Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 28 for “"wavepacket"”.
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WAVEPACKET APPROACHES TO DISSIPATIVE QUANTUM DYNAMICS
Many processes arising in Chemistry, Physics and Biology show quantum effects. Representative examples are chemical reactions involving light atoms, energy transfer in complex environments, electronic and geometrical properties of complex and bulk systems, tunneling phenomena etc. Theoretical …
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Femtosecond laser studies of molecular wavepacket dynamics in the cesium dimer
… have been applied to the study of vibrational wavepacket dynamics in the excited states of the cesium dimer, Cs$\sb2.$ The real-time vibrational motion of the molecule is observed by probing the quantum motion of the wavepacket on a potential surface by a pair of time-delayed ultrafast laser …
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Study of Wavepacket Dynamics in Rubidium Vapor by Means of Time-Frequency Analysis
Wavepackets are excited in rubidium vapor by intense ultrashort (∼100 fs) pulses centered at a wavelength of 620 nm or 770 nm. The generated atomic wavepackets are optically detected via a pump-probe experiment based on axially phase-matched parametric four-wave mixing (FWM). This nonlinear …
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Investigation of Noise Sources in Three-Stream Jets using Turbulence Characteristics
… offset nozzles. An analysis of a one-dimensional wavepacket model was completed to provide understanding of the effect of the various convection velocities seen in the flow. Comparison of a wavepacket with a convection velocity of 0.6Uj to a wavepacket with a convection velocity of 0.8Uj showed …
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Ultrafast Dynamics and Nonlinear Interactions in Alkali Atoms and Diatomics
… D states of the Cesium dimer and to study atomic wavepackets and nonlinear effects in Rubidium and Potassium. Two color, pump-probe techniques have been used to probe the time evolution of wavepackets in the B, C, and D rovibrational levels of Cs$\sb2$. The temporal history of the wavepacket is …
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Development of a Wavelet -Based Algorithm and Fitness Function for Computational and Experimental Quantum Control of Intramolecular Vibration Redistribution
… slowing down the time evolution of vibrational wavepackets in polyatomic molecules---""freezing"" intramolecular vibration redistribution (IVR)---required knowledge of the eigenstate-resolved phase and amplitude structure of the wavepacket. Experiments, however, can not provide such informa tion …
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Theoretical Studies on the ultrafast photodissociation of molecules
… and ability to describe the whole molecule. Wavepacket dynamics are used to probe the reaction mechanism and to calculate the branching ratio. A detailed investigation of electronic structure theory methods forms a large part of this research. We apply it to the FNO molecule, a system in …
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The Effects of Diabatic Heating on Storm Track Dynamics
… global spectral energetics, local energetics and wavepacket maps. Preliminary investigations of linear and nonlinear zonal baroclinic instability and nonlinear baroclinic wavepacket evolution are presented to verify and extend the results of Mak (1998) regarding surface heating effects on modal …
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Semiclassical Scattering for Two and Three Body Systems
… the time propogation of a semiclassical wavepacket over the time domain -∞ < t < ∞. This result has long been known for dimension n ≥ 3, and we extend it to one and two space dimensions. Next, we present a brief mathematical discussion of the three body problem, first in classical …
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Topological phenomena in ultracold atomic gases
… curvature for the semiclassical dynamics of a wavepacket and the collective modes of an ultracold gas. We also study theoretically the dynamics of skyrmion-antiskyrmion pairs in a Bose Einstein condensate. Firstly, we propose a general method by which experiments can map the Berry curvature …
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Three-dimensional solitary waves in dispersive wave systems
… small-amplitude lumps resemble fully localized wavepackets with envelope and crests moving at the same speed, and the wave envelope along with the induced mean-flow component are governed by a coupled Davey-Stewartson equation system of elliptic-elliptic type. The lump profiles feature …
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Stabilization of autoionizing states
… not an energy eigenstate but a non-stationary wavepacket. The evolution of these wavepackets was monitored by changing the timing between the exciting "pump" laser and the stimulating "probe" laser"--Abstract, page iv.</p>
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Exploring Matter-wave Dynamics with a Bose-Einstein Condensate
… the abrupt discontinuity in phase written on the wavepacket in position-space, akin to quantum reflection. Both effects lead to a redistribution of momenta, resulting in a rich interference pattern that may be used to reconstruct the single-particle wavefunction. In a second experiment, we study …
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Atoms, ions and molecules in intense ultrafast laser fields
… their molecular ions. In the ions, vibrational wavepackets have been studied and the phenomena of dephasing and revival observed. Additionally signatures of rotational wavepacket dynamics have been isolated in the neutral molecules. A technique to verify the laser pulse duration at the focus has …
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Sensitive, 3D micromotion compensation in a surface-electrode ion trap
… ion positioning accurate to the ground state wavepacket size (of order 10 nm), but cannot identify ion offsets out of the trap plane with the same accuracy. Schemes for sensitive compensation often have restrictive requirements such as access to a narrow atomic transition. We introduce a new …
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Ultrafast Atomic Dynamics in Arbitrary Light Fields
… a fundamental criterion for coherent spin-orbit wavepacket generation in this process, and demonstrate that its violation may account for the observed suppression of quantum beats in polarisation-anisotropy measurements.
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Quantum Geometry and Topology in Periodically-Strained Graphene
… induce an oscillating trajectory of an electron wavepacket transverse to an applied static electric field. Though analogous to Bloch oscillations, this novel oscillatory behavior is driven entirely by quantum geometry in momentum space instead of band dispersion. While the current from Bloch …
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Nonlinear dynamics of a matter-wave soliton in driven potentials
… solitons may help overcome limitations such as wavepacket spreading in current atom interferometry experiments. A typical matter-wave interferometer involves a condensate trapped in a double-well potential. Being able to manipulate the tunnelling behaviour of a matter-wave soliton in potentials …
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Nonlinear dynamics of a matter-wave soliton in driven potentials
… solitons may help overcome limitations such as wavepacket spreading in current atom interferometry experiments. A typical matter-wave interferometer involves a condensate trapped in a double-well potential. Being able to manipulate the tunnelling behaviour of a matter-wave soliton in potentials …
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Cosmic String Radiation with Adaptive Mesh Refinement
… suppressed with increasing mass, with a complex wavepacket structure that is sensitive to numerical resolution. String network configurations are also simulated, with advanced visualisation of radiation used to reveal new qualitative phenomena as strings reconnect and small loops decay. The …
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