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Full-Text Articles in Physics
Ultrafast Spectroscopy Of Air Lasing In Filaments, Brian Robert Kamer
Ultrafast Spectroscopy Of Air Lasing In Filaments, Brian Robert Kamer
Optical Science and Engineering ETDs
Filamentation in air is a phenomenon that has been extensively investigated for the last two decades. At sufficiently high intensity, even air is a nonlinear medium. These intensities are reached with ultrashort pulses (50 to 100 fs) of more than 1 J energy, which self-focus in air, reach ionizing intensities of oxygen and nitrogen, creating a plasma that defocuses the beam. The air filament is a self-induced waveguide resulting from a balance of focusing and defocusing. In this work new techniques were developed to visualize and analyze this phenomenon through its emission, in particu- lar the UV emission of the …
The Profound Photophysical Effects Of Organic Chromophore Connectivity And Coupling, David J. Walwark Jr
The Profound Photophysical Effects Of Organic Chromophore Connectivity And Coupling, David J. Walwark Jr
Nanoscience and Microsystems ETDs
Through-bond and through-space interactions between chromophores are shown to have wide-ranging effects on photophysical outcomes upon light absorption in organic molecules. In collapsed poly(3-hexylthiophene), through-space coupling creates hybrid chromophores that act as energy sinks for nearby excitons and favorable sites for molecular oxygen to dock. Upon excitation with visible light the highly-coupled chromophores react with the docked oxygen and subsequently do not quench nearby excitons as efficiently. In tetramer arrays of perylene diimide chromophores the central moiety through-bond connectivity is synthesized in two variants which exhibit vastly different single-molecule blinking behavior and theoretically-predicted electronic transition character. In the more-connected tetramer …
Development Of Metallic Magnetic Calorimeters And Paramagnetic Alloys Of Ag And Er For Gamma-Ray Spectroscopy, Linh N. Le
Physics & Astronomy ETDs
A Metallic Magnetic Calorimeter (MMC) is a cryogenic calorimetric particle detector that employs a metallic paramagnetic alloy as the temperature sensor material. MMCs are used in many different applications, but this work will focus on their uses in high energy resolution gamma-ray spectroscopy. This technology is of great interest to the field of Nuclear Forensics and Nuclear Safeguards as a non-destructive assay for isotopic analysis of nuclear samples. The energy resolution of MMCs is an order of magnitude higher than the benchmark High Purity Germanium (HPGe) detectors that are currently used in the field and MMCs are also poised to …