sup *}) excited state.
Shin, Hee Won; Ocola, Esther J.; Kim, Sunghwan; Laane, Jaan
2014-01-01
The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S1(π,π*) electronic excited state. Theoretical calculations at the CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S0 and S1(π,π*) electronic states. In each case the decreased π bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similar molecules. The vibrational levels in both S0 and S1(π,π*) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S1(π,π*) excited state. PMID:25669377
Shin, Hee Won; Ocola, Esther J.; Kim, Sunghwan; Laane, Jaan
2014-01-01
The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S1(π,π*) electronic excited state. Theoretical calculations at the CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S0 and S1(π,π*) electronic states. In each case the decreased π bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similar molecules. The vibrational levels in both S0 and S1(π,π*) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S1(π,π*) excited state.
Rotating structures and Bryan’s effect
CSIR Research Space (South Africa)
Joubert, SV
2009-05-01
Full Text Available In 1890 Bryan observed that when a vibrating structure is rotated the vibrating pattern rotates at a rate proportional to the rate of rotation. During investigations of the effect in various solid and fluid-filled objects of various shapes...
The Generalized Coherent State ansatz: Application to quantum electron-vibrational dynamics
Energy Technology Data Exchange (ETDEWEB)
Borrelli, Raffaele, E-mail: raffaele.borrelli@unito.it [DISAFA, Università di Torino, I-10095 Grugliasco (Italy); Gelin, Maxim F. [Departement of Chemistry, Technische Universität München, D-85747 Garching (Germany)
2016-12-20
A new ansatz for molecular vibronic wave functions based on a superposition of time-dependent Generalized Coherent States is developed and analysed. The methodology is specifically tailored to describe the time evolution of the wave function of a system in which several interacting electronic states are coupled to a bath of harmonic oscillators. The equations of motion for the wave packet parameters are obtained by using the Dirac–Frenkel time-dependent variational principle. The methodology is used to describe the quantum dynamical behavior of a model polaron system and its scaling and convergence properties are discussed and compared with numerically exact results.
Jacovella, Ugo; Gans, Bérenger; Merkt, Frédéric
2015-08-01
Pulsed-field-ionisation zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of 2-butyne (CH3-CC-CH3) and its fully deuterated isotopomer have been recorded in the region of the origin band of the ? ionising transition. The spectral congestion originating from the combined effects of the internal rotation of the methyl groups, the spin-orbit coupling, and the Jahn-Teller effect prevented the full resolution of the rotational structure of the photoelectron spectra. A tentative analysis of the rotational branch structure of the photoelectron spectra using rovibronic photoionisation selection rules derived in the permutation-inversion spin double group G36(M2) suggests a splitting of ∼10.5 cm-1 between the two spin-orbit components E3/2 and E1/2 of the ? 2 E1 ground state and an almost free internal rotation of the methyl groups in the cations. Assignments are proposed for several low-lying vibrational levels of the cations.
Grasseschi, D.; Bahamon, D. A.; Maia, F. C. B.; Castro Neto, A. H.; Freitas, R. O.; de Matos, C. J. S.
2017-09-01
Black phosphorus (BP) is a layered crystalline structure presenting a thickness-tunable direct bandgap and a high charge carrier mobility, with, therefore, enormous interest to photonics, optoelectronics and electronics. However, BP’s high susceptibility to oxidation when exposed to ambient conditions is a critical challenge for its implementation into functional systems. Here, we investigate the degradation of BP flakes exposed to various environmental conditions by synchrotron infrared nanospectroscopy (SINS). As a near-field based technique, SINS provides sub-diffractional mid-infrared images and spectra from nano-sized domains. Supported by density functional theory (DFT) calculations, our SINS spectra reveal the formation of nanoscale PO x domains, with x between 0.5 and 1, and a 100 meV red shift in the bandgap of flakes exposed to air for a few minutes. On the other hand, exposure to air for 24 h led to the preferential formation of H3PO4, with complete removal of the electronic transitions from the mid-infrared spectral window, while a long (1 month) exposure to low O2 levels mainly led to the formation of P4O8 and P4O9 species. The SINS analysis allows correlating the morphology of oxidized samples to the oxide type, thus, contributing to a comprehensive characterization of the BP degradation process.
Directory of Open Access Journals (Sweden)
V. A. Yankovsky
2006-11-01
Full Text Available The traditional kinetics of electronically excited products of O3 and O2 photolysis is supplemented with the processes of the energy transfer between electronically-vibrationally excited levels O2(a1Δg, v and O2(b1Σ+g, v, excited atomic oxygen O(1D, and the O2 molecules in the ground electronic state O2(X3Σg−, v. In contrast to the previous models of kinetics of O2(a1Δg and O2 (b1Σ+g, our model takes into consideration the following basic facts: first, photolysis of O3 and O2 and the processes of energy exchange between the metastable products of photolysis involve generation of oxygen molecules on highly excited vibrational levels in all considered electronic states – b1Σ+g, a1Δg and X3Σg−; second, the absorption of solar radiation not only leads to populating the electronic states on vibrational levels with vibrational quantum number v equal to 0 – O2(b1Σ+g, v=0 (at 762 nm and O2(a1Δg, v=0 (at 1.27 µm, but also leads to populating the excited electronic–vibrational states O2(b1Σ+g, v=1 and O2(b1Σ+g, v=2 (at 689 nm and 629 nm. The proposed model allows one to calculate not only the vertical profiles of the O2(a1Δg, v=0 and O2(b1Σg, v=0 concentrations, but also the profiles of [O2(a1Δg, v≤5], [O2 (b1Σ+g , v=1, 2] and O2(X3Σg−, v=1–35. In the altitude range 60–125 km, consideration of the electronic-vibrational kinetics significantly changes the calculated concentrations of the metastable oxygen molecules and reduces the discrepancy between the altitude profiles of ozone concentrations retrieved from the 762-nm and 1.27-µm emissions measured simultaneously.
Energy Technology Data Exchange (ETDEWEB)
Ravi Kumar, Venkatraman; Umapathy, Siva, E-mail: umapathy@ipc.iisc.ernet.in, E-mail: chandra@bii.a-star.edu.sg [Inorganic and Physical Chemistry Department, Indian Institute of Science, Bangalore 560012 (India); Verma, Chandra, E-mail: umapathy@ipc.iisc.ernet.in, E-mail: chandra@bii.a-star.edu.sg [Bioinformatics Institute - A*STAR, 30 Biopolis Street, # 07-01 Matrix, Singapore 138671 (Singapore); School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551 (Singapore); Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543 (Singapore)
2016-02-14
Solvent plays a key role in diverse physico-chemical and biological processes. Therefore, understanding solute-solvent interactions at the molecular level of detail is of utmost importance. A comprehensive solvatochromic analysis of benzophenone (Bzp) was carried out in various solvents using Raman and electronic spectroscopy, in conjunction with Density Functional Theory (DFT) calculations of supramolecular solute-solvent clusters generated using classical Molecular Dynamics Simulations (c-MDSs). The >C=O stretching frequency undergoes a bathochromic shift with solvent polarity. Interestingly, in protic solvents this peak appears as a doublet: c-MDS and ad hoc explicit solvent ab initio calculations suggest that the lower and higher frequency peaks are associated with the hydrogen bonded and dangling carbonyl group of Bzp, respectively. Additionally, the dangling carbonyl in methanol (MeOH) solvent is 4 cm{sup −1} blue-shifted relative to acetonitrile solvent, despite their similar dipolarity/polarizability. This suggests that the cybotactic region of the dangling carbonyl group in MeOH is very different from its bulk solvent structure. Therefore, we propose that this blue-shift of the dangling carbonyl originates in the hydrophobic solvation shell around it resulting from extended hydrogen bonding network of the protic solvents. Furthermore, the 1{sup 1}nπ{sup ∗} (band I) and 1{sup 1}ππ{sup ∗} (band II) electronic transitions show a hypsochromic and bathochromic shift, respectively. In particular, these shifts in protic solvents are due to differences in their excited state-hydrogen bonding mechanisms. Additionally, a linear relationship is obtained for band I and the >C=O stretching frequency (cm{sup −1}), which suggests that the different excitation wavelengths in band I correspond to different solvation states. Therefore, we hypothesize that the variation in excitation wavelengths in band I could arise from different solvation states leading to
Nataraj, A.; Balachandran, V.; Karthick, T.
2013-01-01
In this work, the vibrational spectral analysis was carried out using Raman and infrared spectroscopy in the range 4000-400 cm-1 and 3500-100 cm-1, respectively, for the 2-hydroxy-5-bromobenzaldehyde (HBB). The experimental spectra were recorded in the solid phase. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G++(d,p) method and basis set. Normal co-ordinate calculations were performed with the DFT force field corrected by a recommended set of scaling factors yielding fairly good agreement between observed and calculated frequencies. Simulation of infrared and Raman spectra utilizing the results of these calculations led to excellent overall agreement with the observed spectral patterns. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The optimized geometric parameters (bond lengths and bond angles) were compared with experimental values of related compound. The stability of the molecule arising from hyper conjugative interactions and the charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), electrophilicity index (ω), hardness (η), chemical potential (μ), and first electron excitation (τ) are all correlated with the HOMO and LUMO energies with their molecular properties. These show that charge transfer occurs within the molecule. Furthermore, molecular electrostatic potential maps (MESP) of the molecule have been calculated.
Electronic structure and time-dependent description of rotational predissociation of LiH
DEFF Research Database (Denmark)
Jasik, P.; Sienkiewicz, J. E.; Domsta, J.
2017-01-01
The adiabatic potential energy curves of the 1Σ+ and 1Π states of the LiH molecule were calculated. They correlate asymptotically to atomic states, such as 2s + 1s, 2p + 1s, 3s + 1s, 3p + 1s, 3d + 1s, 4s + 1s, 4p + 1s and 4d + 1s. A very good agreement was found between our calculated spectroscopic...... parameters and the experimental ones. The dynamics of the rotational predissociation process of the 11Π state were studied by solving the time-dependent Schrödinger equation. The classical experiment of Velasco [Can. J. Phys., 1957, 35, 1204] on dissociation in the 11Π state is explained for the first time...
Sienkiewicz-Gromiuk, Justyna
2018-01-01
The DFT studies were carried out with the B3LYP method utilizing the 6-31G and 6-311++G(d,p) basis sets depending on whether the aim of calculations was to gain the geometry at equilibrium, or to calculate the optimized molecular structure of (benzylthio)acetic acid (Hbta) in the forms of monomer and dimer. The minimum conformational energy search was followed by the potential energy surface (PES) scan of all rotary bonds existing in the acid molecule. The optimized geometrical monomeric and dimeric structures of the title compound were compared with the experimental structural data in the solid state. The detailed vibrational interpretation of experimental infrared and Raman bands was performed on the basis of theoretically simulated ESFF-scaled wavenumbers calculated for the monomer and dimer structures of Hbta. The electronic characteristics of Hbta is also presented in terms of Mulliken atomic charges, frontier molecular orbitals and global reactivity descriptors. Additionally, the MEP and ESP surfaces were computed to predict coordination sites for potential metal complex formation.
Energy Technology Data Exchange (ETDEWEB)
Krewald, S.; Lallena, A.M.; Dehesa, J.S.
1986-02-03
Inelastic electron-scattering form factors of magnetic states in closed-shell nuclei are calculated taking into account the combined effect of the mesonic degrees of freedom and the two-particle-two-hole components of the nuclear wave functions which come from the particle-core vibration coupling. The one-body nucleon- and two-body meson-exchange current contribution to the form factor are evaluated with the same realistic mean field. Application to various high-spin magnetic states of oxygen and lead is made. The comparison with experiment shows an excellent agreement for the states 14/sup -/(6.74 MeV) and 12/sup -/sub(t)(7.06 MeV) in lead, while such is not the case for the second 12/sup -//sub 2/(6.43 MeV) state in lead and the 4/sup -/(18.98 MeV) state in oxygen essentially due to mixing configuration effects and the non-consideration of 3p3h excitations, respectively. (orig.).
Energy Technology Data Exchange (ETDEWEB)
Bhoyar, Priyanka D. [Department of Physics, R.T.M. Nagpur University, Nagpur, 440033 (India); Brik, M.G., E-mail: brik@ut.ee [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing, 400065 (China); Institute of Physics, University of Tartu, Ravila 14C, Tartu, 50411 (Estonia); Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668, Warsaw (Poland); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200, Czestochowa (Poland); Dhoble, S.J., E-mail: sjdhoble@rediffmail.com [Department of Physics, R.T.M. Nagpur University, Nagpur, 440033 (India)
2016-08-15
Electron-vibrational interaction (EVI) in interconfigurational 5d-4f transition of Ce{sup 3+}-doped alkaline-earth chlorophosphates, also known as apatites, is studied for the first time in this work. Using the configurational coordinate model, the main EVI parameters such as Huang-Rhys factor, effective phonon energy and the zero-phonon line (ZPL) position are determined for all samples studied. Photoluminescence characteristics of these compounds are utilized to estimate EVI parameters. As a reliable test validating the obtained results, the emission band shape of was modeled to yield good agreement with experimental emission spectra. The values of EVI parameters were systematically compared for all studied materials as well as with similar systems with halide ions. - Highlights: • EVI in Ce{sup 3+}-doped alkaline-earth halochlorophosphates is studied for the first time in this work. • The EVI parameters are estimated using the configurational coordinate model. • Estimated EVI parameters are validated by modeling emission spectra. • Parameters are systematically compared.
Electron scattering filter design for a single field rotational total skin irradiation.
Pham, Y T; Bubb, I F; Cramb, J A
2005-09-01
The aim of radiotherapy treatment of cutaneous T-cell lymphoma is to irradiate the skin with an appropriately homogeneous dose distribution up to a few millimetres in depth. This can be achieved by applying one of the total skin electron irradiation techniques. An aluminium/polystyrene foam electron scattering filter was designed so that the incident beam is broadened and degraded sufficiently to achieve a mean dose uniformity in a rectangular field of 180 cm height and 40 cm width. This paper reports on the development and construction of the electron scattering filter for use with a Varian 2100C accelerator, without MLCs, with a dose uniformity, over a useful field dimension of 180 cm height and 40 cm width, of +/- 7% about the mean, and an x-ray contamination of less than 2.4% beyond a depth of 3 cm.
Energy Technology Data Exchange (ETDEWEB)
Gregson, Colin R., E-mail: colin.r.gregson@nnl.co.uk [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale CA20 1PG (United Kingdom); Goddard, David T., E-mail: dave.t.goddard@nnl.co.uk [National Nuclear Laboratory, Preston Laboratory, Springfields, Salwick, Preston PR4 0XJ (United Kingdom); Sarsfield, Mark J., E-mail: mark.j.sarsfield@nnl.co.uk [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale CA20 1PG (United Kingdom); Taylor, Robin J., E-mail: robin.j.taylor@nnl.co.uk [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale CA20 1PG (United Kingdom)
2011-05-01
Graphical abstract: Spent Magnox fuel corroding in-situ in storage ponds forms sludges comprised of brucite and other Mg based phases with uranium oxide particles. Display Omitted Research highlights: > Caracterization study of highly radioactive corroded Magnox sludges. > Unique data from samples of actual corroded nuclear fuel. > Combined electron microscopy and vibrational spectroscopy study. > Analysis of particles from legacy spent fuel storage pond at Sellafield. > Supports major UK decommissioning and nuclear clean up challenge. - Abstract: Samples of filtered particulates and sludges, formed from corroding magnesium alloy clad uranium metal ('Magnox') fuel elements, collected from one of the legacy nuclear fuel storage ponds located at Sellafield (UK) were investigated by Environmental Scanning Electron Microscopy with Energy Dispersive X-Ray analysis (ESEM/EDX), micro-Raman spectroscopy and Fourier transform infra-red spectroscopy (FT-IR). ESEM imaging confirmed the dominant morphology to be clusters of interlocking platelets typical of brucite (Mg(OH){sub 2}). EDX analysis was suggestive of some conversion to the related phase, hydrotalcite (Mg{sub 6}Al{sub 2}(CO{sub 3})(OH){sub 16}.4H{sub 2}O), due to elevated levels of Al associated with Mg. Other apparent morphologies were less commonly observed including flaky sheets, consistent with earlier stages of Magnox alloy corrosion. In a few specific cases, rods were also observed suggestive of some conversion to Mg-hydroxycarbonate phases. Discrete phases rich in U were also identified. Fluorescence in the Raman spectroscopy also indicated surface coatings of organic macromolecules and iron sulphide on hematite containing particles, attributed to microbial activity within the open air pond. Some specific differences in the solid phases between pond areas with differing conditions were apparent.
A relation between the rotational g-factor and the electric dipole moment of a diatomic molecule
DEFF Research Database (Denmark)
Sauer, Stephan P. A.
1998-01-01
The relation between the rotational g-factor and the electric dipole moment of a diatomic molecule is investigated. An explicit expression for the irreducible nonadiabatic contribution in terms of excited electronic states is derived. The importance of this expression for the analysis of vibration......-rotational spectra of diatomic molecules is discussed and explicit expressions are presented for the first two fitting parameters in an expansion of the nonadiabatic rotational term in an effective vibration-rotational Hamiltonian. Results of ab initio self-consistent field, multiconfigurational self......-consistent field and second-order polarization propagator approximation calculations of nonadiabatic contributions to rotational g-factors of hydrides and fluorides of Li, B, Al, Ga and monoxides of C, Si and Ge are presented. Problems connected with usage of finite basis sets of one-electron functions...
Yamaki, Masahiro; Teranishi, Yoshiaki; Nakamura, Hiroki; Lin, Sheng Hsien; Fujimura, Yuichi
2016-01-21
The electron angular momentum is a fundamental quantity of high-symmetry aromatic ring molecules and finds many applications in chemistry such as molecular spectroscopy. The stationary angular momentum or unidirectional rotation of π electrons is generated by the excitation of a degenerated electronic excited state by a circularly-polarized photon. For low-symmetry aromatic ring molecules having non-degenerate states, such as chiral aromatic ring molecules, on the other hand, whether stationary angular momentum can be generated or not is uncertain and has not been clarified so far. We have found by both theoretical treatments and quantum optimal control (QOC) simulations that a stationary angular momentum can be generated even from a low-symmetry aromatic ring molecule. The generation mechanism can be explained in terms of the creation of a dressed-state, and the maximum angular momentum is generated by the dressed state with an equal contribution from the relevant two excited states in a simple three-electronic state model. The dressed state is formed by inducing selective nonresonant transitions between the ground and each excited state by two lasers with the same frequency but having different polarization directions. The selective excitation can be carried out by arranging each photon-polarization vector orthogonal to the electronic transition moment of the other transition. We have successfully analyzed the results of the QOC simulations of (P)-2,2'-biphenol of axial chirality in terms of the analytically determined optimal laser fields. The present findings may open up new types of chemical dynamics and spectroscopy by utilizing strong stationary ring currents and current-induced magnetic fields, which are created at a local site of large compounds such as biomolecules.
Wang, Zhi-Qiang; Wu, Cheng-Jun; Wang, Zhen-Hui; Huang, Chao; Huang, Jian; Wang, Jin-Hui; Sun, Tie-Min
2017-10-01
In this study, the stereochemistry of a new isopimarane-type diterpenoid isolated from the Callicarpa macrophylla Vahl, Callicapene M3, was studied by experimental electronic circular dichroism and vibrational circular dichroism with the aid of TDDFT theoretical calculations. The good consistence between the experimental and simulated circular dichroism has clearly confirmed the absolute configuration of the title compound as (4S, 5S, 9S, 10S, 13S, 14S)-14α-hydroxy-7,15-isopimaradien-18-oic acid.
Combescure, D.; Lazarus, A.
2008-12-01
This paper is aimed at presenting refined finite element modelling used for dynamic analysis of large rotating machines. The first part shows an equivalence between several levels of modelling: firstly, models made of beam elements and rigid disc with gyroscopic coupling representing the position of the rotating shaft in an inertial frame; secondly full three-dimensional (3D) or 3D shell models of the rotor and the blades represented in the rotating frame and finally two-dimensional (2D) Fourier model for both rotor and stator. Simple cases are studied to better understand the results given by analysis performed using a rotating frame and the equivalence with the standard calculations with beam elements. Complete analysis of rotating machines can be performed with models in the frames best adapted for each part of the structure. The effects of several defects are analysed and compared with this approach. In the last part of the paper, the modelling approach is applied to the analysis of the large rotating shaft part of the power conversion unit of the GT-MHR nuclear reactor.
Energy Technology Data Exchange (ETDEWEB)
Combescure, D.; Lazarus, A. [CEA Saclay, DEN/DM2S/SEMT/DYN, Dynam Anal Lab, Saclay, (France); Lazarus, A. [Ecole Polytech, Mecan Solides Lab, F-91128 Palaiseau, (France)
2008-07-01
This paper is aimed at presenting refined finite element modelling used for dynamic analysis of large rotating machines. The first part shows an equivalence between several levels of modelling: firstly, models made of beam elements and rigid disc with gyroscopic coupling representing the position of the rotating shaft in an inertial frame; secondly full three-dimensional (3D) or 3D shell models of the rotor and the blades represented in the rotating frame and finally two-dimensional (2D) Fourier model for both rotor and stator. Simple cases are studied to better understand the results given by analysis performed using a rotating frame and the equivalence with the standard calculations with beam elements. Complete analysis of rotating machines can be performed with models in the frames best adapted for each part of the structure. The effects of several defects are analysed and compared with this approach. In the last part of the paper, the modelling approach is applied to the analysis of the large rotating shaft part of the power conversion unit of the GT-MHR nuclear reactor. (authors)
Energy Technology Data Exchange (ETDEWEB)
Zhong, Yu; Li, Xin [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Yang, Qi, E-mail: yangqi@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Wang, Dongbo [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Advanced Water Management Centre, The University of Queensland, QLD 4072 (Australia); Yao, Fubing [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Li, Xiaoming, E-mail: xmli@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Zhao, Jianwei; Xu, Qiuxiang; Zhang, Chang; Zeng, Guangming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China)
2016-04-15
Graphical abstract: Main mechanism of simultaneous bromate and nitrate removal in the RBER. - Highlights: • Cathode of RBER was designed to automatically rotate. • Simultaneous bromate and nitrate removal was achieved by auto-hydrogenotrophic reduction. • The maximum bromate reduction rate estimated by the Monod equation was 109.12 μg/L h. • An electron transfer process and main reaction mechanism in RBER was explored. - Abstract: Simultaneous reduction of bromate and nitrate was investigated using a rotating biofilm-electrode reactor (RBER) with graphite carbon (GC) rods as anode and activated carbon fiber (ACF) bonded with steel ring as cathode. In RBER, the community of denitrifying bacteria immobilized on the cathode surface could completely utilize hydrogen (H{sub 2}) as the electron donor, which was internally produced by the electrolysis of water. The short-term test confirmed that the RBER system could reduce 150–800 μg/L bromate to below 10 μg/L under autotrophic conditions. The reduced bromate was considered to be roughly equivalent to the amount of bromide in effluent, indicating that bromate was completely reduced to bromide without accumulation of by-products. The long-term test (over 120 days) showed that the removal fluxes of bromate and nitrate could be improved by increasing the electric current and decreasing the hydraulic retention time (HRT). But nitrite in effluent was significantly accumulated when the electric current was beyond 10 mA and the HRT was less than 6 h. The maximum bromate reduction rate estimated by the Monod equation was 109.12 μg/L h when the electric current was 10 mA and HRT was 12 h. It was proposed that the electron transfer process in RBER produced H{sub 2} on the surface of the ACF cathode, and the microbial cultures attached closely on the cathode which could completely utilize H{sub 2} as electron donors for reduction of bromate and nitrate.
Mohammed, Omar F.
2014-05-01
We combine ultrafast electronic and vibrational spectroscopy and computational modeling to investigate the photoinduced excited-state intramolecular hydrogen-transfer dynamics in 1,8-dihydroxy-9,10-anthraquinone (DHAQ) in tetrachloroethene, acetonitrile, dimethyl sulfoxide, and methanol. We analyze the electronic excited states of DHAQ with various possible hydrogen-bonding schemes and provide a general description of the electronic excited-state dynamics based on a systematic analysis of femtosecond UV/vis and UV/IR pump-probe spectroscopic data. Upon photoabsorption at 400 nm, the S 2 electronic excited state is initially populated, followed by a rapid equilibration within 150 fs through population transfer to the S 1 state where DHAQ exhibits ESIHT dynamics. In this equilibration process, the excited-state population is distributed between the 9,10-quinone (S2) and 1,10-quinone (S1) states while undergoing vibrational energy redistribution, vibrational cooling, and solvation dynamics on the 0.1-50 ps time scale. Transient UV/vis pump-probe data in methanol also suggest additional relaxation dynamics on the subnanosecond time scale, which we tentatively ascribe to hydrogen bond dynamics of DHAQ with the protic solvent, affecting the equilibrium population dynamics within the S2 and S1 electronic excited states. Ultimately, the two excited singlet states decay with a solvent-dependent time constant ranging from 139 to 210 ps. The concomitant electronic ground-state recovery is, however, only partial because a large fraction of the population relaxes to the first triplet state. From the similarity of the time scales involved, we conjecture that the solvent plays a crucial role in breaking the intramolecular hydrogen bond of DHAQ during the S2/S1 relaxation to either the ground or triplet state. © 2014 American Chemical Society.
National Aeronautics and Space Administration — Structural damage to ball grid array interconnects incurred during vibration testing has been monitored in the prefailure space using resistance spectroscopy-based...
Pulse shape optimization for electron-positron production in rotating fields
Fillion-Gourdeau, François; Hebenstreit, Florian; Gagnon, Denis; MacLean, Steve
2017-07-01
We optimize the pulse shape and polarization of time-dependent electric fields to maximize the production of electron-positron pairs via strong field quantum electrodynamics processes. The pulse is parametrized in Fourier space by a B -spline polynomial basis, which results in a relatively low-dimensional parameter space while still allowing for a large number of electric field modes. The optimization is performed by using a parallel implementation of the differential evolution, one of the most efficient metaheuristic algorithms. The computational performance of the numerical method and the results on pair production are compared with a local multistart optimization algorithm. These techniques allow us to determine the pulse shape and field polarization that maximize the number of produced pairs in computationally accessible regimes.
Heumann, Thatcher R; Esiashvili, Natia; Parker, Sareeta; Switchenko, Jeffrey M; Dhabbaan, Anees; Goodman, Michael; Lechowicz, Mary Jo; Flowers, Christopher R; Khan, Mohammad K
2015-05-01
To report our experience with rotational total skin electron irradiation (RTSEI) in cutaneous T-cell lymphoma (CTCL), and to examine response by disease stage and race. We reviewed our outcomes for 68 CTCL patients who received RTSEI (≥ 30 Gy) from 2000 to 2013. Primary outcomes were complete clinical response (CCR), recurrence-free survival (RFS), and overall survival (OS). Using log-rank tests and Cox proportional hazards, OS and RFS were compared across tumor stages at time of RTSEI with further racial subgroup analysis. Median age at diagnosis and at time of radiation was 52 and 56 years, respectively. Median follow-up was 5.1 years, 49% were African American, and 49% were female. At time of treatment, 18, 37, and 13 patients were T stage 2, 3, and 4, respectively. At 6 weeks after RTSEI, overall CCR was 82% (88%, 83%, and 69% for T2, T3, and T4, respectively). Median RFS was 11 months for all patients and 14, 10, and 12 months for stage T2, T3, and T4, respectively. Tumor stage was not associated with RFS or CCR. Maintenance therapy after RTSEI was associated with improved RFS in both crude and multivariable analysis, controlling for T stage. Median OS was 76 months (91 and 59 months for T3 and T4, respectively). With the exception of improved OS in African Americans compared with whites at stage T2, race was not associated with CCR, RFS, or OS. These results represent the largest RTSEI clinical outcomes study in the modern era using a dual-field rotational technique. Our observed response rates match or improve upon the standard set by previous outcome studies using conventional TSEI techniques, despite a large percentage of advanced CTCL lesions in our cohort. We found that clinical response after RTSEI did not seem to be affected by T stage or race. Published by Elsevier Inc.
Energy Technology Data Exchange (ETDEWEB)
Heumann, Thatcher R. [Emory University School of Medicine, Emory University, Atlanta, Georgia (United States); Esiashvili, Natia [Department of Radiation Oncology, Emory University, Atlanta, Georgia (United States); Winship Cancer Institute (WCI), Emory University, Atlanta, Georgia (United States); Parker, Sareeta [Department of Dermatology, Emory University, Atlanta, Georgia (United States); Switchenko, Jeffrey M. [Biostatistics Shared Core Resource at WCI, Emory University, Atlanta, Georgia (United States); Dhabbaan, Anees [Department of Radiation Oncology, Emory University, Atlanta, Georgia (United States); Winship Cancer Institute (WCI), Emory University, Atlanta, Georgia (United States); Goodman, Michael [Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia (United States); Lechowicz, Mary Jo; Flowers, Christopher R. [Department of Radiation Oncology, Emory University, Atlanta, Georgia (United States); Department of Hematology and Oncology, Emory University, Atlanta, Georgia (United States); Khan, Mohammad K., E-mail: drkhurram2000@gmail.com [Department of Radiation Oncology, Emory University, Atlanta, Georgia (United States); Winship Cancer Institute (WCI), Emory University, Atlanta, Georgia (United States)
2015-05-01
Purpose: To report our experience with rotational total skin electron irradiation (RTSEI) in cutaneous T-cell lymphoma (CTCL), and to examine response by disease stage and race. Methods and Materials: We reviewed our outcomes for 68 CTCL patients who received RTSEI (≥30 Gy) from 2000 to 2013. Primary outcomes were complete clinical response (CCR), recurrence-free survival (RFS), and overall survival (OS). Using log–rank tests and Cox proportional hazards, OS and RFS were compared across tumor stages at time of RTSEI with further racial subgroup analysis. Results: Median age at diagnosis and at time of radiation was 52 and 56 years, respectively. Median follow-up was 5.1 years, 49% were African American, and 49% were female. At time of treatment, 18, 37, and 13 patients were T stage 2, 3, and 4, respectively. At 6 weeks after RTSEI, overall CCR was 82% (88%, 83%, and 69% for T2, T3, and T4, respectively). Median RFS was 11 months for all patients and 14, 10, and 12 months for stage T2, T3, and T4, respectively. Tumor stage was not associated with RFS or CCR. Maintenance therapy after RTSEI was associated with improved RFS in both crude and multivariable analysis, controlling for T stage. Median OS was 76 months (91 and 59 months for T3 and T4, respectively). With the exception of improved OS in African Americans compared with whites at stage T2, race was not associated with CCR, RFS, or OS. Conclusions: These results represent the largest RTSEI clinical outcomes study in the modern era using a dual-field rotational technique. Our observed response rates match or improve upon the standard set by previous outcome studies using conventional TSEI techniques, despite a large percentage of advanced CTCL lesions in our cohort. We found that clinical response after RTSEI did not seem to be affected by T stage or race.
Zhong, Yu; Li, Xin; Yang, Qi; Wang, Dongbo; Yao, Fubing; Li, Xiaoming; Zhao, Jianwei; Xu, Qiuxiang; Zhang, Chang; Zeng, Guangming
2016-04-15
Simultaneous reduction of bromate and nitrate was investigated using a rotating biofilm-electrode reactor (RBER) with graphite carbon (GC) rods as anode and activated carbon fiber (ACF) bonded with steel ring as cathode. In RBER, the community of denitrifying bacteria immobilized on the cathode surface could completely utilize hydrogen (H2) as the electron donor, which was internally produced by the electrolysis of water. The short-term test confirmed that the RBER system could reduce 150-800μg/L bromate to below 10μg/L under autotrophic conditions. The reduced bromate was considered to be roughly equivalent to the amount of bromide in effluent, indicating that bromate was completely reduced to bromide without accumulation of by-products. The long-term test (over 120 days) showed that the removal fluxes of bromate and nitrate could be improved by increasing the electric current and decreasing the hydraulic retention time (HRT). But nitrite in effluent was significantly accumulated when the electric current was beyond 10mA and the HRT was less than 6h. The maximum bromate reduction rate estimated by the Monod equation was 109.12μg/Lh when the electric current was 10mA and HRT was 12h. It was proposed that the electron transfer process in RBER produced H2 on the surface of the ACF cathode, and the microbial cultures attached closely on the cathode which could completely utilize H2 as electron donors for reduction of bromate and nitrate. Copyright © 2015 Elsevier B.V. All rights reserved.
Tennyson, Jonathan; Bernath, Peter F.; Brown, Linda R.; Campargue, Alain; Császár, Attila G.; Daumont, Ludovic; Gamache, Robert R.; Hodges, Joseph T.; Naumenko, Olga V.; Polyansky, Oleg L.; Rothman, Laurence S.; Vandaele, Ann Carine; Zobov, Nikolai F.; Dénes, Nóra; Fazliev, Alexander Z.; Furtenbacher, Tibor; Gordon, Iouli E.; Hu, Shui-Ming; Szidarovszky, Tamás; Vasilenko, Irina A.
2014-07-01
This paper is the fourth of a series of papers reporting critically evaluated rotational-vibrational line positions, transition intensities, pressure dependences, and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. This paper presents energy level and transition data for the following doubly and triply substituted isotopologues of water: D216O, D217O, and D218O. The MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure is used to determine the levels, the lines, and their self-consistent uncertainties for the spectral regions 0-14 016, 0-7969, and 0-9108 cm-1 for D216O, D217O, and D218O, respectively. For D216O, D217O, and D218O, 53 534, 600, and 12 167 lines are considered, respectively, from spectra recorded in absorption at room temperature and in emission at elevated temperatures. The number of validated energy levels is 12 269, 338, and 3351 for D216O, D217O, and D218O, respectively. The energy levels have been checked against the ones determined, with an average accuracy of about 0.03 cm-1, from variational rovibrational computations employing exact kinetic energy operators and an accurate potential energy surface. Furthermore, the rovibrational labels of the energy levels have been validated by an analysis of the computed wavefunctions using the rigid-rotor decomposition (RRD) scheme. The extensive list of MARVEL lines and levels obtained is deposited in the Supplementary Material of this paper, in a distributed information system applied to water, W@DIS, and on the official MARVEL website, where they can easily be retrieved.
Ulenikov, O. N.; Gromova, O. V.; Bekhtereva, E. S.; Ziatkova, A. G.; Sklyarova, E. A.; Kuznetsov, S. I.; Sydow, C.; Bauerecker, S.
2017-11-01
The rotational structure of the (111) and (021) vibrational states is determined for the first time from the high resolution analysis of the ν1 +ν2 +ν3 -ν2 and 2ν2 +ν3 -ν2 ;hot; bands. The 480 and 74 transitions of these bands (Jmax /Kamax = 45/14 and 15/12 respectively) were assigned in the spectra, which have been recorded with the Bruker IFS 120 Fourier transform infrared (FTIR) spectrometer. A weighted fit analysis allowed us to generate a set of 5 fitted parameters for the (111) state and 4 fitted parameters for the (021) state. Calculation with the 9 parameters, obtained from the fit, reproduces the initial 363 energy values (about 550 assigned experimental transitions) of two vibrational states with the drms deviations of 3.2 ×10-4 cm-1 , which is comparable with the experimental uncertainties of very weak transitions of the ν1 +ν2 +ν3 -ν2 and 2ν2 +ν3 -ν2 ;hot; bands in our experiment.
Electron-excited molecule interactions
Energy Technology Data Exchange (ETDEWEB)
Christophorou, L.G. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA). Dept. of Physics)
1991-01-01
In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10{sup 6} to 10{sup 7} times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs.
Gascooke, Jason R; Lawrance, Warren D
2013-02-28
The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are ∣V3(S1)∣ = 33.4 ± 1.0 cm(-1), ∣V3(S0)∣ = 20.0 ± 1.0 cm(-1), V6(S1) = -10.7 ± 1.0 cm(-1), and V6(S0) = -1.7 ± 1.0 cm(-1). The methyl rotor is also found to couple with van der Waals vibration; specifically, the m(") = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m(") = 1. The coupling constant is determined to be 1.9 cm(-1), which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.
Gascooke, Jason R.; Lawrance, Warren D.
2013-02-01
The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are |V3(S1)| = 33.4 ± 1.0 cm-1, |V3(S0)| = 20.0 ± 1.0 cm-1, V6(S1) = -10.7 ± 1.0 cm-1, and V6(S0) = -1.7 ± 1.0 cm-1. The methyl rotor is also found to couple with van der Waals vibration; specifically, the m″ = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m″ = 1. The coupling constant is determined to be 1.9 cm-1, which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.
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L. S. Konev
2015-09-01
Full Text Available Numerical method for calculation of forward and backward waves of intense few-cycle laser pulses propagating in an optical waveguide with dispersion and cubic nonlinearity of electronic and electronic-vibration nature is described. Simulations made with the implemented algorithm show that accounting for Raman nonlinearity does not lead to qualitative changes in behavior of the backward wave. Speaking about quantitative changes, the increase of efficiency of energy transfer from the forward wave to the backward wave is observed. Presented method can be also used to simulate interaction of counterpropagating pulses.
VáÅa, Martin; Houfek, Karel
2017-02-01
A two-dimensional model of the resonant electron-molecule collision processes with one nuclear and one electronic degree of freedom introduced by K. Houfek, T. N. Rescigno, and C. W. McCurdy [Phys. Rev. A 73, 032721 (2006), 10.1103/PhysRevA.73.032721] is reformulated within the time-dependent framework and solved numerically using the finite-element method with the discrete variable representation basis, the exterior complex scaling method, and the generalized Crank-Nicolson method. On this model we illustrate how the time-dependent calculations can provide deep insight into the origin of oscillatory structures in the vibrational excitation cross sections if one evaluates the cross sections not only at sufficiently large time to obtain the final cross sections, but also at several characteristic times which are given by the evolution of the system. It is shown that all details of these structures, especially asymmetrical peaks, can be understood as quantum interference of several experimentally indistinguishable processes separated in time due to a resonant capture of the electron and the subsequent vibrational motion of the negative molecular ion. Numerical results are presented for the N2-like, NO-like, and F2-like models and compared with ones obtained within the time-independent approach and within the local complex potential approximation.
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Vita Solomko
2016-01-01
Full Text Available The energetic structures and conformations of trimethine cyanine dye molecules were investigated. For research, group theoretical and quantum chemical calculation methods were used. The theoretical group analysis of electronic and vibrational structure of molecules was carried out. Also, the energetic structures and conformations of the molecule of this dye were studied. Research shows that the investigated molecule may reside in three different conformational states, one of which is highly symmetric (symmetry C2v and the other two with low symmetry. The third conformer is characterized by lowering of binding energy of the electronic system by 0.23 eV, and the long-wavelength absorption band is shifted to lower energies. Also the group theoretical analysis of the trimethine cyanine molecule had allowed systematizing the vibrational and electronic quantum transitions and identifying the bands in the absorption spectra. It is shown that the excitation of the molecule in S1-state causes trans-cis-isomerization. The presence of the barrier of ~0.1 eV allows the fluorescence process to compete with isomerization process, but isomerization causes a decrease in the fluorescence quantum yield of the dye.
Gao, Yan; Zhang, Liqun; Wang, Yong; Li, Haoran
2010-03-04
Attenuated total reflection infrared spectroscopy and density functional theory calculation have been employed to study the spectral properties of imidazolium-based ionic liquids (ILs) with different anions. ILs based on 1-butyl-3-methylimidazolium cation with different anions, OH(-), CF(3)CO(2)(-), HSO(4)(-), H(2)PO(4)(-), Cl(-), PF(6)(-), and BF(4)(-), are investigated in the present work. It has been shown that the C(2)-H stretching vibration of the imidazolium ring is closely related to the electron density of H-bonding between the two closest cations and anions for pure ILs. The electron density of H-bonding between cation and anion with different anions decreases in the order [OH](-) > [H(2)PO(4)](-) > [HSO(4)](-) > [CF(3)CO(2)](-) > [Cl](-) > [BF(4)](-) > [PF(6)](-). For aqueous ILs, with increasing water content, the aromatic C-H stretching vibration of the imidazolium cation showed systematic blue-shifts. Especially for BmimOH, the nu(C(2))(-H) undergoes a drastic blue-shift by 58 cm(-1), suggesting that the formation of the strong hydrogen bonds O-H...O may greatly weaken the electron density of H-bonding between the cation and anion of ILs.
Costa, Renyer A.; Oliveira, Kelson M. T.; Costa, Emmanoel Vilaça; Pinheiro, Maria L. B.
2017-10-01
A combined experimental and theoretical DFT study of the structural, vibrational and electronic properties of strychnobrasiline and 12-hydroxy-10,11-dimethoxystrychnobrasiline is presented using the Becke three-parameter Lee-Yang-Parr function (B3LYP) and 6-311G(2d,p) basis set. The theoretical geometry optimization data were compared with the X-ray data for a similar structure in the associated literature, showing close values. The calculated HOMO-LUMO gap values showed that the presence of substituents in the benzene ring influences the quantum properties which are directly related to the reactive properties. Theoretical UV spectra agreed well with the measured experimental data, with bands assigned. In addition, Natural Bond Orbitals (NBOs), Mapped molecular electrostatic potential surface (MEPS) and NLO calculations were also performed at the same theory level. The theoretical vibrational analysis revealed several characteristic vibrations that may be used as a diagnostic tool for other strychnobrasiline type alkaloids, simplifying their identification and structural characterization. Molecular docking calculations with DNA Topoisomerase II-DNA complex showed binding free energies values of -8.0 and -9.5 kcal/mol for strychnobrasiline and 12-hydroxy-10,11-dimethoxystrychnobrasiline respectively, while for amsacrine, used for the treatment of leukemia, the binding free energy ΔG presented a value of -10.0 kcal/mol, suggesting that strychnobrasiline derivative alkaloids might exhibit an antineoplastic activity.
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S. P. Novoselov
2015-01-01
Full Text Available Periodic vibration in the form of distorted sine wave or other complex shapes are most common in the real moving objects, where the device can be exploited on the basis of flexible modules. This kind of exposure directly affects the reliability of the construction in general. The objective of the work was the creation of an experimental device for the study of mechanical vibrations and the dependencies of their impact on the operated device.Research of mechanical vibrations and the dependencies of their influence on the device will allow finding solutions to the problems of reliability of radio electronic devices. It developed an experimental device and automatic adaptive system for control own resonant frequency of the flexible module. As a result of the experiments has been identified according to mechanical influences on the output parameters of the devices. This will take into account and to apply this experience in the design and manufacture of devices with the use of flexible printed circuit boards.
Chain, Fernando; Iramain, Maximiliano Alberto; Grau, Alfredo; Catalán, César A. N.; Brandán, Silvia Antonia
2017-01-01
N-(3,4-dimethoxybenzyl)-hexadecanamide (DMH) was characterized by using Fourier Transform infrared (FT-IR) and Raman (FT-Raman), Ultraviolet- Visible (UV-Visible) and Hydrogen and Carbon Nuclear Magnetic Resonance (1H and 13C NMR) spectroscopies. The structural, electronic, topological and vibrational properties were evaluated in gas phase and in n-hexane employing ONIOM and self-consistent force field (SCRF) calculations. The atomic charges, molecular electrostatic potentials, stabilization energies and topological properties of DMH were analyzed and compared with those calculated for N-(3,4-dimethoxybenzyl)-acetamide (DMA) in order to evaluate the effect of the side chain on the properties of DMH. The reactivity and behavior of this alkamide were predicted by using the gap energies and some descriptors. Force fields and the corresponding force constants were reported for DMA only in gas phase and n-hexane due to the high number of vibration normal modes showed by DMH, while the complete vibrational assignments are presented for DMA and both forms of DMH. The comparisons between the experimental FTIR, FT-Raman, UV-Visible and 1H and 13C NMR spectra with the corresponding theoretical ones showed a reasonable concordance.
Covington, Cody L; Raghavan, Vijay; Smuts, Jonathan P; Armstrong, Daniel W; Polavarapu, Prasad L
2017-11-01
The absolute configuration (AC) of an axially chiral sulfonate (aCSO), 3,5-dimethyl-2-(naphthalen-1-yl)-6-(naphthalen-1-yl)benzenesulfonate (labeled as aCSO5), was investigated using optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) spectroscopies. All three methods led to the same conclusion and the AC of aCSO5 is reliably determined to be (-)-(aR, aR), or conversely (+)-(aS, aS). © 2017 Wiley Periodicals, Inc.
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Bulent Yardimoglu
2004-01-01
Full Text Available The purpose of this paper is to extend a previously published beam model of a turbine blade including the centrifugal force field and root flexibility effects on a finite element model and to demonstrate the performance, accuracy and efficiency of the extended model for computing the natural frequencies. Therefore, only the modifications due to rotation and elastic root are presented in great detail. Considering the shear center effect on the transverse displacements, the geometric stiffness matrix due to the centrifugal force is developed from the geometric strain energy expression based on the large deflections and the increase of torsional stiffness because of the axial stress. In this work, the root flexibility of the blade is idealized by a continuum model unlike the discrete model approach of a combination of translational and rotational elastic springs, as used by other researchers. The cross-section properties of the fir-tree root of the blade considered as an example are expressed by assigning proper order polynomial functions similar to cross-sectional properties of a tapered blade. The correctness of the present extended finite element model is confirmed by the experimental and calculated results available in the literature. Comparisons of the present model results with those in the literature indicate excellent agreement.
Energy Technology Data Exchange (ETDEWEB)
Zakharenko, O.; Motiyenko, R. A.; Aviles Moreno, J.-R.; Huet, T. R., E-mail: Therese.Huet@univ-lille1.fr [Laboratoire de Physique des Lasers, Atomes et Molécules, UMR8523 CNRS – Université Lille 1, Bâtiment P5, F- 59655 Villeneuve d’Ascq Cedex (France); Jabri, A. [Laboratoire Inter-universitaire des Systèmes Atmosphériques, CNRS - Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex (France); Institute for Physical Chemistry, RWTH Aachen University, Aachen (Germany); Kleiner, I. [Laboratoire Inter-universitaire des Systèmes Atmosphériques, CNRS - Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex (France)
2016-01-14
Methacrolein is a major oxidation product of isoprene emitted in the troposphere. New spectroscopy information is provided with the aim to allow unambiguous identification of this complex molecule, characterized by a large amplitude motion associated with the methyl top. State-of-the-art millimeter-wave spectroscopy experiments coupled to quantum chemical calculations have been performed. For the most stable s-trans conformer of atmospheric interest, the torsional and rotational structures have been characterized for the ground state, the first excited methyl torsional state (ν{sub 27}), and the first excited skeletal torsional state (ν{sub 26}). The inverse sequence of A and E tunneling sub-states as well as anomalous A-E splittings observed for the rotational lines of v{sub 26} = 1 state clearly indicates a coupling between methyl torsion and skeletal torsion. A comprehensive set of molecular parameters has been obtained. The far infrared spectrum of Durig et al. [Spectrochim. Acta, Part A 42, 89–103 (1986)] was reproduced, and a Fermi interaction between ν{sub 25} and 2ν{sub 27} was evidenced.
Kaliski, S
2013-01-01
This book gives a comprehensive overview of wave phenomena in different media with interacting mechanical, electromagnetic and other fields. Equations describing wave propagation in linear and non-linear elastic media are followed by equations of rheological models, models with internal rotational degrees of freedom and non-local interactions. Equations for coupled fields: thermal, elastic, electromagnetic, piezoelectric, and magneto-spin with adequate boundary conditions are also included. Together with its companion volume Vibrations and Waves. Part A: Vibrations this work provides a wealth
Lymperakis, L.; Neugebauer, J.; Himmerlich, M.; Krischok, S.; Rink, M.; Kröger, J.; Polyakov, V. M.
2017-05-01
The adsorption of hydrogen at nonpolar GaN (1 1 ¯00 ) surfaces and its impact on the electronic and vibrational properties is investigated using surface electron spectroscopy in combination with density functional theory (DFT) calculations. For the surface mediated dissociation of H2 and the subsequent adsorption of H, an energy barrier of 0.55 eV has to be overcome. The calculated kinetic surface phase diagram indicates that the reaction is kinetically hindered at low pressures and low temperatures. At higher temperatures ab initio thermodynamics show, that the H-free surface is energetically favored. To validate these theoretical predictions experiments at room temperature and under ultrahigh vacuum conditions were performed. They reveal that molecular hydrogen does not dissociatively adsorb at the GaN (1 1 ¯00 ) surface. Only activated atomic hydrogen atoms attach to the surface. At temperatures above 820 K, the attached hydrogen gets desorbed. The adsorbed hydrogen atoms saturate the dangling bonds of the gallium and nitrogen surface atoms and result in an inversion of the Ga-N surface dimer buckling. The signatures of the Ga-H and N-H vibrational modes on the H-covered surface have experimentally been identified and are in good agreement with the DFT calculations of the surface phonon modes. Both theory and experiment show that H adsorption results in a removal of occupied and unoccupied intragap electron states of the clean GaN (1 1 ¯00 ) surface and a reduction of the surface upward band bending by 0.4 eV. The latter mechanism largely reduces surface electron depletion.
Inoue, Takeshi; Ando, S.; Aoki, T.; Arikawa, H.; Ezure, S.; Harada, K.; Hayamizu, T.; Ishikawa, T.; Itoh, M.; Kato, K.; Kawamura, H.; Uchiyama, A.; Aoki, T.; Asahi, K.; Furukawa, T.; Hatakeyama, A.; Hatanaka, K.; Imai, K.; Murakami, T.; Nataraj, H. S.; Sato, T.; Shimizu, Y.; Wakasa, T.; Yoshimi, A.; Yoshida, H. P.; Sakemi, Y.
Toward an experimental search for an electron electric dipole moment by using laser cooled francium atoms, a development of a rubidium (Rb) atomic magnetometer based on a nonlinear magneto-optical rotation (NMOR) effect is presented. In order to obtain a narrow linewidth of the NMOR spectrum, a wall relaxation time of a paraffin coated glass cell, which confined the Rb atom, was experimentally confirmed. A residual field inside a magnetic shield was also evaluated.
Energy Technology Data Exchange (ETDEWEB)
Jacobson, A.R.
1977-07-01
This report proposes a device which can overcome certain of the compromises of conventional Faraday rotation methods and at the same time measure the optical phase as well as the polarization. This would be useful for unfolding the Faraday rotation signal using the line-of-sight density along exactly the same path. Preliminary design parameters using a CO/sub 2/ laser are presented.
Vibration characteristics of casing string under the exciting force of an electric vibrator
Directory of Open Access Journals (Sweden)
Yiyong Yin
2017-11-01
Full Text Available Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface. To popularize this technique, it is necessary to solve the key problem of how to make cementing string generate downhole radial vibration in the WOC stage. For this purpose, an electric vibrator was developed. With this vibrator, electric energy is converted into mechanical energy by means of a high-temperature motor vibration unit. The motor vibration unit rotates the eccentric block through an output shaft to generate an exciting source, which produces an axial-rotating exciting force at the bottom of the casing string. Then, the vibration characteristics of vertical well casing string under the exciting force were analyzed by using the principal coordinate analysis method, and the response model of casing string to an electric vibrator was developed. Finally, the effects of casing string length, exciting force and vibration frequency on the vibration amplitude at the lowermost of the casing string were analyzed based on a certain casing program. It is indicated that the casing string length and the square of vibration frequency are inversely proportional to the vibration amplitude at the lowermost of the casing string, and the exciting force is proportional to the vibration amplitude at the lowermost of the casing string. These research results provide a theoretical support for the application of vibration cementing technology to the cementing sites with different requirements on well depth and amplitude.
Pajot, Bernard
2013-01-01
This book outlines, with the help of several specific examples, the important role played by absorption spectroscopy in the investigation of deep-level centers introduced in semiconductors and insulators like diamond, silicon, germanium and gallium arsenide by high-energy irradiation, residual impurities, and defects produced during crystal growth. It also describes the crucial role played by vibrational spectroscopy to determine the atomic structure and symmetry of complexes associated with light impurities like hydrogen, carbon, nitrogen and oxygen, and as a tool for quantitative analysis of these elements in the materials.
Languy, Fabian; Vandenrijt, Jean-François; Thizy, Cédric; Rochet, Jonathan; Loffet, Christophe; Simon, Daniel; Georges, Marc P.
2016-12-01
We present our investigations on two interferometric methods suitable for industrial conditions dedicated to the visualization of vibration modes of aeronautic blades. First, we consider long-wave infrared (LWIR) electronic speckle pattern interferometry (ESPI). The use of long wavelength allows measuring larger amplitudes of vibrations compared with what can be achieved with visible light. Also longer wavelengths allow lower sensitivity to external perturbations. Second, shearography at 532 nm is used as an alternative to LWIR ESPI. Both methods are used in time-averaged mode with the use of phase-stepping. This allows transforming Bessel fringes, typical to time averaging, into phase values that provide higher contrast and improve the visualization of vibration mode shapes. Laboratory experimental results with both techniques allowed comparison of techniques, leading to selection of shearography. Finally a vibration test on electrodynamic shaker is performed in an industrial environment and mode shapes are obtained with good quality by shearography.
Kovács, Z.; Harko, T.
2011-11-01
We present a full general relativistic numerical code for estimating the energy-momentum deposition rate (EMDR) from neutrino pair annihilation (?). The source of the neutrinos is assumed to be a neutrino-cooled accretion disc around neutron and quark stars. We calculate the neutrino trajectories by using a ray-tracing algorithm with the general relativistic Hamilton's equations for neutrinos and derive the spatial distribution of the EMDR due to the annihilations of neutrinos and antineutrinos around rotating neutron and quark stars. We obtain the EMDR for several classes of rotating neutron stars, described by different equations of state of the neutron matter, and for quark stars, described by the Massachusetts Institute of Technology (MIT) bag model equation of state and in the colour-flavour-locked (CFL) phase. The distribution of the total annihilation rate of the neutrino-antineutrino pairs around rotating neutron and quark stars is studied for isothermal discs and accretion discs in thermodynamical equilibrium. We demonstrate both the differences in the equations of state for neutron and quark matter and rotation with the general relativistic effects significantly modify the EMDR of the electrons and positrons generated by the neutrino-antineutrino pair annihilation around compact stellar objects, as measured at infinity.
Wong, Bryan M; Steeves, Adam H; Field, Robert W
2006-09-28
A one-dimensional local bend model is used to describe the variation of electronic properties of acetylene in vibrational levels that embody large amplitude local motions on the S0 potential energy surface. Calculations performed at the CCSD(T) and MR-AQCC levels of theory predict an approximately linear dependence of the dipole moment on the number of quanta in either the local bending or local stretching excitation. In the local mode limit, one quantum of stretching excitation in one CH bond leads to an increase of 0.025 D in the dipole moment, and one quantum of bending vibration in the CCH angle leads to an increase of 0.068 D. The use of a one-dimensional model for the local bend is justified by comparison to the well-established polyad model which reveals a decoupling of the large amplitude bending from other degrees of freedom in the range of Nbend = 14-22. We find that the same one-dimensional large amplitude bending motion emerges from two profoundly different representations, a one-dimensional cut through an ab initio, seven-dimensional Hamiltonian and the three-dimensional (l = 0) pure-bending experimentally parametrized spectroscopic Hamiltonian.
Suvitha, A.; Periandy, S.; Boomadevi, S.; Govindarajan, M.
2014-01-01
In this work, the vibrational spectral analysis is carried out by using Raman and infrared spectroscopy in the range 100-4000 cm-1and 50-4000 cm-1, respectively, for pycolinaldehyde oxime (PAO) (C6H6N2O) molecule. The vibrational frequencies have been calculated and scaled values are compared with experimental FT-IR and FT-Raman spectra. The structure optimizations and normal coordinate force field calculations are based on HF and B3LYP methods with 6-311++G(d,p) basis set. The results of the calculation shows excellent agreement between experimental and calculated frequencies in B3LYP/6-311++G(d,p) basis set. The optimized geometric parameters are compared with experimental values of PAO. The non linear optical properties, NBO analysis, thermodynamics properties and mulliken charges of the title molecule are also calculated and interpreted. A study on the electronic properties, such as HOMO and LUMO energies, are performed by time-dependent DFT (TD-DFT) approach. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) are performed. The effects due to the substitutions of CHdbnd NOH ring are investigated. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.
Prabavathi, N; Nilufer, A; Krishnakumar, V
2014-01-01
The FTIR and FT-Raman spectra of 1-(m-(trifluoromethyl)phenyl)piperazine [TFMPP] have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of the compound was obtained by the density functional theory using 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. A detailed interpretation of the infrared and Raman spectra were also reported based on potential energy distribution (PED). UV-Vis spectrum of the compound was recorded and the electronic properties HOMO and LUMO energies were measured by TD-DFT approach. Furthermore, molecular electrostatic potential is performed and also the calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Copyright © 2013 Elsevier B.V. All rights reserved.
Azamat, D. V.; Belykh, V. V.; Yakovlev, D. R.; Fobbe, F.; Feng, D. H.; Evers, E.; Jastrabik, L.; Dejneka, A.; Bayer, M.
2017-08-01
The spin relaxation dynamics of Ce3 + ions in heavily cerium-doped YAG crystals is studied using pulse-electron paramagnetic resonance and time-resolved pump-probe Faraday rotation. Both techniques address the 4 f ground state, while pump-probe Faraday rotation also provides access to the excited 5 d state. We measure a millisecond spin-lattice relaxation time T1, a microsecond spin coherence time T2, and a ˜10 ns inhomogeneous spin dephasing time T2* for the Ce3 + ground state at low temperatures. The spin-lattice relaxation of Ce3 + ions is due to modified Raman processes involving the optical phonon mode at ˜125 cm-1 . The relaxation at higher temperature goes through a first excited level of the 5/2 2F term at about ℏ ω ≈228 cm-1 . Effects provided by the hyperfine interaction of the Ce3 + with the 27Al nuclei are observed.
Using Diffusion Monte Carlo to Probe Rotational Excited States
Petit, Andrew S.; McCoy, Anne B.
2009-06-01
Since its inception in 1975 by Anderson, has been successfully applied to a wide range of electronic and vibrational problems. In the latter case, it has been shown to be a powerful method for studying highly fluxional systems exhibiting large amplitude vibrational motions. We report here our recent work developing a new DMC algorithm capable of treating rotational excited states. We first develop the appropriate coordinates, nodal structures, and re-crossing corrections for this problem. Then, using H_3O^+ and D_3O^+ as model systems, we show that our method can successfully describe a range of rotational states from mid0,0,0> to {1}/{√{2}} (mid10,10,0 > + mid 10,-10,0 >). In particular, we examine the combined effects of rotational and zero-point vibrational motion on the geometric structure of the molecules. Finally, we find the mid 10,0,0 > state to be somewhat problematic but show that the problem is straightforward to identify and has a well-defined solution. J. B. Anderson, J. Chem. Phys., 63, 1499 (1975). X. Huang, S. Carter, and J. Bowman, J. Chem. Phys., 118, 5431 (2003).
Line shapes in inelastic electron tunneling spectroscopy of single-molecule junctions
Meierott, S.; Néel, N.; Kröger, J.
2017-11-01
Spectroscopic line-shape analyses for single-C60 vibrational modes are presented for two kinds of scanning tunneling microscope experiments. Inelastic electron tunneling spectroscopy is performed for C60 molecules with different adsorption geometries on Pb(111). Depending on the C60 adsorption site and rotational orientation, the lowest unoccupied molecular orbital exhibits varying degrees of overlap with C60 vibrational energies. Concomitantly, the line shapes of vibrational modes are affected according to expectations for on-resonance inelastic electron tunneling. Inelastic electron transport is further studied for decreasing tip-C60 distances covering tunneling and contact ranges. Line-shape changes signaling a conductance increase rather than the expected decrease upon exciting vibrational quanta are observed. A phenomenological approach is suggested to understand the dissimilar behavior of the junction conductance in the different electron transport ranges.
Energy Technology Data Exchange (ETDEWEB)
Hoffer, Saskia [Univ. of California, Berkeley, CA (United States)
2002-01-01
Electron based surface probing techniques can provide detailed information about surface structure or chemical composition in vacuum environments. The development of new surface techniques has made possible in situ molecular level studies of solid-gas interfaces and more recently, solid-liquid interfaces. The aim of this dissertation is two-fold. First, by using novel sample preparation, Low Energy Electron Diffraction (LEED) and other traditional ultra high vacuum (UHV) techniques are shown to provide new information on the insulator/vacuum interface. The surface structure of the classic insulator NaCl has been determined using these methods. Second, using sum frequency generation (SFG) surface specific vibrational spectroscopy studies were performed on both the biopolymer/air and electrode/electrolyte interfaces. The surface structure and composition of polyetherurethane-silicone copolymers were determined in air using SFG, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). SFG studies of the electrode (platinum, gold and copper)/electrolyte interface were performed as a function of applied potential in an electrochemical cell.
Li, Peng; Zhang, Chongxiao; Kim, Junyoung; Yu, Liangyao; Zuo, Lei
2014-04-01
Regenerative semi-active suspensions can capture the previously dissipated vibration energy and convert it to usable electrical energy for powering on-board electronic devices, while achieve both the better ride comfort and improved road handling performance at the same time when certain control is applied. To achieve this objective, the power electronics interface circuit connecting the energy harvester and the electrical loads, which can perform simultaneous vibration control and energy harvesting function is in need. This paper utilized a buck-boost converter for simultaneous semi-active vibration control and energy harvesting with electromagnetic regenerative shock absorber, which utilizes a rotational generator to converter the vibration energy to electricity. It has been found that when the circuit works in discontinuous current mode (DCM), the ratio between the input voltage and current is only related to the duty cycle of the switch pulse width modulation signal. Using this property, the buck-boost converter can be used to perform semi-active vibration control by controlling the load connected between the terminals of the generator in the electromagnetic shock absorber. While performing the vibration control, the circuit always draw current from the shock absorber and the suspension remain dissipative, and the shock absorber takes no additional energy to perform the vibration control. The working principle and dynamics of the circuit has been analyzed and simulations were performed to validate the concept.
Li, Y. G.; Zhou, Y.; Deng, Z. C.; Li, Y.; Wang, H. X.; Yuan, B. S.; Yi, J.; Yin, Z. J.; Ji, X. Q.; Wu, T. Y.; Chen, W. J.; Chen, W.; Yu, L. M.; Zhang, Y. P.; Li, L. C.; Shi, Z. B.; Liu, Yi.; Yan, L. W.; Yang, Q. W.; Ding, X. T.; Xu, M.; Duan, X. R.
2017-11-01
A novel two-laser Polarimeter-Interferometer (PIer) diagnostic scheme, in which Faraday rotation angle (αF) and electron density (ne) can be simultaneously measured by taking advantage of two lasers and two detectors for each channel, has been successfully demonstrated on HL-2A tokamak through upgrading one channel of existing monofunctional Faraday-effect polarimeter. In comparison with the conventional three-laser PIer diagnostic, two-laser PIer generates only one intermediate frequency (IF), avoiding the overlap of IF frequency bands, so as to increase the time resolution and decrease the phase noise of system. The single channel two-laser PIer was firstly put into operation in 2016 HL-2A experimental campaign, and both Faraday rotation angle and electron density phase have been measured with a fast time resolution of 1.0 μs and a phase resolution of 0.1o and 1.0o, respectively. This work is valuable for next step far-infrared (FIR) laser PIer construction on HL-2M tokamak, as well as the future International Thermonuclear Experimental Reactor (ITER).
Li, Ping; Amirjalayer, Saeed; Hartl, František; Lutz, Martin; de Bruin, Bas; Becker, René; Woutersen, Sander; Reek, Joost N H
2014-05-19
A pyridyl-functionalized diiron dithiolate complex, [μ-(4-pyCH2-NMI-S2)Fe2(CO)6] (3, py = pyridine (ligand), NMI = naphthalene monoimide) was synthesized and fully characterized. In the presence of zinc tetraphenylporphyrin (ZnTPP), a self-assembled 3·ZnTPP complex was readily formed in CH2Cl2 by the coordination of the pyridyl nitrogen to the porphyrin zinc center. Ultrafast photoinduced electron transfer from excited ZnTPP to complex 3 in the supramolecular assembly was observed in real time by monitoring the ν(C≡O) and ν(C═O)NMI spectral changes with femtosecond time-resolved infrared (TRIR) spectroscopy. We have confirmed that photoinduced charge separation produced the monoreduced species by comparing the time-resolved IR spectra with the conventional IR spectra of 3(•-) generated by reversible electrochemical reduction. The lifetimes for the charge separation and charge recombination processes were found to be τCS = 40 ± 3 ps and τCR = 205 ± 14 ps, respectively. The charge recombination is much slower than that in an analogous covalent complex, demonstrating the potential of a supramolecular approach to extend the lifetime of the charge-separated state in photocatalytic complexes. The observed vibrational frequency shifts provide a very sensitive probe of the delocalization of the electron-spin density over the different parts of the Fe2S2 complex. The TR and spectro-electrochemical IR spectra, electron paramagnetic resonance spectra, and density functional theory calculations all show that the spin density in 3(•-) is delocalized over the diiron core and the NMI bridge. This delocalization explains why the complex exhibits low catalytic dihydrogen production even though it features a very efficient photoinduced electron transfer. The ultrafast porphyrin-to-NMI-S2-Fe2(CO)6 photoinduced electron transfer is the first reported example of a supramolecular Fe2S2-hydrogenase model studied by femtosecond TRIR spectroscopy. Our results show that TRIR
Kaderoglu, Cagil; Surucu, Gokhan; Erkisi, Aytac
2017-10-01
The structural, mechanical, electronic and lattice dynamical properties of the PrYbO3 compound from the ABO3-type perovskite family have been investigated by performing the first-principles density functional theory calculations using the generalized-gradient approximation (GGA) with corrected Coulomb interactions (GGA+U). Structural parameters, formation energies and phase transition pressures for the five possible phases of this compound have been calculated. Then, the spin-dependent electronic band structure and corresponding density of states (DOS) have been plotted. Also, the shear modulus, Young's modulus, Poisson's ratio, G/ B ratio, hardness and anisotropy factors have been calculated to investigate mechanical behavior of this material. Furthermore, the phonon dispersion curves have also been plotted as corresponding phonon PDOS. According to our calculations, the orthorhombic phase of the five phases of PrYbO3 is the most stable one and exhibits a half-metallic character, which can therefore be a candidate for spintronic applications.
2014-07-22
The Journal of Chemical Physics , ( 2012): 0. doi: 10.1063/1.4752654 Atanu Bhattacharya, Yuanqing Guo, Elliot R. Bernstein. A comparison of the decomposition of electronically excited nitro-containing molecules with energetic moieties C–NO2, N–NO2, and O–NO2, The Journal of Chemical Physics , ( 2012): 0. doi: 10.1063/1.3668139 Yuanqing Guo, Atanu Bhattacharya, Elliot R. Bernstein. Ultrafast S1 to S0 Internal Conversion Dynamics for Dimethylnitramine through a Conical
Vibrational spectroscopy and analytical electron microscopy studies of Fe-V-O and In-V-O thin films
Vuk, A S; Drazic, G; Colomban, P
2002-01-01
Orthovanadate (M sup 3 sup + VO sub 4; M= Fe, In) and vanadate (Fe sub 2 V sub 4 O sub 1 sub 3) thin films were prepared using sol-gel synthesis and dip coating deposition. Using analytical electron microscopy (AEM), the chemical composition and the degree of crystallization of the phases present in the thin Fe-V-O films were investigated. TEM samples were prepared in both orientations: parallel (plan view) and perpendicular (cross section) to the substrate. In the first stages of crystallization, when the particle sizes were in the nanometer range, the classical identification of phases using electron diffraction was not possible. Instead of measuring d values, experimentally selected area electron diffraction (SAED) patterns were compared to calculated (simulated) patterns in order to determine the phase composition. The problems of evaluating the ratio of amorphous and crystalline phases in thin films are reported. Results of TEM and XRD as well as IR and Raman spectroscopy showed that the films made at lo...
Energy Technology Data Exchange (ETDEWEB)
Asgari, R.; Polini, M.; Carnevale, V.; Tosi, M.P
2003-08-01
We evaluate the elementary excitations of both spin-singlet and spin-triplet paired crystalline phases of a two-dimensional system of electrons in a perpendicular magnetic field. We use the harmonic Hamiltonian derived from a truncation of the intercell interactions at dipolar terms and treat it within a circular-cell approximation. At this level the excitations are of two types, i.e. a discrete spectrum of localized vibrorotational modes and a continuum of dispersive magneto-oscillations. The eigenfunctions and eigenfrequencies of the intracell dynamics depend on a single parameter, which contains the electron density and the magnetic length, and are exhibited as functions of this parameter for various sets of values of the radial and angular-momentum quantum numbers. The propagating excitations describe collective oscillations of the centre of mass of the electron pairs and derive, as in the usual unpaired crystal phase, from the magnetic-field-induced shifts of plasmons and transverse phonons of the crystal in zero field. Several illustrations of their dispersion curves are given. Possible extensions of the theory to include anharmonicity and higher intercell couplings are briefly discussed.
Vibrations of a pipe on elastic foundations
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
is investigated. Two cases of elastic foundations are considered: rotational and both linear and rotational. The major findings are the variations in frequency with flow velocity and displacements at different points and times. Keywords. Cantilevered pipe; vibrations of pipes; elastic foundations; exter- nal transverse force. 1.
Dissociative electron attachment to HBr: A temperature effect
Fedor, Juraj; Cingel, M.; Skalný, J. D.; Scheier, P.; Märk, T.D.; Čížek, M.; Kolorenč, P.; Horáček, J
2007-01-01
The effects of rovibrational temperature on dissociative electron attachment to hydrogen bromide has been investigated from the experimental and theoretical point of view. Theoretical calculations based on the nonlocal resonance model predict a strong temperature effect on the Br⁻ fragment ion yield due to population of higher vibrational and rotational states. A crossed beam experimental setup consisting of a temperature controlled effusive molecular beam and a trochoidal electron monochroma...
Energy Technology Data Exchange (ETDEWEB)
Tiryaki, B. [Hacettepe University (Turkey). Dept. of Mining Engineering
2003-12-01
The paper examines the prediction and optimisation of machine vibrations in longwall shearers. Underground studies were carried out at the Middle Anatolian Lignite Mine, between 1993 and 1997. Several shearer drums with different pick lacing arrangements were designed and tested on double-ended ranging longwall shearers employed at the mine. A computer program called the Vibration Analysis Program (VAP) was developed for analysing machine vibrations in longwall shearers. Shearer drums that were tested underground, as well as some provided by leading manufacturers, were analyzed using these programs. The results of the experiments and computer analyses are given in the article. 4 refs., 9 figs.
Role of initial vibrational and rotational
Indian Academy of Sciences (India)
research attention has been paid to N(4S) + H2 →. NH + H and its ... Though many researchers have explored the. N(4S)+H2 and NH + ..... diatom. Thus, probably, the more obvious effect of the initial excitation in the N(4S) + H2 reaction may also be related to the heavier attacking N atom and lower moment of inertia of H2 ...
Fernandez Carmona, P; Collette, C; Esposito, M; Guinchard, M; Janssens, S; Kuzmin, A; Moron Ballester, R
2011-01-01
In order to achieve the required levels of luminosity in the CLIC linear collider, mechanical stabilization of quadrupoles to the nanometre level is required. The paper describes a design of hybrid electronics combining an analogue controller and digital communication with the main machine controller. The choice of local analogue control ensures the required low latency while still keeping sufficiently low noise level. Furthermore, it reduces the power consumption, rack space and cost. Sensitivity to radiation single events upsets is reduced compared to a digital controller. The digital part is required for fine tuning and real time monitoring via digitization of critical parameters.
Cross Sections for Electron Collisions with Acetylene
Song, Mi-Young; Yoon, Jung-Sik; Cho, Hyuck; Karwasz, Grzegorz P.; Kokoouline, Viatcheslav; Nakamura, Yoshiharu; Tennyson, Jonathan
2017-03-01
Cross section data are compiled from the literature for electron collisions with the acetylene (HCCH) molecule. Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment. The data derived from swarm experiments are also considered. For each of these processes, the recommended values of the cross sections are presented. The literature has been surveyed through early 2016.
Cross Sections for Electron Collisions with Methane
Energy Technology Data Exchange (ETDEWEB)
Song, Mi-Young, E-mail: mysong@nfri.re.kr; Yoon, Jung-Sik [Plasma Technology Research Center, National Fusion Research Institute, 814-2 Osikdo-dong, Gunsan, Jeollabuk-do 573-540 (Korea, Republic of); Cho, Hyuck [Department of Physics, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Itikawa, Yukikazu [Institute of Space and Astronautical Science, Sagamihara 252-5210 (Japan); Karwasz, Grzegorz P. [Faculty of Physics, Astronomy and Applied Informatics, University Nicolaus Copernicus, Grudziadzka 5, 87100 Toruń (Poland); Kokoouline, Viatcheslav [Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States); Nakamura, Yoshiharu [6-1-5-201 Miyazaki, Miyamae, Kawasaki 216-0033 (Japan); Tennyson, Jonathan [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
2015-06-15
Cross section data are compiled from the literature for electron collisions with methane (CH{sub 4}) molecules. Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment. The data derived from swarm experiments are also considered. For each of these processes, the recommended values of the cross sections are presented. The literature has been surveyed through early 2014.
Wickens, Christopher D.; Aretz, Anthony; Harwood, Kelly
1989-01-01
Three experiments are reported that examine the difference between north-up and track-up maps for airborne navigation. The results of the first two experiments, conducted in a basic laboratory setting, identified the cost associated with mental rotation, when a north-up map is used. However, the data suggest that these costs are neither large nor consistent. The third experiment examined a range of tasks in a higher fidelity helicopter flight simulation, and associated the costs of north-up maps with a cognitive component related to orientation, and the costs of track-up maps with a cognitive component related to inconsistent landmark location. Different tasks are associated with different dependence on these components. The results are discussed in terms of their implications for map design, and for cognitive models of navigational processes.
Energy Technology Data Exchange (ETDEWEB)
Witek, Henryk A.; Irle, Stephen; Zheng, Guishan; De Jong, Wibe A.; Morokuma, Keiji
2006-12-07
The self-consistent charge density-functional tight-binding (SCC-DFTB) method is employed for studying various molecular properties of small fullerenes: C₂₈, C₆₀, and C₇₀. The computed optimized bond distances, vibrational infrared and Raman spectra, vibrational densities of states, and electronic densities of states are compared with experiment (where available) and density functional theory (DFT) calculations using various basis sets. The presented DFT benchmark calculations using the correlation-consistent polarized valence triple zeta (cc-pVTZ) basis set of Dunning are at present the most extensive calculations on harmonic frequencies of these species. Possible limitations of the SCC-DFTB method for the prediction of molecular vibrational and optical properties are discussed. The presented results suggest that SCC-DFTB is a computationally feasible and reliable method for predicting vibrational and electronic properties of such carbon nanostructures comparable in accuracy with small to medium size basis set DFT calculations at the computational cost of standard semiempirical methods.
Powell, B J; Bernstein, N; Brake, K; McKenzie, Ross H; Meredith, P; Pederson, M R
2016-01-01
We report first principles density functional calculations for hydroquinone (HQ), indolequinone (IQ) and semiquinone (SQ). These molecules are believed to be the basic building blocks of the eumelanins, a class of bio-macromolecules with important biological functions (including photoprotection) and with potential for certain bioengineering applications. We have used the DeltaSCF (difference of self consistent fields) method to study the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), Delta_HL. We show that Delta_HL is similar in IQ and SQ but approximately twice as large in HQ. This may have important implications for our understanding of the observed broad band optical absorption of the eumelanins. The possibility of using this difference in Delta_HL to molecularly engineer the electronic properties of eumelanins is discussed. We calculate the infrared and Raman spectra of the three redox forms from first principles. Each of the molecules ...
Single-molecule vibrational spectroscopy of water molecules using an LT-STM
Matsumoto, Chikako; Kim, Yousoo; Motobayashi, Kenta; Kawai, Maki
2006-03-01
Single-molecule vibrational spectroscopy has attracted considerable attention as a powerful tool for nanoscale chemistry. The adsorption of water molecules on metal surfaces plays an important role in understanding many phenomena in nature, such as heterogeneous catalysis and corrosion, etc. The structure of water at low coverage has been investigated on a variety of transition-metal surfaces with various techniques. But the microscopic understanding of the adsorption feature of single water molecules is still unclear. We report molecular scale study of adsorption behaviors of water molecules on Pt (111) surface at 4.7 K by use of single-molecule vibrational spectroscopy with the scanning tunneling microscopy (STM). The Pt (111) surface was dosed with a small amount of water molecules (cherry blossom', which can be explained by one of the water molecules rotating around the other. Inelastic electron tunneling spectroscopy using the STM was utilized to determine vibrational modes of individual water dimers.
DEFF Research Database (Denmark)
Pedersen, Morten Stejner; Rasmussen, Jesper; Nielsen, Stefan Kragh
2017-01-01
We demonstrate measurements of spectra of O-mode electron cyclotron resonance heating (ECRH) waves scattered collectively from microscopic plasma fluctuations in ASDEX Upgrade discharges with an ITER-like ECRH scenario. The measured spectra are shown to allow determination of the main ion...
Energy Technology Data Exchange (ETDEWEB)
Shi, Li Bin, E-mail: slb0813@sohu.com; Wang, Yong Ping; Dong, Hai Kuan
2015-02-28
Graphical abstract: - Highlights: • Cr, Mn and Fe doped graphene is more active to adsorb HCN molecule than pristine graphene. • The conductivity of Fe and Mn doped graphene hardly changes after adsorption HCN molecule. • The conductivity of Cr doped graphene can be affected significantly due to HCN adsorption. • The Cr, Mn and Fe may destroy the long range order in graphene. • Phonon density of states suggests that Cr doped graphene is stable. - Abstract: The adsorption energy, electronic structure, lattice vibration and magnetic properties of Cr, Mn and Fe doped graphene with and without HCN adsorption are investigated by the first principles based on density functional theory. The physisorption and chemisorption have been identified. In the paper, Cr-NG, Mn-NG and Fe-NG denote HCN adsorption on Cr, Mn and Fe doped graphene with N atom toward the adsorption site. It is found that the adsorption energy is −1.36 eV for Fe-NG, −0.60 eV for Mn-NG and −0.86 eV for Cr-NG. The Cr-NG will convert from half-metallic behavior to semiconductor after adsorbing HCN molecule, which indicates that the conductivity changes significantly. Phonon density of states (PDOS) shows that the long range order in graphene can be destroyed by doping Fe, Mn and Cr. The imaginary frequency mode in PDOS suggests that Fe and Mn doped graphene is unstable, while Cr doped graphene is stable. The electronic properties are sensitive toward adsorbing HCN, indicating that Cr doped graphene is a promising sensor for detecting HCN molecule. This study provides a useful basis for understanding of a wide variety of physical properties on graphene.
Energy Technology Data Exchange (ETDEWEB)
Barmscheid, Dennis; Varwig, Steffen; Greilich, Alex; Schwan, Alexander; Mueller, Crispin; Yakovlev, Dmitri R.; Bayer, Manfred [Experimentelle Physik II, TU Dortmund, D-44221 Dortmund (Germany); Yugova, Irina A. [Experimentelle Physik II, TU Dortmund, D-44221 Dortmund (Germany); Institute of Physics, St. Petersburg State University, 198504 St. Petersburg (Russian Federation); Reuter, Dirk; Wieck, Andreas D. [Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)
2012-07-01
The investigation of charge carrier spin dynamics in quantum dots plays an important role for the developement of spintronics. For this we perform pump-probe Faraday rotation and ellipticity experiments on self-assembled (In,Ga)As/GaAs quantum dot ensembles. Due to an excitation with a train of pump pulses, the phase of the spin precessions in the inhomogeneous QD-ensemble is synchronized to the laser repetition time T{sub R}. By two pump excitation scheme, with pumps separated by delay T{sub D}, the spins have to fulfill two phase synchronization conditions simultaneously and show rephasing within T{sub D} and T{sub R}-T{sub D}. This leads to increases of the signal amplitude, called bunches, every multiple of T{sub D}. It can be shown, that these bunches are different phenomena than the spin echoes, which occur after spin rotations. We show how this method provides an additional opportunity to study the interaction of electrons and holes with the nuclei.
Balakrishnan, K.; Kaul, S. N.
2002-04-01
We report the observation of a linear relationship between the magnetic contribution to Young's modulus, ΔE/E0, and inverse magnetic susceptibility χ-1 for amorphous weak itinerant-electron ferromagnets Fe90Zr10 and Fe91Zr9 in the asymptotic critical region near the ferromagnetic-paramagnetic phase transition. The proportionality ΔE(T)/E0~χ-1(T) is shown to provide as accurate a means of determining the asymptotic critical exponent γ and the leading ``correction-to-scaling'' amplitudes for susceptibilty from the ΔE/E0 data as a direct measurement of magnetic susceptibilty does. Similarly, the well-known relation between the magnetic contributions to sound velocity and specific heat is fully exploited to extract accurate estimates for the universal critical amplitude ratio A+/A- and the asymptotic critical exponents α+/- for the specific heat from the sound velocity data. The presently determined values of α+/- and γ, together with the reported value for spontaneous magnetization critical exponent β, not only obey the scaling equalities α+=α- and α+2β+γ=2 but also assert that the atomic magnetic moments in the alloys in question interact with one another through an attractive interaction which decays faster than 1/r5 with the interatomic spacing, r.
Faizan, Mohd; Bhat, Sheeraz Ahmad; Alam, Mohammad Jane; Afroz, Ziya; Ahmad, Shabbir
2017-11-01
A combined experimental and theoretical study of the structure, vibrational spectra and electronic spectra of 2-amino-4-hydroxy-6-methylpyrimidine in the ground electronic state are reported. Anharmonic frequencies for the most stable conformer have been simulated using GVPT2, VSCF and PT2-VSCF methods with potential energy surface calculated using MP2 and DFT level of theory with 6-311G(d,p) basis set. The vibrational spectra (FTIR and FT-Raman) are interpreted in terms of fundamental, combination and overtone bands. It is found that the experimental and the VPT2 computed frequencies are in well agreement. The experimental and the calculated UV-Vis spectrum in gas and ethanol solvent are found comparable. Furthermore, HOMO-LUMO analysis, NLO, MEP, and natural charges of the molecule are also reported.
Wu, Liang; Tse, Wang-Kong; Brahlek, M; Morris, C M; Aguilar, R Valdés; Koirala, N; Oh, S; Armitage, N P
2015-11-20
We have utilized time-domain magnetoterahertz spectroscopy to investigate the low-frequency optical response of the topological insulator Cu_{0.02}Bi_{2}Se_{3} and Bi_{2}Se_{3} films. With both field and frequency dependence, such experiments give sufficient information to measure the mobility and carrier density of multiple conduction channels simultaneously. We observe sharp cyclotron resonances (CRs) in both materials. The small amount of Cu incorporated into the Cu_{0.02}Bi_{2}Se_{3} induces a true bulk insulator with only a single type of conduction with a total sheet carrier density of ~4.9×10^{12}/cm^{2} and mobility as high as 4000 cm^{2}/V·s. This is consistent with conduction from two virtually identical topological surface states (TSSs) on the top and bottom of the film with a chemical potential ~145 meV above the Dirac point and in the bulk gap. The CR broadens at high fields, an effect that we attribute to an electron-phonon interaction. This assignment is supported by an extended Drude model analysis of the zero-field Drude conductance. In contrast, in normal Bi_{2}Se_{3} films, two conduction channels were observed, and we developed a self-consistent analysis method to distinguish the dominant TSSs and coexisting trivial bulk or two-dimensional electron gas states. Our high-resolution Faraday rotation spectroscopy on Cu_{0.02}Bi_{2}Se_{3} paves the way for the observation of quantized Faraday rotation under experimentally achievable conditions to push the chemical potential in the lowest Landau level.
Energy Technology Data Exchange (ETDEWEB)
Li, D.W. [Hitachi, Ltd., Tokyo (Japan); Kaneko, S. [The University of Tokyo, Tokyo (Japan); Hayama, S. [Toyama Prefectural University, Toyama (Japan)
1999-07-25
In this study, the stability of annular leakage-flow-induced vibrations was investigated theoretically and experimentally for a translationally and rotationally coupled two-degree-of-freedom system. The critical flow rate was both theoretically and experimentally obtained as a function of the passage increment ratio and the eccentricity of the passage. A good agreement between the theoretical and experimental results was obtained. It was discovered both theoretically and from the experiments that instability will occur in the case of a divergent passage: the eccentricity of the passage lowers the stability of the systems. (author)
Cis-trans isomerization in the S1 state of acetylene: identification of cis-well vibrational levels.
Merer, Anthony J; Steeves, Adam H; Baraban, Joshua H; Bechtel, Hans A; Field, Robert W
2011-06-28
A systematic analysis of the S(1)-trans (Ã(1)A(u)) state of acetylene, using IR-UV double resonance along with one-photon fluorescence excitation spectra, has allowed assignment of at least part of every single vibrational state or polyad up to a vibrational energy of 4200 cm(-1). Four observed vibrational levels remain unassigned, for which no place can be found in the level structure of the trans-well. The most prominent of these lies at 46 175 cm(-1). Its (13)C isotope shift, exceptionally long radiative lifetime, unexpected rotational selection rules, and lack of significant Zeeman effect, combined with the fact that no other singlet electronic states are expected at this energy, indicate that it is a vibrational level of the S(1)-cis isomer (Ã(1)A(2)). Guided by ab initio calculations [J. H. Baraban, A. R. Beck, A. H. Steeves, J. F. Stanton, and R. W. Field, J. Chem. Phys. 134, 244311 (2011)] of the cis-well vibrational frequencies, the vibrational assignments of these four levels can be established from their vibrational symmetries together with the (13)C isotope shift of the 46 175 cm(-1) level (assigned here as cis-3(1)6(1)). The S(1)-cis zero-point level is deduced to lie near 44 900 cm(-1), and the ν(6) vibrational frequency of the S(1)-cis well is found to be roughly 565 cm(-1); these values are in remarkably good agreement with the results of recent ab initio calculations. The 46 175 cm(-1) vibrational level is found to have a 3.9 cm(-1) staggering of its K-rotational structure as a result of quantum mechanical tunneling through the isomerization barrier. Such tunneling does not give rise to ammonia-type inversion doubling, because the cis and trans isomers are not equivalent; instead the odd-K rotational levels of a given vibrational level are systematically shifted relative to the even-K rotational levels, leading to a staggering of the K-structure. These various observations represent the first definite assignment of an isomer of acetylene
Cis-trans isomerization in the S1 state of acetylene: Identification of cis-well vibrational levels
Merer, Anthony J.; Steeves, Adam H.; Baraban, Joshua H.; Bechtel, Hans A.; Field, Robert W.
2011-06-01
A systematic analysis of the S1-trans ({tilde A}1Au) state of acetylene, using IR-UV double resonance along with one-photon fluorescence excitation spectra, has allowed assignment of at least part of every single vibrational state or polyad up to a vibrational energy of 4200 cm-1. Four observed vibrational levels remain unassigned, for which no place can be found in the level structure of the trans-well. The most prominent of these lies at 46 175 cm-1. Its 13C isotope shift, exceptionally long radiative lifetime, unexpected rotational selection rules, and lack of significant Zeeman effect, combined with the fact that no other singlet electronic states are expected at this energy, indicate that it is a vibrational level of the S1-cis isomer ({tilde A}1A2). Guided by ab initio calculations [J. H. Baraban, A. R. Beck, A. H. Steeves, J. F. Stanton, and R. W. Field, J. Chem. Phys. 134, 244311 (2011)], 10.1063/1.3570823 of the cis-well vibrational frequencies, the vibrational assignments of these four levels can be established from their vibrational symmetries together with the 13C isotope shift of the 46 175 cm-1 level (assigned here as cis-3161). The S1-cis zero-point level is deduced to lie near 44 900 cm-1, and the ν6 vibrational frequency of the S1-cis well is found to be roughly 565 cm-1; these values are in remarkably good agreement with the results of recent ab initio calculations. The 46 175 cm-1 vibrational level is found to have a 3.9 cm-1 staggering of its K-rotational structure as a result of quantum mechanical tunneling through the isomerization barrier. Such tunneling does not give rise to ammonia-type inversion doubling, because the cis and trans isomers are not equivalent; instead the odd-K rotational levels of a given vibrational level are systematically shifted relative to the even-K rotational levels, leading to a staggering of the K-structure. These various observations represent the first definite assignment of an isomer of acetylene that was
Dias, Jerry Ray
2016-06-09
The results herein demonstrate that the methods of circumscribing and the facile calculation of Hückel molecular orbital (HMO) eigenvalues by mirror-plane fragmentation have a broad application in the construction of carbon cluster series and the systematic study of trends in their electronic properties. In comparing open-ended nanotubes and their isomeric elongated fullerenes (bicapped nanotubes), we show that the former are more aromatic but the latter are more conjugated and that progressive elongation increases aromaticity and conjugation in both. Recursion equations that will allow one to obtain the eigenvalues to all 5-endcapped nanotubes are given.
Energy Technology Data Exchange (ETDEWEB)
Lorenci, V.A. de; Svaiter, N.F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)
1996-11-01
It was investigated which mapping has to be used to compare measurements made in a rotating frame to those made in an inertial frame. Using a non-Galilean coordinate transformation, the creation-annihilation operators of a massive scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state(a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. Polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view were analysed. 65 refs.
Carbon Nanotube Tape Vibrating Gyroscope
Tucker, Dennis Stephen (Inventor)
2016-01-01
A vibrating gyroscope includes a piezoelectric strip having length and width dimensions. The piezoelectric strip includes a piezoelectric material and carbon nanotubes (CNTs) substantially aligned and polled along the strip's length dimension. A spindle having an axis of rotation is coupled to the piezoelectric strip. The axis of rotation is parallel to the strip's width dimension. A first capacitance sensor is mechanically coupled to the spindle for rotation therewith. The first capacitance sensor is positioned at one of the strip's opposing ends and is spaced apart from one of the strip's opposing faces. A second capacitance sensor is mechanically coupled to the spindle for rotation therewith. The second capacitance sensor is positioned at another of the strip's opposing ends and is spaced apart from another of the strip's opposing faces. A voltage source applies an AC voltage to the piezoelectric strip.
Rotational Doppler Effect: A Probe for Molecular Orbitals Anisotropy.
Miao, Quan; Travnikova, Oksana; Gel'mukhanov, Faris; Kimberg, Victor; Sun, Yu-Ping; Thomas, T Darrah; Nicolas, Christophe; Patanen, Minna; Miron, Catalin
2015-05-07
The vibrationally resolved X-ray photoelectron spectra of X2Σg+(3σg−1) and B2Σu+(2σu−1) states of N2+ were recorded for different photon energies and orientations of the polarization vector. Clear dependencies of the spectral line widths on the X-ray polarization as well as on the symmetry of the final electronic states are observed. Contrary to the translational Doppler, the rotational Doppler broadening is sensitive to the photoelectron emission anisotropy. On the basis of theoretical modeling, we suggest that the different rotational Doppler broadenings observed for gerade and ungerade final states result from a Young's double-slit interference phenomenon.
Das, Pratik Kr.; Mandal, Nibir; Arya, A.
2017-02-01
Naturally occurring zinc sulfide (ZnS) contains a substantial amount of iron (Fe) in its crystal structure. This study explores the possible effects of such Fe impurity on the physical properties of its two phases: B3 and B1, crystallizing in a cubic system with zinc blend (ZB, space group: F-43m) and rock salt (RS, space group: Fm-3m) structures. We have performed ab-initio calculations within density functional theory (DFT) to determine the equilibrium volumes of B3- and B1-ZnS phases, doped with Fe in varying concentrations (0% to 25%), and their corresponding lattice structures. Using the enthalpy cross-over, we determine the pressure-dependent B3 to B1 transition as a function of Fe concentration. Our DFT calculations suggest an inverse relation of the transition pressure with Fe content. For pure ZnS, the transition occurs at 17 GPa, which drops to ˜12 GPa for 25% Fe. This study also provides a first-hand analysis of the elastic constants (C11, C12, and C44) to show the effects of Fe impurity on the mechanical properties of ZnS phases. Their values generally drop due to Fe and the differences widen with increasing pressure. Fe causes large softening of C44, especially for the B1 phase. We have also performed phonon calculations to characterize the vibrational properties and explain the pressure dependent structural instability of the B3- ZnS. Finally, our calculations of the electronic structures show a transition of semi-conductor to conductor behavior of ZnS with incorporation of Fe impurity.
2009-01-01
Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.
Arjunan, V.; Anitha, R.; Durgadevi, G.; Marchewka, M. K.; Mohan, S.
2017-04-01
The conformational analysis of 1-(diaminomethylene)thiourea (MTU) has been done to find out the more stable conformer. The more stable geometry of MTU and 2-imino-4-thiobiuret (ITB) are optimised with B3LYP method using 6-311++G** and cc-pVTZ basis sets. The molecules are not planar. The complete molecular structural parameters and thermodynamic properties of the optimised geometry have been determined. The molecule of MTU is not a planar but twisted. The MEP of MTU lies in the region from +1.175e × 10-2 to -1.175e × 10-2 while the total electron density spread between +6.371e × 10-2 and -6.371e × 10-2. The MEP of ITB distributed between +1.179e × 10-2 and -1.179e × 10-2 while the total electron density of ITB lies in the region +7.729e × 10-2 and -7.729e × 10-2. The energies of important MOs of the compound were also evaluated from DFT method. The LUMO shows that the nitrogen and sulphur atoms are the most nucleophilic attacking sites whereas the HOMO reveals that nitrogen, sulphur and carbon atoms are for the electrophilic substitutions. The vibrational frequencies of the fundamental modes of the compounds have been precisely assigned, analysed and the theoretical results were compared with the experimental wavenumbers. 1H and 13C NMR isotropic chemical shifts were determined and the assignments are compared with the experimental values. In MTU molecule, the n → π* transitions such as n(N5) → π*C4-S6 and n(N1) → π*C2-N3 interactions are strongly stabilised by 66.60 and 41.24 kcal mol-1, respectively. In the case of ITB compound, the stabilisation energy of lone pair donor orbital, n(N5) → σ*C4-S6 is 46.03 kcal mol-1. The dual descriptors Δfk, Δsk and Δωk values clearly indicate that the order of nucleophilic attack in MTU is S6 > N11 > N1 > N5 > N3 while in ITB the order follows as N1 > N11 > N5>S6 > N3.
Yang, Pan; Pang, Min; Li, Ming; Shen, Wei; He, Rongxing
2015-12-05
Geometrical optimizations of the ground and first excited states of benzimidazole and indene were performed using the density functional theory (DFT) and its time-dependent extension methods (TD-DFT), respectively. Their vibrationally resolved (1)Lb ((1)A')↔S0 ((1)A') absorption and fluorescence spectra were simulated within the Franck-Condon approximation including the Herzberg-Teller (HT) and Duschinsky effects. Calculated results revealed that, with the HT and Duschinsky effects getting involved, the simulated weak (1)Lb ((1)A')↔S0 ((1)A') electronic spectra of the two molecules excellently reproduce the experimental findings. Based on the experimental data and other theoretical results, we tentatively assigned most of the vibrational normal modes which emerged in the experimental spectra of the two molecules. The present theoretical insights are expected to help us understand the nature of electronic transitions in the vibrationally resolved absorption and fluorescence spectra of benzimidazole and its analogues. Copyright © 2015 Elsevier B.V. All rights reserved.
Poisson, Lionel; Maksimenska, Raman; Soep, Benoît; Mestdagh, Jean-Michel; Parker, David H; Nsangou, Mama; Hochlaf, Majdi
2010-03-11
In this paper we report an experimental study of the time-resolved response of the molecule 1,4-diazabicyclo[2.2.2]octane (DABCO) to 266.3 nm electronic excitation of the S(1) state with a femtosecond laser. Rotational decoherence and vibrational oscillation within the S(1) state are observed. We performed state-of-the-art ab initio calculations on the ground and low electronic states of the neutral molecule and the cation, which assist in the assignment of the observed photoelectron signals. Using our theoretical and spectroscopic data, the experimental findings are interpreted in terms of an unusual quantum interference between two different vibrational modes, with only the nu = 1 level of each mode being populated.
Vibration-Powered Radiation of Quaking Magnetar
Bastrukov, S.; Yu, J. W.; Xu, R. X.; Molodtsova, I.
2011-01-01
In juxtaposition with the standard model of rotation-powered pulsar, the model of vibration-powered magnetar undergoing quake-induced torsional Alfvén vibrations in its own ultrastrong magnetic field experiencing decay is considered. The presented line of argument suggests that the gradual decrease of frequencies (lengthening of periods) of long-periodic-pulsed radiation detected from a set of X-ray sources can be attributed to magnetic-field-decay-induced energy conversion from seismic vibra...
(1) (1)A' ← X (1)A' Electronic Transition of Protonated Coronene at 15 K.
Rice, C A; Hardy, F-X; Gause, O; Maier, J P
2014-03-20
The electronic spectrum of protonated coronene in the gas phase was measured at vibrational and rotational temperatures of ∼15 K in a 22-pole ion trap. The (1) (1)A' ← X (1)A' electronic transition of this larger polycyclic aromatic hydrocarbon cation has an origin band maximum at 14 383.8 ± 0.2 cm(-1) and shows distinct vibrational structure in the (1) (1)A' state. Neither the origin nor the strongest absorptions to the blue coincide with known diffuse interstellar bands, implying that protonated coronene is not a carrier.
Lekner, John
2008-01-01
Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…
Novikov, V. P.; Popik, M. V.; Samdal, S.; Vilkov, L. V.; Volden, H. V.
1995-06-01
A nonparametric numerical algorithm is suggested for calculation of the torsional potential from gas electron diffraction data using Tikhonov's method of regularization. A new approach to determine the admissible interval of the regularization parameter using Hamilton's statistical test has been considered. Applied to this reinvestigation of m-bromonitrobenzene it was confirmed that this algorithm only allows the determination of the form of the torsional potential function near its minimum. The barrier to internal rotation was estimated to be 4.6-5.4 kcal mol -1 as interpolated by Fourier series with proper parameterization. The most important structural parameters ( ra in Ångströms, ∠ α in degrees) are: r(CC) av = 1.399(3), r(CN) = 1.459(16), r(NO) = 1.244(3), r(CBr) = 1.884(6), r(CH) = 1.099(20), ∠CC NC = 123.9(1.4), ∠C NCC Br = 116.8(1.5), ∠C NCC = 116.6(1.9), ∠CNO = 118.8(0.8). The structure parameters are compared with those obtained previously for o-, m-, and p-bromonitrobenzenes.
Vassiliev, Dmitri
2017-04-01
We consider an infinite three-dimensional elastic continuum whose material points experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points are described mathematically by attaching to each geometric point an orthonormal basis that gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory, we choose the coframe and a density. We write down the general dynamic variational functional for our rotational theory of elasticity, assuming our material to be physically linear but the kinematic model geometrically nonlinear. Allowing geometric nonlinearity is natural when dealing with rotations because rotations in dimension three are inherently nonlinear (rotations about different axes do not commute) and because there is no reason to exclude from our study large rotations such as full turns. The main result of the talk is an explicit construction of a class of time-dependent solutions that we call plane wave solutions; these are travelling waves of rotations. The existence of such explicit closed-form solutions is a non-trivial fact given that our system of Euler-Lagrange equations is highly nonlinear. We also consider a special case of our rotational theory of elasticity which in the stationary setting (harmonic time dependence and arbitrary dependence on spatial coordinates) turns out to be equivalent to a pair of massless Dirac equations. The talk is based on the paper [1]. [1] C.G.Boehmer, R.J.Downes and D.Vassiliev, Rotational elasticity, Quarterly Journal of Mechanics and Applied Mathematics, 2011, vol. 64, p. 415-439. The paper is a heavily revised version of preprint https://arxiv.org/abs/1008.3833
Millimetre Wave Rotational Spectrum of Glycolic Acid
Kisiel, Zbigniew; Pszczolkowski, Lech; Bialkowska-Jaworska, Ewa; Charnley, Steven B.
2016-01-01
The pure rotational spectrum of glycolic acid, CH2OHCOOH, was studied in the region 115-318 GHz. For the most stable SSC conformer, transitions in all vibrational states up to 400 cm(exp -1) have been measured and their analysis is reported. The data sets for the ground state, v21 = 1, and v21 = 2 have been considerably extended. Immediately higher in vibrational energy are two triads of interacting vibrational states and their rotational transitions have been assigned and successfully fitted with coupled Hamiltonians accounting for Fermi and Coriolis resonances. The derived energy level spacings establish that the vibrational frequency of the v21 mode is close to 100 cm(exp -1). The existence of the less stable AAT conformer in the near 50 C sample used in our experiment was also confirmed and additional transitions have been measured.
Prabakaran, A.; Muthu, S.
2014-01-01
In the present work, the characterization of 7-(1,3-dioxolan-2-ylmethyl)-1,3-dimethylpurine-2,6-dione (7DDMP26D) molecule was carried out by quantum chemical method and vibrational spectral techniques. The FT-IR (4000-400 cm-1) and FT-Raman (4000-100 cm-1) spectra of 7DDMP26D were recorded in solid phase. The UV-Vis absorption spectrum of the 7DDMP26D was recorded in the range of 200-400 nm. The molecular geometry, harmonic vibrational frequencies and bonding features of 7DDMP26D in the ground state have been calculated by HF and DFT methods using 6-31G(d,p) basis set. The complete vibrational frequency assignments were made by normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMF). The molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO). The electronic properties, such as excitation energies, absorption wavelength, HOMO and LUMO energies were performed by time-depended DFT (TD-DFT) approach. The other molecular properties like electrostatic potential (ESP), Fukui function and thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the calculation results were analyzed to simulate infrared, FT-Raman and UV spectra of the title compound which shows better agreement with observed spectra.
DEFF Research Database (Denmark)
Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen
2012-01-01
lab studies in that we found a decreased detection rate in busy environments. Here we test with a much larger sample and age range, and contribute with the first vibration sensitivity testing outside the lab in an urban public...
Rotational energy surfaces of molecules exhibiting internal rotation
Ortigoso, Juan; Hougen, Jon T.
1994-08-01
Rotational energy surfaces [W. G. Harter and C. W. Patterson, J. Chem. Phys. 80, 4241 (1984)] for a molecule with internal rotation are constructed. The study is limited to torsional states at or below the top of the barrier to internal rotation, where the extra (torsional) degree of freedom can be eliminated by expanding eigenvalues of the torsion-K-rotation Hamiltonian as a Fourier series in the rotational degree of freedom. For acetaldehyde, considered as an example, this corresponds to considering vt=0, 1, and 2 (below the barrier) and vt=3 (just above the barrier). The rotational energy surfaces are characterized by locating their stationary points (maxima, minima, and saddles) and separatrices. Rather complicated catastrophe histories describing the creation and annihilation of pairs of stationary points as a function of J are found at moderate J for given torsional quantum number (vt) and symmetry species (A,E). Trajectories on the rotational energy surface which quantize the action are examined, and changes from rotational to vibrational trajectories caused by changes in the separatrix structure are found as a function of J for vt=2. The concept of a ``best'' quantization axis for the molecule-fixed component of the total angular momentum is examined from a classical point of view, and it is shown that labeling ambiguities encountered in the literature for torsion-rotation energy levels, calculated numerically in the rho-axis system, can be eliminated by reprojecting basis-set K values onto an axis passing through an appropriate stationary point on the rotational energy surface.
Xu, Yuntao; Xiong, Bo; Chang, Yih-Chung; Pan, Yi; Lo, Po Kam; Lau, Kai Chung; Ng, C Y
2017-04-12
We report detailed absolute integral cross sections (σ's) for the quantum-rovibrational-state-selected ion-molecule reaction in the center-of-mass collision energy (Ecm) range of 0.05-10.00 eV, where (vvv) = (000), (100), and (020), and . Three product channels, HCO+ + OH, HOCO+ + H, and CO+ + H2O, are identified. The measured σ(HCO+) curve [σ(HCO+) versus Ecm plot] supports the hypothesis that the formation of the HCO+ + OH channel follows an exothermic pathway with no potential energy barriers. Although the HOCO+ + H channel is the most exothermic, the σ(HOCO+) is found to be significantly lower than the σ(HCO+). The σ(HOCO+) curve is bimodal, indicating two distinct mechanisms for the formation of HOCO+. The σ(HOCO+) is strongly inhibited at Ecm 0.4 eV by (100) vibrational excitation. The Ecm onsets of σ(CO+) determined for the (000) and (100) vibrational states are in excellent agreement with the known thermochemical thresholds. This observation, along with the comparison of the σ(CO+) curves for the (100) and (000) states, shows that kinetic and vibrational energies are equally effective in promoting the CO+ channel. We have also performed high-level ab initio quantum calculations on the potential energy surface, intermediates, and transition state structures for the titled reaction. The calculations reveal potential barriers of ≈0.5-0.6 eV for the formation of HOCO+, and thus account for the low σ(HOCO+) and its bimodal profile observed. The Ecm enhancement for σ(HOCO+) at Ecm ≈ 0.5-5.0 eV can be attributed to the direct collision mechanism, whereas the formation of HOCO+ at low Ecm < 0.4 eV may involve a complex mechanism, which is mediated by the formation of a loosely sticking complex between HCO+ and OH. The direct collision and complex mechanisms proposed also allow the rationalization of the vibrational inhibition at low Ecm and the vibrational enhancement at high Ecm observed for the σ(HOCO+).
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2002-01-01
The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through ori...
Kumari, Sudesh; Yang, Dong-Sheng
2013-12-19
Group 6 metal-bis(mesitylene) sandwich complexes are produced by interactions between the laser-vaporized metal atoms and mesitylene vapor in a pulsed molecular beam source, identified by photoionization time-of-flight mass spectrometry, and studied by pulsed-field ionization zero-electron kinetic energy spectroscopy and density functional theory calculations. Although transition metal-bis(arene) sandwich complexes may adopt eclipsed and staggered conformations, the group 6 metal-bis(mesitylene) complexes are determined to be in the eclipsed form. In this form, rotational conformers with methyl group dihedral angles of 0 and 60° are identified for the Cr complex, whereas the 0° rotamer is observed for the Mo and W species. The 0° rotamer is in a C(2v) symmetry with the neutral ground state of (1)A1 and the singly positive charged ion state of (2)A1. The 60° rotamer is in a C(i) symmetry with the neutral ground state of (1)A(g) and the ion state of (2)A(g). Partial conversion of the 60 to 0° rotamer is observed from He to He/Ar supersonic expansion for Cr-bis(mesitylene). The unsuccessful observation of the 60° rotamer for the Mo and W complexes is the result of its complete conversion to the 0° rotamer in both He and He/Ar expansions. The adiabatic ionization energies of the 0° rotamers of the three complexes are in the order of Cr-bis(mesitylene) < W-bis(mesitylene) < Mo-bis(mesitylene), which is different from that of the metal atoms. These metal-bis(mesitylene) complexes have lower ionization energies than the corresponding metal-bis(benzene) and -bis(toluene) species.
Energy Technology Data Exchange (ETDEWEB)
Wang, Xue B.; Woo, Hin-koon; Wang, Lai S.
2005-08-01
We demonstrate vibrational cooling of anions via collisions with a background gas in an ion trap attached to a cryogenically controlled cold head (10 ? 400 K). Photoelectron spectra of vibrationally cold C60- anions, produced by electrospray ionization and cooled in the cold ion trap, have been obtained. Relative to spectra taken at room temperature, vibrational hot bands are completely eliminated, yielding well resolved vibrational structures and a more accurate electron affinity for neutral C60. The electron affinity of C60 is measured to be 2.683 ? 0.008 eV. The cold spectra reveal complicated vibrational structures for the transition to the C60 ground state due to the Jahn-Teller effect in the ground state of C60-. Vibrational excitations in the two Ag modes and eight Hg modes are observed, providing ideal data to assess the vibronic couplings in C60-.
Free-Vibration Analysis of Structures
Gupta, K. K.
1984-01-01
Unified numerical procedure for free-vibration analysis of structures developed and incorporated into EIGSOL computer program. Dynamic response analysis of primary importance in design of wide range of practical structures such as space-craft, buildings, and rotating machineries. Procedure determines natural frequencies and associated modes in structural design.
Spectroscopy of Vibrational States in Diatomic Iodine Molecules
Mulholland, Mary; Harrill, Charles H.; Smith, R. Seth
2015-04-01
This project is focused on understanding the vibrational structure of iodine, which is a homonuclear diatomic molecule. A 20 mW, 532 nm cw diode laser was used to selectively excite neutral iodine molecules to a higher energy electronic state. By performing spectroscopy on the transitions from this state to a lower energy electronic state, the data only showed those vibrational bands which connect the two electronic states. Since a number of vibrational levels are populated in the higher energy electronic state, the transitions to all of the allowed vibrational levels in the lower energy electronic state provided sufficient data to determine the vibrational structures of both states. Emission spectra were collected with an Ocean Optics USB4000 Compact CCD Spectrometer. The spectrometer had a range of 500 - 770 nm with a resolution of approximately 0.5 nm and was sensitive enough to resolve the vibrational states in diatomic iodine molecules. The results were compared to a simple harmonic oscillator model.
Invisible Electronic States and Their Dynamics Revealed by Perturbations
Merer, Anthony J.
2011-06-01
Sooner or later everyone working in the field of spectroscopy encounters perturbations. These can range in size from a small shift of a single rotational level to total destruction of the vibrational and rotational patterns of an electronic state. To some workers perturbations are a source of terror, but to others they are the most fascinating features of molecular spectra, because they give information about molecular dynamics, and about states that would otherwise be invisible as a result of unfavorable selection rules. An example of the latter is the essentially complete characterization of the tilde{b}^3A_2 state of SO_2 from the vibronic perturbations it causes in the tilde{a}^3B_1 state. The S_1-trans state of acetylene is a beautiful example of dynamics in action. The level patterns of the three bending vibrations change dramatically with increasing vibrational excitation as a result of the vibrational angular momentum and the approach to the isomerization barrier. Several vibrational levels of the S_1-cis isomer, previously thought to be unobservable, can now be assigned. They obtain their intensity through interactions with nearby levels of the trans isomer.
Wind Turbine Rotors with Active Vibration Control
DEFF Research Database (Denmark)
Svendsen, Martin Nymann
This thesis presents a framework for structural modeling, analysis and active vibration damping of rotating wind turbine blades and rotors. A structural rotor model is developed in terms of finite beam elements in a rotating frame of reference. The element comprises a representation of general...... formulation. The element provides an accurate representation of the eigenfrequencies and whirling modes of the gyroscopic system, and identifies lightly damped edge-wise modes. By adoption of a method for active, collocated resonant vibration of multi-degree-of-freedom systems it is demonstrated...... that these are geometrically well separated. For active vibration control in three-bladed wind turbine rotors the present work presents a resonance-based method for groups of one collective and two whirling modes. The controller is based on the existing resonant format and introduces a dual system targeting the collective...
Transverse vibration of nematic elastomer Timoshenko beams.
Zhao, Dong; Liu, Ying; Liu, Chuang
2017-01-01
Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.
Chain, Fernando E.; Ladetto, María Florencia; Grau, Alfredo; Catalán, César A. N.; Brandán, Silvia Antonia
2016-02-01
In the present work, the structural, topological and vibrational properties of four members of the N-benzylamides series derived from Maca (Lepidium meyenii) whose names are, N-benzylpentadecanamide, N-benzylhexadecanamide, N-benzylheptadecanamide and N-benzyloctadecanamide, were studied combining the FTIR, FT-Raman and 1H and 13C-NMR spectroscopies with density functional theory (DFT) and ONION calculations. Furthermore, the N-benzylacetamide, N-benzylpropilamide and N-benzyl hexanamide derivatives were also studied in order to compare their properties with those computed for the four macamides. These seven N-benzylamides series have a common structure, C8H8NO-R, being R the side chain [-(CH2)n-CH3] with a variable n number of CH2 groups. Here, the atomic charges, molecular electrostatic potentials, stabilization energies, topological properties of those macamides were analyzed as a function of the number of C atoms of the side chain while the frontier orbitals were used to compute the gap energies and some descriptors in order to predict their reactivities and behaviors in function of the longitude of the side chain. Here, the force fields, the complete vibrational assignments and the corresponding force constants were only reported for N-benzylacetamide, N-benzyl hexanamide and N-benzylpentadecanamide due to the high number of vibration normal modes that present the remains macamides.
Energy Technology Data Exchange (ETDEWEB)
Maxwell, H.
1996-12-01
This paper is the first of two papers which describe the Predictive Maintenance Program for rotating machines at the Palo Verde Nuclear Generating Station. The organization has recently been restructured and significant benefits have been realized by the interaction, or {open_quotes}synergy{close_quotes} between the Vibration Program and the Lube Oil Analysis Program. This paper starts with the oldest part of the program - the Vibration Program and discusses the evolution of the program to its current state. The {open_quotes}Vibration{close_quotes} view of the combined program is then presented.
Theory of vibration protection
Karnovsky, Igor A
2016-01-01
This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...
Vasilevskyi, Oleksandr M.; Kulakov, Pavlo I.; Dudatiev, Igor A.; Didych, Volodymyr M.; Kotyra, Andrzej; Suleimenov, Batyrbek; Assembay, Azat; Kozbekova, Ainur
2017-08-01
The paper presents the structural diagram and mathematical model of a vibration diagnostic system to measure angular velocities of two interconnected electric motors. The system is based on vibration signals and the control signals of the motor mechanical parameters. The measurement procedure of the rotor rotational speed is based on vibration signals during synchronization. The procedure presented allows simultaneous measurement and synchronization frequencies of rotation to diagnose of the motors' mechanical parts. The calculated reduced error of synchronizing frequencies of rotation of the rotors, which is 0.45% of the measurement range of frequencies of rotation from 0 to 80Hz.
Vibrational characterization of different benzene phases on flat and vicinal Si(100) surfaces.
Naydenov, Borislav; Widdra, Wolf
2007-10-21
Based on high-resolution electron energy loss spectroscopy and temperature-programmable desorption, benzene chemisorption on vicinal and nominally flat Si(100) surfaces has been studied for various adsorption, annealing, and site blocking treatments. Three different chemisorbed benzene (C6H6 and C6D6) phases with distinct thermal desorption characteristics and different vibrational spectra have been separated and characterized on both substrates. All three phases are identified as 1,4-cyclohexadiene-like structures with butterfly geometry. Whereas the dominant phase is di-sigma bonded to the two Si atoms of a single Si-Si dimer, the benzene orientation (double bond orientation) in the other phases is rotated. Di-sigma bonding to Si atoms of adjacent Si-Si dimer for the latter cases is most likely. Coverage and temperature dependent conversions between the different phases have been addressed by vibrational spectroscopy.
Theoretical methods for small-molecule ro-vibrational spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Lodi, Lorenzo; Tennyson, Jonathan, E-mail: j.tennyson@ucl.ac.u [University College London, Department of Physics and Astronomy, Gower Street, London WC1E 6BT (United Kingdom)
2010-07-14
The solution of the first principle equations of quantum mechanics provides an increasingly accurate and predictive approach for solving problems involving atoms and small molecules. A general introduction to the methods used for the ab initio calculation of rotational-vibrational spectra of small molecules is presented, with a strong focus on triatomic systems. The use of multi-reference electronic structure methods to compute molecular potential-energy and dipole-moment surfaces is discussed. Issues related to the construction of such surfaces and the inclusion of corrections due to relativistic and non-Born-Oppenheimer effects are reviewed. The derivation of exact, internal-coordinate nuclear-motion-effective Hamiltonians and their solution using a discrete-variable representation are discussed. Sample results for the water molecules are used throughout the tutorial to illustrate the theoretical and numerical issues in such calculations. (phd tutorial)
2012-08-15
Acetylene S1 State,’’ J. Phys. Chem. A (feature article) 115, 11921-11943 (2011). 5. S. H. Lipoff and D. R. Herschbach, “Low-Energy Limit for...triplet states) and how these mechanisms may be experimentally characterized. Throughout this project, the spin-orbit interaction of the acetylene S1...Laser Excited Metastables (SEELEM) experiments, largely because we have accumulated an unprecedentedly complete description of the vibrational levels
Conical Intersections Between Vibrationally Adiabatic Surfaces in Methanol
Dawadi, Mahesh B.; Perry, David S.
2014-06-01
The discovery of a set of seven conical intersections (CI's) between vibrationally adiabatic surfaces in methanol is reported. The intersecting surfaces represent the energies of the two asymmetric CH stretch vibrations, νb{2} and νb{9}, regarded as adiabatic functions of the torsional angle, γ, and COH bend angle, ρ. One conical intersection, required by symmetry, is located at the C3v geometry where the COH group is linear (ρ = 0°); the other six are in eclipsed conformations with ρ = 62° and 94°. The three CI's at ρ = 62° are close to the equilibrium geometry (ρ = 71.4°), within the zero-point amplitude of the COH bending vibration. CI's between electronic surfaces have long been recognized as crucial conduits for ultrafast relaxation, and recently Hamm, and Stock have shown that vibrational CI's may also provide a mechanism for ultrafast vibrational relaxation. The ab initio data reported here are well described by an extended Zwanziger and Grant model for E ⊗ e Jahn-Teller systems in which Renner-Teller coupling is also active. However, in the present case, the distortion ρ from C3v symmetry is much larger than is typical in the Jahn-Teller coupling of electronic surfaces and accordingly higher-order terms in ρ are required. The present results are also consistent with the two-state model of Xu et al. The cusp-like features, which they found along the internal-rotation path, are explained in the context of the present work in terms of proximity to the CI's. The presence of multiple CI's near the torsional minimum energy path impacts the role of geometric phase in this three-fold internal-rotor system. When the dimensionality of the low-frequency space is extended to include the CO bond length as well as γ and ρ, the individual CI's become seams of CI's. It is shown that the CI's at ρ = 62° and 94° lie along the same seam of CI's in this higher dimensional space. P. Hamm and G. Stock, Phys. Rev. Lett., 109, 173201, (2012) P. Hamm, and G
Ramos, J. M.; de M. Cruz, M. T.; Costa, A. C., Jr.; Ondar, G. F.; Ferreira, Glaucio B.; Raniero, L.; Martin, A. A.; Versiane, O.; Téllez Soto, C. A.
2012-11-01
The aspartateguanidoacetatenickel (II) complex, [Ni(Asp)(GAA)], was synthesized and structural analysis was performed by means of the experimental methods: determination of the C, H, N and O contents, thermogravimetry, infrared and Raman spectroscopy. DFT:B3LYP/6-311G(d, p) calculations have been performed giving optimized structure and harmonic vibrational wavenumbers. Second derivative of the FT-infrared, FT-Raman and Surface Raman Enhanced Scattering (SERS) spectra, and band deconvolution analysis were also performed. Features of the FT-infrared, FT-Raman and SERS confirmed theoretical structure prediction. Full assignment of the vibrational spectrum was also supported by a carefully analysis of the distorted geometries generated by the normal modes. The Natural Bond Orbital analysis (NBO) was also carried out as a way to study the Ni (II) hybridization leading to the pseudo planar geometry of the framework, and the extension of the atomic N and O hybrid orbital of the different amino acids in the bond formation. Bands of charge transfer and d-d transitions were assigned in the UV-Vis spectrum.
Fragmentation of molecular ions in slow electron collisions
Energy Technology Data Exchange (ETDEWEB)
Novotny, Steffen
2008-06-25
The fragmentation of positively charged hydrogen molecular ions by the capture of slow electrons, the so called dissociative recombination (DR), has been investigated in storage ring experiments at the TSR, Heidelberg, where an unique twin-electron-beam arrangement was combined with high resolution fragment imaging detection. Provided with well directed cold electrons the fragmentation kinematics were measured down to meV collision energies where pronounced rovibrational Feshbach resonances appear in the DR cross section. For thermally excited HD{sup +} the fragmentation angle and the kinetic energy release were studied at variable precisely controlled electron collision energies on a dense energy grid from 10 to 80 meV. The anisotropy described for the first time by Legendre polynomials higher 2{sup nd} order and the extracted rotational state contributions were found to vary on a likewise narrow energy scale as the rotationally averaged DR rate coefficient. Ro-vibrationally resolved DR experiments were performed on H{sub 2}{sup +} produced in distinct internal excitations by a novel ion source. Both the low-energy DR rate as well as the fragmentation dynamics at selected resonances were measured individually in the lowest two vibrational and first three excited rotational states. State-specific DR rates and angular dependences are reported. (orig.)
A Spectroscopic Survey of Electronic Transitions of C$_6$H, $^{13}$C$_6$H, and C$_6$D
Bacalla, Xavier; Linnartz, Harold; Ubachs, Wim; Zhao, Dongfeng
2016-01-01
Electronic spectra of C$_6$H are measured in the $18\\,950-21\\,100$ cm$^{-1}$ domain using cavity ring-down spectroscopy of a supersonically expanding hydrocarbon plasma. In total, 19 (sub)bands of C$_6$H are presented, all probing the vibrational manifold of the B$^2\\Pi$ electronically excited state. The assignments are guided by electronic spectra available from matrix isolation work, isotopic substitution experiments (yielding also spectra for $^{13}$C$_6$H and C$_6$D), predictions from ab initio calculations as well as rotational fitting and vibrational contour simulations using the available ground state parameters as obtained from microwave experiments. Besides the $0_0^0$ origin band, three non-degenerate stretching vibrations along the linear backbone of the C$_6$H molecule are assigned: the $\
Energy Technology Data Exchange (ETDEWEB)
Naudin, M. [Conservatoire National des Arts et Metiers (CNAM), 75 - Paris (France)]|[FRAMATOME, 92 - Paris-La-Defense (France); Pugnet, J.M. [Conservatoire National des Arts et Metiers (CNAM), Grenoble-1 Univ., 38 (France)]|[FRAMATOME, 92 - Paris-La-Defense (France)
1999-07-01
Vibration phenomena are sources of mechanical incidents in turbomachineries. A calculation of the Eigenmodes of machine parts and a knowledge of their possible excitation during the machine operation can greatly improve the reliability and availability of the equipments. The development of computer tools and in particular the use of finite-element codes has allowed a more and more precise calculation of Eigenmodes and Eigenfrequencies. However, the analysis of excitation sources remains sometimes insufficient to explain and anticipate some complex vibrational phenomena encountered in rotative machines. The aim of this paper is to present, using two different examples, the methodology to be used in order to perform a complete vibrational analysis of mechanical components. The following aspects are reviewed successively: 1 - the damped vibrational system: study of the free motion, study of the response to an harmonic forced excitation; 2 - vibrational analysis of turbine blades: steam turbine blades, Eigenmodes of mobile blades, excitation sources, Campbell diagram, calculation of static and dynamical stresses, Haigh diagram, acceptance criteria and safety coefficient, influence of corrosion; 3 - dynamical analysis of the bending of a lineshaft: different flexion Eigenmodes, stiffness and damping of bearings, calculation of flexion Eigenmodes, excitation sources, vibrational stability of the lineshaft and vibration level; 3 - generalization: vibration of blades, shaft dynamics, alternative machines. (J.S.) 10 refs.
Li, P.; Amirjalayer, S.; Hartl, F.; Lutz, M.; de Bruin, B.; Becker, R.; Woutersen, S.; Reek, J.N.H.
2014-01-01
Photoinduced electron transfer in a supramolecular ZnTPP·Fe2S2 complex is investigated using femtosecond infrared spectroscopy, infrared spectro-electrochemistry, and DFT calculations. We find that the electron density is delocalized over the diiron core and the naphthalimide ligand, which explains
Resonant vibration control of wind turbine blades
DEFF Research Database (Denmark)
Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker
2010-01-01
The paper deals with introduction of damping to specific vibration modes of wind turbine blades, using a resonant controller with acceleration feedback. The wind turbine blade is represented by three-dimensional, two-node finite elements in a local, rotating frame of reference. The element....... The efficiency of the resonant controller is demonstrated for a representative turbine blade exposed to turbulent wind loading. It is found that the present explicit tuning procedure yields close to optimal tuning, with very limited modal spill-over and effective reduction of the vibration amplitudes....
The photodissociation and reaction dynamics of vibrationally excited molecules
Energy Technology Data Exchange (ETDEWEB)
Crim, F.F. [Univ. of Wisconsin, Madison (United States)
1993-12-01
This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.
Energy Technology Data Exchange (ETDEWEB)
Kamusella, Sirko
2017-03-01
In this thesis the superconducting and magnetic phases of LiOH(Fe,Co)(Se,S), CuFeAs/CuFeSb, and LaFeP{sub 1-x}As{sub x}O - belonging to the 11, 111 and 1111 structural classes of iron-based arsenides and chalcogenides - are investigated by means of {sup 57}Fe Moessbauer spectroscopy and muon spin rotation/relaxation (μSR). Of major importance in this study is the application of high magnetic fields in Moessbauer spectroscopy to distinguish and characterize ferro- (FM) and antiferromagnetic (AFM) order. A user-friendly Moessbauer data analysis program was developed to provide suitable model functions not only for high field spectra, but relaxation spectra or parameter distributions in general. In LaFeP{sub 1-x}As{sub x}O the reconstruction of the Fermi surface is described by the vanishing of the Γ hole pocket with decreasing x. The continuous change of the orbital character and the covalency of the d-electrons is shown by Moessbauer spectroscopy. A novel antiferromagnetic phase with small magnetic moments of ∼ 0.1 μ{sub B} state is characterized. The superconducting order parameter is proven to continuously change from a nodal to a fully gapped s-wave like Fermi surface in the superconducting regime as a function of x, partially investigated on (O,F) substituted samples. LiOHFeSe is one of the novel intercalated FeSe compounds, showing strongly increased T{sub C} = 43 K mainly due to increased interlayer spacing and resulting two-dimensionality of the Fermi surface. The primary interest of the samples of this thesis is the simultaneously observed ferromagnetism and superconductivity. The local probe techniques prove that superconducting sample volume gets replaced by ferromagnetic volume. Ferromagnetism arises from magnetic order with T{sub C} = 10 K of secondary iron in the interlayer. The tendency of this system to show (Li,Fe) disorder is preserved upon (Se,S) substitution. However, superconductivity gets suppressed. The results of Moessbauer spectroscopy
Photopolymer diffractive optical elements in electronic speckle pattern shearing interferometry
Mihaylova, Emilia; Naydenova, Izabela; Duignan, Barry; Martin, Suzanne; Toal, Vincent
2006-09-01
In this paper we present an electronic speckle pattern shearing interferometer using a photopolymer diffractive optical element in the form of a holographic grating, in combination with a ground glass to shear the images. The sheared images on the ground glass are further imaged onto a CCD camera. The distance between the grating and the ground glass can be used to control the shear and to vary the sensitivity of the system. The direction of sensitivity is easily controlled by rotation of the diffraction grating around its normal. Introducing photopolymer holographic gratings in ESPSI gives the advantage of using high aperture optical elements at relatively low cost. The fact that the diffractive optical element is a photopolymer layer on glass substrate with thickness of 2 mm makes for a compact optical system. The system was successfully used for detection of the resonant frequencies of a vibrating object. Most of the published work on vibration analysis is analytical. Very few experimental results are available in the literature. The well known laser Doppler vibrometers (LDV) and accelerometers used for modal analysis are pointwise measurement techniques, although multipoint LDV is available at significant cost. Electronic speckle pattern techniques suitable for experimental detection of the resonant frequencies of vibrating objects are very promising for vibration analysis because they are whole field and non-contact. A finite element model is developed for prediction of the vibration modes of the object under test. Detection of vibrational modes of aluminium diaphragm is demonstrated and compared with the theoretical model. The results obtained are very promising for future application of ESPSI systems with HOEs, for modal analysis. A significant advantage of shearography over electronic speckle pattern interferometry is that ESPSI is relatively insensitive to external disturbances. Another advantage of the proposed system is that it could be easily converted
Directory of Open Access Journals (Sweden)
Zili Zhang
2014-11-01
Full Text Available Lateral tower vibrations of offshore wind turbines are normally lightly damped, and large amplitude vibrations induced by wind and wave loads in this direction may significantly shorten the fatigue life of the tower. This paper proposes the modeling and control of lateral tower vibrations in offshore wind turbines using active generator torque. To implement the active control algorithm, both the mechanical and power electronic aspects have been taken into consideration. A 13-degrees-of-freedom aeroelastic wind turbine model with generator and pitch controllers is derived using the Euler–Lagrangian approach. The model displays important features of wind turbines, such as mixed moving frame and fixed frame-defined degrees-of-freedom, couplings of the tower-blade-drivetrain vibrations, as well as aerodynamic damping present in different modes of motions. The load transfer mechanisms from the drivetrain and the generator to the nacelle are derived, and the interaction between the generator torque and the lateral tower vibration are presented in a generalized manner. A three-dimensional rotational sampled turbulence field is generated and applied to the rotor, and the tower is excited by a first order wave load in the lateral direction. Next, a simple active control algorithm is proposed based on active generator torques with feedback from the measured lateral tower vibrations. A full-scale power converter configuration with a cascaded loop control structure is also introduced to produce the feedback control torque in real time. Numerical simulations have been carried out using data calibrated to the referential 5-MW NREL (National Renewable Energy Laboratory offshore wind turbine. Cases of drivetrains with a gearbox and direct drive to the generator are considered using the same time series for the wave and turbulence loadings. Results show that by using active generator torque control, lateral tower vibrations can be significantly mitigated for
Review of magnetostrictive vibration energy harvesters
Deng, Zhangxian; Dapino, Marcelo J.
2017-10-01
The field of energy harvesting has grown concurrently with the rapid development of portable and wireless electronics in which reliable and long-lasting power sources are required. Electrochemical batteries have a limited lifespan and require periodic recharging. In contrast, vibration energy harvesters can supply uninterrupted power by scavenging useful electrical energy from ambient structural vibrations. This article reviews the current state of vibration energy harvesters based on magnetostrictive materials, especially Terfenol-D and Galfenol. Existing magnetostrictive harvester designs are compared in terms of various performance metrics. Advanced techniques that can reduce device size and improve performance are presented. Models for magnetostrictive devices are summarized to guide future harvester designs.