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 82 for “"Photoexcitation"”.
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Photoexcitation of nuclear isomers
Thesis: B.S., Massachusetts Institute of Technology, Department of Physics, 1955
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Vacuum-ultraviolet photoexcitation of some non-metal halides
… H, Cl or Br) has been studied following gaseous photoexcitation in the range 9-22 eV using synchrotron radiation. Fluorescence excitation, dispersed emission and action spectra have been recorded to probe the molecule in this way. Photoexcitation of these molecules has resulted in the population …
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Photofragmentation of carbonyl sulfide (Ocs) following core-shell photoexcitation and photoionization
… study the formation of cations and anions after photoexcitation and photoionization of OCS in the vicinity of the S 2p, C 1s and O 1s thresholds. Singly charged cations are produced predominantly at the pi* and Rydberg resonances while dications are major products of dissociative channels above …
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Photoexcitation of rare earth and metal-halide molecules in the ultraviolet
In the search for new sources of light and gain media for lasers, lanthanide fluoride powders and rare earth tri-iodide salts in vapor phase have been studied spectroscopically by photopumping in the ultraviolet. Knowing the spectral response of these molecules with respect to incident light and …
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Quantum chemical investigation of electron delocalization patterns during photoexcitation in Fischer carbene complexes: a theoretical study
Electron (de)localization is notoriously difficult to study. However, it is critically important for fundamental understanding of various photophysical and photochemical processes, including those that occur during light-harvesting in various solar energy devices. This work presents the novel …
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Mechanism and Applications of large and persistent photoconductivity in cadmium sulfide
… electrical conductivity changes as a result of photoexcitation of new charge carriers. In some semiconductors, photoconductivity is accompanied with enormous conductivity change and long decay time after photoexcitation is ceased. This effect is called large and persistent photoconductivity …
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Time resolved dynamics of charge density waves in solids : an uncorrelated and a correlated case
… about their nonequilibrium properties following photoexcitation. In this thesis, we use time resolved optical measurements to characterize the nonequilibrium dynamics of charge density wave systems. In the time resolved optical experiments in this work, an ultrashort (< 100 fs) pump pulse …
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Chlorine dioxide photochemistry in solution: time-resolved resonance Raman and femtosecond pump-probe studies
… conversion is investigated. Following OClO photoexcitation, subpicosecond geminate recombination of the primary ClO and O photofragments resulting in the reformation of ground-state OClO is observed. The quantum yield for this process is found to be solvent dependent. Newly formed OClO is …
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Single-shot spectroscopy of solid-state photoinduced dynamics far from equilibrium
… with strong electron-phonon coupling respond to photoexcitation across dimension, timescale, and excitation density. Dimensionality is explored qualitatively between the PtI chain sample and bismuth samples of varying thickness. The time evolution upon laser excitation is monitored from the …
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Investigations of Ice Photodynamics: Molecular Dynamics Studies and an Apparatus for Solid Sample Velocity Map Imaging
… recombine, or are trapped in the ice matrix. Photoexcitation is described using ground and excited ab initio potential energy surfaces for H2O. Additionally, the impact of including flexible water models, zero point energy consistent vibrational motion, and a secondary reaction (formation of …
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Experimental and theoretical studies of the ScI, YI, Hg2, and XeI diatomic molecules
… of the ScI molecule from 300 nm to 1000 nm with photoexcitation by a krypton fluorine (KrF) excimer laser at 248 nm are described. At least five new electronic and vibrational transitions of ScI were observed and analyzed. Emission spectra of YI spanning the 250 - 940 nm spectral region were also …
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Antimalarial Evaluation of Quinoline-triazoleMn(I) and Re(I) PhotoCORMs
… evaluated for their CO-releasing properties upon photoexcitation with UV light at 365 nm. Both complexes release CO upon photoexcitation in DCM, DMSO/PBS and DMSO/growth medium solutions. The rate of CO-release is medium-dependent and the Mn-1 complex releases CO faster than the Mn-2 complex. The …
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Electronic excitation and atomic forces in optically excited group V semimetals
… We propose a method for increasing the impact of photoexcitation on symmetry-breaking modes by a suitable choice of photon energy, which would apply to a variety of materials. We are also interested in the dynamics of the coherent phonons themselves. Recently, it has been shown that optical …
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Quantum Mechanical/molecular Mechanical Studies of F(1)-Atpase and a Plant Photoreceptor
… signal transmission following the initial photoexcitation event.
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Spectroscopic Studies of Organic Photovoltaic Non-Fullerene Acceptors
… NFAs. We propose theoretically that the primary photoexcitation in thin films of the archetypal NFA Y6 is a manifold of hybrid Frenkel-charge transfer (HFCT) dimer states. This manifold gives rise to the characteristic steady-state absorption band in the visible and near-infrared regions. Through …
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Magnetism and superconductivity out of equilibrium: Towards ultrafast superconducting spintronics
… process is critically slowed down when the photoexcitation intensity is commensurate with the superconductivity condensation energy, which we elucidate through the time-dependent Landau theory of phase transitions. On the other hand, the sub-nanosecond recovery time displays signs of a …
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Synthesis and Assembly of Dihydroindolizines on Gold Surfaces for Light Induced Work Function Alterations
… pyridinium (1643 cm-1) stretch as a function of photoexcitation. Structural assignments of this photochromophore are corroborated to density function theory calculations. Conformational changes in the monolayers appear in parallel with work function changes and are consistent with both its rate …
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Ion-molecule reaction mass spectrometry and vacuum-ultraviolet negative photoion spectroscopy
… negative ions have been detected following photoexcitation of 24 gaseous molecules. The majority of the molecules studied are halogen-substituted methanes. Product anions resulting from unimolecular ion-pair dissociation reactions were detected, and their ion yields recorded in the range …
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Implementing Solvothermally Synthesized Carbon Nanodots into Dye-Sensitized Solar Cells to Enhance External Quantum Efficiency in the Ultraviolet
… showed fluorescent properties under ultraviolet photoexcitation between λex = 295 − 385nm with solvochromatic and inner-filtering effects which were very similar to that of CNDs derived from the strictly hydrothermal CND synthesis method in the first part of this thesis. Upon the application of …
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VISIBLE-LIGHT-ACTIVE SEMICONDUCTOR HETEROJUNCTIONS FOR ENHANCED PHOTOCATALYTIC ACTIVITY
… of the electron-hole pairs generated by the photoexcitation. High recombination of photo excited charge carriers and limited efficiency under the visible light are the two limiting factors in the development of efficient semiconductor-based photocatalysts.
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