The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Gerhard Schwaab - One of the best experts on this subject based on the ideXlab platform.
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Strong Anisotropy in Liquid Water upon Librational Excitation Using Terahertz Laser Fields
Journal of Physical Chemistry B, 2020Co-Authors: Fabio Novelli, Luis Ruiz Pestana, Kochise Bennett, Federico Sebastiani, Ellen M. Adams, N. Stavrias, Thorsten Ockelmann, Alejandro Colchero, Claudius Hoberg, Gerhard SchwaabAbstract:Tracking the excitation of water molecules in the homogeneous liquid is challenging due to the ultrafast dissipation of rotational excitation energy through the hydrogen-bonded network. Here we demonstrate strong transient anisotropy of liquid water through librational excitation using single-color pump-probe experiments at 12.3 THz. We deduce a third-order response of χ3 exceeding previously reported values in the optical range by 3 orders of magnitude. Using a theory that replaces the nonlinear response with a material property amenable to molecular dynamics simulation, we show that the rotationally Damped Motion of water molecules in the librational band is resonantly driven at this frequency, which could explain the enhancement of the anisotropy in the liquid by the external terahertz field. By addition of salt (MgSO4), the hydration water is instead dominated by the local electric field of the ions, resulting in reduction of water molecules that can be dynamically perturbed by THz pulses.
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Strong Anisotropy in Liquid Water upon Librational Excitation using Terahertz Laser Fields
arXiv: Chemical Physics, 2018Co-Authors: Fabio Novelli, Luis Ruiz Pestana, Kochise Bennett, Federico Sebastiani, Ellen M. Adams, N. Stavrias, Thorsten Ockelmann, Alejandro Colchero, Claudius Hoberg, Gerhard SchwaabAbstract:Orienting water molecules in the homogeneous liquid is challenging due to the ultrafast dissipation of rotational excitation energy through the hydrogen-bonded network. Here we demonstrate strong transient anisotropy of liquid water through librational excitation using single-color pump-probe experiments at 12.3 THz, with the birefringence exceeding previously reported values by three to five orders of magnitude. Using a theory that replaces the third order response with a material response property amenable to molecular dynamics simulation, we show that the rotationally Damped Motion of water molecules in the librational band is resonantly driven at this frequency, thereby enhancing the liquid anisotropy by the external Terahertz field. By addition of salt (MgSO4), the hydration water is instead dominated by the local electric field of the ions, resulting in reduction of water molecules that can be dynamically perturbed by THz pulses.
S. H. Simpson - One of the best experts on this subject based on the ideXlab platform.
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Transverse spin forces and non-equilibrium particle dynamics in a circularly polarized vacuum optical trap
Nature Communications, 2018Co-Authors: V. Svak, O. Brzobohatý, M. Šiler, P. Jákl, J. Kaňka, P. Zemánek, S. H. SimpsonAbstract:Here, the authors provide a vivid demonstration of the dynamic effect of transverse spin momentum in an optical beam in free space revealed by placing a dielectric bead in a counter-propagating optical beam trap in vacuum. We provide a vivid demonstration of the mechanical effect of transverse spin momentum in an optical beam in free space. This component of the Poynting momentum was previously thought to be virtual, and unmeasurable. Here, its effect is revealed in the inertial Motion of a probe particle in a circularly polarized Gaussian trap, in vacuum. Transverse spin forces combine with thermal fluctuations to induce a striking range of non-equilibrium phenomena. With increasing beam power we observe (i) growing departures from energy equipartition, (ii) the formation of coherent, thermally excited orbits and, ultimately, (iii) the ejection of the particle from the trap. As well as corroborating existing measurements of spin momentum, our results reveal its dynamic effect. We show how the under-Damped Motion of probe particles in structured light fields can expose the nature and morphology of optical momentum flows, and provide a testbed for elementary non-equilibrium statistical mechanics.
Igor Andrianov - One of the best experts on this subject based on the ideXlab platform.
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Transitions from Strongly to Weakly Nonlinear Motions of Damped Nonlinear Oscillators
Nonlinear Dynamics, 1999Co-Authors: G. Salenger, Alexander F Vakakis, Leonid Manevitch, Oleg Gendelman, Igor AndrianovAbstract:We construct analytical approximations for the transition from strongly nonlinear, early-time oscillations to weakly nonlinear, late-time Motions of single degree of freedom, Damped, nonlinear oscillators. Two methods are developed. The first relies on (a) derivation of an analytic solution for the initial value problem of an exactly integrable Damped system, (b) development of separate early- and late-time approximations to the Damped Motion using the integrable solution, and (c) patching of the two approximations in the time domain by imposing continuity conditions on the composite solution at the point of matching. The second approach relies on a multiple-scales application of the method of nonsmooth transformations first developed by Pilipchuck, but complemented with a corrected frequency-amplitude relation. This improved relation is obtained by developing two separate frequency-amplitude asymptotic expansions in the frequency-amplitude plane, that are valid for large and small amplitudes, respectively, and then matching them using two-point diagonal Padé approximants. Comparisons between analytical approximations and numerical results validate the two approaches developed
Fabio Novelli - One of the best experts on this subject based on the ideXlab platform.
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Strong Anisotropy in Liquid Water upon Librational Excitation Using Terahertz Laser Fields
Journal of Physical Chemistry B, 2020Co-Authors: Fabio Novelli, Luis Ruiz Pestana, Kochise Bennett, Federico Sebastiani, Ellen M. Adams, N. Stavrias, Thorsten Ockelmann, Alejandro Colchero, Claudius Hoberg, Gerhard SchwaabAbstract:Tracking the excitation of water molecules in the homogeneous liquid is challenging due to the ultrafast dissipation of rotational excitation energy through the hydrogen-bonded network. Here we demonstrate strong transient anisotropy of liquid water through librational excitation using single-color pump-probe experiments at 12.3 THz. We deduce a third-order response of χ3 exceeding previously reported values in the optical range by 3 orders of magnitude. Using a theory that replaces the nonlinear response with a material property amenable to molecular dynamics simulation, we show that the rotationally Damped Motion of water molecules in the librational band is resonantly driven at this frequency, which could explain the enhancement of the anisotropy in the liquid by the external terahertz field. By addition of salt (MgSO4), the hydration water is instead dominated by the local electric field of the ions, resulting in reduction of water molecules that can be dynamically perturbed by THz pulses.
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Strong Anisotropy in Liquid Water upon Librational Excitation using Terahertz Laser Fields
arXiv: Chemical Physics, 2018Co-Authors: Fabio Novelli, Luis Ruiz Pestana, Kochise Bennett, Federico Sebastiani, Ellen M. Adams, N. Stavrias, Thorsten Ockelmann, Alejandro Colchero, Claudius Hoberg, Gerhard SchwaabAbstract:Orienting water molecules in the homogeneous liquid is challenging due to the ultrafast dissipation of rotational excitation energy through the hydrogen-bonded network. Here we demonstrate strong transient anisotropy of liquid water through librational excitation using single-color pump-probe experiments at 12.3 THz, with the birefringence exceeding previously reported values by three to five orders of magnitude. Using a theory that replaces the third order response with a material response property amenable to molecular dynamics simulation, we show that the rotationally Damped Motion of water molecules in the librational band is resonantly driven at this frequency, thereby enhancing the liquid anisotropy by the external Terahertz field. By addition of salt (MgSO4), the hydration water is instead dominated by the local electric field of the ions, resulting in reduction of water molecules that can be dynamically perturbed by THz pulses.
Alexander F Vakakis - One of the best experts on this subject based on the ideXlab platform.
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Transitions from Strongly to Weakly Nonlinear Motions of Damped Nonlinear Oscillators
Nonlinear Dynamics, 1999Co-Authors: G. Salenger, Alexander F Vakakis, Leonid Manevitch, Oleg Gendelman, Igor AndrianovAbstract:We construct analytical approximations for the transition from strongly nonlinear, early-time oscillations to weakly nonlinear, late-time Motions of single degree of freedom, Damped, nonlinear oscillators. Two methods are developed. The first relies on (a) derivation of an analytic solution for the initial value problem of an exactly integrable Damped system, (b) development of separate early- and late-time approximations to the Damped Motion using the integrable solution, and (c) patching of the two approximations in the time domain by imposing continuity conditions on the composite solution at the point of matching. The second approach relies on a multiple-scales application of the method of nonsmooth transformations first developed by Pilipchuck, but complemented with a corrected frequency-amplitude relation. This improved relation is obtained by developing two separate frequency-amplitude asymptotic expansions in the frequency-amplitude plane, that are valid for large and small amplitudes, respectively, and then matching them using two-point diagonal Padé approximants. Comparisons between analytical approximations and numerical results validate the two approaches developed
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Experimental study of non-linear transient Motion confinement in a system of coupled beams
Journal of Sound and Vibration, 1996Co-Authors: J. Aubrecht, Alexander F Vakakis, Tsu-chin Tsao, Joseph BentsmanAbstract:Abstract An experimental study of non-linear confinement of transient Motions in a flexible structure consisting of two weakly coupled cantilever beams with active grounding non-linearities has been carried out. The experimental fixture and the control methodology used for implementing the active non-linearities are discussed in detail. It has been found that the system with active non-linearities possesses Motion confinement properties, that is, transient Motions originating at one of the beams become spatially confined mainly to the directly excited beam, with small amounts of vibrational energy “leaking” to the unexcited one. As the Damped Motion decays the non-linear effects diminish and the Motion confinement phenomenon becomes less evident. The experimental results are in agreement with analytical predictions. The implementation of non-linear Motion confinement in vibration and shock isolation designs of repetitive systems is discussed.
