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You searched for subject:(quantum beat laser). Showing records 1 – 2 of 2 total matches.

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University of Oxford

1. Seamons, Scott Andrew. The collision dynamics of OH(A)+H2.

Degree: PhD, 2015, University of Oxford

This thesis presents a joint experimental and theoretical study of a bimolecular collision between OH(A) and H2 diatoms. The study focuses on the relationship between the initial, <b><i>j</i></b>, and final rotational angular momentum, <b><i>j'</i></b>. This relationship is explored from both a scalar point of view by measuring rotational energy transfer (RET), and a vectorial viewpoint by considering the collisional depolarisation. The experimental technique used in this investigation, Zeeman quantum beat spectroscopy, is first demonstrated by applying it to the determination of the lab-frame orientation of OH(X) photofragments following the photolysis of H2O2. The H2O2 is photolysed by circularly-polarised light at 248 nm, and Zeeman quantum beat spectroscopy probes the angular momentum orientation as a function of the photofragment spin-rotation level. The results of this experiment are compared with orientation parameters predicted by a simulation that couples the rotation of the parent molecule to the torsional motion during bond cleavage. The calculations from the model agree qualitatively with those from the experiment. The Zeeman quantum beat spectroscopy technique is then used to monitor the evolution of angular momentum polarisation of OH(A) radicals during collisions with H2. The technique allows for the determination of depolarisation cross sections for oriented and aligned distributions, as a result of collisions with H2. Alongside this, cross sections for collisional quenching to non-reactive OH(X)+H2 and reactive H2O+H products are determined. By resolving the fuorescence with a monochromator the contributions to depolarisation from elastic collisions (the elastic depolarisation cross sections) are measured alongside cross sections for RET. Cross sections for total depolarisation and rotational energy transfer demonstrate only weak dependence on the rotational quantum number of the OH(A) radical, <i>N</i>OH. Competing quenching processes that fall with <i>N</i>OH are likely a considerable cause of this weak dependence. Furthermore, the polarisation of the angular momentum of OH(A) is randomised following RET. The elastic depolarisation cross sections make only a small contribution to the depolarisation and fall with increasing <i>N</i>OH. Collectively these trends have not been seen previously in similar studies on OH(A) collisions with atomic colliders. For the theoretical calculations, a four-atom quasi-classical trajectory (QCT) method has been developed, utilising Lagrangian multipliers to fix the OH(A) and H2 bonds. The calculations demonstrate that collisions involving the formation of complexes that survive for several rotational periods are prevalent in this collision system, and that these lead to large amounts of depolarisation. The calculations also demonstrate that RET in the H2 diatom supports higher levels of RET in OH(A) than seen in…

Subjects/Keywords: 541; Physical & theoretical chemistry; Photochemistry and reaction dynamics; Spectroscopy and molecular structure; Laser Spectroscopy; Chemistry & allied sciences; Atmospheric chemistry; collision dynamics; quantum beat spectroscopy; hydrogen peroxide photolysis; ion imaging; molecular beam

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APA (6th Edition):

Seamons, S. A. (2015). The collision dynamics of OH(A)+H2. (Doctoral Dissertation). University of Oxford. Retrieved from http://ora.ox.ac.uk/objects/uuid:36319557-1efa-4840-8f46-c15479945a0c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680412

Chicago Manual of Style (16th Edition):

Seamons, Scott Andrew. “The collision dynamics of OH(A)+H2.” 2015. Doctoral Dissertation, University of Oxford. Accessed October 30, 2020. http://ora.ox.ac.uk/objects/uuid:36319557-1efa-4840-8f46-c15479945a0c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680412.

MLA Handbook (7th Edition):

Seamons, Scott Andrew. “The collision dynamics of OH(A)+H2.” 2015. Web. 30 Oct 2020.

Vancouver:

Seamons SA. The collision dynamics of OH(A)+H2. [Internet] [Doctoral dissertation]. University of Oxford; 2015. [cited 2020 Oct 30]. Available from: http://ora.ox.ac.uk/objects/uuid:36319557-1efa-4840-8f46-c15479945a0c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680412.

Council of Science Editors:

Seamons SA. The collision dynamics of OH(A)+H2. [Doctoral Dissertation]. University of Oxford; 2015. Available from: http://ora.ox.ac.uk/objects/uuid:36319557-1efa-4840-8f46-c15479945a0c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680412

2. Sete, Eyob Alebachew. Quantum Coherence Effects in Novel Quantum Optical Systems.

Degree: PhD, Physics, 2012, Texas A&M University

Optical response of an active medium can substantially be modified when coherent superpositions of states are excited, that is, when systems display quantum coherence and interference. This has led to fascinating applications in atomic and molecular systems. Examples include coherent population trapping, lasing without inversion, electromagnetically induced transparency, cooperative spontaneous emission, and quantum entanglement. We study quantum coherence effects in several quantum optical systems and find interesting applications. We show that quantum coherence can lead to transient Raman lasing and lasing without inversion in short wavelength spectral regions – extreme ultraviolet and x-ray – without the requirement of incoherent pumping. For example, we demonstrate transient Raman lasing at 58.4 nm in Helium atom and transient lasing without inversion at 6.1 nm in Helium-like Boron (triply-ionized Boron). We also investigate dynamical properties of a collective superradiant state prepared by absorption of a single photon when the size of the sample is larger than the radiation wavelength. We show that for large number of atoms such a state, to a good approximation, decays exponentially with a rate proportional to the number of atoms. We also find that the collective frequency shift resulting from repeated emission and reabsorption of short-lived virtual photons is proportional to the number of species in the sample. Furthermore, we examine how a position-dependent excitation phase affects the evolution of entanglement between two dipole-coupled qubits. It turns out that the coherence induced by position-dependent excitation phase slows down the otherwise fast decay of the two-qubit entanglement. We also show that it is possible to entangle two spatially separated and uncoupled qubits via interaction with correlated photons in a cavity quantum electrodynamics setup. Finally, we analyze how quantum coherence can be used to generate continuous-variable entanglement in quantum-beat lasers in steady state and propose possible implementation in quantum lithography. Advisors/Committee Members: Scully, Marlan O. (advisor), Zubairy, Muhammad S. (committee member), Kocharovskaya, Olga (committee member), Chen, Goong (committee member).

Subjects/Keywords: Quantum coherence effects; extreme ultraviolet and x-ray lasers; transient lasing without inversion; transient Raman lasing; superradiance; Collective Lamb (frequency) shift; dipole-coupled qubit entanglement; light-to-matter entanglement transfer; quantum beat laser; continuous-variable entanglement; quantum lithography

QUANTUM-BEAT LASER ∗ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 A… …96 Schematic of a quantum-beat laser coupled to a squeezed reservoir (N,M) in… …in which we study the role of dephasing on entanglement created in a quantum-beat laser… …CONTROLLED ENTANGLEMENT IN A QUANTUMBEAT LASER: APPLICATION TO QUANTUM LITHOGRAPHY… …to-matter entanglement. Chapter VI deals with generation of entanglement in quantum-beat… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Sete, E. A. (2012). Quantum Coherence Effects in Novel Quantum Optical Systems. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11400

Chicago Manual of Style (16th Edition):

Sete, Eyob Alebachew. “Quantum Coherence Effects in Novel Quantum Optical Systems.” 2012. Doctoral Dissertation, Texas A&M University. Accessed October 30, 2020. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11400.

MLA Handbook (7th Edition):

Sete, Eyob Alebachew. “Quantum Coherence Effects in Novel Quantum Optical Systems.” 2012. Web. 30 Oct 2020.

Vancouver:

Sete EA. Quantum Coherence Effects in Novel Quantum Optical Systems. [Internet] [Doctoral dissertation]. Texas A&M University; 2012. [cited 2020 Oct 30]. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11400.

Council of Science Editors:

Sete EA. Quantum Coherence Effects in Novel Quantum Optical Systems. [Doctoral Dissertation]. Texas A&M University; 2012. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11400

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