Thèses sur le sujet « Two dimensional visible spectroscopy »
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Townsley, Christopher Mark. « Optical spectroscopy of two-dimensional hole systems in the quantum limit ». Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312067.
Texte intégralHarris, Janet Caroline. « Optical spectroscopy of correlated two-dimensional electrons ». Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390497.
Texte intégralZhang, Xu Ph D. Massachusetts Institute of Technology. « Two-dimensional crystals : spectroscopy and electronic applications ». Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112036.
Texte intégralCataloged from PDF version of thesis.
Includes bibliographical references (pages 159-177).
The success in creating atomically thin and mechanically robust two-dimensional (2D) crystals, starting with graphene, has unveiled new possibilities for next generation of ultrafast and ubiquitous electronics. One critical distinction between 2D crystals and 3D crystals is that 2D crystals are all-surface materials. Therefore, it is essential to understand how 2D materials interact with their environments and how this interaction impacts their electronic properties. From a practical perspective, it also provides us with a unique tool to tailor the electronic properties of 2D materials through surface functionalization. In the first half of this thesis, a suite of X-ray techniques is used to investigate how the surface functionalizing dopants will impact the electronic and chemical states of graphene. Based on this study, we develop an effective and non-invasive doping method for graphene through plasma-based chlorination. In order to make system-level 2D electronics successful, a flexible and ubiquitous energy harvesting solution is indispensable. Therefore, the second part of this thesis is dedicated to the development of a MoS₂ 2H-1T phase heterojunction-based GHz flexible rectifier as an enabling component for wireless energy harvester. It is the first flexible rectifier operating up to the X-band and it covers most of the unlicensed industrial, scientific and medical (ISM) radio band, including the Wi-Fi channels. By integrating this rectifier with an antenna, the MoS₂-enabled rectenna successfully demonstrates direct energy harvesting of electromagnetic (EM) radiation in the Wi-Fi band and lights up a commercial light-emitting diode (LED) with zero external bias (battery-free). Moreover, our MoS₂ rectifier also realizes successful frequency conversion as a mixer beyond 10 GHz on flexible substrates. This work provides a universal energy harvesting building block that can be integrated with various wearable electronic systems and paves the way towards using the existing Wi-Fi infrastructure as an energy hotspot for wireless charging.
by Xu Zhang.
Ph. D.
Kraft, Robert A. (Robert Arthur) 1970. « In vivo two-dimensional NMR correlation spectroscopy ». Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85271.
Texte intégralGardner, Elizabeth Mary. « Two-dimensional infrared spectroscopy for protein analysis ». Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5602.
Texte intégralPaul, Jagannath. « Coherent Response of Two Dimensional Electron Gas probed by Two Dimensional Fourier Transform Spectroscopy ». Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6738.
Texte intégralJohnson, Mark Thomas. « Photoelectron spectroscopy of two-dimensional materials and surfaces ». Thesis, University of Cambridge, 1987. https://www.repository.cam.ac.uk/handle/1810/250898.
Texte intégralMignuzzi, Sandro. « Near-field optical spectroscopy of two-dimensional materials ». Thesis, King's College London (University of London), 2017. https://kclpure.kcl.ac.uk/portal/en/theses/nearfield-optical-spectroscopy-of-twodimensional-materials(2e5e7a6b-d2b5-4242-bab7-3a66bd6c8c25).html.
Texte intégralChan, Ho Bun 1969. « Tunneling spectroscopy of the two-dimensional electron gas ». Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9387.
Texte intégralIncludes bibliographical references (p. 155-161).
We measure the single particle density of states (DOS) of a two-dimensional electron system (2DES) in a GaAs/AlGaAs heterostructure. Using a technique that we call "Time Domain Capacitance Spectroscopy" (TDCS), we measure the complete current-voltage characteristics for tunneling into the 2DES without making ohmic contacts to it. TDCS detects the tunneling current in regimes difficult to access by conventional methods, such as when the in-plane conductance is low. For the first time we detect the contributions of localized states to the tunneling current. The DOS of an interacting 2DES in the diffusive limit displays logarithmic energy dependence near the Fermi level. Using TDCS, we measure the voltage dependence of the tunneling conductance of a semiconductor 2DES and observe the logarithmic Coulomb anomaly for the first time in 2D systems other than thin metal films. As we increase the density, this suppression in tunneling conductance narrows and recedes. Nevertheless suppression reappears when we apply a magnetic field perpendicular to the 2D plane. We find that the tunneling conductance depends linearly on voltage near zero bias for all magnetic field strengths and electron densities. Moreover, the slopes of this linear gap are strongly field dependent. The data are suggestive of a new model of the tunneling gap in the presence of disorder and screening. We also use TDCS to study the interactions among electronic spins. By applying excitations less than kT, we observe that equilibrium tunneling into spin-polarized quantum Hall states (v=l, 3, 1/3) occurs at two distinct tunneling rates for samples of very high mobility. Some electrons tunnel into the 2DES at a fast rate while the rest tunnel at a rate up to 2 orders of magnitude slower. Such novel double-rate tunneling is not observed at even-integer filling fractions where the 2DES is not spin-polarized. The dependence of the two rates on magnetic field, temperature and tunnel barrier thickness suggests that slow in-plane spin relaxation, possibly related to formation of Skyrmions, leads to a bottleneck for tunneling of electrons.
by Ho Bun Chan.
Ph.D.
Zhang, Tianhao. « Optical two-dimensional Fourier transform spectroscopy of semiconductors ». Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3315815.
Texte intégralNagata, Yuki. « Two-dimensional spectroscopy in solid, liquid, and surface ». 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136791.
Texte intégralHarris, C. Thomas (Charles Thomas). « Terahertz waveguide spectroscopy of two-dimensional plasmons in GaAs ». Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62452.
Texte intégralCataloged from PDF version of thesis.
Includes bibliographical references (p. 85-88).
The electrical characteristics of high-mobility, two-dimensional electron gas (2DEG) systems, such as GaAs quantum wells, have been well-studied at low frequencies and in extreme conditions of high magnetic fields and ultralow temperatures. While high-frequency excitations of 2DEGs have been examined to some extent from microwave to terahertz (THz) frequencies, a fundamental understanding of the physical properties of 2DEGs in this range have by no means been mastered. To address this matter, this thesis focused on studying a fundamental, high-frequency collective excitation, known as the plasmon, to better understand plasmon damping and coupling mechanisms in GaAs quantum well 2DEGs. The experiments utilized THz waveguide spectroscopy to study the low-temperature behavior of 2D plasmons.
by C. Thomas Harris.
S.M.
Docherty, Callum James. « Terahertz spectroscopy of graphene and other two-dimensional materials ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:98c03952-dc3f-442b-bbc0-d8397645cc1b.
Texte intégralHe, Keliang. « Optical Spectroscopy of Two-Dimensional Transition Metal Dichalcogenides (TMDCs) ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1387468973.
Texte intégralZhang, Yaqing Ph D. Massachusetts Institute of Technology. « Two-dimensional terahertz rotational spectroscopy in the gas phase ». Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122715.
Texte intégralCataloged from PDF version of thesis.
Includes bibliographical references.
Two-dimensional (2D) coherent spectroscopy has been developed to study molecular dynamics and structures for decades, but its extension into the terahertz (THz) regime remains rare. In this thesis, I describe several experiments using two-dimensional terahertz rotational spectroscopy. Employing intense THz electromagnetic fields and the differential chopping technique, we have extended multi-dimensional coherent spectroscopy into the THz regime. We have observed rotational dynamics of linear, symmetric-top, and asymmetric-top molecular species, indicating that 2D THz spectroscopy is an incisive tool for investigating collective quantum effects of the rotational degree of freedom. Based on the quantum mechanical rigid rotor model, we have developed simulation and calculation approaches to disentangling spectroscopic signals from molecular rotations.
We have shown ultrafast 2D THz photon echo spectroscopy of gaseous acetonitrile samples, revealing J-state-resolved rotational dynamics in symmetric-top molecular rotors. We have revealed nonlinear rotational couplings and many-body interactions in water vapor, uncovering the strongly correlated nature of rotational quantum states in water molecules. Additionally, experimental evidence of linear and nonlinear THz spectroscopy of stable water dimers in the vicinity of atmospheric conditions has been observed. We have reported dual-type rotational couplings and a propensity for the K-state-dependent cross-peaks in sulfur dioxide, highlighting distinct rotational properties in slightly asymmetric-top molecules. We have measured the quartic THz effect using two-dimensional THz-Raman hybrid spectroscopy, opening the way for understanding and applications of higher-even-order THz-matter coherences beyond the linear and quadratic THz field effects.
Utilizing the density matrix and time propagation approaches, we have developed a set of simulation and calculation methodologies to characterize rotational dynamics in the gas phase based on the quantum mechanical rigid-rotor model. Our work shows the remarkable capability of 2D THz spectroscopy to interrogate rotational dynamics in the gas phase, laying a foundation for understanding and manipulation of nonlinear light-molecule interactions via multi-dimensional coherent THz spectroscopy.
by Yaqing Zhang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry
Golla, Dheeraj, et Dheeraj Golla. « Ultrafast Dynamics of Two Dimensional Materials ». Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626303.
Texte intégralDeFlores, Lauren P. « Multi-mode two-dimensional infrared spectroscopy of peptides and proteins ». Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43732.
Texte intégralThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Vita.
Includes bibliographical references.
In this thesis, a methodology for understanding structural stability of proteins through multi-mode two-dimensional infrared (2D IR) spectroscopy is developed. The experimental framework for generation of broadband infrared lasers and robust new approaches to 2D IR spectroscopy are demonstrated. Long-term phase stability is achieved through the development of a passively stabilized diffractive optic and wedge interferometer. A new approach for acquisition of 2D IR spectra in the pump-probe geometry reduces overall experimental complexity. These technological advances extend the capabilities of 2D IR to further resolve inter- and intramolecular couplings, relaxation pathways and structural kinetics in complex systems. Characterization of multi-mode spectra is first performed on model protein systems to reveal detailed information on the effects of solvation and structure on the amide vibrations. Differences in vibrational coupling, transition dipole angles and the anharmonic potential of the amide vibrations of isotopologues of N-methylacetamide arise from significant change in the local mode composition of the amide II band due to isotopic substitution of the peptide group. Extension of multi-mode 2D IR to study the amide I'-II' spectra of an ideal protein system, poly-L-lysine, provides direct evidence for the structural sensitivity of the amide II' vibration, particularly to the !-helix moiety. This structural sensitivity arises from through bond coupling and structure induced symmetry and orientation of adjacent residues. Integration of these tools with hydrogen exchange techniques allows for the protein structural kinetics and stability to be observed through protein-solvent interactions with enhanced structural sensitivity relative to amide I spectroscopy alone.
The amide II' diagonal provides a measure of the degree of exchange and the cross peaks between the structurally sensitive amide I/I' vibration and the solvent exposure sensitive amide II and II' modes reveal the location of exchange. Partial exchange of the secondary structure of ubiquitin is revealed by correlation of the different amide signatures through analysis of cross peak line shapes, positions and amplitudes. Results provide direct evidence for a highly stable helix and labile "-sheet structure.
by Lauren P. DeFlores.
Ph.D.
Demirdöven, Nurettin 1974. « Coherent two-dimensional infrared spectroscopy : a study of coupled vibrations ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17653.
Texte intégralVita.
Includes bibliographical references.
This thesis provides an introduction to experimental techniques used in two-dimensional (2D) infrared (IR) spectroscopy, outlines how third-order nonlinear response of a multi-level vibrational system is calculated, and provides a detailed methodology of line shape analysis in 2D spectroscopy. Specific emphasis is given to inherent sensitivity of 2D spectroscopy to correlated spectral broadening. The signatures of highly correlated transition energy fluctuations in a model system of two strongly coupled carbonyl stretching vibrations are reflected by the elongation of the cross peaks along the diagonal of the 2D spectrum. The dynamics of this correlation is monitored by the changes in the 2D line shapes and successfully modeled using a correlated spectral diffusion model. The sensitivity of 2D IR spectroscopy to interactions between multiple vibrational coordinates is also explored in conformationally complex polypeptides and proteins with well-defined secondary structures. 2D IR spectroscopy of β-hairpins and globular proteins with antiparallel (AP) β-sheet domains is studied to identify 2D markers of AP β-sheet conformation. The experiments on β-hairpins and proteins with varying percentage of β-sheet character showed that the formation of cross peaks between the two characteristic vibrational modes of AP β-sheets is a marker of AP β-sheet secondary structure. The intensity, location and line shapes of the cross peaks are qualitatively related to the size, geometry and the conformational variations in the AP β-sheet structure.
by Nurettin Demirdöven.
Ph.D.
Yankowitz, Matthew Abraham. « Local Probe Spectroscopy of Two-Dimensional van der Waals Heterostructures ». Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/594649.
Texte intégralKnighton, Brittany E. « Nonlinear Ultrafast Excitation and Two-Dimensional Terahertz Spectroscopy of Solids ». BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9190.
Texte intégralFolpini, Giulia. « Exploring Nonresonant Interactions in Condensed Matter by Two-Dimensional Terahertz Spectroscopy ». Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18860.
Texte intégralMultidimensional Terahertz spectroscopy is used to investigate the nonlinear response of condensed matter systems. A multioctave-spanning THz source based on frequency mixing in organic crystals is developed and used to study the libration band of water nanodroplets confined in DOPC micelles. Nonresonant THz radiation is used to coherently control the mid-infrared emission of an intersubband transition of GaAs quantum wells. Finally, 2D THz spectroscopy is used to study the nonlinear response of a soft mode in an aspirin molecular crystal.
Rödel, Tobias. « Two-dimensional electron systems in functional oxides studied by photoemission spectroscopy ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS197/document.
Texte intégralMany transition metal oxides (TMOs) show complex physics, ranging from ferroelectricity to magnetism, high-Tc superconductivity and colossal magnetoresistance. The existence of a variety of ground states often occurs as different degrees of freedom (e.g. lattice, charge, spin, orbital) interact to form different competing phases which are quite similar in energy. The capability to epitaxially grow heterostructures of TMOs increased the complexity even more as new phenomena can emerge at the interface. One typical example is the two-dimensional electron system (2DES) at the interface of two insulating oxides, namely LaAlO3/SrTiO3, which shows metal-to-insulator transitions, magnetism or gate-tunable superconductivity. The origin of this thesis was the discovery of a similar 2DES at the bare surface of SrTiO3 fractured in vacuum, making it possible to study its electronic structure by angle-resolved photoemission spectroscopy (ARPES).In this thesis, the study of well-prepared surfaces, instead of small fractured facets, results in spectroscopic data showing line widths approaching the intrinsic value. This approach allows a detailed analysis of many-body phenomena like the renormalization of the self-energy due to electron-phonon interaction.Additionally, the understanding of the electronic structure of the 2DES at the surface of SrTiO3(001) was given an additional turn by the surprising discovery of a complex spin texture measured by spin-ARPES. In this thesis data is presented which contradicts these conclusions and discusses possible reasons for the discrepancy.One major motivation of this thesis was the question if and how the electronic structure and the properties of the 2DES can be changed or controlled. In this context, the study of 2DESs at (110) and (111) surface revealed that the electronic band structure of the 2DES (orbital ordering, symmetry of the Fermi surface, effective masses) can be tuned by confining the electrons at different surface orientations of the same material, namely SrTiO3.A major achievement of this thesis is the generalization of the existence of a 2DES in SrTiO3 to many other surfaces and interfaces of TMOs (TiO2 anatase, CaTiO3, BaTiO3) and even simpler oxides already used in modern applications (ZnO). In all these oxides, we identify oxygen vacancies as the origin for the creation of the 2DESs.In anatase and other doped d0 TMOs, both localized and itinerant electrons (2DES) can exist due to oxygen vacancies. Which of the two cases is energetically favorable depends on subtle differences as demonstrated by studying two polymorphs of the same material (anatase and rutile).In CaTiO3, the oxygen octahedron around the Ti ion is slightly tilted. This symmetry breaking results in the mixing of different d-orbitals demonstrating again why and how the electronic structure of the 2DES can be altered.In BaTiO3, the creation of a 2DES results in the coexistence of the two, usually mutual exclusive, phenomena of ferroelectricity and metallicity in the same material by spatially separating the two.Moreover, this work demonstrates that the 2DES also exists in ZnO which is - compared to the Ti-based oxides - rather a conventional semiconductor as the orbital character of the itinerant electrons is of s and not d-type.The main result of this thesis is the demonstration of a simple and versatile technique for the creation of 2DESs by evaporating Al on oxide surfaces. A redox reaction between metal and oxide results in a 2DES at the interface of the oxidized metal and the reduced oxide. In this thesis the study of such interfacial 2DESs was limited to photoemission studies in ultra high vacuum. However, this technique opens up the possibility to study 2DESs in functional oxides in ambient conditions by e.g. transport techniques, and might be an important step towards cost-efficient mass production of 2DESs in oxides for future applications
Draeger, Simon [Verfasser], et Tobias [Gutachter] Brixner. « Rapid Two-Dimensional One-Quantum and Two-Quantum Fluorescence Spectroscopy / Simon Draeger ; Gutachter : Tobias Brixner ». Würzburg : Universität Würzburg, 2020. http://d-nb.info/1203068247/34.
Texte intégralRobyr, Pierre Stéphane. « Two-dimensional polarization-transfer NMR spectroscopy for studying ordered and disordered solids / ». [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10968.
Texte intégralLymer, Katherine. « Two-dimensional spectroscopy of γ-aminobutyric acid on a clinical MRI scanner ». Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/28462.
Texte intégralSmith, K. I. « The two-dimensional nuclear magnetic resonance spectroscopy analysis of peptides in solution ». Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377720.
Texte intégralZhao, Liang. « Optical properties of two-dimemsional Van der Waals crystals : from terahertz to visible ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1433378350.
Texte intégralBaniasadi, Fazel. « Structure Characterization and Electronic Properties Investigation of Two-Dimensional Materials ». Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103904.
Texte intégralDoctor of Philosophy
Graphite (consisting of graphene as building blocks) and TMDS in bulk form are layered and with exfoliation one can reach to few layers which is called two-dimension. Two dimensional materials like graphene have been used in researches vastly due to their unique properties, e.g. high carrier mobility, and tunable electronic properties. Transition metal dichalcogenides (TMDs) with a general formula of MX2, where M represents transition metal elements (groups 4-10) and X represents chalcogen elements (S, Se or Te), are another family of two-dimensional materials which have been extensively studied in the past few years. Besides exfoliation, there are also synthesis methods to produce two dimensional materials, e.g. chemical vapor deposition and chemical vapor transport. Normally, after synthesizing these materials, researchers investigate structure and electronic properties of these materials. There might be some atoms which no longer exist in the structure; hence, those are replaced by either vacancies or other elements which all of them are called defects. In chapter 1, defects in graphene and transition metal dichacolgenides were investigated, carefully. Later, dynamic behavior of defects in these materials were investigated and finally, the effect of defects on the electronic properties of the two dimensional materials were investigated. Chapter two talks about a case study which is two dimensional 1T-PtSe2. In this chapter, 5 different kinds of defects were studied using scanning tunneling microscopy and spectroscopy investigations and density functional theory was used to prove our assumptions of the origin of defects. Also, another thing which is investigated by researcher is that how atoms in two dimensional materials vibrate and how the number of layers in the two dimensional material influences vibrations of atoms. Other than this, electronic properties of these materials is dependent upon the number of layers. When these materials are synthesized, there is a stress applied to the material due the mismatch between the material and its substrate, so it is worth investigating the effect of stress (strain) on the structure, and electronic properties of the material of interest. For this purpose, 2M-WS2 was exfoliated on Si/SiO2 substrate and the layer dependency of its vibrational modes was investigated using Raman spectroscopy and density functional theory calculation. Also, in order to investigate the influence of stress (strain) on the electronic properties of two dimensional 2M-WS2, a single monolayer of this materials underwent a series of strains in density functional theory calculations and the effect of strain on the electronic properties of this material was investigated.
Klix, Christian Ludwig [Verfasser]. « Spectroscopy of displacements in a two-dimensional colloidal glass former / Christian Ludwig Klix ». Konstanz : Bibliothek der Universität Konstanz, 2014. http://d-nb.info/1096333554/34.
Texte intégralKehoe, Thomas Bernard. « Optical spectroscopy of two-dimensional hole systems in the integer quantum hall regime ». Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249084.
Texte intégralDe, Marco Luigi Ph D. Massachusetts Institute of Technology. « The molecular dynamics of hydrogen-bonding explored with broadband two dimensional infrared spectroscopy ». Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105022.
Texte intégralCataloged from PDF version of thesis. Vita
Includes bibliographical references (pages 317-352).
It is no overstatement to claim that hydrogen bonding is the most important intermolecular interaction. On a day-to-day basis, we encounter the peculiar effects of hydrogen bonding in liquid water; however, it is well appreciated that hydrogen bonding is immensely important in many contexts and, in particular, in biological ones. Despite this apparent significance, a general molecular picture of the dynamics of hydrogen-bonding systems is lacking. Over the last two decades, ultrafast multidimensional infrared spectroscopy has emerged as powerful technique for studying molecular dynamics in the condensed phase. By taking advantage of the complex relationship between a molecular oscillator's frequency and its environmental structure, we may understand molecular dynamics from an experimental perspective. However, the study of hydrogen bonding poses a significant technical challenge in that the interaction gives rise to broad resonances in the mid-infrared absorption spectrum. Traditional methods for generating short pulses of mid-infrared light are fundamentally limited in the bandwidth they can produce. Oftentimes, the width of a hydrogen-bonded oscillator's absorption resonance exceeds the broadest bandwidth mid-infrared laser pulse. In this thesis, I describe our development and use of a novel source of short, broadband mid-infrared light pulses that span the entire region of high-frequency molecular vibrations. We use this source as a probe in two-dimensional infrared spectroscopy experiments to study a wide variety hydrogen-bonding systems, including hydrogen-bonded dimers and protein films, with a particular emphasis on liquid water. Across these systems, we observe fascinating trends in the changes in molecular dynamics with increasing complexity of hydrogen bonding. In particular, we find experimental evidence for large deformations of the nuclear potential energy surface, giving rise to extremely anharmonic and collective dynamics. The effect is most dramatic in liquid water, where the rapidly fluctuating hydrogen-bond network results in vibrational excitons wherein O-H stretching motion is delocalized over multiple molecules. In this case, the nuclear potential energy surface is so complex that even simple changes in the mass of the oscillators result in qualitatively different dynamics.
Funding from U.S. Department of Energy DE-FG02-99ER14988 and DE-SC0014305
by Luigi De Marco.
Ph. D. in Physical Chemistry
Vaughan, Joshua Charles. « Two-dimensional ultrafast pulse shaping and its application to coherent control and spectroscopy ». Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32492.
Texte intégralVita.
Includes bibliographical references (p. 167-182).
This thesis develops powerful new methods for shaping femtosecond laser pulses in two dimensions and explores their application to coherent control of propagating lattice excitations and degenerate four-wave mixing spectroscopy. Pulse shaping in two dimensions is achieved by manipulating the spectral components of ultrashort laser pulses within many horizontal slices of the pulse. Each horizontal slice is independently shaped by means of a two-dimensional liquid crystal spatial light modulator, and taken together the shaped regions form sophisticated optical waveforms with time-dependent spatial profiles. Automated optical control over coherent lattice responses that are both time- and position-dependent across macroscopic length scales is demonstrated. Two- dimensional (2D) femtosecond pulse shaping was used to generate excitation light fields that were directed toward distinct regions of crystalline samples, producing terahertz-frequency lattice vibrational waves that emanated outward from their multiple origins at lightlike speeds. Interferences among the waves resulted in fully specified far-field responses, including tilted, focusing, or amplified wavefronts. Generation and coherent amplification of terahertz travelling waves and terahertz phased-array generation are also demonstrated. A novel approach to coherent nonlinear optical spectroscopy based on 2D femtosecond pulse shaping is introduced. Multiple phase-stable output beams are created and overlapped at the sample in a phase-matched boxcars geometry via 2D femtosecond pulse shaping.
(cont.) The pulse timing, shape, phase, and spectral content within all beams may be specified, yielding an unprecedented level of control over the interacting fields in nonlinear spectroscopic experiments. Heterodyne detection and phase cycling of the nonlinear signal is easily implemented due to the excellent phase stability between each output beam. This approach combines the waveform generation capabilities of magnetic resonance spectroscopy with the wavevector specification and phase-matching of nonlinear optical spectroscopy, yielding the signal selectivity and control capabilities of both. Results on three prototype systems will be used to illustrate the exciting possibilities with this method.
by Joshua Charles Vaughan.
Ph.D.
Valduga, De Almeida Camargo Franco. « Unravelling vibrational and electronic coherences via two-dimensional electronic spectroscopy of zinc-porphyrins ». Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/63645/.
Texte intégralYang, Ming. « Ultrafast two-dimensional infrared spectroscopy of hydrogen-bonded base pairs and hydrated DNA ». Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2012. http://dx.doi.org/10.18452/16561.
Texte intégralThe structure of DNA molecule and the interactions with its surrounding water is a hot topic for long time. In this thesis, we employ the nonlinear spectroscopy, including femtosecond pump-probe and two-dimensional infrared (2D IR) experiment, to study the vibrational dynamics of the systems. Double-stranded DNA short oligomers containing 23 alternating adenine-thymine base pairs were studied at different hydration levels by femtosecond 2D IR spectroscopy. For a DNA film at 0% relative humidity, the transient spectra enable a separation of the NH stretching mode of thymine from the symmetric and asymmetric NH2 stretching modes of adenine and determine the individual line shapes. For the NH stretch of thymine, the spectra demonstrate an essential homogeneous broadening, whereas for the symmetric and asymmetric NH2 stretches a pronounced and time-independent inhomogeneous broadening suggests a disorder in DNA structure. An energy transfer from the asymmetric NH2 stretch of adenine to the NH stretch of thymine is also observed. When the relative humidity increases, the increased water molecules have limited influence on the positions and line shapes of NH stretching frequencies, suggesting the spectral dynamics governed by DNA rather than water fluctuations. In contrast, the OH stretching mode of water shell around hydrated DNA undergoes a spectral diffusion on a 500 fs time scale, which is slower than the neat water. The guanosine-cytidine (GC) base pairs in chloroform solution were investigated to understand the interactions within base pairs. A local mode representationof NH stretching mode is adopted, consisting two free NH groups of G and C and three hydrogen bonded NH groups. The coupling and relaxation dynamics of the NH stretching excitations are studied by femtosecond pump-probe and 2D IR experiments. The results demonstrate a lifetime shortening upon the formation of hydrogen bonds, and an energy transfer between two hydrogen-bonded NH stretches.
Lin, Yu-Pu. « Functionalization of two-dimensional nanomaterials based on graphene ». Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4727.
Texte intégralIn order to promote 2D materials like graphene to their numerous applications, new methodsaltering their electronic and chemical properties have to be mastered. In this thesis, theprocesses of chemical doping and hydrogenation of monolayer graphene grown on SiC are investigated. Nitrogen atoms are successfully substituted in the graphene lattice using plasma-basedmethods. The bonding configurations of the incorporated N can be controlled via the nature and energy of exposing species and the thickness of the pristine graphene. An n-type doping, revealed by angle-resolved inverse photoemission spectroscopy (ARIPES), is found in most N-doped graphene and is assigned to the presence of graphitic-N. Hydrogenations of the buffer layer of graphene (BLG) on SiC at ambient or high temperatures saturate the remaining Si dangling bonds at BLG/SiC interface in two different ways, either by inducing additional C-Si bonds or by H intercalation. This results in 2D materials with distinct characters, an insulating, graphane-like H-BLG or a quasi-free-standing graphene, which may be used as a new concept for the engineering of graphene-based devices. The interactions between pi-conjugated molecules and the functionalized graphene are also investigated. The unoccupied states of molecules are altered by the presence of incorporated N, but the degradation of molecules due to low-energy electron exposure seems not enhanced by the doping nitrogen under the studied conditions. Nevertheless, the functionalization of graphene is demonstrated and its electronic and chemical properties are carefully studied, which should help to faster further applications employing functionalized graphene
Rule, Kirrily. « Magnetic ordering in the two dimensional antiferromagnet, FePS₃ ». Monash University, School of Physics and Materials Engineering, 2004. http://arrow.monash.edu.au/hdl/1959.1/9725.
Texte intégralKhan, Assad Ullah. « Thin-Film Polymer Nanocomposites Composed of Two-Dimensional Plasmonic Nanoparticles and Graphene ». Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/101942.
Texte intégralDoctor of Philosophy
Kozawa, Daichi. « Behavior of photocarrier in atomically thin two-dimensional semiconducting materials for optoelectronics ». Kyoto University, 2015. http://hdl.handle.net/2433/199420.
Texte intégralMagill, Brenden A. « Microwave spectroscopy of edge and bulk modes of two dimensional electrons in magnetic field ». Thesis, The Florida State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3564920.
Texte intégralEdge magnetoplasmons (EMPs) and pinning mode resonances in two dimensional electron systems (2DESs) can both be thought of as lower hybrid modes of cyclotron and plasma resonances. This dissertation describes low temperature microwave spectroscopy of both of these modes. EMPs have oscillating charge confined at the 2DES edge by the combination of the perpendicular magnetic field and the electrostatic potential that produces the edge. Pinning mode resonances are from electron solids oscillating against confinement provided by disorder in the bulk of the 2DES.
The first part of this dissertation concerns the search for a mode similar to an EMP but confined solely by a linear magnetic inhomogeneity in the perpendicular magnetic field (Bz). While we do not observe such an excitation, we do observe a marked reduction in the velocity of an EMP in the presence of a Bz-inhomogeneity.
In the second part of this dissertation, we investigate pinning modes in “wide'' quantum well samples, for which the effective electron-electron interaction is softened at short range due to the vertical extent of the wavefunction. We observe a pinning mode resonance whose peak frequency (fpk ) vs Landau level filling (ν) shows an anomalous increase as ν moves away from ν = 1 under roughly the same conditions as anomalous quantum Hall effects observed previously in DC transport. A region of ν with enhanced fpk is interpreted as evidence for a new electron solid phase.
Khalil, Munira 1975. « A tale of coupled vibrations in solution told by coherent two-dimensional infrared spectroscopy ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16607.
Texte intégralVita.
Includes bibliographical references.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Coherent two-dimensional infrared (2D IR) spectroscopy is used as a tool for investigating the molecular structure and dynamics of coupled vibrations in solution on a picosecond timescale. The strongly coupled asymmetric and symmetric carbonyl stretches of Rh(CO)₂C₅H₇0₂ (RDC) dissolved in hexane serve as a convenient model system. Fourier transform 2D IR spectra are obtained from heterodyne-detected third-order nonlinear signals using a sequence of broad bandwidth femtosecond IR pulses. A 2D IR correlation spectrum with absorptive lineshapes results from the addition of 2D rephasing and non-rephasing spectra, which sample conjugate frequencies in the evolution time period. The 2D IR correlation spectrum contains peaks with different positions, signs, amplitudes and lineshapes. The positions of the peaks map the transition frequencies between the ground, singly, and doubly excited states of the system, and thus describe the anharmonic vibrational potential. Peak amplitudes reflect the relative magnitudes and orientations of the transition dipole moments in the molecular frame, the electrical anharmonicity of the system, and the vibrational relaxation dynamics. The 2D line shapes are sensitive to the complicated system-bath interactions in solution. 2D IR spectra taken with varying polarization conditions and as a function of a variable waiting time can be used to isolate and quantify these spectroscopic observables. The polarization-selective 2D IR spectra of RDC in hexane are analyzed in terms of two coupled local coordinates to obtain their mutual orientation and the magnitude of the coupling between them. Evidence of vibrational coherence transfer between close-lying transition frequencies is indicated by the presence of extra induced peaks in 2D IR
(cont.) rephasing spectra. The data is modeled by using Redfield theory to account for coherence transfer, vibrational dephasing and population relaxation in a multilevel vibrational system. Building on the studies of the RDC model system, 2D IR spectroscopy is used to study the thermal denaturation of RNase A by characterizing the temperature-dependent Amide I band. A nonlinear IR probe is used to study the early events in the laser temperature-jump initiated denaturation of RNase A.
by Munira Khalil.
Ph.D.
Stone, Katherine Walowicz. « Coherent multi-exciton dynamics in semiconductor nanostructures via two-dimensional Fourier transform optical spectroscopy ». Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/49554.
Texte intégralThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 139-149).
The Coulomb correlations between photoexcited charged particles in materials such as photosynthetic complexes, conjugated polymer systems, J-aggregates, and bulk or nanostructured semiconductors produce a hierarchy of collective electronic excitations (i.e. excitons, biexcitons, etc.) which may be harnessed for applications in quantum optics, light-harvesting, or quantum information technologies. These excitations represent correlations among successively greater numbers of electrons and holes, and their associated multiple-quantum coherences could reveal detailed information about complex many-body interactions and dynamics. However, unlike single-quantum coherences involving excitons, multiple-quantum coherences do not radiate and they have largely eluded direct observation and characterization. In this work, I present a novel optical technique, two-quantum two-dimensional Fourier transform optical spectroscopy, which allows direct observation of the dynamics of multiple-exciton states that reflect the correlations of their constituent electrons and holes. The approach is based on closely analogous methods in nuclear magnetic resonance, in which multiple phase-coherent fields are used to drive successive transitions such that multiple-quantum coherences can be accessed and probed. A spatiotemporal femtosecond pulse shaping technique has been used to overcome the challenge of control over multiple, noncollinear phase-coherent optical Fields in the experimental geometries that are used to isolate selected signal contributions through wavevector matching.
(cont.) Results from a GaAs quantum well system reveal distinct coherences of biexcitons that are formed from two identical excitons or from two excitons whose holes are in di®erent spin sublevels ("heavy-hole" and "light-hole" excitons). The biexciton binding energies and dephasing dynamics are determined, and changes in the dephasing rates as a function of the excitation density are observed, revealing still higher-order correlations due to exciton-biexciton interactions. Two-quantum coherences due to four-particle correlations that do not involve bound biexciton states but that in°uence the exciton properties are also observed and characterized. I also present one-quantum two-dimensional Fourier transform optical spectroscopy measurements which show that the higher-order correlations isolated by two-quantum techniques are highly convolved with two-particle correlations in the conventional one-quantum measurements.
by Katherine Walowicz Stone.
Ph.D.
Wickramasinghe, Thushan E. « Growth Techniques and Optical and Electrical Characterization of Quantum Confined Zero-Dimensional and Two-Dimensional Device Structures ». Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou156631995093606.
Texte intégralPannell, Daniel K. (Daniel Kirk). « A Study of Intra- and Interaggregate Exchange Processes of Alkyllithium Compounds Using One- and Two- Dimensional NMR Spectroscopy ». Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc278360/.
Texte intégralFroehlicher, Guillaume. « Optical spectroscopy of two-dimensional materials : graphene, transition metal dichalcogenides and van der Waals heterostructures ». Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE033/document.
Texte intégralIn this project, we have used micro-Raman and micro-photoluminescence spectroscopy to study two-dimensional materials (graphene and transition metal dichalcogenides) and van der Waals heterostructures. First, using electrochemically-gated graphene transistors, we show that Raman spectroscopy is an extremely sensitive tool for advanced characteri-zations of graphene samples. Then, we investigate the evolution of the physical properties of N-layer semiconducting transition metal dichalcogenides, in particular molybdenum ditelluride (MoTe2) and molybdenum diselenide (MoSe2). In these layered structures, theDavydov splitting of zone-center optical phonons is observed and remarkably well described by a ‘textbook’ force constant model. We then describe an all-optical study of interlayer charge and energy transfer in van der Waals heterostructures made of graphene and MoSe2 monolayers. This work sheds light on the very rich photophysics of these atomically thin two-dimensional materials and on their potential in view of optoelectronic applications
Peng, Chunte Sam. « Two-dimensional infrared spectroscopy of nucleic acids : application to tautomerism and DNA aptamer unfolding dynamics ». Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91113.
Texte intégralCataloged from PDF version of thesis. Vita.
Includes bibliographical references.
The structural dynamics of nucleic acids are intimately related to their biological functions; however, our ability to study these molecular dynamics has been largely impeded by the lack of techniques that possess both high time resolution and structural sensitivity. The motivation for the work in this thesis was to develop and apply two-dimensional infrared spectroscopy (2D IR) as a new experimental tool to investigate nucleic acid dynamics. Infrared spectroscopy is sensitive to structural changes of nucleic acids and 2D IR offers sub-picosecond time resolution. 2D IR spectroscopy is advantageous over the linear infrared absorption spectroscopy because the vibrational spectrum is spread onto two frequency axes, giving rise to the structurally sensitive cross-peaks. These cross-peaks allow the determination of vibrational couplings, which encode chemical bond connectivity, distance and orientation. However, 2D IR spectroscopy of nucleic acids is underdeveloped due to the difficulties in modeling highly delocalized and coupled vibrations of nucleobases. This thesis initiated the efforts to develop 2D IR spectroscopy of nucleic acids by first characterizing the 2D IR spectra and vibrational eigenstates of nucleobases, using a model of multiple anharmonically coupled oscillators. With pronounced cross-peaks existing between all the vibrations for a give nucleobase, 2D IR spectroscopy was shown to be capable of distinguishing between different tautomers, using pyridone as a model system. Coupled with a laser-induced temperature-jump (T-jump), 2D IR was used to monitor rapidly exchanging tautomers in real time under physiological conditions on the nanosecond timescale. Systematically characterizing the tautomer exchange rates as a function of various experimental variables lead to a two-state concerted mechanism involving bridging water wires for the lactam-lactim tautomerization of 6-chloro-2-pyridone. This method was then applied to study the tautomerism of a deoxycytidine analog, KP1212, which is an anti-HIV drug. Multiple tautomers, including the normally rare enol tautomers, were found under physiological conditions. This observation supports the rare tautomer hypothesis, which states that each tautomer displays a distinct base-pairing preference, eventually leading to mutations and population collapse of the HIV viruses. Beyond studies on the single nucleotide level, 2D IR was used to characterize the structural dynamics of thrombin-binding aptamer (TBA), which is a 15mer DNA folded into a guanine-quadruplex (G-quadruplex). The 2D IR spectral signatures of G-quadruplex were established, and T-jump transient 2D IR was employed to investigate the unfolding dynamics of TBA. A mechanism of the early unfolding of TBA was proposed: A ~100 nanosecond response was attributed to the local deformation of the G-quadruplex, and a few-microsecond response was ascribed to be the fraying of the 3'-tail of TBA. This observation was consistent with a mechanism suggested by molecular dynamics simulations. Finally, the dissociation of double-stranded DNA formed by TBA and its complementary strand was found to be on the timescale of tens to hundreds of microseconds. The experiments in this thesis demonstrate the capability of 2D IR to investigate nucleic acid dynamics spanning a wide range of timescales.
by Chunte Sam Peng.
Ph. D.
Guan, Shenheng. « Fourier transform ion cyclotron resonance mass spectrometry : Personal computer-based instrument and two-dimensional spectroscopy ». Scholarly Commons, 1989. https://scholarlycommons.pacific.edu/uop_etds/3367.
Texte intégralRai, Rachel H. « Crystallization of Two-Dimensional Transition Metal Dichalcogenides for Tailored Optical Properties ». University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1565191101735252.
Texte intégralEichel, Rüdiger-Albert. « New concepts in two-dimensional pulse electron paramagnetic resonance spectroscopy : resolution enhancement by magnetic field modulation / ». Zürich : [s.n.], 2001. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14394.
Texte intégralGrainger, David S. « The application of the maximum entropy method to one- and two-dimensional nuclear magnetic resonance spectroscopy ». Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291092.
Texte intégralJo, Ju-Yeon. « Full molecular dynamics simulations of molecular liquids for single-beam spectrally controlled two-dimensional Raman spectroscopy ». Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263491.
Texte intégral