When a large piece of space debris forced a change of flight plan for a recent U.S. Space Shuttle mission, the concept that we are trashing space as well as Earth finally attained broad public awareness. Almost a million pieces of debris have been generated by 35 years of spaceflight, and now threaten long-term space missions. The most economical solution to this problem is to cause space debris items to reenter and burn up in the atmosphere. For safe handling of large objects, it is desired to do this on a precomputed trajectory. Due to the number, speed, and spacial distribution of the objects, a highly agile source of mechanical impulse, as well as a quantum leap in detection capability are required. For reasons we will discuss, we believe that the best means of accomplishing these goals is the system we propose here, which uses a ground-based laser system and active beam phase error correcting beam director to provide the impulse, together with a new, computer-intensive, very high-resolution optical detection system to locate objects as small as 1 cm at 500-km range. Illumination of the objects by the repetitively pulsed laser produces a laser-ablation jet that gives the impulse to de-orbit the object. A laser of just 20-kW average power and state-of-the-art detection capabilities could clear near-Earth space below 100-km altitude of all space debris larger than 1 cm but less massive than 100 kg in about 4 years, and all debris in the threatening 1-20-cm size range in about 2 years of continuous operation. The ORION laser would be sited near the Equator at a high altitude location (e.g., the Uhuru site on Kilimanjaro), minimizing turbulence correction, conversion by stimulated Raman scattering, and absorption of the 530-nm wavelength laser beam. ORION is a special case of Laser Impulse Space Propulsion (LISP), studied extensively by Los Alamos and others over the past 4 years.
A series of recently synthesized 1,3‐disubstituted imidazo[1,5‐a]pyridines (IPs) and ‐quinolines (IQs) targeting at increased efficiency of luminescence is investigated. The properties of molecules in solution as well as their change in the solid state are reported and assessed regarding possible application in organic electronics. The influence of increased ring size by substitution, e.g., exchanging phenyl to naphthalenyl, as well as pyridyl to quinolinyl moieties, and by means of a larger IQ fluorophore is discussed. A higher oscillator strength and quantum yield can be achieved. Frontier orbital energies are estimated based on cyclic voltammetry and density functional theory (DFT) calculations. Single crystals of molecules are grown. A red‐shift in the photoluminescence spectra found for crystals of IQs compared with those in solution is proposed to be caused by intermolecular coupling based on the parallel stacking of the enlarged fluorophore units. Thin films deposited by physical vapor deposition exhibit similar effects, showing promise as active layers in organic light‐emitting diodes (OLEDs). An amorphous morphology is inferred for these films from both spectral broadening in photoluminescence and atomic force microscopy. An OLED test structure is prepared, using the most efficient IQ lumophore and demonstrating the feasibility of obtaining electroluminescence from such thin films.
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